Metal-organic framework (MOF) materials share some common features with metalloenzymes including site-isolated metal centers that template dynamic substrate activation within a functionalized cavity or pocket. We report the light-induced reversible binding of CO2 in a cerium-based MOF, Ce-UiO-66-NH2, incorporating an amino functionalized linker, which enables photoreduction of CO2 to CO in H2O without using sacrificial agents. A production rate for CO of 126 μmol·g-1·h-1 with 100% selectivity is observed, outperforming its non-amine analogue (Ce-UiO-66) and benchmark catalysts reported to date. In situ infrared, X-ray absorption, electron paramagnetic resonance and transient absorption spectroscopy reveal that photoexcitation induces a ligand-to-metal charge transfer to generate transient open Ce(III) sites that bind CO2 in a μ-(η1-O)(η1-C) binding mode. This binding is reversible and activates CO2 for subsequent photoreduction to CO. This work will promote the design of photocatalysts capable of synthesizing fuels from CO2.

The spin-crossover material [Fe(NH2trz)3](NO3)2 belongs to the class of 1D triazole-based polymeric SCO complexes. It exhibits a thermal phase transition, with a 28 K wide thermal hysteresis, characterized by phase transition temperatures T↑ = 346 K upon warming and T↓ = 318 K upon cooling. This hysteretic thermal phase transition is unusual because it is associated with two competing symmetry-breaking phenomena: a ferroelastic distortion upon warming from the low-spin (LS) trigonal phase to the high-spin (HS) triclinic phase, and a unit cell tripling upon cooling from the HS phase to the LS phase. Magnetic, spectroscopic and X-ray diffraction measurements reveal a clear coupling between the spin transition and the two competing symmetry changes. Since there is no group-subgroup relationship between the LS and HS phases, the phase transition can only be discontinuous. However, the detailed analysis shows that the situation is more complex, since both LS and HS phases are two daughter phases of a parent high-symmetry phase. The phase transitions are then rationalized within the frame of our theoretical model based on the Landau theory of phase transitions, which considers the coupling of the spin transition to both types of competing symmetry-breakings between the LS and HS phases. The theoretical approach reproduces the experimental findings and explains the origin of this hysteretic spin transition.

We report a systematic study of the structural and magnetic evolution in CeAlSi1-xGex, a series of materials which provide a tunable platform for exploring magnetism in noncentrosymmetric Ce-based intermetallics. Polycrystalline samples and single crystals were synthesized using arc melting and flux growth techniques. Structural characterization by X-ray diffraction shows a continuous increase in the unit-cell parameters with increasing Ge content, with no evidence of a structural phase transition across the series. Magnetization measurements reveal a suppression of the ferromagnetic ordering temperature of CeAlSi with increasing Ge substitution, indicating a crossover toward anti-ferromagnetic behaviour in Ge-rich compositions. Neutron diffraction measurements performed on selected compositions show that weak magnetic intensity appears on some structural Bragg peaks below the magnetic ordering temperature. These results elucidate the relationship between chemical substitution, crystal structure, and magnetic ground states in CeAlSi1-xGex, and establish this system as a model platform for studying compositionally tuned magnetic order in noncentrosymmetric materials.

We report a systematic study of the structural and magnetic evolution in CeAlSi 1– x Ge x , a series of materials which provide a tunable platform for exploring magnetism in noncentrosymmetric Ce-based intermetallics. Polycrystalline samples and single crystals were synthesized using arc melting and flux growth techniques. Structural characterization by X-ray diffraction shows a continuous increase in the unit-cell parameters with increasing Ge content, with no evidence of a structural phase transition across the series. Magnetization measurements reveal a suppression of the ferromagnetic ordering temperature of CeAlSi with increasing Ge substitution, indicating a crossover toward antiferromagnetic behaviour in Ge-rich compositions. Neutron diffraction measurements performed on selected compositions show that weak magnetic intensity appears on some structural Bragg peaks below the magnetic ordering temperature. These results elucidate the relationship between chemical substitution, crystal structure, and magnetic ground states in CeAlSi 1– x Ge x , and establish this system as a model platform for studying compositionally tuned magnetic order in noncentrosymmetric materials.

Lithium tantalum phosphate (LiTa 2 PO 8 ) is among the fastest oxide Li + conductors, yet the relationship between the disordered Li + substructure and ion transport remains unclear owing to the coexistence of competing structural models and the lack of local experimental probes of Li + dynamics. Here, we combine powder neutron diffraction (PND), bond valence site energy (BVSE) calculations and muon spin relaxation (μ + SR) spectroscopy to establish a microscopic picture for Li + diffusion. Rietveld refinement of the structure using the PND data indicates that the Li + substructure is best described with two partially occupied sites, while BVSE identifies low-energy 1D diffusion channels that become interconnected to form a 3D percolating network. μ + SR reveals two thermally activated dynamical regimes, corresponding to localized Li + hopping at low temperatures and long-range diffusion above 210 K, with an activation energy of 0.300(25) eV. Combining the refined crystal structure with the μ + SR hopping rates yields a Li + self-diffusion coefficient of 5.4 × 10 -10 cm 2 s -1 at 290 K, thereby providing a unified structural and dynamical description of Li + transport in LiTa 2 PO 8 .

We report bulk magnetic properties of the monoclinic lanthanide tantalates, M'-LnTaO4 (Ln = Tb, Dy, Ho, Er), where the magnetic Ln3+ ions are arranged on a distorted 2D square lattice. The heavier analogue M'-YbTaO4 has been investigated as a spin-orbit-coupled, quasi-two-dimensional frustrated magnet, and the properties of the other M'-LnTaO4 are expected to vary depending on the electronic configuration of the Ln ion, namely Kramers vs non-Kramers behaviour and different crystal electric field parameters. In this work, powder neutron diffraction is used to confirm the crystal structure for Ln = Tb, Ho, Er, and to determine the magnetic structure of M'-TbTaO4, which displays long-range antiferromagnetic (AFM) order below T_N = 2.1 K. The Tb3+ moments are aligned primarily along the c-axis with AFM nearest-neighbour interactions. Susceptibility data suggest that M'-DyTaO4 may display short-range ordering around 2.7 K, while M'-HoTaO4 and M'-ErTaO4 show AFM correlations but do not order above 1.8 K. Measurements of the magnetic specific heat provide evidence for a Kramers doublet ground state in M'-ErTaO4, similar to its heavier analogue M'-YbTaO4.

We report bulk magnetic properties of the monoclinic lanthanide tantalates, M ′ − L n TaO 4 ( L n = Tb, Dy, Ho, Er), where the magnetic L n 3 + ions are arranged on a distorted 2D square lattice. The heavier analog M ′ − YbTaO 4 has been investigated as a spin-orbit-coupled, quasi-two-dimensional frustrated magnet, and the properties of the other M ′ − L n TaO 4 are expected to vary depending on the electronic configuration of the L n ion, namely, Kramers vs non-Kramers behavior and different crystal electric field parameters. In this work, powder neutron diffraction is used to confirm the crystal structure for L n = Tb, Ho, Er, and to determine the magnetic structure of M ′ − TbTaO 4 , which displays long-range antiferromagnetic (AFM) order below T N = 2.1 K . The Tb 3 + moments are aligned primarily along the c axis with AFM nearest-neighbor interactions. Susceptibility data suggest that M ′ − DyTaO 4 may display short-range ordering around 2.7 K, while M ′ − HoTaO 4 and M ′ − ErTaO 4 show AFM correlations but do not order above 1.8 K. Measurements of the magnetic specific heat provide evidence for a Kramers doublet ground state in M ′ − ErTaO 4 , similar to its heavier analog M ′ − YbTaO 4 .

where the magnetic Ln3+ ions are arranged on a distorted 2D square lattice. The heavier analog M'-YbTaO4 has been investigated as a spin-orbit-coupled, quasi-two-dimensional frustrated magnet, and the properties of the other M'-LnTaO4 are expected to vary depending on the electronic configuration of the Ln ion, namely, Kramers vs non-Kramers behavior and different crystal electric field parameters. In this work, powder neutron diffraction is used to confirm the crystal structure for Ln = Tb, Ho, Er, and to determine the magnetic structure of M'-TbTaO4, which displays long-range antiferromagnetic (AFM) order below TN = 2.1 K. The Tb3+ moments are aligned primarily along the c axis with AFM nearest-neighbor interactions. Susceptibility data suggest that M'-DyTaO4 may display short-range ordering around 2.7 K, while M'-HoTaO4 and M'-ErTaO4 show AFM correlations but do not order above 1.8 K. Measurements of the magnetic specific heat provide evidence for a Kramers doublet ground state in M'-ErTaO4, similar to its heavier analog M'-YbTaO4.

Nanoconfinement within microporous carbon can profoundly alter the phase behavior of hydrogen (H2), offering a potential route to dense, solid-state H2 storage at moderate pressures. In this study, time-of-flight (ToF) neutron diffraction is used to investigate the crystalline phases of H2 and deuterium (D2) confined within a nanoporous activated carbon (TE7) dosed at 77 K to initial H2 pressures of 1–50 bar, corresponding to nominal 77 K filling fractions of Θ77K = 0.33–0.57, and subsequently sealed and cooled to 2.5–13 K for neutron diffraction measurements. The results reveal the formation of both hexagonal close-packed (HCP) and face-centered cubic (FCC) H2 crystal phases with a higher proportion of the FCC phase observed in the micropores. Notably, the FCC phase is stabilized up to 13 K—four times higher temperature than in bulk H2. Double-Voigt line shape analysis of the neutron diffraction data reveals nanoscale coherent domain sizes (≈16 nm FCC, ≈6 nm HCP) suggesting crystal growth restriction in the pores. Additionally, Rietveld refinement shows that greater densification is achieved in smaller pores, in this case sub-nanometer pores. However, only mild unit cell contraction is observed compared with that reported in other studies of H2 confined in nanoporous carbons at low-filling fractions. In contrast, D2 exhibits only a broad diffraction feature, indicative of an amorphous phase or nanosized crystallites. These findings provide direct structural evidence demonstrating the effect of nanoconfinement on H2 phase stability, crystal morphology, and density—informing future design of porous materials for solid-state H2 storage.

Systematic strategies to design properties such as ferroelectricity or magnetoelectric coupling are well established in simple perovskite materials, but they remain scarce in more complex framework structures. Using a hexagonal polytype of the ternary manganite AMnO3 (A = Ba, Sr, Ca) as a model system, we introduce a symmetry-guided design principle in which an inversion-breaking rigid-unit mode (RUM) serves as a single structural instability generating both polar and ferromagnetic orders within a bulk material. Symmetry analysis and first-principles calculations reveal that co-operative tilts of the Mn2O9 bioctahedral dimers generate both a spontaneous polarization and a ferromagnetic moment. High-resolution diffraction and magnetic susceptibility measurements show the structural and magnetic orders persist as high as 450 K and 280 K, respectively, highlighting the untapped potential of framework structures which deviate from simple perovskite motifs to be designed to host useful ferroic properties. Our approach establishes a transferable symmetry-based framework to engineer ferroelectric and magnetoelectric states across chemically diverse framework architectures.

Abstract There remains much ambiguity regarding the structure of red phosphorus. We report the adsorption and photo-polymerisation of P4 molecules encapsulated in an indium(III)-based metal-organic framework to afford a double-helical chain composite comprising of [P8] units. The similarity between the Raman spectrum of bulk red phosphorus and of the metal-organic framework – (P8)n adduct suggests the presence of such helical chains in the structure of amorphous red phosphorus. This provides crystallographic evidence of the structural building blocks of the red phosphorus allotrope stabilized within the pores of a metal-organic host. The (P8)n inclusion compound is an air-stable semiconductor with a band gap of 2.3 eV, which is relevant for gas detection and photo-catalysis. We demonstrate that this phosphorus adduct demonstrates a 10-fold increase in conversion in the oxidation of methyl orange dye compared with the parent metal-organic framework material.

We report a neutron diffraction study using epithermal neutrons to probe the origin of negative magnetization (NM) and its correlation with exchange bias and electronic transport in Gd2CoRuO6. This double perovskite crystallizes in the monoclinic P21/n space group and exhibits magnetic ordering at TC 51 K. Magnetization measurements reveal NM below the compensation temperature (Tcomp approximate to 11 K), which shifts to lower temperatures with increasing magnetic field and vanishes for H 500 Oe. Low temperature (6 K) neutron diffraction study shows that Co2+ and Ru4+ sublattices undergo a canted antiferromagnetic type ordering with antiferromagnetic spin alignment along the c axis and a ferromagnetic component along the b axis, while no ordered magnetic moment is detected for Gd3+ ions. Specific heat exhibits a sharp )-anomaly at 3.5 K, confirming the long-range magnetic ordering of Gd3+ sublattice. The observed NM behavior in M(T) curves is explained by polarization of Gd3+ moments induced by the internal field from the canted Co/Ru sublattice, consistent with Cooke's model. A detailed examination of field-cooled M vs H curves reveals the presence of exchange bias and its sign reversal around the Tcomp in the sample. Interestingly, exchange-bias magnitude depends on the maximum field applied during the hysteresis measurements. Furthermore, the coercivity and remnant magnetization values, derived from the M(H) curves, exhibit a minimum around Tcomp. Electrical resistivity follows a semiconducting variable-range hopping model below 100 K, with a sharp increase below 50 K coinciding with TC, indicating a strong coupling between structural distortions, magnetic interactions, and charge localization. These findings reveal an intricate coupling of structural, magnetic, and electronic degrees of freedom in Gd2CoRuO6, highlighting its potential for spintronic and magnetic device applications where tunable compensation and exchange bias effects and their intertwined behavior are desirable.

We report the solvent-free synthesis of a crystalline heterometallic imidazolate derivative with formula [Fe1Zn2(im)6(Him)2], designated MUV-25, incorporating both iron and zinc. The structure imposes strict positional constraints on the metal centres due to the lattice containing distinct geometric coordination sites, tetrahedral and octahedral. As a consequence, each metal is exclusively directed to its specific coordination site, ensuring precise spatial organization within the lattice. Atom locations were meticulously monitored utilizing X-ray diffraction (single crystal and total scattering) and XAS techniques, demonstrating that the tetrahedral sites are occupied exclusively by zinc, and the octahedral sites are occupied by iron. This combination of metal centres results, upon heating, in a structural phase transformation to the zni topology at a very low temperature. Further heating causes the melting of the solid, yielding a heterometallic MOF-derived glass. The methodology lays the groundwork for tailoring crystalline structures to advance the development of novel materials capable of melting and forming glasses upon cooling.

Molybdenum oxides have attracted considerable attention in heterogeneous catalysis and energy storage applications owing to the unusual chemical flexibility of the Mo center. Unlike many transition metals, molybdenum can shift between several oxidation states without losing structural integrity, largely due to the stabilizing role of oxo-bridged linkages. This versatility gives rise to an extraordinary diversity of structural motifs that can be tailored for specific catalytic and electrochemical functions. In this study, we investigate the elusive structure and nuclear dynamics of the monohydrate (MoO3· H2O) and dihydrate (MoO3· 2H2O) phases of β-MoO3, an important family of precursors for molybdenum oxide–based hybrid materials. We employ a combined experimental and computational approach to explore the local environment and nuclear dynamics of protons in water confined within the interlamellar space of the β-MoO3 layers. High-resolution neutron diffraction confirms the established structure of the dihydrate phase while revealing hydrogen-sublattice disorder in the metastable monohydrate. Complementary computational analysis, including harmonic lattice dynamics and ab initio Born–Oppenheimer molecular dynamics simulations, provides deeper insight into proton confinement in these systems, yielding plausible models of their local structure. These findings further validated through temperature-dependent inelastic neutron scattering and neutron Compton scattering, which probe the vibrational response and proton momentum distributions, respectively. The joint analysis of experimental data and molecular dynamics simulations identifies rotationally bound, orientationally disordered water molecules as the mechanism underlying proton disorder in β-MoO3· H2O. Overall, the results reveal pronounced differences in water ordering and proton dynamics between the mono- and dihydrate forms, offering a detailed quantum-mechanical description of the hydrogen behavior in hydrated molybdenum trioxides and highlighting the interplay between the thermal effect and the confinement-induced local proton dynamics.

We report the rapid microwave-assisted solvothermal synthesis of a Cu-MOF (metal-organic framework) with open metal sites, focusing on understanding its CO2 capture properties in relation to phase purity and stability. A combined experimental and theoretical approach is used to identify the MOF's structural features involved in the adsorption process. Specifically, Cu(i) defects are found to play an important role in the CO2 adsorption process, with the Cu-1 sample, synthesized using an optimized ligand/Cu precursor ratio for the highest phase purity, exhibiting more abundant Cu(i) defects as well as the highest adsorption capacity. Grand canonical Monte Carlo simulations show that the Cu(i) sites exhibit a greater affinity for CO2 adsorption compared to the Cu(ii) sites. In situ soft and hard X-ray absorption fine structure spectroscopic techniques confirm the conversion of Cu(i) to Cu(ii) upon CO2 chemisorption, with this conversion being more pronounced in the core of the particles. The simulations are used to estimate the fraction of Cu(i) defects and Cu(ii) sites present within the Cu-1 and to validate the experimental isotherm. Overall, this study provides insights into the CO2 capture properties of this type of Cu-MOF and highlights the importance of phase purity and the role of defects in achieving high adsorption performance.

Rapidly developing science and technology demand new materials with versatile and promising properties for practical applications. In this context, pseudo-octahedral iron(II) spin crossover (SCO) complexes are particularly appealing - not only for their fundamental scientific interest but also for their potential as key components in the development of multifunctional switchable molecular materials and novel technological applications. This work presents the synthesis and structure of a new mononuclear SCO complex [FeII(L)2]0*nMeOH (n = 2, 0) where L is the asymmetrically substituted tridentate ligand [4-trifluoromethylphenyl-(1H-1,2,4-triazol-5-yl)-6-(1H-pyrazol-1-yl)pyridine]. Due to high trigonal distortion, the solvated form (n = 2) remains high spin (HS) at all temperatures. In contrast, the more regular Oh geometry of the unsolvated form, 4CF3, favors a complete spin transition (ST) at room temperature, which has been investigated, in the pressure interval 0-0.64 GPa, by means of its magnetic and optical properties. Contrary to intuition and experience, the increase of pressure on 4CF3 denotes a radically abnormal behavior of this ST, involving: i) decrease of the characteristic temperatures, ii) increase of the high-spin molar fraction in the temperature range where the low-spin state is stable at ambient pressure; iii) increase of the thermal hysteresis width; and iv) above certain threshold pressure, full stabilization of the high-spin state. All these observations have been explained in the framework of a thermodynamic that model based on the elastic interactions.

Photocatalytic synthesis of hydrogen peroxide (H2O2) from oxygen (O2) is a challenging process. Metal-organic framework (MOF) materials are emerging photocatalysts with potential tunable light absorption properties. Herein, we report a rhenium (Re) modified Zr-based MOF, Re10-MFM-67, in which active Re sites are incorporated into MFM-67 by partial replacement of 9,9'-bianthracene-10,10'-dicarboxylic acid (H2L1) with a [(H2L2)ReI(CO)3Cl] (H2L2 = 2,2'-bipyridine-5,5'-dicarboxylic acid) moiety. Re10-MFM-67 (10 refers to the molar percentage content of Re complex within the material) exhibits broadband light absorption with an exceptional rate of formation of H2O2 from O2 of 8.50 mmol gcat-1 h-1 and a record turnover frequency (TOF) of 28.7 h-1 under visible light irradiation (λ > 400 nm). Synchrotron powder X-ray diffraction (SPXRD) and neutron powder diffraction (NPD) confirm the structure of Re10-MFM-67, and together with extended X-ray absorption fine structure (EXAFS) analysis establish the coordination environment and binding of the [ReI(CO)3Cl] moiety within the framework structure. In situ electron paramagnetic resonance (EPR) spectroscopy suggests that photocatalytic H2O2 generation on Re10-MFM-67 occurs via a two-step oxygen reduction reaction (ORR) pathway with the superoxide anion formed as an intermediate. This study promotes the design of MOF-based photocatalysts with conjugated ligands for efficient photosynthesis.

We investigated the thermodynamic properties and spin exchanges of the polar magnet LiFeV2O7 through experiments and density functional theory calculations. LiFeV2O7 crystallizes in a polar monoclinic Cc structure, where Fe3+ (S = 5/2) ions form diamond chains along the [101] direction, each surrounded by four neighboring chains. The compound undergoes long-range antiferromagnetic ordering at T N approximate to 5 K, which decreases under an external magnetic field. Below T N, it exhibits multiferroic behavior, and a 1/3-magnetization plateau above a critical field of 4.3 T. Neutron diffraction measurement at 1.5 K reveals a collinear magnetic structure with k = (0, 1, 0) with unequal spin moments on monomer and dimer sites of the diamond chains (3.41(1) vs 1.56(1) mu B). These unique magnetic properties stem from strongly antiferromagnetic dimer spin exchange and weakly antiferromagnetic dimer-monomer spin exchanges. This results in a small energy gap between the magnetic ground and excited states below T N and induces thermal spin fluctuations at the monomer and dimer sites reducing their moments. The further reduction of the moment at the dimer sites is ascribed to quantum spin fluctuations of the dimer sites.

An exotic range of magnetic (and other) properties have been observed in A2Mo3O8 materials (where A is a single or mix of transition metals) making understanding their chemistry and physics timely. We have investigated the structural-property relationships in Mn2Mo3O8 and the related materials, MnFeMo3O8, MnCoMo3O8 and MnZnMo3O8. We report a detailed powder diffraction analysis confirming ferrimagnetic structures for Mn2Mo3O8 and MnFeMo3O8. Differing rates of spin ordering on crystallographically distinct sites (tetrahedral or octahedral) gives rise to magnetic hysteresis, which abruptly disappears in 2 K data. This appears to be correlated with ion displacement and/or electrostriction effects, which also relax at 2 K. We confirm an antiferromagnetic structure type for MnCoMo3O8 and no discernible magnetic ordering within the temperature range studied for MnZnMo3O8. For MnZnMo3O8 we suggest a small amount of site disorder acts to suppress magnetic ordering. This suggests that magnetic properties can be tuned both through A-site cation order and choice of A-site cations.