Owing to their dynamic phase behaviour and unique gas sorption properties, flexible metal–organic frameworks (MOFs) have emerged as a promising class of materials for applications in gas-related technologies and beyond. Resolving the crystal structures of the distinct phases is essential for understanding their transformation mechanisms and rational tuning framework responsiveness. Here, we revisit the prototypical flexible MOFs ZIF-7 (Zn(bim)₂, bim⁻ = benzimidazolate) and ZIF-9 (Co(bim)₂) and resolve the long-standing ambiguity surrounding their guest-free narrow-pore (np) phases. Using microcrystal three-dimensional electron diffraction combined with powder X-ray diffraction (PXRD) and density functional theory calculations, we determine the crystal structures of both np phases. The results rectify previous structural models and incomplete structural descriptions of the np phase of ZIF-7 and establish the structure of the np phase of ZIF-9. In contrast to the high-symmetry, guest-accommodating large-pore (lp) phases, the np phases adopt distorted, densely packed frameworks with strongly deformed sodalite cages, reduced void fractions, and enhanced framework densities. Variable-temperature PXRD and differential scanning calorimetry further reveal metal-dependent anisotropic thermal expansion of the np phases and entropy-driven np–lp transitions.

Bioderived metal–organic frameworks (bioMOFs) have attracted interest as functional materials for medical-related applications due to their biocompatibility and structural tunability. However, the integration of external stimulus responsiveness into bioMOF architectures while preserving the framework integrity remains a significant challenge. Herein, we report the synthesis and comprehensive characterization of magneto-responsive nanocomposites based on the microporous Bi(III)-ellagate bioMOF SU-101 incorporating ultrasmall magnetic nanoparticles. We demonstrate the successful integration of magnetic nanoparticles and the loading of fluorescent cargo within the MOF matrix without compromising its structural integrity. The resulting magnetic nanocomposites exhibit a well-defined magnetic response under high-frequency alternating (AMF) and low-frequency rotating (RMF) magnetic fields that enable remote modulation of thermal and mechanical effects, leading to significant cargo release and a marked reduction in cancer cell viability. Moreover, magnetic resonance imaging (MRI) relaxivity measurements confirm the potential of these nanocomposites as magnetic resonance contrast agents. Overall, these results highlight the strong potential of magnetically responsive bioMOF SU-101-based nanocomposites as multifunctional platforms for biomedical applications.

Densely functionalized alkenes are often utilized as excellent tools for further functionalization of molecules. Recent progress in their synthesis includes nucleophilic addition to vinylbenziodoxolones (VBX) and vinylbenziodoxoles (VBO) to reach alkenes with complete regio- and stereocontrol. In this work, we leverage the inherent properties of mechanochemistry to enable an efficient transition metal-free one-pot route to 1,2-heteroatom-substituted (Z)-alkenes directly from ethynylbenziodoxol(on)es (EBX/EBO), avoiding the isolation of VBX/VBO. We demonstrate a high-yielding synthesis of a large variety of N/O/S-VBX reagents, which, combined with a telescoped nucleophilic addition, delivers a wide range of novel, complex (Z)-alkenes. This one-pot strategy would be challenging to develop in solution due to a mismatch in reaction solvents, and the unique mechanochemical activation offered by solventless, solid-state mixing also enables formation of products whose synthesis is inefficient with solvent-based methods.

The coordination chemistry of some six–coordinated manganese(III) complexes with oxygen donor ligands in the solid state has been studied by EXAFS. The structures of tris(acetylacetonato)manganese(III), as purchased and recrystallized from methanol and acetone, show that they have non–centrosymmetric tetragonally elongated octahedral coordination with significantly different axial Mn–O bond distances due to pseudo-Jahn-Teller distortion. When recrystallization was performed in 2–propanol and acetonitrile, a partial reduction to tris(bis(μ₂–acetylacetonato)manganese(II)) was observed. Solid manganese(III) phosphate hydrate is shown to have the same kind of non–centrosymmetric tetragonally elongated octahedral coordination, while the crystallographic study reports centrosymmetric coordination with an axial Mn–O bond distance equal to the mean of the distances observed by EXAFS. A literature survey has been performed to study the symmetry of six-coordinated metal ions with possibility to form Jahn-Teller distorted complexes, those with d⁹, high–spin d⁴ and low–spin d⁷ electron configuration. It shows that when a compound crystallizes in a non–centrosymmetric space group or when the metal ion is out of the center of symmetry in a centrosymmetric space group, the axial M–O bond distances are significantly different. In crystallographic studies a random orientation of the axial bonds in tetragonally elongated octahedral complexes results in seemingly centrosymmetric complexes even though the axial bond distances are different in the individual complexes. The literature survey was used to estimate the ionic radii of the chromium(II), manganese(III), nickel(III) and silver(II) ions in their low– and high–spin states.

Flexible metal–organic frameworks (MOFs) are dynamic materials that combine long-range structural order with reversible stimulus-responsive phase transitions. In this study, we report the synthesis and characterization of two isoreticular flexible MOFs, TPPM-CPW(Me) and TPPM-CPW(Ph), constructed by combining the ligand tetra-4-(4-pyridyl)phenylmethane (TPPM) with specific Cu(II) paddle-wheel (CPW) secondary building units (SBUs). These MOFs exhibit reversible transitions between open- and closed-pore forms triggered by external stimuli, such as temperature- and pressure-induced guest removal and uptake. The stability of these frameworks is influenced by the residual equatorial groups on the Cu(II) SBUs, with phenyl-functionalized TPPM-CPW(Ph) displaying dynamic behavior characteristic of third-generation soft porous crystals. Notably, TPPM-CPW(Ph) exhibited high adsorption affinity toward fluorinated guests, including SF₆ and volatile anesthetics (VAs) such as desflurane and sevoflurane. This material, when used in solid-phase microextraction (SPME) as fiber coating for the preconcentration of these VAs in air, outperformed commercial CAR/PDMS fibers, underscoring the potential of these versatile flexible MOFs in addressing environmental challenges associated with the use of volatile fluorinated compounds.

Carmine is a red pigment made from dried cochineal, a scale insect that has been a source of brilliant scarlet reds in clothing and art for more than two millennia, with records dating back to 700 BC. Since the 16th century, it has been intensely traded all over the world and was one of the most important trade goods for the Spanish empire at its economic peak. Despite still being used on an industrial scale, with hundreds of metric tonnes produced annually, the exact molecular and crystal structures of the dyestuff remains undetermined. Notably, both modern-day commercial carmine and pigments prepared following historical recipes show strikingly similar diffraction patterns, indicating a common crystalline structure. Here we show that the crystal structure of carmine can, at last, be determined using three-dimensional electron diffraction measurements, revealing a tetranuclear complex that assembles into a nanoporous supramolecular structure with pore diameters of approximately 1.8 nm, held together by intermolecular hydrogen bonding. Our results establish a definite structure of carmine, unveiling a surprisingly complicated arrangement in a long-used commodity with economic and cultural impact, while also highlighting the serendipitous creation of a man-made supramolecular material that dates back hundreds if not thousands of years.

Understanding the structure of Ru(V)-oxo species is crucial for designing novel catalysts for sustainable energy applications, such as water splitting for green hydrogen production. This study reports the EPR detection of a Ru(V)-oxo intermediate stabilized by terpyridine and phenanthroline carboxylate ligands. The interaction between the carboxylate group and the ruthenium center, along with PCET-dependent hemilability under oxidative conditions, plays a critical role in achieving the high-valent state. Subtle changes in the coordination environment around the central metal also proved to be essential. Low-temperature NMR, high-resolution mass spectrometry, UV–Vis spectroscopy, and density functional theory calculations support these findings.

The V-shaped linker molecule 2,5-furandicarboxylic acid (H₂FDC), which can be derived from lignocellulosic biomass, was used in a systematic screening with various iron salts and led to the discovery of a new iron-based metal–organic framework (Fe-MOF) with the composition [Fe₃(μ₃-O)(FDC)₃(OH)(H₂O)₂]·5H₂O·H₂FDC, designated as CAU-52 (CAU = Christian-Albrechts-Universität zu Kiel). The crystal structure of CAU-52 was determined using 3D electron diffraction (3D ED) and further refined by Rietveld refinement against powder X-ray diffraction (PXRD) data. CAU-52 contains the well-known trinuclear [Fe₃(μ₃-O)]⁷⁺ cluster as the inorganic building unit (IBU) that is six-connected by FDC^2– ions to form the pcu net. The connectivity leads to two types of cubic cages, similar to the ones observed in soc-MOFs. Comprehensive characterization of the title compound, including N₂ and water vapor sorption measurements, confirmed its chemical composition. CAU-52 exhibits microporosity toward nitrogen with a type-I isotherm (77 K), yielding a specific surface area of a_s,BET = 1077 m²/g. The H₂O sorption measurement at 298 K leads to an isotherm that exhibits three steps. The water sorption capacity was determined to be 390 mg/g, and it decreases slightly in subsequent sorption cycles. The MOF is stable up to 250 °C in air and chemically resistant in various solvents.

Pesticides have become a common environmental pollutant in bodies of water in recent decades, negatively affecting the aquatic ecosystems along with their living organisms. In this regard, thiabendazole (TBZ) has emerged as one of the most detected pesticides in wastewater due to its widespread application in agriculture. Despite its toxicological effects and persistence, no technology is currently available for its efficient removal. Recent adsorption strategies using eco-friendly porous materials have emerged as an effective, low-cost, and easy-to-operate alternative for water pollutant removal. Among them, metal–organic frameworks (MOFs) were selected here as attractive adsorbents due to their outstanding water stability and a priori, compatible pore sizes with the TBZ molecule. Upon screening of 8 MOFs with different natures and structures, the most promising material was the microporous bismuth(III)-ellagate SU-101, with remarkable removal efficiencies (89% in just 5 min). The material was successfully shaped into micrometric pellets and packed into a column for its suitable implementation in a continuous flow device, simulating a real decontamination environment by using pollutant-doped tap water. This SU-101 column was able to efficiently eliminate TBZ during 4.6 consecutive days, with the absence of significant MOF degradation (< 1.5%), and was successfully regenerated (88%) preserving functionality over 2 cycles. These resulting outcomes pave the way for further SU-101 implementation in real decontamination processes.

In the field of metal-organic frameworks, the use of yttrium(iii) cations and the formation of 3D inorganic building units are rather rare. Here we report an yttrium(iii) metal-organic framework based on the V-shaped ditopic linker 4,4′-oxydibenzoate, oba2−: [Y16(μ-OH2)(μ3-OH)8(oba)20(dmf)4]·7H2O·7dmf, 1, which was solvothermally prepared, with single crystal X-ray diffraction revealing an unusual 3D metal secondary building unit. When activated at 200 °C, 1 desolvated to form compound 2, [Y16(μ-OH2)(μ3-OH)8(oba)20]·6H2O, retaining the same structure with a 3% shrinkage in unit cell volume.