Due to the fast energy transfer from Cs3Cu2I5 to MAPbI3, the device response time to X‐rays is dramatically reduced by nearly 30 times to 36.6 ns, which enables fast X‐ray detection capability by a large area detector arrays within 1 s. Moreover, Cs3Cu2I5 exists at the grain boundaries of MAPbI3 crystals, and blocks the paths of mobile ions of perovskite, leading to the lowest detectable dose rate of hybrid X‐ray detector is thus reduced by 1.5 times compared with control MAPbI3 direct‐type semiconductor, and 10 times compared with the Cs3Cu2I5 indirect‐type scintillator. The direct/indirect hybrid wafer also exhibits improved operation stability at ambient conditions without any encapsulation. This new kind of hybrid X‐ray detectors provides strong competitiveness by combining the advantages of both direct perovskite semiconductors and indirect perovskite scintillators for next‐generation products.Metal halide perovskite scintillators encounter unprecedented opportunities in indirect ionizing radiation detection due to their high quantum yields. However, the long scintillation lifetime of microseconds upon irradiation, known as the afterglow phenomenon, obviously limits their fast development. Here, a new type of hybrid X‐ray detector wafer combining direct methylamine lead iodide (MAPbI 3Cu2I5 to MAPbI3, the response time of the hybrid device is dramatically reduced from 1 µs to 36.6 ns, which promotes the development of X‐ray fast dynamic imaging. This new kind of hybrid X‐ray perovskite detector provides an opportunity for existing scintillators with serious afterglow phenomenon.Direct‐indirect hybrid perovskite X‐ray detector is prepared through a fast‐tableting process. Due to the fast energy transfer from Cs According to the detection mechanism, X‐ray detectors are divided into indirect‐type scintillators and direct‐type semiconductors. Direct‐type semiconductor attenuates the X‐rays, generates electron‐hole pairs, and then outputs the charge signals under a large electric field. Advanced direct‐type detector materials include Si, α‐Se, Ge, Cd1‐xZnxTe , and so on. However, Si and α‐Se are limited by their low atomic number and low attenuation coefficients, and the complex integration process of CZT involves technical difficulty and increased cost. In recent years, halide perovskite semiconductors have been discovered as excellent candidates for X‐ray detectors in enhancing the sensitivity in direct detection mode for low dosage imaging due to their strong stopping power, large mobility‐lifetime product (µτ), low defect density, tunable bandgap, easy synthesis method, etc., which are even superior to a commercial α‐Se semiconductor. Next milestone of a direct‐type perovskite X‐ray detector can be expected toward large‐area flat‐panel integration for fast medical CT imaging. However, one big obstacle faced for perovskite semiconductors is the serious ion migration effect of perovskite ions, especially under a large electric field to extract the charges induced by X‐rays, thus impairing the device signal‐to‐noise ratio (SNR) and accelerating the degradation of perovskite‐based electronic devices.Sensitive X‐ray detectors are widely deployed in medical examination, radiotherapy, product quality inspection, security checks, aerospace navigation, and other fields due to the unique penetration capability of X‐rays.2, 3 which avoids applying large bias and ions migration effect. The development of indirect‐type X‐ray detection is relatively mature, and now dominating the markets of CT products. However, there are only limited scintillators available due to the stringent requirements of ionizing radiation detection. For example, some classic scintillators such as NaI (Tl), CsI (Tl), YAlO3 (Ce), and Bi4Ge3O12 crystals are grown by the Czochralski method at temperatures above 1700 °C, and the fabrication conditions are harsh and expensive. In addition, UV–vis light will be scattered in the scintillation crystal, which seriously limits the collected quantum efficiency and spatial resolution due to the cross‐talk problem at neighbor pixels, and increases the difficulty and cost when coupled with CMOS or CCDs image sensors. More importantly, most scintillators surfer serious afterglow problems, which often causes an ultra‐long radiative lifetime and device response time. Foreign ions doping partially solved this problem, but limited ions matched the energy level and crystal lattice of host scintillators. Perovskite scintillators were discovered possessing high quantum yield, tunable emission peak position, and little self‐absorption with large stokes shift due to the self‐trapped excitons (STE) effect. However, the STE process also causes serious afterglow phenomenon with slow charge carrier recombination velocity and long recombination lifetime of microseconds or longer. Therefore, it is still challenging for perovskite X‐ray detectors to compete with traditional X‐ray detectors in comprehensive practical performance.Indirect‐type X‐ray detectors based on scintillation crystals first convert X‐rays into UV–vis photons, and followed by photodetector detection through image sensors, such as complementary metal‐oxide semiconductor (CMOS), charge‐coupled devices (CCDs), thin‐film phototransistor (TFT) arrays, and so on,20 whi3) semiconductor with indirect‐type zero‐dimensional cesium copper iodide (Cs3Cu2I5) scintillator, which can both effectively attenuate the X‐rays and generate collectible charge carriers. The mixed powders were tableted through a high pressure of 0.3 GPa, and the hybrid wafer showed a fast response time of 36.3 ns through the energy transfer process, which is nearly 30 times shorter than the scintillation afterglow of 1.07 µs for pure Cs3Cu2I5 scintillator. Fast X‐ray detection capability is also demonstrated by the hybrid detector arrays array in a large device area, and corresponding spatial resolution is also consistent with the pixel size, avoiding the isotropic light scattering effect of a scintillator.In this article, we developed a novel hybrid perovskite X‐ray detector by combining direct‐type methylamine lead iodide  with a quantum yield up to 89%. Thus Cs3Cu2I5 crystal can serve as scintillator material to convert the high‐energy X‐ray photons into UV–vis light  is one of the most important figure‐of‐merit for a scintillator, and the LY of Cs3Cu2I5 is directly measured by assuming that the emission intensity of the scintillation process is uniform in all directions. The LY of Cs3Cu2I5 was derived according to the following equations:1N is the number of photons emitted by a scintillator, 0I is the emission light intensity, hυ is the emission photon energy, 1S is the surface area of a sphere with a radius of the distance between the silicon diode photodetector and emission center, t is scintillation time, 2N is the theoretically produced photon numbers by one X‐ray photon, D is X‐ray dose rate, Φ is the X‐ray absorption rate of the sample, mµ is mass attenuation coefficient, and E is the average photon energy of X‐rays. The LYs of Cs3Cu2I5 under different X‐ray dose rates are roughly calculated and shown in the Figure 3Cu2I5 is independent of the exposed dose rate of X‐rays, and exhibits an average value of 26 000 photons MeV−1, close to the reported value of 29 000 ± 580 photons MeV−1 (see Supporting Information for details), indicating the high quality and good reproducibility of synthesized Cs3Cu2I5 scintillator. Scintillator decay time is another important figure‐of‐merit for a scintillator to determine the detector response time. The short decay time of tens of nanoseconds is necessary for dynamic medical CT imaging during multiple‐angle‐scanning. Figure 3Cu2I5 gives a very long decay lifetime of 1.07 µs, agreeing with many reported perovskite scintillators due to the STE effect, which is still limiting perovskite scintillators to step forward toward commercialization.Dimer polyhedrons of [Cu3Cu2I5 and MAPbI3 are both responsive to X‐rays, cheap, easily available raw materials, and simple synthesized routes, we used the tablet compression method to fabricate direct and indirect hybrid X‐ray detectors, which cannot only save the crystals growth time, but also achieve large area flat panel by simply employing large‐sized molds. More importantly, our hybrid X‐ray detector dramatically reduced the X‐ray response time from scintillation afterglow lifetime of 1.07 µs to 36.6 ns in the photocurrent response tests  and PL spectrum for MAPbI3, Cs3Cu2I5, and hybrid samples , consistent with the PLE spectrum of Cs3Cu2I5, indicating the energy transfer from Cs3Cu2I5 to MAPbI3. Another evidence is shown from the PL spectrum, and the fluorescence of Cs3Cu2I5 in the hybrid sample was quenched, while the fluorescence of MAPbI3 in the hybrid sample was enhanced at the same condition. This also indicates an energy transfer process from the Cs3Cu2I5 to MAPbI3, in consistent with the emerging fast radiative recombination path shown in PL lifetime characterization in Figure Considering Csed molds.33 Mor2.23 semiconductor, and the induced charges are directly collected through the continuous MAPbI3 phase under applied bias  measurements of hybrid samples with different mixed ratios, and no unexpected diffraction peak was observed  results also confirmed that Cs+ and Pb2+ were uniformly distributed in the hybrids, and there was no phase separation  calculation was also carried out to analyze the energy band structure of the hybrid materials. The calculations indicate that the hybrid material possesses direct bandgaps of 1.6 eV at the Γ point, which is in good consistent with the reported bandgaps (1.5 eV) of MAPbI3. It can also be clearly seen that the introduction of Cs3Cu2I5 does not introduce additional trap states within the bandgap of MAPbI3  are more frequently used for medical imaging, we focused on the device response to hard X‐rays with an accelerating voltage of 120 kVp. Materials attenuation equation can be described as follows:I is the transmitted photon flux intensity, 0I is the incident photon flux intensity, mµ is the mass attenuation coefficient, ρ is the density of the material, and l is the photon interaction length with materials. The required thickness of hybrid layers gradually increases a little bit as the increase of the Cs3Cu2I5 contents, since the X‐ray absorption coefficient of MAPbI3 is larger than that of Cs3Cu2I5.Considering the escaped PL emission from hybrid tablets surface, we covered a thin layer of MAPbI follows:38/Cr. The lowest detectable dose is one of the most important figures‐of‐merit for X‐ray detection during medical CT imaging, since exposed high dosage may cause disease like cancer. Although a high sensitivity of MAPbI3 wafer is often observed as shown in Figure 3Cu2I5 contents. The 30% Cs3Cu2I5 device has the lowest detection dose rate of 0.41 μGyair s–1, much lower than the practical dose rate of 5.5 μGyair s–1 during CT imaging. This value is also 1.5 times lower than the direct‐type MAPbI3 semiconductor, and 10 times lower than that of the Cs3Cu2I5 scintillator as summarized in Figure 3 phase, and the charges recombination velocity should be the same, thus the electrical signals contribution can be simply determined by the stopping power difference of two phases and energy transfer efficiency between them  analyzer coupled with a low noise current amplifier, and the noise current of 30% Cs3Cu2I5 device is obviously lower than the direct‐type MAPbI3 device, and close to the instrument noise  image of the hybrid wafer is shown in Figure  imaging.39 ThiFigure3Cu2I5 wafer is 5.4 × 107 Ω cm, ≈1.21 times larger than that of the MAPbI3 wafer. It should be noted that although the bulk resistivity of the Cs3Cu2I5 wafer is over two orders magnitude larger than the MAPbI3 wafer, signal and device noise can both influence the device X‐ray detection limit. We directly characterized the device SNR to see the difference between MAPbI3 wafer and hybrid wafer. It can be clearly seen that the hybrid wafer has improved SNR compared with the MAPbI3 wafer at high electric field range , and γ‐Butyrolactone  were purchased from Aladdin. Cesium iodide  was purchased from Energy Chemical, and N,N‐dimethylformamide  was purchased from Sinopharm. All these chemicals were used without any further purification.Cuprous iodide , Lead iodide  was reported in the literature.41 In 3 and Cs3Cu2I5 crystals were ground with a mortar and pestle for 30 min to achieve uniform mixed powders. First, the mixed powders were mounted into a pie shape mold through a compressor, and subsequently were subjected to a pressure of 0.3 GPa through a hydraulic press (FW‐4A) for 5 min. The targeting thickness could be obtained by adjusting the precursor loading amount. The wafer was then annealed on the hot plate at 100 °C for 10 min in the air for further crystallization. The area of the wafer is 1.326 cm2.MAPbI60 (30 nm) and BCP (10 nm) were sequentially deposited on the surface of the active layer by thermal evaporation, followed by depositing 50 nm Cr cathode under 5 × 10−4 Pa. Then Spin coating a layer of Spiro‐MeOTAD  and thermal deposition of 50 nm Au anode on the bottom surface of the corresponding wafer, respectively.The electron transport layers C3Cu2I5 doping with different mass ratios was measured with RF‐6000 with excitation light of 320 nm. The time‐resolved PL of the hybrid samples was measured by FLS980 with a 280 nm excitation source. The PL decay signals of hybrid samples were monitored at the emission maxima of Cs3Cu2I5, and a bandpass filter was applied before the detector to ensure that the fluorescence generated was from Cs3Cu2I5. The noise current of the devices was measured under dark at the different frequencies at −100 V reverse bias and the data were recorded by the SR830 DSP lock‐in amplifier. The X‐ray detection was carried out under X‐ray irradiation with an energy of 120 keVp. The acceleration voltage of the X‐ray tube was 120 kV, and the peak photon energy was thus 120 keVp. The operating current of the X‐ray tube was tuned to 50 mA. The radiation dose rate was calibrated with a commercial dosimeter from Germany . To test the stable operation conditions, the X‐ray detector based on the hybrid device was stored in ambient air condition at room temperature with the humidity of ≈30%, and no encapsulation was applied. In X‐ray sensitivity testing of devices, error bars were used to represent the distribution of data, where the height of the error bars was ±standard error. Three groups of the same conditions were taken to get the current signal value, then its average value was taken to calculate its standard error. All statistical analyses were performed in Origin 9.0.The XRD measurement was performed by Rigaku X‐ray diffractometer (SmartLab 3). The UV–vis spectra of the wafers were collected by UV‐2600 spectrophotometer operating from 200 to 800 nm. The steady‐state PL of CsThe authors declare no conflict of interest.H.W. conceived and supervised the project. L.L. grew single crystals, fabricated the detectors, measured the optoelectronic properties, and X‐ray detectors sensitivity. W.L. contributed to optoelectronic measurements and theoretical DFT calculation. X.F. assisted in drawing the mechanism diagram. All authors analyzed the data. H.W. and L.L. wrote the manuscript, and all the authors commented and reviewed the manuscript.Supporting InformationClick here for additional data file.


II cages showing guest‐tunable circularly polarized luminescence (CPL). An enantiopure helicene‐based ligand (M or P configuration) is coupled with a non‐chiral emissive fluorenone‐based ligand (A or B) to form a series of Pd2L2L′2 assemblies. The modular strategy allows to impart the chiral information of the helicenes to the overall supramolecular system, resulting in CPL from the non‐chiral component. Guest binding results in a 4‐fold increase of CPL intensity. The principle offers potential to generate libraries of multifunctional materials with applications in molecular recognition, enantioselective photo‐redox catalysis and information processing.Multicomponent metallo‐supramolecular assembly allows the rational combination of different building blocks. Discrete multifunctional hosts with an accessible cavity can be prepared in a non‐statistical fashion. We employ our shape‐complementary assembly (SCA) method to achieve for the first time integrative self‐sorting of heteroleptic Pd II cations with an enantiopure helicene‐based ligand and non‐chiral but emissive fluorenone ligands yields a series of Pd2L2L′2 heteroleptic coordination cages, showing circularly polarized luminescence (CPL) from the non‐chiral moiety. Modulation of the chiroptical properties is achieved by ligand modification or guest binding, achieving an up to 4‐fold enhancement of CPL intensity.Integrative self‐assembly of Pd Metal‐mediated self‐assembly of discrete architectures, possessing confined and accessible nanosized cavities, is a consolidated area of supramolecular chemistry.4, 5 OHowever, the vast majority of the reported compounds are based on only one type of ligand per assembly, limiting the possibilities to combine several properties and achieve multifunctional supramolecular hosts. While mixing different ligands of similar size and shape can in principle lead to heteroleptic systems, this often results in a statistical mixture of all the possible constituents. Hence, such an approach suffers from a lack of control over stoichiometry and stereochemistry, and complicates the examination and definition of clear structure‐function relationships. To overcome this, in the last few years, several rational strategies to exclusively obtain heteroleptic cages (i.e. species comprising multiple differentiable ligands) in a non‐statistical fashion have been developed.2L2L′2 heteroleptic cages showing chiroptical properties deriving from cooperative effects between all of the constituents. The heteroleptic cages are self‐assembled from a banana‐shaped bis‐pyridyl ligand having a fluorenone‐backbone with emissive properties (namely ligands A and B), a helicene‐based homochiral ligand (M or P enantiomers) and PdII cations. Remarkably, the overall properties of the system derive from the combination of the three building blocks. The PdII metal centers act as structural nodes to assemble a host with an inner cavity large enough to host a small anionic guest. At the same time, the homochiral ligands impart a twist to the overall structure, transferring their chiral information and resulting in CPL emission from the achiral fluorophore‐based ligands .Enantiomerically pure helicene‐based ligands, in strategy.20, 61M with metal salt [Pd(CH3CN)4](BF4)2 leads to cage Pd2M4 whose solid state structure was not yet reported. Here, crystals suitable for X‐ray structure analysis were obtained by slow vapor diffusion of ethyl ether into an acetonitrile solution. Homochiral cage Pd2M4 crystallizes in P1 space group, with the asymmetric unit containing one cage molecule 2L2L′2 species. Although the N⋅⋅⋅N distance of fluorenone‐based ligands A or B is larger than that of ligand M or P, previous studies indeed showed that helicenes can behave like a mechanical spring, with a modulation of the helical pitch influencing their structure and chiroptical properties.II, A, and M in a 1 : 1 : 1 ratio in CD3CN at 80 °C for 8 h resulted in a complicated, yet well‐resolved NMR spectrum with two sets of signals, indicating the formation of a discrete heteroleptic assembly . 1H NMR analysis showed significant downfield shifting of the pyridyl protons (Δδ≈0.4 ppm), confirming the coordination of the ligands to the Pd2+ metal ions. NOESY correlation between protons H6 and H6′ of the antiparallelly arranged, dissimilar halves of ligand A, together with DFT calculations (Supporting Information), support the exclusive formation of the cis‐configured heteroleptic cage. In addition, the exclusive formation of the heteroleptic Pd2A2M2 cage was confirmed by high‐resolution electrospray ionization mass spectroscopy (HR‐ESI MS), showing a series of peaks assigned to [Pd2A2M2+n BF4]n)+ were then used to gain more structural insight into the system and to adequately explain the splitting modes observed in the NMR spectra . This means that to form the heteroleptic structure, ligand M adopts a more stretched conformation to fit its rather rigid counterpart ligand A, again emphasizing the spring‐like behaviour of helically twisted helicene. As can be seen from the model, after heteroleptic cage formation, the mirror plane of ligand A perpendicular to the plane defined by its backbone is removed due to the absence of a mirror plane in the helicene ligand M. Hence, the upper and lower halves of both ligands are no longer equivalent, resulting in the observed splitting of proton signals into two sets. Careful analysis of the splitting pattern, together with COSY and NOESY spectra, allowed us to assign all signals unambiguously .The Pd⋅⋅⋅Pd distance in the model was measured to be 12.32 Å, which is larger than the distance measured in the homoleptic PdM/P, given by the helicenes’ spring‐like behaviour, inspired us to study the assembly of heteroleptic cages using even longer ligand B as counterpart, with the aim to further modulate the cavity size. Although, according to DFT models of both cages, the N⋅⋅⋅N distance of ligand B is significantly larger than that of A (14.82 Å vs. 13.16 Å), when combined with P, we obtained a 1H NMR spectrum with a similar splitting pattern to what previously observed for Pd2A2M2 , supporting the formation of a slightly larger cage structure as compared to Pd2A2M2 . Once more, the opposite enantiomer Pd2B2M2 was also obtained, showing an identical NMR spectrum . HR‐ESI MS again confirmed the formation of a dinuclear heteroleptic cage Pd2B2M2 by showing a series of peaks assigned to [Pd2B2M2+n BF4]n)+. The DFT‐optimized model (ωb97xd/def2‐SVP) of Pd2B2M2 gave a Pd⋅⋅⋅Pd distance of 13.63 Å. The longer Pd⋅⋅⋅Pd distance compared with that of Pd2A2M2 suggests that the flexible helicene ligand is able to stretch accordingly to match its counterpart.The structural flexibility of ligands 2A2(M/P)2 and Pd2B2(M/P)2 with different cavity sizes, we studied the interaction with an anionic guest, with the goal to subsequently investigate the chiroptical effect of molecular recognition. The host–guest interactions with 1,3‐propane bis‐sulfonate as guest (G) were initially investigated by NMR titrations. Upon gradual addition of the guest to Pd2A2M2 in CD3CN, inward pointing pyridine protons H7 from both ligands undergo a downfield shift (Δδ≈1.0 ppm), indicating guest binding inside the cavity. In a similar way, addition of G to Pd2B2M2 also results in guest encapsulation with slow‐exchange dynamics. Upon addition of 0.4 equiv guest, both empty cage and host–guest complex are distinguishable, while addition of 1.0 equiv guest results in a single set of 1H NMR signals, indicating the formation of [G@Pd2B2M2]. Unfortunately, determination of association constants was hampered by borderline solubility and apparent aggregation (onset of precipitation>1 equiv guest), leading to rather noisy NMR traces. Further confirmation comes from HR‐ESI‐MS studies, where it was possible to detect the exclusive formation of [G@Pd2A2M2]2+ . Trapped ion mobility spectrometry (ESI‐TIMS‐TOF) for the 2+ peaks of both empty host [2BF4+Pd2A2M2]2+ and host–guest complex [G@Pd2A2M2]2+ yielded collisional cross sections (CCS) of 524.3 Å2 and 521.7 Å2, respectively, confirming an inside binding mode and showing a slight contraction of the host–guest complex . A comparison of DFT‐optimized models of the empty host and host–guest complex proved helpful to understand this behaviour , as the Pd⋅⋅⋅Pd distance in [G@Pd2B2M2]2+ is indeed smaller than in the empty cage, consistent with the CCS measurement and explainable by the propensity of the dianionic guest to pull the cage's PdII‐faces slightly together.Having in hand two sets of heteroleptic cages PdA and M/P present similar absorption spectra with absorption bands in the range of 200–400 nm. Specifically, M/P is characterized by a band centred at 292 nm and a broad shoulder in the range 325–400 nm, while ligand A presents two bands at 285 and 300 nm, and a broad band between 325 and 375 nm . Upon PdII coordination, the absorption bands of the homoleptic cages Pd2(M/P)4 are red shifted, while for Pd2A4 the spectrum resembles the one of the free ligands, with slight variations in the relative intensity of the different bands .Having the multifunctional heteroleptic cages and host–guest complexes in hand, we investigated their (chir)optical properties. All employed ligands are based on well‐known chromophores. Both ligands 2A2(M/P)2 are characterized by a broad absorption band between 275 and 300 nm and a shoulder around 350 nm, that basically corresponds to the superposition of both ligands. Using the helicene based ligands as enantiomerically pure compound bestows the system with a chiroptical fingerprint. CD spectra in acetonitrile of both M and P ligands show strong bands at 350 and 300 nm, with a negative exciton couplet for the M enantiomer, and perfect mirror image for the P enantiomer . We then studied the heteroleptic cages, to see if the chiral information imparted from the helicenes to the overall structure is transferred to the fluorenone‐based ligands. CD spectra of Pd2A2(M/P)2 2 2 show a broad emission band around 510 nm, slightly red‐shifted compared to the free ligand 2 exhibit an emission at 520 nm . Interestingly, all the heteroleptic cages exhibit a CPL effect, matching the fluorescence spectra and therefore originating from the non‐chiral fluorenone ligands A or B 2 and 0.4×10−3 for Pd2B2(M/P)2. However, the chiroptical properties derive from the synergistic interaction of the two different ligands, mediated by the PdII metal centres, and thus mark the first multifunctional heteroleptic cage assembly showing a CPL emission. Interestingly, the two fluorenone ligands differ only by the nature of the linker, being an alkyne for A and a 1,4‐phenylene group for B. This variation results in a difference of the |glum| values in the two heteroleptic cages. Trying to rationalize this, we compared the DFT models of the two heteroleptic cages. As has been shown previously in theoryA and B modulate the helical pitch of the helicene ligand, resulting in a different degree of chirality transfer. The helical pitch in Pd2A2M2 is smaller than that in Pd2B2M2 2 and G@Pd2B2(M/P)2 results in a pronounced bathochromic shift  of the emission, together with an amplification of the CPL effect 2 and 1.5×10−3 for G@Pd2B2(M/P)2. DFT analysis, as well as ion mobility data, shows how accommodation of the guest inside the cavity, results in a shrinkage of the cage, with a reduction of the Pd⋅⋅⋅Pd distances. A narrowing effect on the CCS signal as observed when comparing insets in Figure Having shown that our heteroleptic cages are able to bind a guest molecule, we then investigated the effect of the molecular recognition process on the chiroptical properties. Addition of m Figure b, S23. A2L2L′2 cages, for the first time. The overall properties derive from the synergy of the three building blocks, one ligand (M/P) carries the chiral information, the other ligand (A or B) brings emission properties, while coordination to PdII cations allows to create a discrete cavity. The spring‐like behaviour of the helicene ligands allows to control their helical pitch, adapting in size to match the second ligand and adjust to guest binding. The chiroptical consequences of combining the ligands into a self‐assembled cage and the guest influence were studied by CD spectroscopy, however, complicated by the overlap of the absorption bands of both ligands. On the other hand, CPL analysis allowed to unambiguously show the chirality transfer and guest modulation in the system by limiting the readout to only the emissive ligand, hence simplifying the chiroptical analysis. We demonstrated how a rather simple modification of the non‐chiral ligand can result in a change in CPL intensity, paving the way for new strategies to achieve modular tunability of chiroptical properties in self‐assembled compounds and materials. Furthermore, guest recognition was shown to shift and enhance the CPL output, showing the potential of such systems for molecular recognition and imaging applications based on a chiroptical readout.In conclusion, we successfully applied the shape‐complementary assembly approach (SCA) to achieve integrative self‐sorting of a series of CPL‐active heteroleptic PdThe authors declare no conflict of interest.1As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.Supporting InformationClick here for additional data file.


However, the lack of the long-sought molecular consensus about the synergistic effect between the adsorption and in-situ catalytic reaction hinders its development. Herein, we illustrate the synergistic promotions between CO2 capture and in-situ conversion through constructing the consecutive high-temperature Calcium-looping and dry reforming of methane processes. With systematic experimental measurements and density functional theory calculations, we reveal that the pathways of the reduction of carbonate and the dehydrogenation of CH4 can be interactively facilitated by the participation of the intermediates produced in each process on the supported Ni–CaO composite catalyst. Specifically, the adsorptive/catalytic interface, which is controlled by balancing the loading density and size of Ni nanoparticles on porous CaO, plays an essential role in the ultra-high CO2 and CH4 conversions of 96.5% and 96.0% at 650 °C, respectively.The integrated CO 2 capture and conversion (iCCC) technology has been booming for carbon neutrality. Here the authors optimized the Ni–CaO composite catalyst to promote iCCC involving consecutive high-temperature Calcium-looping and dry reforming of methane and illustrated their synergistic promotions at the suitable catalyst interface.The integrated CO Among various CCUS technologies, the integrated CO2 capture and conversion (iCCC) has attracted more and more interests since it shows great advantages in saving energies and costs for CO2 compression and transportation involved in the conventional CCUS processes5. More significantly, when the iCCC technology is applied to the CO2 capture from the high-temperature flue gas, its thermo-energy can be directly converted into the chemical energy during CO2 conversion, resulting in high energy efficiency7.Carbon capture, utilization and storage (CCUS) technology can play a crucial role to restrain the global warming of no more than 1.5 °C above pre-industrial levels8. Then, the synergistic promotion effects between the CO2 capture and in situ conversion may result in both high and stable CO2 capture capacity and conversion efficiency10. Currently, the reported DFMs in most iCCC processes are CaO-based composites largely due to its excellent theoretical CO2 capacity (17.8 mmol g−1) at high temperatures12. Instead of the calcination regeneration at above 900 °C in the traditional Calcium looping (CaL)14, the in situ conversion of captured CO2 may significantly lower the regeneration temperature and thus overcome the bottleneck problems of high energy penalties and CaO sintering. Meanwhile, catalysts such as Rh15, Ru16, Ni17, Fe18, and Co19 in C1 chemistry of methanation, reverse water gas shift reaction (RWGS), and dry reforming of methane (DRM), are usually combined within iCCC processes for the CO2 conversion. However, the development of DFMs has underlined the gap in mechanism investigation, that the interactions and synergy effects between sorbents and catalysts of DFMs need significant molecular-level understanding to break through the efficiency limitation of DFMs20. So far, even the nature of the active sites in DFMs and its role in the conversion of captured CO2 are still under debate, and it is not clear if the adsorption site can solely accommodate the CO2 and its catalytic conversion can only occur at other positions23, or the captured CO2 can be also activated at the adsorption site for direct reaction with the incoming H species produced on the nearby catalytic sites27. Therefore, how the synergistic effects between the adsorptive and catalytic sites may work at the DFMs interface and what types of elementary steps are involved in the consecutive reaction pathways need intensive research for the development of efficient iCCC strategy28.Intuitively, the successful application of iCCC lies in the development of dual-functional materials (DFMs), of which the adsorptive sites and catalytic sites are intimately close to each other2 and CH4 into valuable syngas with equimolar H2 and CO. The challenges in the development of DRM mainly come from the high energy consumption due to the strong endothermic nature of this reaction and the corresponding high-temperature (>800 °C)29. Moreover, it also suffers from the catalyst deactivation caused by the coking30. Currently, most studies focus on developing efficient DRM catalysts for the activation of the two reactants, while the strategies to take advantage of their coupled reactions are still limited.At the same time, the dry reforming of methane (DRM) is a very useful reaction, which can convert two major greenhouse gases of CO2 capture and in-situ conversion on the Ni–CaO DFM in a molecular way. Density functional theory (DFT) calculations of the corresponding model catalyst with a Ni4 cluster on the CaO(100) substrate disclosed the synergistic reaction pathways of the direct conversion of CaCO3 by the DRM, which settles the debate about the role of captured CO2 on conversion. More importantly, the mechanism of synergistic promotions provided the in-depth understanding of the long-sought consensus about the consecutive reactions involved in CaL@DRM and inspired the design and fabrication of DFMs with enriched interface between the catalytic site and adsorptive site. With the controlled loading density and the growth of Ni nanoparticles in the nanoconfined space of porous CaO substrate, such optimized Ni–CaO DFMs can give rise to high conversion efficiencies for both CO2 and CH4, superior to all the reported performance of conventional catalysts and DFMs for the DRM process. We anticipate that the findings will help to build an efficient way to boost the iCCC technology for Carbon Neutrality, and to shine the light on the general understanding of consecutive reactions.Herein, we chose the most representative high-temperature iCCC technology by integrating the Calcium-looping and dry reforming of methane (CaL@DRM) processes. For the first time, we demonstrated the synergistic promotion effects between COx, x denotes the loading weight percentage of Ni in sample, see 4 could be particularly difficult in the in situ CO2 conversion by DRM. The temperature programed surface reaction (TPSR) was first used to evaluate the CaL CO2 capture process, CH4 dehydrogenation and CaL@DRM processes on pure CaO and Ni–CaO-10 DFM, respectively. For the CO2 capture from the simulated flue gas through the CaL process, Ni–CaO-10 exhibited similar CO2-TPSR performances as CaO, giving a downward CO2 adsorption peak centered at 650 °C (carbonation) and an upward CO2 release peak at 850 °C (decarbonization)  is an endothermic reaction, it will be more favorable to occur under higher temperature. Thus, the thermal cracking of CH4 was determined in this work when the temperature was high enough even without the help of any catalyst, giving rise to the CH4–TPSR curves of the pure CaO sample and the CaO after CO2 pre-adsorption (CaCO3), together with the H2 formation, above 800 °C  may even participate in the reduction of the adsorbed CO2 at CaO32. Moreover, since no obvious CO2 signal was observed, we may suggest that the captured CO2 (CaCO3) can be indeed effectively reduced by CH4 to produce syngas. It is also worth mentioning that the peak values of CO and H2 are centered at 600–650 °C, much lower than the reported operating temperatures of 700–800 °C of the conventional DRM33, demonstrating the significant promotions between CO2 capture at CaO and its in-situ conversion through DRM. However, we also found that after the CaL@DRM processes, the Ni–CaO-10 lost its silver-like metallic luster and appeared black in color, suggesting that the bottleneck problem of the carbon deposition in the conventional DRM may still exist29. Therefore, we highly anticipated that a better understanding of how the CO2 adsorption and DRM conversion occur in an interactive way in our CaL@DRM processes would help guide further optimization of the Ni–CaO dual-functional materials.The most convenient approach for the construction of possible CaL@DRM iCCC catalysts is to combine the adsorptive sites (CaO) and the catalytic sites (Ni) in one DFM Fig. . So, we  °C Fig. . Whereas °C Fig. , which i4–CaO  bond and two (CO2)O–Ca bonds, i.e., a carbonate-like adsorbed species (*CO2) occurs  is 1.21 eV, slightly stronger than that of the CO2 on the Ni4 cluster (Eads = 1.19 eV), and similar results can be also obtained from supported Ni13 clusters  around the Ni4 cluster are all very close with each other, indicating the moderate mobility of the adsorbed CO2 on the CaO(100) surface37. Notably, the dispersion corrections by using the DFT–D2 method39 and Hubbard U correction40 were also considered in the calculation of Ni based materials, and the calculated results showed that the overall trend of CO2 adsorption at different sites of the Ni4–CaO(100) surface were consistent with that obtained without Grimme D2 or U corrections , which are 0.32 eV, 1.21 eV, 1.62 eV and 2.61 eV, respectively  is quite difficult, since the calculated endothermic reaction energy is as high as 4.39 eV. From calculated energetics of the above three different pathways, it can be concluded that the *COOH pathway is more favorable for the H-assisted *CO2 dissociation  surface, as the captured *CO2 can be readily converted with the help of *H from the CH4 dehydrogenation.To illuminate the molecular mechanism of the synergistic promotions, we constructed the model Ni–CaO DFM with 4-atoms Ni clusters being supported on the CaO(100) substrate, namely Ni4, rather high energy barriers need to be overcome when the intermediate *CH2 species undergoes deeper dehydrogenation  at the Ni sites to form *CHxOH  surface, which provides another strong evidence of the synergistic promotions. It is also worth mentioning that the novel pathway of the CH4 dehydrogenation disclosed here suggests the important role of the suitable interface of Ni–CaO DFM as it may stride across the carbon deposition in the conventional DRM.In addition, one may notice that in the above direct dehydrogenation of CHies Fig. . So, the46. In the CO2 capture stage, the optimized carbonate-like adsorbed *CO2 species one the CaO(100) surface obtained from DFT calculations was used, and the calculated asymmetric stretching frequencies are at 1740 and 905 cm−1  on the CaO surface at 1789 and 876 cm−1, and of the calcite (CaCO3) at 1540 and 2504 cm−1 can be clearly observed in the DRIFTS spectra  gives the peak at 1362 cm−1  at 2940 cm−1 may also support the *OH-assistant CH4 dehydrogenation48. As expected, the CO peak at 2142 cm−1 gradually increases with the decrease of carbonate peak at 1789 cm−151. Again, since no CO2 peak was observed, it can be further clarified that the captured *CO2 (CaCO3) is indeed directly reduced into CO through the in situ CaL@DRM pathway.We further verified this synergistic mechanism for the CaL@DRM processes through the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and the density-functional perturbation theory (DFPT) calculationm−1 Fig. . Corresptra Fig. 47. Afterm−1 Fig. . AccordiOOH Fig. 48. These2 capture and in-situ conversion, where the reaction efficiency of the *H-assistant *CO2 conversion and the *OH-assistant CH4 dehydrogenation should be compatible with each other. In the current work, the Ni–CaO DFMs synthesized by a simple sol–gel method all exhibited a branched coral-like porous morphology  patterns of all samples showed the successful transformation of NiO (JCPD 47-1049) to Ni (JCPD 04-0850), with the dominant CaO crystals being unchanged (JCPD 48-1467)  of total Ni on Ni–CaO-2.5, Ni–CaO-5, and Ni–CaO-10, respectively  Fig. . The mos67) Fig. . Along w JCPD 48-67 , all the Ni–CaO-x  DFMs exhibited excellent CO2 adsorption capacities  reached 86.4% (84.3%), 94.1% (90%), and 95.4% (92.7%) on these catalysts, respectively; and the determined RH/C in the syngas products were 0.88, 1.06, and 1.24 , resulting in the RH/C lower than 1. By contrast, too high loading density of Ni on the Ni–CaO-10 will also lead to the mismatching between the CO2 conversion and *OH-assistant CH4 dehydrogenation, resulting in the CH4 dehydrogenation by itself on the Ni particles, and hence the RH/C larger than 1. It was further confirmed the deposited carbon formed on Ni–CaO-10 rather than Ni–CaO-5 in CaL@DRM process by Raman spectra  DFMs with the Ni particle size (d) ranging from 8.2 to 17.2 nm were obtained  DFMs also gave improved CO2 adsorption and conversion with the decreased size of Ni nanoparticles. Specifically, Ni–CaO-5(8.2), with the smallest Ni particle size, exhibited the maximum CO2 capture capacity of 12.8 mmol g-1 and the best CO2 and CH4 conversion of 96.5% and 96.0%, respectively, together with the syngas production yield as high as 0.452 mmol s−1 gNi−1  DFM had a much better resistance to carbon deposition compared with the Ni-Ca@Zr and Ni–CaO catal@sorbent53.To elaborate upon the importance of interface structures for the iCCC performance, we regulate the size of Ni nanoparticles by varying the amount of soft template at the fixed loading of Ni 5 wt%) in the sol-gel process. As the result of the different nanoconfined spaces constructed by the template, a series of Ni–CaO-5 shows a maximum at 650 °C  packed reactor were conducted, and the results showed an extremely stable CO2 and CH4 conversions of 96.5% and 96.0%, respectively, with only a slight decrease in the cyclic CO2 capture capacity 2·4H2O, 99.99%), nickel nitrate hexahydrate (Ni(NO3)2·6H2O, 99.99%), urea(CO(NH2)2, 99.99%) and citric acid monohydrate  were purchased from Sinopharm. All chemicals were in the analytical reagent-grade and used as received. Deionized water was used in all synthesis and washing processes.Calcium nitrate tetrahydrate 2·4H2O and 7.50 g of citric acid monohydrate were dissolved in 20 mL of distilled water at room temperature under stirring for 0.5 h. Then specific amounts of Ni(NO3)2·6H2O were added into the mixture under stirring for an additional 0.5 h. Then, the mixture was continuously stirred at 90 °C to form a translucent pale-green sol. The sol was transferred in an oven at 120 °C for 12 h to obtain a dried gel. The dried gel was calcined in a muffle furnace under air at 800 °C for 4 h at a temperature ramp rate of 2 °C min−1 to produce the Ni–CaO-x dual function materials, where x represents the weight fraction of Ni. The DFMs were fully reduced by H2 at 700 °C for 2 hours before use. In addition, pure CaO was also prepared as a reference sample according to the above-mentioned procedures.Ni–CaO-d) DFMs loading the same Ni loading (5 wt%), prepared by the modified sol–gel method, different molar ratio  of soft organic template (citric acid and urea) with metal precursor were dissolved in water. The other prepared steps are the same as above. But the dried gel firstly was calcined under N2 at 800 °C for 2 h and then calcined under air at 600 °C for 2 h. Ni–CaO-5(d) samples under investigation have varying Ni mean particle sizes (d), as listed in Supplementary Table For Ni–CaO-5(−1. Scanning electron microscopy (SEM) was conducted on a Helios G4 UC SEM-FIB (15 kV). Samples were pre-treated via Pt sputtering before the observation. Transmission electron microscopy (TEM) and Scanning transmission electron microscopy (STEM) images were performed on a Thermo-Fisher Talos F200X  equipped with an energy dispersive spectrometer (EDS) for determining the elemental distribution. High angle annular dark field (HAADF)-STEM images were recorded by using a convergence semi angle of 11 mrad, and inner and outer collection angles of 59 and 200 mrad, respectively. Nitrogen adsorption-desorption isotherms were measured at 77 K using a Micromeritics ASAP-2020, from which the specific surface area and the pore size distribution of samples were calculated based on the Brunauer–Emmett–Teller (BET) model and the Barrett–Joyner–Halenda (BJH) approach, respectively. Before the measurement, the samples were degassed at 200 °C for 5 h. Elemental analysis was performed using an inductively coupled plasma atomic emission spectrometer . X-ray photoelectron spectroscopy (XPS) of the samples were recorded on a Thermo-Scientific K-Alpha Spectrometer. All peaks were corrected by setting the C 1 s peak of 284.6 eV as the reference. Fourier transform infrared spectra (FTIR) was performed on a NEXUS 470 spectrometer in the range of 4000–400 cm−1. Prior to the measurement, the sample was mixed with potassium bromide and pressed into a wafer.Powder X-ray diffraction (PXRD) patterns were obtained on a Bruker D8 Advance X-ray powder diffractometer equipped with a Cu sealed tube (λ = 1.54 Å) at a scan rate of 0.02 s2-TPR) was carried out on an automated chemisorption flow analyzer , equipped with a thermal conductivity detector to optimize the reduction conditions of DFMs. In a typical experiment, 50 mg of the calcined sample was loaded in a quartz reactor and heated to 300 °C in the nitrogen atmosphere (50 mL min−1) for the dehydration. After the temperature was cooled down to 50 °C, the gas was switched into 10 vol% H2 balanced with Ar (50 mL min−1). Subsequently, the temperature was increased again with a heating rate of 10 °C min−1.The temperature-programmed reduction in hydrogen  was pretreated under 10 vol% H2 balanced with N2 at 700 °C for 30 min. For the CaL process determined by the CO2-TPSR test, samples were heated from 50 to 900 °C with a heating rate of 10 °C min−1 under the gas flow of 10 vol% CO2 balanced with N2 at a rate of 50 ml min−1. For the CH4 dehydrogenation process determined by the CH4-TPSR test, the operation conditions are the same except the gas flow changed into 5 vol% CH4 balanced with N2. For the CaL@DRM processes, the sample was exposed to a gas flow of 10 vol.% CO2 balanced with N2 at a rate of 50 ml min−1 for 30 min at 650 °C to make DFMs saturated with CO2. Then the sample was cooled down to 50 °C. Afterwards, the CH4-TPSR test was carried out under the same conditions as above. The nondispersive infrared analyzer  was used to monitor the concentration changes of each substance  participated during all TPSRs in effluents.The temperature programmed surface reaction (TPSR) was performed on Autochem 2720. The performance of the Calcium looping (CaL) CO−1 per 64 scans with a resolution of 4 cm−1. Prior to each testing, the sample (∼5 mg) was pre-reduced in the atmosphere of 10 vol% H2 balanced with He (25 ml min−1) at 700 °C for 2 h. Then, the gas was switched into N2 to remove the residual H2 for 30 min by decreasing the temperature to 600 °C, and the background reference signals were collected. The CO2 capture was performed in the atmosphere of 10 vol% CO2 balanced with N2 (50 mL min−1) for 10 min. After the N2 elution for 8 min, the in situ CO2 conversion was performed by switching the gas into 5 vol% CH4 balanced with N2 (50 mL min−1) for another 10 min.The produced intermediates during CaL@DRM process were monitored by an in situ diffuse reflectance infrared Fourier transform spectroscopy , equipped with a diffuse reflection attachment reaction cell (DRK-3 Praying Mantis Harrik). The spectra were recorded in the range of 3000–750 cm2 capture and in situ conversion (CaL@DRM processes) were conducted in one fixed-bed column. The flow rates of N2, CO2, H2, and CH4 were controlled by the mass flow controllers (Horiba Metron), respectively. The products in the outlet gas were analyzed by the gas chromatography  with a thermal conductivity detector (TCD) and a flame ionization detector (FID). In addition, an in situ nondispersive infrared analyzer  was used to monitor the concentration changes of CO, CH4, H2, and CO2 continuously. In a typical experiment, approximately 0.1 g DFMs was added to a quartz tube (Φ10 mm × 150 mm) and packed with height of about 10 mm, then placed in the reactor furnace. The first step was the sample prereduction, which was carried out at 700 °C in the gas flow of 10 vol% H2 balanced with N2 at a rate of 50 ml min−1 for 2 h. The second step was the CO2 capture, in which the gas was switched to the simulated flue gas of 10 vol% CO2 balanced with N2 at 50 ml min−1 (WHSV = 30 L g−1 h−1) and at a specific temperature such as 600, 650, 700, and 750 °C for 1 h. The third step was the purge. The pipeline was purged with pure N2 for 5 min. The fourth step was the in situ conversion, in which the temperature was kept the same as in CO2 capture, and the gas was switched to 5 vol% CH4 balanced with N2 at a flowrate of 50 ml min−1. Moreover, we performed the blank test in the same fixed bed under the same operating conditions by using an inert material (SiO2) with similar particle size to that of DFMs.The CO2 adsorption capacity (q) was calculated by Eq.  is the conversion of CO2 or CH4, Fi,in, and Fi,out, represent the molar flow rate of CO2 or CH4 in the inlet gas and the outlet gas, respectively. ts is the duration time of the in-situ conversion step.The COi) of CO or H2 was calculated by Eq.  of syngas was determined by the ratio between H2 and CO concentrations in the outlet gas.The H2 capture step was skipped, and the feeding gas was changed into the mixture of 10 vol% CO2 and 10 vol% CH4 balanced with N2.For comparison, the conventional DRM test was also conducted as above, except that the CO57. The projector augmented wave (PAW) method58 and the Perdew–Burke–Ernzerhof (PBE)59 functional under the generalized gradient approximation (GGA)60 were applied throughout the calculations. The kinetic energy cut-off was set to 400 eV, and the force threshold in structure optimization was 0.05 eV Å−1. We used a large vacuum gap of 15 Å to eliminate the interactions between neighboring slabs. By adopting these calculation settings, the optimized lattice constant of CaO is 4.80 Å, which is in good agreement with the experimental value of 4.80 Å61. For the model construction, the Ni4 cluster to simplify the theoretical calculation model cluster is widely used as a classic which could well reflect the characteristic of simulated nanoparticles in the DFT calculation64. Therefore, we built a p (4×4) surface slab containing five atom layers for CaO(100) and Ni4 supported CaO(100) surfaces. The top four atom layers of these slabs were allowed to fully relax, while the bottom atom layer was kept fixed to mimic the bulk region. A 2 × 2 × 1 k-point mesh was used in calculations of all these models. Calculation of the IR spectrum for the adsorbed of CO2 and COOH species on the Ni4–CaO(100) surfaces using the Born charges and the density functional perturbation theory (DFPT)46. For comparison, we also constructed the model Ni–CaO DFM with Ni 13-atom Ni clusters being supported on the CaO(100) substrate, namely Ni13–CaO(100).All spin-polarized DFT calculations were carried out using the Vienna Ab–Initio Simulation Package (VASP)67. The adsorption energy of species X on the surface (Eads(X)) was calculated by the Eq.  indicates an exothermic adsorption process, and the more positive the Eads(X) is, the more strongly the adsorbate X binds to the surface.The transition states (TS) of surface reactions were located using a constrained optimization scheme and were verified when (i) all forces on the relaxed atoms vanish and (ii) the total energy is a maximum along the reaction coordination, but it is a minimum with respect to the rest of the degrees of freedom the Eq. :4\documeSupplementary InformationPeer Review File


We found that the results from two experiments are qualitatively similar to each other. During the forcing-on period, a dominant warming in the upper troposphere over the tropics and on the surface at high latitudes led to a slowdown in the Hadley circulation, but the poleward atmospheric energy transport was enhanced due to an increase in specific humidity. This counteracted the reduction in poleward oceanic energy transport owing to the suppression of the meridional overturning circulation in both Hemispheres. After returning the original CO2 level, the hemispheric thermal contrast was reversed, causing a southward shift of the intertropical convergence zone. To reduce the hemispheric thermal contrast, the northward energy transports in the atmosphere and ocean surface were enhanced while further weakening of the global-scale Atlantic meridional overturning circulation led to southward energy transport in the deep ocean.To investigate the response of the general circulation and global transport of heat through both atmosphere and ocean to two-types of carbon dioxide removal scenario, we performed an earth system model experiment in which we imposed a pulse-type quadrupling of CO Fortunately, the Paris Agreement of December 2015, i.e., the United Nations agreement on maintaining the increase in global average temperature at well below 2 °C from pre-industrial levels and that efforts to limit the temperature increase to 1.5 °C should be pursued, provides hope that the worst scenario for future climate change can be avoided. However, scientific and more quantitatively accurate projections of future climate change, in terms of spatiotemporal aspects, are required to mitigate the climate crisis in the most efficient manner.Since the Industrial Revolution, the climate of the Earth has undergone unprecedented changes. Such climate change is caused by high and abrupt emissions of greenhouse gases4. One such projection is the so-called “abrupt4 × CO2” experiment endorsed in CMIP5, in which atmospheric carbon dioxide (CO2) is instantaneously quadrupled and then kept constant for 150 years. Such a step-function type of changes in CO2 levels may not be realistic, but does have an advantage in understanding the fundamental behavior of climate system than more complicated scenarios could do. Good et al.5 revealed that the climate behavior illustrated by the “abrupt4 × CO2” simulations is also applicable to more realistic projections such as the representative concentration pathway scenarios, indicating that the “abrupt4 × CO2” simulations can be used to help make future projections computationally less expensive7.Future projections can be obtained from the state-of-the-art general circulation model simulations under various scenarios, particularly the Coupled Model Intercomparison Project phase 5 and 6 2 levels are abruptly not only increased but also decreased. We used a “4 × CO2pulse” experiment, in which the atmospheric CO2 concentration was instantaneously quadrupled from a pre-industrial (PI) level and maintained as constant for 50 years. The CO2 level was then instantaneously reduced to the PI level. This experiment is similar to the “abrupt4 × CO2” experiment in the warming stage but differs in that it also considers an abrupt decrease in CO2. Such a change is more analogous to the carbon dioxide removal model intercomparison project (CDRMIP) endorsed in CMIP68. In CDRMIP experiment, atmospheric CO2 concentrations are gradually increased by 1% per year until they reach four times the initial level and then decreased toward the initial level in a mirror pathway. In this study, we investigated how closely the global and regional climate adjustments in the 4 × CO2pulse experiment—with its abrupt change in CO2 levels—resembled those in the CDRMIP experiment with a gradual CO2 change.As an extension of previous studies, this work examines the changes in atmospheric and oceanic general circulation when CO7 focused mainly on the global mean surface air temperature (GMST) and global mean oceanic heat uptake. These two physical quantities are key metrics of climate change projections, but regional climate change must be substantially more informative to human life. The GMST can be stabilized through a balance between incoming solar energy and outgoing terrestrial radiative energy. However, stabilizing regional climates also requires dynamic energy transport to reduce the heating imbalance between net surplus radiative energy and net loss radiative energy. Therefore, to address regional climate change associated with global warming, both local radiative energy balances and the energy transfer processes should be fully understood.The aforementioned studies10 and the migration of the Intertropical Convergence Zone11 (ITCZ) are known to be strongly influenced by the meridional atmospheric heat transport (AHT). Likewise, local sea surface temperature (SST) responses to greenhouse gas forcing is determined by surface energy exchanges with the atmosphere, oceanic heat uptake into the deep ocean, and oceanic heat transport (OHT). Therefore, to understand a process related to regional climate change, it is necessary to investigate how atmospheric and oceanic general circulation and heat transport will respond to changing CO2 forcing. Previous studies have shown that when CO2 levels quadruple, as modeled in CMIP5, poleward OHT decreases, possibly due to a weakened Atlantic meridional overturning circulation12 (AMOC), but AHT increases by an amount that nearly compensates for this13. Such compensation could be interpreted as a climate-state invariance of total meridional heat transport  in a changing climate, i.e., the so-called Bjerknes Compensation16 (BJC). However, other studies argued that the climate-state invariance in MHT could be imperfect due to changes in sea ice cover15 or cloud cover17. Furthermore, the BJC may be time scale-dependent18 such that as the time scale increases, the BJC could reach an equilibrium16. This suggests that BJC could also be influenced by the time scale of forcing. So far, AHT and OHT have been documented for a warming trend but are not well documented for a cooling trend. The 4 × CO2pulse experiment conducted for this study will provide insights into understanding the changes in AHT, OHT, and the BJC under both global warming and cooling conditions.As representative regional responses to greenhouse gas forcing, polar amplification2pulse and CDRMIP experiments could provide a clue on a climate reversibility, which is an ability for restoring toward its initial climate state21. The opposite case refers irreversibility. Irreversibility of a climate system could occur when a climate component passes a threshold such as ‘tipping point’; and/or when the response timescale of a climate component is relatively longer compared to a forcing timescale22. Such irreversible climate change usually accompanies a hysteresis behavior. For example, a strong hysteresis behavior of Atlantic Meridional Overturning Circulation (AMOC) could lead to an irreversible climate change23, and a strong oceanic thermal inertia over Southern Ocean could be a cause for irreversible climate change24. In this regard, the investigation of OHT gives a sense of where the irreversible climate change would occur by showing a place for the oceanic heat accumulation.The CO2 that would allow, to some extent, the reversibility of climate system to be addressed, as was the main purpose of the CDRMIP; (2) regional climate response, especially focusing converging and/or diverging of energies associated with general circulation and meridional heat transport; and (3) transient response of AHT and OHT. In “This study aims to investigate the following: (1) global climate response to abrupt increases and decreases in CO2 pulse experiment (hereafter 4 × CO2PLS) was performed using the Community Earth System Model version 1.225. This model is composed of atmosphere with an approximately 1° × 1° horizontal resolution and 30 vertical levels (The Community Atmospheric Community Atmospheric Model version 5)26; ocean with an approximately 1° × 0.3° resolution near the equator, with a gradual increase to 0.5° near the pole and 60 vertical levels 27; sea ice (The Community Ice Code version 4); and land surface including the carbon–nitrogen cycle (Community Land Model version 4)28.In this study, a 4 × CO2PLS experiment, CO2 levels four times that of the PI level (1148 ppm) was switched on for 50 years and then immediately switched off to allow PI levels (287 ppm) to be reached again. Integral durations for the PI perpetual, 4 × CO2 forcing-on, and restoration periods were 201, 50, and 250 years, respectively  using the same model as 4 × CO2PLS was also performed. For 4 × CO2CDR, the atmospheric CO2 concentration was increased by 1% annually until it reached four times the present-day (PD) level (367 ppm). This was followed immediately by a symmetric decrease until the CO2 concentration reached the PD level  was applied for 220 years. This experiment included a total of 28 ensemble members; therefore, the results of this study as given in this study all refer to 28-member ensemble means.A CDRMIP-type experiment . Here, the MLD was defined as the shallowest depth where the local, interpolated buoyancy gradient matched the maximum buoyancy gradient between the surface and any discrete depth within the water column2PLS and then compared it with the results from the 4 × CO2CDR. By switching on CO2 forcing in 4 × CO2PLS, the GMST increased abruptly, up to 4 °C, within 10 years and rather slowly, by 0.5 °C, for the remaining 40 years  and Southern Hemisphere (GMST only in the SH) show behavior similar to the GMST, except that the GMST in the NH was warmer than the GMST in the SH during the forcing-on period; the opposite was true during the early forcing-off period. In other words, there were abrupt asymmetric changes in hemispheric warming/cooling between the forcing-on and forcing-off periods. This hemispherically different response is primary caused by an hemispheric asymmetry in heat capacity associated with different land-mass distribution.We first analyzed the global climate response in the 4 × COThe change in the global-averaged upper ocean temperature (GUOT) was almost identical to that of the GMST, but the maximum temperature of the former was approximately 3 °C Fig. c. The glThe ocean temperature response is different in the Northern Hemisphere (NH) and the Southern Hemisphere (SH) Fig. d. During19 . The southward OHT in NH was also observed during the forcing-on period in the 4 × CO2PLS experiment (Fig. In recent decades, north Atlantic warm holes that have been suggested as being related to reductions in OHT associated with the slowdown of the AMOC have been observed in the north AtlanticIn the atmosphere, the MMC on the pressure coordinate is expressed as a mass stream function, that is:55. The energetic constraint indicates that the total energy transport must act to maintain a local energy balance56; therefore, the zonal-mean net heating of the atmosphere, 54:Meridional AHT is computed using an energetic constraint55. The meridional OHT was computed using dynamical processes as follows:h is from H1 to H2. For the upper ocean, H1 and H2 are the MLD and surface, respectively; for the lower ocean, H1 and H2 are 2000 m and MLD, respectively. It should be noted that OHT computed by using Eq. (The AHT computed using a traditional method such as dynamic process produces results very similar to those computed by energetic constraints


To date, few data are available on the prognostic role of lymphocyte subsets in pediatric Graves’ Disease (GD). The aim of this retrospective study is to analyze the role of lymphocyte subtypes in predicting the severity of GD.Data of 10 pediatric subjects aged <18 years with GD onset in the period November 2017–April 2021 were collected. The lymphocyte population was assessed at the onset of GD as well as hormonal and clinical data. The follow-up period was 2.4 ± 0.8 years.(p = 0.04) and 0.81 (p = 0.004) respectively; that between CD4+ /CD8+ ratio and the TRAb titer at diagnosis and after 6, 12 and 24 months was 0.89, 0.89, 0.73 and 0.77 respectively . The correlation coefficient of anti-thyroid drug (ATD) dose after 6 and 12 months with CD4+ /CD8 ratio was 0.88 and 0.78 (p = 0.001 and p = 0.02 respectively). Patients with a higher CD4+ /CD8+ ratio at diagnosis displayed higher fT3 levels  and higher TRAb titers .Pearson correlation coefficient between CD4+ /CD8+ ratio and fT3 levels and thyroid volume at diagnosis was 0.72 CD4+/CD8+ ratio appears as a promising predictive tool to be considered together with other prognostic factors to better manage pediatric GD. These preliminary data need to be confirmed over a longer follow-up period and in larger cohorts. Graves-Basedow disease (GD) is the most common cause of thyrotoxicosis in pediatric age even if it is considered a rare disease with an incidence of 0.3–14/100.000. The male-to-female ratio is 1:4 with the exception of the GD subtype with high IgG4 levels which appears to be more frequent in males –8. YoungGD is considered an autoimmune disorder and to date the reasons for the activation of autoimmunity are still unkown but it is believed that multifactorial pathogenesis underlies GD, including polygenic susceptibility, environment and pre-existing diseases . It is aThe aim of this prospective study is to analyze peripheral blood lymphocyte subtypes in pediatric patients with newly diagnosed GD and to investigate the potential predictive role in disease severity.From the electronic medical records, the data of all patients aged <18 years referred to the Department of Pediatric Endocrinology of Regina Margherita Children’s Hospital for onset of GD in the period November 2017–April 2021 were collected. The Ethics Committee of the City of Health and Science University Hospital of Turin approved the study . Informed consent was obtained by all parents of subjects included in the study. The diagnostic criteria for GD included: (1) elevated serum levels of thyroid hormones fT4 and fT3; (2) suppressed serum TSH levels; (3) positive serum TRAb titer. Patients with thyrotoxicosis due to hashitoxycosis or Plummer adenoma were excluded.© Analyzer family with in vitro assay for the quantitative determination. The lymphocyte population was assessed at the onset of GD. The ultrasound data included the presence of goitre, the echogenic pattern, the vascularization of the gland and the presence of nodules. The volume of the thyroid gland was calculated using the formula: volume = 0.5 × (length × anterior-posterior depth × transverse width) and the results were expressed in SDS  according to the reference values provided by Vitti et al. [The complete thyroid hormone profile  and the TRAb titre were assessed at the onset of the disease and then every six months in the first 2 years. TPOAb and TGAb titres were also evaluated at the onset of the disease. Laboratory analyses were performed by Liaisoni et al. .Pubertal development according to Tanner stages, the presence of other autoimmune diseases or other co-morbidities unrelated to GD, and familiarity for thyroid disease have also been reported. All subjects were treated with methimazole at 0.2–0.5 mg/kg/day as initial treatment and 0.1–0.2 mg/kg/day as a maintenance dosage.Statistical analysis was performed using Graphpad 7 software  with ANOVA test to compare means between groups and Pearson’s coefficient for correlation between variables. Post-hoc tests after ANOVA were performed by Scheffe, LSD and Duncan Bonferroni tests.The data from the 10 subjects  with newly diagnosed GD over a follow-up period of 2.4 ± 0.8 years are presented in Table p = 0.001). The dose of ATD at diagnosis and at 12 months (0.33 ± 0.1 and 0.23 ± 0.1 mg/kg/day) with respect of the doses at 6 and 24 months  displayed the same trend. Mean thyroid volume was 2.98 ± 0.47 SDS  at diagnosis with high levels of fT4 (55.09 ± 4.7 pmol/L) and fT3 (22.58 ± 2.87 pmol/L). The titre of TRAb was higher at diagnosis and at 12 months (18.25 ± 3.49 and 17.7 ± 6.1 UI/L) and displayed lower levels at 6 and 24 months , mean T cell count was 1.93 ± 0.6 109/L , while mean B cell count was 0.38 ± 0.09 109/L . Mean CD4+ count was 1.06 ± 0.11 109/L , whereas CD8+ count was 0.65 ± 0.11 109/L  and the mean ratio of CD4+/CD8+ T cell subtype was 2.19 ± 0.9 . Pearson’s correlation coefficient between CD4+/CD8+ ratio at diagnosis and fT3 levels and thyroid volume at diagnosis was 0.72 (p = 0.04) and 0.81 (p = 0.004) respectively . The correlation coefficient of the ATD dose after 6 and 12 months with the CD4+/CD8 ratio also showed a similar course  and higher TRAb titre  compared to subjects with normal ratio (4/10).Mean total lymphocyte count was 2.65 ± 0.7 10After 2 years of follow-up, 2/10 patients underwent thyroidectomy for a persistent thyrotoxic state despite the increase of ATD dose, 3/10 had remission of the disease and 6/10 are still being treated with ATD. The differences of clinical features at GD onset are represented in Table p = 0.01). The same trend was observed for TRAb levels  and thyroid volume . Scheffe, LSD and Duncan Bonferroni tests confirmed the differences in TRAb levels and thyroid volume between patients in the remission group and those who underwent definitive treatment, while the CD4+/CD8+ ratio was significantly different between the three categories of patients (remission vs definitive treatment vs long-term treatment).CD4+/CD8+ ratio was higher in the subjects who underwent thyroidectomy with respect of subjects who had disease remission and long-term medical treatment approach  of taking a higher daily dose of ATD than maintenance dose (0.1–0.2 mg/kg/daily) and a higher CD4+/CD8+ ratio was 4 and 2.25 at 6 and 12 months from diagnosis respectively. The RR of having a thyroid volume greater than SDS > 2 and a higher CD4+/CD8+ ratio was 3.Graves Disease (GD) is the most common cause of thyrotoxicosis in pediatric age; however, its management is still challenging with many questions still open on the duration of the medical approach with ATD and when definitive treatment should be considered. Currently, ATD treatment is administered for at least 3 years and can be stopped when TRAb levels have been low for several months. Longer periods of ATD may be considered if remission likelihood is low. Definitive treatment should be considered when patients remain thyrotoxic despite the use of high doses of ATD, in patients who develop serious ATD-related side effects and in subjects with relapse [Most Authors report lower remission rates than adults (15–40% vs 40–85%) with patients relapsing mainly in the first 6–12 months after ATD discontinuation. The overall remission rate during ATD treatment in pediatric age is 28.8% . YoungerTo date, few data are available on the correlation of lymphocyte parameters and the outcome of GD in pediatric age. Chen et al. observed a higher CD4+/CD8+ ratio, lower percentages of CD3+ CD8+ T cells and higher percentages of CD3− CD19+ cells in children and adolescents with Grave’s ophthalmopathy (GO), although non independent after excluding effect of the TRAb titre . In anotImmunological and hormonal remission were considered as parameters of disease severity, with patients undergoing definitive treatment classified as having the most severe manifestation of GD. In our study the CD4+/CD8+ ratio was the only lymphocyte parameter significantly related to disease severity as subjects underwent thyroidectomy after 2 years of follow-up showed higher ratio than subjects with disease remission and long-term medical treatment approach.A positive correlation was observed between CD4+/CD8+ ratio and fT3 levels and diagnosis and TRAb titre at diagnosis and after 6, 12, and 24 months. The same trend was also observed for thyroid volume and the daily dose of ATD. Subjects with a higher CD4+/CD8+ ratio also had a higher risk of having a thyroid volume >2 SDS and a higher ATD dose. Patients with a higher ratio seem to be at higher risk of developing the more severe manifestations of GD (patients undergoing definitive treatment after 2 years of follow-up or to long-term treatment approach, even if this hypothesis need to be confirmed in larger multicentric studies with greater cohorts, given the rarity of GD. We believe that this lymphocyte subset parameter should be considered as predictive for outcome, along with other factors considered, such as age, sex, fT3 and TRAb levels at diagnosis and thyroid volume. To our knowledge, this is the first study in pediatric age reporting the relation of CD4+/CD8+ ratio to disease severity. Lymphocyte subgroups should be evaluated at the time of GD diagnosis as methimazole and other ATD drugs interfere with the immune system.The limitations of the present study lie mainly in the size of the cohort which limits the statistical strength of our data, although the rarity of GD in pediatric age must be considered.Among the parameters of the lymphocyte population, the elevated CD4+/CD8+ ratio appears to be positively correlated with higher fT3 levels and goiter size at diagnosis, higher TRAb titre in the first 2 years, and higher ATD dose in the first year after the diagnosis. Thus, this ratio could be considered as a promising predictive tool, together with the other prognostic factors to better manage pediatric GD, even if these preliminary data need to be confirmed over a longer follow-up period and in larger cohorts.


Although the resultant compounds are inert toward the C−H bonds of benzene, they yield selective and uncatalyzed biaryl formation when reacted with readily available aryl bromides.Hydrocarbon‐soluble β‐diketiminato phenylcalcium derivatives, which display various modes of Ca−μ 2Hg and [(BDI)CaH]2. The compounds were shown to react with bromoarenes through a direct SNAr displacement of halide, leading to the uncatalyzed formation of biaryl molecules.Isolable and hydrocarbon‐soluble β‐diketiminato calcium phenyls are accessible from the reaction of Ph These processes were observed to induce apparent copper metal deposition. Analysis of the solution by 1H NMR spectroscopy, however, indicated that it was accompanied by the formation of a variety of products, including DippBDI‐H and [(DippBDI)2Ca],With the production of compounds 2 with Ph2Hg induced a rapid bubbling and the formation of a grey precipitate, assumed to be elemental mercury. The identities of the desired phenylcalcium products were found to be dependent on the reaction stoichiometry . These signals emerged simultaneously alongside a new (1H) Ca−H environment at δ=4.81 ppm while, in common with previously described phenylcalcium derivatives such as 4 and 5, is marginally elongated in comparison to those observed in compound 10 . Consistent with the lower 4‐coordinate geometry of their constituent calcium centers, however, both these latter distances are shorter than the analogous measurements across the only previously reported neutral, but 5‐coordinate, species to feature twofold, Ca−μ2‐C−Ca bridging .9 is effectively orthogonal to that defined by the Ca1−C30−Ca1′−H least squares plane (88.4°), the corresponding angle subtended with the plane defined by the Ca1−C30−Ca1′−C30′ unit in compound 10 is only 24.88°. This feature, which does not appear to be precedented in any previous σ‐aryl organometallic derivative, is accompanied by a close approach  between the ortho‐CH units of the phenyl substituents and the calcium atoms.The origins of these observations were resolved by X‐ray diffraction analysis of compounds 9 and 10 by density functional theory (DFT) at the B3PW91‐D3 level of theory in the gas phase (9_opt and 10_opt). As shown in Figures S76, S77 and Tables S2 and S3, the computed bond lengths and angles accurately reproduce the experimental values. In accordance with the experimental results, compound 10_opt also displays short distances between the ortho‐CH units of the phenyl substituents and the calcium atoms (in the 2.427–2.469 Å range). To establish the relationship between the orientation of the phenyl rings and the energy of the complexes, we optimized complex 9 starting from a structure with the phenyl substituent almost coplanar to the plane defined by the Ca1−C30−Ca1′−H unit (9′_opt). Significantly, 9′_opt displays a phenyl group oriented at an angle of ca. 30° with respect to the plane defined by the Ca1−C30−Ca1′−H unit and is 4.6 (3.2) kcal mol−1 less stable than the 9_opt analogue containing an orthogonal phenyl group. The smaller angle between the phenyl plane and the Ca1−C30−Ca1′−H plane is likely to increase the steric hindrance between the phenyl moiety and the substituents of the DippBDI ligands, causing an elongation of the Ca−N distances (in the 2.344–2.368 Å range for 9′_opt compared to 2.334–2.355 Å for 9_opt) and a consequent destabilization of the structure. Following the same approach, we optimized complex 10 starting from a structure with both the phenyl substituents orthogonal to the plane defined by the Ca1−C30−Ca1′−C30′ unit (10′_opt). The resulting 10′_opt displays one phenyl group orthogonal to the Ca1−C30−Ca1′−C30′ plane, while the other is oriented at an angle of ca. 30° with respect to the same plane. Although 10′_opt is more stable by 4.0 (5.8) kcal mol−1, in contrast to its 10_opt analogue and the crystallized compound 10, one of the two phenyl ligands remains in an orthogonal orientation. These adjustments again result in a reduction of the steric interactions between the phenyl groups and the BDI substituent and a contraction of the Ca−N bonds (in the 2.344–2.365 Å range for 10′_opt compared to 2.373–2.387 Å for 10_opt). The observed orientation of the phenyl ligands may, therefore, be judged to be dictated by a balance between the stabilizing interaction of the ortho‐CH units of the phenyl substituents with the coordinatively unsaturated calcium atoms and the steric hindrance between the phenyl groups and the DippBDI substituents.In order to shed light on the contrasting orientation of the phenyl rings we optimized the structures of compounds 9 and 10 in hand, we assessed their thermal stability in C6D6 solution by 1H NMR spectroscopy. In contrast to previous observations of alkylcalcium species derived from compound 2 (Scheme DippBDI)2Ca],2 is itself known to undergo slow C−D/Ca−H exchange with C6D6,9 or 10 and the benzene solvent. Previous observations have shown that compound 2 can induce the hydrodehalogenation of C6H5X  to provide benzene and the respective dimeric calcium hydride/halides and dihalides.NAr‐type displacement of the halide. While compound 4 has been reported as completely unreactive toward PhX , Westerhausen has previously demonstrated that biaryl formation can be achieved by reaction of such arylcalcium iodides with haloarenes under nickel‐catalyzed (Kumada‐type) conditions.With compounds 10 with a range of aryl bromides  conversion to a single new β‐diketiminato calcium species (11) and the relevant cross‐coupled biaryl product, the identification of which was confirmed in situ by comparison of its NMR spectra to that of an authenticated sample and subsequent analysis by GC‐mass spectrometry (see the Supporting Information). Identical reactions performed at 60 °C provided similarly selective conversion to the biaryl products but were accompanied by redistribution of the heteroleptic calcium species to [(DippBDI)2Ca].11 was highly selective and characterized by the emergence of a single new DippBDI γ‐methine signal at δ=4.77 ppm.With these observations in mind, therefore, we undertook a study of the reactivity of compound s Scheme . Initial11) proved unstable, such that removal of volatiles also invariably led to the isolation of significant quantities of [(DippBDI)2Ca]. The structure of 11 was confirmed, however, by an X‐ray diffraction analysis performed on crystals isolated directly from the reaction mixture resulting from treatment of compound 10 with bromobenzene  Å] is comparable to the analogous measurements observed in compounds 9 and 10, the Ca1−C33 distance [2.8047(16) Å] is elongated by the adoption of an alternative η6‐interaction with the Ca1 center. While unsymmetrical, the range of Ca1−Cphenyl distances thus imposed [2.8047(16)–2.9093(17) Å] are all significantly shorter than those arising in the cationic components of [(DippBDI)Ca(C6H6)]+[A]− [A=Al{OC(CF3)3}4 or B(C6F5)4] (ca. 2.93 Å) in which a neutral molecule of benzene solvent is bound to cationic calcium centers that are coordinated by an identical β‐diketiminate ligand.Bulk samples of this new arylcalcium species  for completeness. Starting from the dicalcium diphenyl complex, after the formation of a bromobenzene adduct , a SNAr‐type transition state (BrTS‐BC) has been located , whose formation is exothermic by 76.2 kcal mol−1. The latter reaction energy indicates that the experimental timescale for the completion of the reaction is a direct consequence of the height of this barrier. The subsequent Ph/Br substitution via a second SNAr‐type transition state has been also computed . Although the reaction would be viable from both a kinetic and thermodynamic point of view, the experimentally observed decomposition of complex 11 in solution via Schlenk‐type equilibration presumably prevents the reaction from continuing toward the previously reported bromide derivative, [(BDI)CaBr]2.Calculations were carried out at the DFT level B3PW91‐D3) to provide insight into the formation of complex PW91‐D3 t2Hg and [(BDI)CaH]2. Although these compounds are inert toward the C−H bonds of benzene, they yield selective and uncatalyzed biaryl formation when reacted with readily available aryl bromides. We are continuing to extend this methodology to study the structures and reactivity of a wider range of heavier alkaline earth aryl derivatives.In conclusion, we have shown that isolable and hydrocarbon‐soluble phenylcalcium derivatives are accessible from reactions of PhSupporting Information: Experimental details, NMR spectra, X‐ray crystallography,The authors declare no conflict of interest.As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re‐organized for online delivery, but are not copy‐edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors.Supporting InformationClick here for additional data file.Supporting InformationClick here for additional data file.Supporting InformationClick here for additional data file.


The results imply that the distinct magnetic sites play an important role in the magnetocaloric behaviour of the family.The nuclear and magnetic structures of Mn 3Fe2Si3 are investigated in the temperature range from 20 to 300 K. The magnetic properties of Mn3Fe2Si3 were measured on a single crystal. The compound undergoes a paramagnetic to antiferromagnetic transition at TN2 ≃ 120 K and an antiferromagnetic to antiferromagnetic transition at TN1 ≃ 69 K. A similar sequence of magnetic phase transitions is found for the parent compound Mn5Si3 upon temperature variation, but the field-driven transition observed in Mn5Si3 is not found in Mn3Fe2Si3, resulting in a strongly reduced magnetocaloric effect. Structurally, the hexagonal symmetry found for both compounds under ambient conditions is preserved in Mn3Fe2Si3 through both magnetic transitions, indicating that the crystal structure is only weakly affected by the magnetic phase transition, in contrast to Mn5Si3 where both transitions distort the nuclear structure. Both compounds feature a collinear high-temperature magnetic phase AF2 and transfer into a non-collinear phase AF1 at low temperature. While one of the distinct crystallographic sites remains disordered in the AF2 phase in the parent compound, the magnetic structure in the AF2 phase involves all magnetic atoms in Mn3Fe2Si3. These observations imply that the distinct sites occupied by the magnetic atoms play an important role in the magnetocaloric behaviour of the family.The nuclear and magnetic structures of Mn Neighbouring ∞[(M1)Si3] chains share common edges with each other and form channels which are occupied by chains of empty octahedra of composition ∞[□(M2)3]  The nature of the magnetic ordering changes depending on the composition. While for small values of x ≥ 3 show a direct MCE , while the parent compound Mn5Si3 shows an inverse MCE, i.e. the magnetic entropy rises with the application of the field and the material cools down. The inverse MCE is observed at the transition from a collinearly ordered arrangement of the spins to a non-coplanar arrangement  Compounds with an Fe content (iii) The availability of two significantly different sites for the paramagnetic atoms within the structure gives the opportunity to elucidate the role of magnetic atoms occupying multiple sites in magnetocaloric materials.et al., 2017et al., 2020(iv) In addition, large single crystals of the compounds up to 10 cm in length and 1–2 cm diameter are readily available. This is of advantage when it comes to elucidating the underlying crystal and magnetic structures, the magnetic anisotropy, or the spin and/or lattice dynamics .Single crystals of Mn al. 2015. Chemica2.2.0H ≤ 9 T using the vibrating sample magnetometer (VSM) option of a PPMS and PPMS Dynacool from Quantum Design, respectively. Isothermal measurements were performed to identify the magnetic phases for the different directions of the applied field and to determine the magnetic entropy change ΔSiso. As the magnetization curves became featureless for H ∥ [001] for T > TN1, isotherms were only recorded up to 73 K for this field direction. In the case of Mn5Si3, the field-dependent magnetization was measured in sweep mode, i.e. the field was varied at a rate of 5 mT s−1 and the magnetization was recorded continuously. For Mn3Fe2Si3, preliminary measurements had shown that the measured magnetization changes with the thermomagnetic history. Therefore, we employed the following temperature protocol: The samples were initially cooled to 140 K. Subsequently a field of 9 T was applied and the sample was cooled to the target temperature at a rate of 5 K min−1, and then a field loop between 9 T and −9 T was recorded. At the end of the loop, the sample was again heated to 140 K and cooled to the next target temperature to ensure as identical starting conditions for the magnetization loop as possible.Fragments of the oriented single crystal with a mass of 6–12 mg were cut using spark erosion. Measurements of the magnetization parallel and perpendicular to the hexagonal [001] direction with varying temperature and magnetic field were carried out in the temperature region between 5 and 380 K and magnetic fields in the range −9 T ≤ μ2.3.3Fe2Si3 powder were recorded using the POWGEN diffractometer at Oak Ridge National Laboratory  and the other with CWL = 2.665 Å (1.0701–22.9342 Å).Time-of-flight neutron powder diffraction data on about 5 g of Mn2.4.T = 300, 250, 200, 150, 125, 100, 80, 60, 40 and 20 K) using an open-flow helium cryostat. Data were reduced with the CrysAlisPro software  at a wavelength of λ = 0.44279 Å using a MarCCD165 detector. Data sets were collected upon cooling  and (ii) have been reported in the various magnetization studies on single crystals and powders  for H ⊥ [001]. Below ∼30 K, we observe for both field directions a nearly constant ∂M/∂H for |μ0H| < 0.6 T, labelled (iv). This feature has already been observed in the literature but has not been discussed in detail . This feature disappears for the field parallel to [001] at TN1 but persists even beyond TN2 for the perpendicular direction.In Mn3Fe2Si3 exhibits a much lower slope ∂M/∂H (compare the range of the colour bars on the right-hand side of the panels). In the low-temperature phase AF1 (T < TN1 = 69 K), we observe the features labelled (c) and (a) for the field parallel and perpendicular to the [001] direction. For both field directions we find only one feature when varying the field at constant temperature, in agreement with pulsed field measurements on powders  and two narrow kinks at finite field, which disappear just at TN2 ≃ 120 K, labelled (b). For this composition, the slope ∂M/∂H is enhanced for very small fields above TN2 for both field directions.MnSiso employing the Maxwell relation: 5Si3, the strong increase in magnetization when entering the AF2 phase from the AF1 phase results in the rather strong inverse MCE .In the refinement of the neutron powder data, a pseudo-Voigt profile function and a background described by ten terms of Legendre polynomials combined with 70 manually assigned background points were used. An absorption correction according to Larson & Von Dreele 2004 and a cosupporting information: CCDC reference numbers 2202008–2202017.For the single-crystal refinements, the occupancies for the Mn and Fe sites were fixed to the values obtained from refinement of the neutron powder data. Further details concerning the refinement, together with atomic coordinates and displacement parameters, are given in Tables S2–S4 in the 3.2.2.3Fe2Si3 crystallizes in the hexagonal space group P63/mcm at all measured temperatures with unit-cell parameters a = 6.8534 (3) Å and c = 4.7556 (2) Å [V = 193.437 (15) Å3] at room temperature, in good agreement with the literature  site in the [(M1)Si6] octahedra is occupied by 76.5 (1) at.% Fe and 23.4 (1) at.% Mn, while the M2 (Wyckoff position 6g) site is occupied by 15.6 (1) at.% Fe and 84.4 (1) at.% Mn. This preferential incorporation of Fe and Mn atoms onto the two sites is in agreement with earlier observations .The unit-cell parameters and unit-cell volume of Mn3Fe2Si3 decrease with decreasing temperature, with no clear sign of a response to the transition from the antiferromagnetic AF1 to the antiferromagnetic AF2 phase, or to the transition from the antiferromagnetic AF2 phase to the paramagnetic PM phase . The interatomic distances between metal atoms located on the same sites are reduced more significantly than the distances between metal atoms located on different sites .Within the standard deviations, all interatomic distances between paramagnetic atoms in Mn3Fe2Si3 with that of Mn5Si3  While the symmetry remains hexagonal in Mn al. 2012 for the  al. 1992.M1—M1 distance in Mn5Si3 is clearly changed at the AF2–AF1 transition, while this is not observed for Mn3Fe2Si3. Assuming that the monoclinic model from the literature for the AF1 phase of Mn5Si3 is correct  The ed Fig. 6.M2—M2 distances in Mn5Si3 clearly show a change of slope, a trend that is not observed for Mn3Fe2Si3.(iii) At the AF2–AF1 transition, the M1)Si6] and [□(M2)6] octahedra were calculated using the program Octadist 6] octahedra show a more pronounced distortion than the [(M1)Si6] octahedra. However, while for Mn3Fe2Si3 the angular distortion of the [□(M2)6] octahedra is decreased at the PM to AF2 transition and the distortion of [(M1)Si6] stays nearly constant over the whole temperature range, in Mn5Si3 the distortion of the [□(M2)6] octahedra seems to increase at the PM–AF2 transition, while the distortion of the [(M1)Si6] octahedra seems to decrease at the AF2–AF1 transition. Furthermore, in contrast to Mn3Fe2Si3 where all six Mn—Si distances in an octahedron are equal at all temperatures (and therefore Δ = 0), in Mn5Si3 a sudden increase in the distance distortion parameter Δ of the [□(M2)6] octahedra is observed at the temperature of the PM–AF2 transition and an additional sharp increase in the distance distortion is observed for the [(M1)Si6] octahedra at the AF2–AF1 transition  and assuming one magnetic propagation vector [khex = kortho = (010)], eight different orthorhombic models with different magnetic moment directions are derived (Table S8).The neutron powder diffraction diagrams of Mni3 Fig. 8 show the3Fe2Si3 was transformed to the orthohexagonal setting , space group Ccmm.For the refinements, the nuclear structure of MnPCnan clearly gives the best agreement factor, both at 90 and 20 K (Table S9). Figs. 9a) and 9b) show the corresponding Rietveld refinements.From the eight refined models, the one in magnetic space group TAF1–AF2 ≃ 70 K < T < TAF2–PM ≃ 120 K) the model in magnetic space group PCnan fits the measured neutron diffraction pattern very well. The only exception is the 010 reflection [see inset in Fig. 9a)] which is significantly broader than all other magnetic peaks and only disappears completely at 150 K.For the data at 90 K (and 105 K), which correspond to the stability region of the AF2 phase (TAF1–AF2 ≃ 70 K), the intensities of the newly arising magnetic peaks are underestimated in the refinement based on magnetic space group PCnan. In particular, the 230 reflection, which is weak but clearly visible, has an intensity that is calculated to be zero in this model [see inset in Fig. 9b)]. We therefore decided to lower the magnetic symmetry for the 20 K data further. For this, the nuclear structure was transformed to the different maximum translationengleiche subgroups of Ccmm, while still restricting the nuclear structure to hexagonal symmetry. For each of the different subgroups, the different magnetic models were then derived and refined. On the basis of the agreement factors (Tables S10 and S11), the model in magnetic space group PC2221 (derived from the C2221 space group) clearly appears to be the best of the 40 refined models. The Rietveld refinement of this model is shown in Fig. 9c).At 20 K, that is in the stability field of the AF1 phase , no components of magnetic moments are allowed parallel to the c axis (Table S8). Magnetic moments on the Mn1/Fe1 sites are aligned along the [010] direction. Moments are allowed along the [100] direction for the Fe21/Mn21 site, and in the ab plane for Fe22/Mn22. However, at 105 and 90 K, all refined Mx components for these sites are zero within error  μB at 105 K, respectively. When taking into account the standard deviations, the ordered moment on the Fe21/Mn21 sites is not significantly different from zero. Thus, of the Fe/Mn sites forming the empty octahedra, only two-thirds carry an ordered moment in the AF2 phase. Within these octahedra, the atoms at the same height z have their spins aligned in an antiparallel way. At 90 K, the observed magnetic ordering of the AF2 phase is very similar to the structure at 105 K and only the magnitude of the refined magnetic moments on Fe1/Mn1 and Fe22/Mn22 is slightly increased, with values of 0.82 (8) μB and 0.76 (8) μB, respectively  μB at 20 K. Moments on the M1 sites  keep their orientation parallel to the b axis, and all allowed Mx components on the M21/M22 sites are still refined to zero within their standard deviation .The magnetic structure of Mn5Si3, the PM–AF2 transition is accompanied by a structural phase transition from hexagonal to orthorhombic, while in Mn3Fe2Si3 the structure remains hexagonal and only the magnetic structure has a reduced symmetry. In both Mn5Si3 and Mn3Fe2Si3, the moments on the M22 site are ordered, while the Mn21 site shows no ordered moment. A major difference is the order on the M1 sites, which are preferentially occupied by Fe atoms in Mn3Fe2Si3: here they carry an ordered moment in the AF2 phase which is aligned along b, while in Mn5Si3 no ordered moment is observed on the M1 site in the AF2 phase. Upon further cooling a non-collinear structure is formed in both compounds below the temperature TN1 ≃ 70 K. The structure of this phase has been extensively discussed for Mn5Si3 in the past. The structures as described by Brown et al.  are hardly reflected in any abrupt changes of the crystal structure {only the angular distortions of the [(M1)Si6] octahedra decrease slightly at the PM–AF2 transition}. This is significantly different in Mn5Si3 where the AF2–PM transition is combined with a change of space-group symmetry and where at the AF2–AF1 transition the interatomic M1—M1 distances change drastically and the octahedral distortions also show a pronounced change.It is striking that in MnM1 site in Mn5Si3 in the AF2 phase was in particular due to the Mn1—Mn1 distance being too short (2.397 Å), which was supposed to be below the critical distance that would permit magnetic ordering on the manganese  and the second is 2.448 Å at 60 K (2.457 Å at 12 K). So, if one assumes the monoclinic model to be correct, only half of these distances are above the critical distance. The substitution of Mn atoms with Fe atoms on the M1 site leads to an even smaller M1—M1 distance of 2.371 Å at the PM–AF2 transition, but ordering of the spins on these sites might well be permitted. The orbitals of the smaller Fe atoms – which predominantly occupy the M1 site – overlap less and hence the bandwidth is narrower, allowing the formation of an ordered moment Si6] octahedra and the formation of an ordered moment on the M1 sites at the AF2–AF1 transition. We argue that the site disorder in Mn3Fe2Si3 and the substitution of Mn atoms with the smaller Fe atoms provide additional space for the magnetic atoms, so that the magnetic order affects the crystal structure only weakly. The only pronounced effect that we observe on the crystal structure is the reduction of the angular distortions in the [□(M2)6] octahedra, which are mainly built by the larger Mn atoms.In earlier work it was assumed that the absence of an ordered moment on the  al. 2014  global, I. DOI: 10.1107/S1600576722007440/iu5027Isup2.hklStructure factors: contains datablock(s) I. DOI: 10.1107/S1600576722007440/iu5027sup3.pdfAdditional tables and figures. DOI: Click here for additional data file.10.1107/S1600576722007440/iu5027sup4.binZIP archive of data at various temperatures. DOI: 2191657, 2202008, 2202009, 2202010, 2202011, 2202012, 2202013, 2202014, 2202015, 2202016, 2202017CCDC references: