CSD 2502206: Experimental Crystal Structure Determination

The Cambridge Structural Database · 2026-02-04

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CSD 2502205: Experimental Crystal Structure Determination

The Cambridge Structural Database · 2026-02-04

An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Sculpting the Pores of a Metal–Organic Framework to Enhance Mixture Separation: An Illustrative Study based on Xe/Kr Separation

ChemRxiv · 2026-04-13 · 1 citations

Postsynthetic modification (PSM) of metal–organic frameworks (MOFs) is an attractive approach for enhancing functionality and boosting performance of these nanoporous materials. Often PSM relies on elaboration of either metal nodes or organic linkers of candidate MOFs. Herein, we introduce an alternative approach, sculpting the pores of a zirconium-based MOF, NU-903, with a size-matching Keggin polyoxometalate (POM) and apply the approach to separation of Xe/Kr mixtures as a test application. The computationally optimized structure of POM@NU-903 showed that the original 3-dimensional pore network was sculpted to a 2-dimensional pore. Although the pore volume decreased by 20%, Xe and Kr uptake capacities were nearly doubled at 298 K and 1 bar, with significantly boosted selectivity and heat of adsorption. Given the agreement between computational and experimental results and the great variety of MOFs and POMs, we envision a sizable library of pore-sculpted MOFs for demonstration and optimization of desired chemical separations.

Deterministic Control of Sn ³⁺ Valence and Electronic Phase Evolution in AgSnSe ₂

Journal of the American Chemical Society · 2026-02-03

Understanding how unusual oxidation states influence material properties is important for both fundamental science and energy applications. AgSnSe2 is particularly intriguing because it stabilizes the rare and long-debated Sn3+ oxidation state, whose true existence and role have remained enigmatic for many years. In this work, we employ X-ray photoelectron spectroscopy, Mössbauer spectroscopy, and X-ray absorption spectroscopy to directly probe the oxidation state of Sn and its evolution under chemical substitution. All experimental evidence consistently confirms the presence of Sn in the +3 oxidation state in AgSnSe2. Complementary density functional theory calculations further corroborate this assignment. By substituting Sn with Sb, we systematically control the electronic state and its impact on the material’s physical properties. At low Sb concentrations, AgSnSe2 retains superconductivity with a transition temperature of ∼5 K, while increasing Sb content deterministically drives a metallic-to-semiconducting transition through progressive suppression of superconductivity. Spectroscopic analyses show that Sb substitution provides deterministic control of the Sn oxidation state, evolving from a uniform +3 configuration in AgSnSe2 to a mixed +2/+4 valence-skipping regime at higher Sb levels, thereby establishing a direct chemical handle over the material’s electronic phase. This tunability demonstrates that the Sn oxidation state in AgSnSe2 can be precisely engineered through Sb substitution, enabling controlled electronic phase transitions and establishing AgSnSe2 as a promising platform for quantum and energy-related applications.

Thorium metal–organic framework crystallization for efficient recovery from rare earth element mixtures

Chemical Science · 2025-01-01 · 18 citations

Rare earth (RE) elements are critical materials that underpin many modern technologies, particularly in the clean energy industry. Despite their importance, these vital resources are difficult to obtain due to the presence of numerous metals and radioactive contaminants, such as thorium, that are present in RE ores. Current processing methods, which are dominated by homogeneous solvent extraction, are inefficient and produce substantial hazardous waste. In this work, we describe an alternative strategy to separate thorium from REs through metal-organic framework (MOF) crystallization. Starting from a mixture of thorium and rare earth ions in solution, we utilize the simple carboxylate ligand trimesic acid to selectively crystallize a novel thorium MOF, NU-2500, leaving the remaining rare earth ions in solution. By leveraging the increased oxophilicity of Th(iv) compared to RE(iii) ions, we observe the exclusive formation of the thermodynamically preferred Th-MOF product. This valence-selective crystallization strategy occurs rapidly (within 30 minutes) at mild temperatures (80 °C) with an environmentally-friendly ethanol/water solvent system to produce phase-pure NU-2500 containing >98% molar fraction of thorium. Sequestering the radioactive Th(iv) ions within a solid framework enables facile separation of REs through simple filtration. We demonstrate that our selective crystallization platform retains its high selectivity for Th crystallization even at low initial Th concentrations and in complex mixtures with multiple different REs. We anticipate that further insights into the kinetics and thermodynamics of MOF crystallization can be applied to additional challenging industrial separations.

Electronically Tunable Low-Valent Uranium Metallacarboranes

Inorganic Chemistry · 2025-03-03

Uranium metallocenes have played a pivotal role in advancing the understanding of low-valent uranium chemistry since the inception of this field, and they still find continued use today. Functionalization strategies for cyclopentadienyl (Cp) ligands used in uranium metallocenes have predominately focused on modifying the steric properties of the ligand through the incorporation of alkyl or silyl groups, which offer limited control over the electronic properties. Moreover, due to the flat, two-dimensional nature of Cp, functional groups will affect the coordination geometry of the uranium metallocene and can potentially present challenges in decoupling steric and electronic effects. In comparison, uranium metallacarboranes, which are boron cluster-based metallocene analogues that feature three-dimensional dianionic dicarbollide (dc) ligands, present a versatile platform that is potentially capable of not only stabilizing the low-valent uranium center but also providing control over the electronic properties of the resulting complex without significantly modifying the coordination geometry through the incorporation of a diverse range of groups onto the dc ligand at vertices directed away from the uranium center. In this work, we synthesized a series of uranium metallacarboranes featuring B-functionalized dc ligands with increasingly electron withdrawing aryl groups. A combination of cyclic voltammetry and density functional theory studies confirms that this strategy offers predictable control over the electronic properties of the uranium center. More broadly, this work establishes uranium metallacarboranes as a highly tunable class of complexes potentially capable of unlocking new insights into low-valent uranium chemistry.

Tunable Negative Thermal Expansion in Layered Perovskite Ba₃Zr₂S₇

Inorganic Chemistry · 2025-05-25 · 3 citations

We simulated the thermal expansion coefficient (TEC) of the layered perovskite sulfide Ba3Zr2S7 (P42/mnm symmetry) from first principles. The calculated ambient pressure and room-temperature volumetric TEC is 38 × 10–6 K–1, which makes the material suitable for use in conventional PV devices. We further predicted low-temperature, pressure-tunable negative thermal expansion (NTE) in Ba3Zr2S7 that arises from a quasi-2D vibration mechanism shared by other n = 2 Ruddlesden–Popper oxides Ca3Ti2O7, Ca3Zr2O7, and Sr3Zr2O7. We computationally found a pressure-induced phase transition to a structure in the monoclinic crystal system. Experimental investigation of this system as a function of pressure supported by in situ diffraction studies in a diamond anvil cell confirmed a phase change at high pressures to a new polymorph that likely exhibits P2/c symmetry. Our simulations show that the quasi-2D mechanism and proximity to a mechanochemical transition enhance the NTE response. These features may be used to design NTE in other layered perovskites.

Interplay between Two Structure Types in the Incommensurately Modulated A_14+2/3Ta₈Se_46+2/3 Compounds (A = Rb, Cs)

Inorganic Chemistry · 2025-01-27 · 2 citations

Incommensurately modulated crystals are a rare class of materials that are notoriously difficult to characterize properly. We have synthesized two new incommensurately modulated compounds, Rb14+2/3Ta8Se46+2/3 and Cs14+2/3Ta8Se46+2/3, based on the M2Q11 (M = Nb, Ta; Q = S, Se) unit using high-temperature solid-state synthesis. Using superspace crystallography in combination with second harmonic generation measurements, we confirmed both materials to be noncentrosymmetric, falling into the superspace group P1(αβγ)0, while the basic cell suggests C2/c. These materials can be structurally understood as ordered combinations of two known structure types, A6Ta4Se22 and A12Ta6Se35 (A = K, Rb, Cs). While both modulated compounds share structural similarities with the aforementioned known phases, they represent novel structures rather than a literal combination of the two phases, such as a composite. Additionally, both Rb14+2/3Ta8Se46+2/3 and Cs14+2/3Ta8Se46+2/3 were optically and thermally characterized, revealing identical band gaps of 1.63 eV and congruent melting points at 434 and 417 °C, respectively.

Deterministic Control of Sn3+ Valence and Electronic Phase Evolution in AgSnSe2

Research Square · 2025-12-08

Tuning optical properties and local lone-pair off-centering in “hollow” FA _{1− <i>x</i>} { <i>en</i> } _<i>x</i> Pb _{<i>η</i> − <i>y</i>} Sn _<i>y</i> Br ₃ perovskites

Chemical Science · 2025-10-31

hollow perovskites. These compounds have wide ranging optical gaps from 1.9 eV (deep red) to 2.6 eV (light yellow), combining the anomalous bandgap red-shifting of Pb/Sn mixing with the blue-shifting effects of the organic substitution. Average and local structural studies employing single crystal X-ray diffraction and total X-ray scattering pair distribution function analyses respectively suggest strong incoherent off-centering distortions that are locally correlated with Sn concentration. The inclusion of ethylenediammonium dications appears to regulate metal off-centering, opening new opportunities of research into this phenomenon.