The synthesis of four novel crystalline zeolitic imidazolate framework (ZIF) structures using a mixed-ligand approach is reported. The inclusion of both imidazolate and halogenated benzimidazolate-derived linkers leads to glass-forming behavior by all four structures. Melting temperatures are observed to depend on both electronic and steric effects. Solid-state NMR and terahertz (THz)/Far-IR demonstrate the presence of a Zn-F bond for fluorinated ZIF glasses. In situ THz/Far-IR spectroscopic techniques reveal the dynamic structural properties of crystal, glass and liquid phases of the halogenated ZIFs, linking the melting behavior of ZIFs to the propensity of the ZnN4 tetrahedra to undergo thermally-induced deformation. The inclusion of halogenated ligands within MOFglasses improves their gas uptake properties.

Methods to produce glass forming metal–organic frameworks (MOFs) rely on solvothermal syntheses which have high energy requirements, low yields and large teratogenic solvent usage. We present mechanochemical methods to overcome these issues.

Metal–organic framework crystal-glass composites (MOF-CGCs) are materials in which a crystalline MOF is dispersed within a MOF glass. In this work, we explore the room-temperature stabilization of the open-pore form of MIL-53­(Al), usually observed at high temperature, which occurs upon encapsulation within a ZIF-62­(Zn) MOF glass matrix. A series of MOF-CGCs containing different loadings of MIL-53­(Al) were synthesized and characterized using X-ray diffraction and nuclear magnetic resonance spectroscopy. An upper limit of MIL-53­(Al) that can be stabilized in the composite was determined for the first time. The nanostructure of the composites was probed using pair distribution function analysis and scanning transmission electron microscopy. Notably, the distribution and integrity of the crystalline component in a sample series were determined, and these findings were related to the MOF-CGC gas adsorption capacity in order to identify the optimal loading necessary for maximum CO2 sorption capacity.

The study of polymorphic zeolitic imidazolate frameworks demonstrates the influence of linker chemistry and framework structure on their thermal behaviour.

Defect engineering is used to augment the porosity of MIL-100. Incorporation of defects leads to structural collapse and ultimately causes amorphisation. Pair distribution function analysis reveals a stepwise collapse of the hierarchical structure.

Melt-quenched metal−organic framework (MOF) glasses have gained significant interest as the first new category of glass reported in 50 years. In this work, an amine-functionalized zeolitic imidazolate framework (ZIF), denoted ZIF-UC-6, was prepared and demonstrated to undergo both melting and glass formation. The presence of an amine group resulted in a lower melting temperature compared to other ZIFs, while also allowing material properties to be tuned by post-synthetic modification (PSM). As a prototypical example, the ZIF glass surface was functionalized with octyl isocyanate, changing its behavior from hydrophilic to hydrophobic. PSM therefore provides a promising strategy for tuning the surface properties of MOF glasses.

The field of metal–organic frameworks (MOFs) is still heavily focused upon crystalline materials. However, solid-liquid transitions in both MOFs and their parent coordination polymer family are now receiving increasing attention...

Metal−organic framework (MOF) glasses provide new perspectives on many material properties due to their unique chemical and structural nature. Their mechanical properties are of particular interest because glasses are inherently brittle, which limits their applications as structural materials. Here we perform strainrate-dependent uniaxial micropillar compression experiments on a g ZIF-62, a g ZIF-UC-5, and a g TIF-4, a series of MOF glasses with different substituting linker molecules, and find that these glasses show substantial plasticity, at least on the micrometer scale. At a quasi-static strain rate of 0.001 s −1 , the micropillars yielded at approximately 0.32 GPa and subsequently deformed plastically up to 35% strain, irrespective of the type of substituting linker. With increasing strain rate, the yield strength of a g ZIF-62 evolved with the strain-rate sensitivity m = 0.024 to reach a yield strength of 0.44 GPa at a strain rate of 510 s −1 . On the basis of this relatively low strain-rate sensitivity and the absence of serrated flow, we conclude that structural densification is the predominant mechanism that accommodates such extensive plasticity.