Melt-Quenched Glasses of Metal–Organic Frameworks

Abstract

Crystalline solids dominate the field of metal-organic frameworks (MOFs), with access to the liquid and glass states of matter usually prohibited by relatively low temperatures of thermal decomposition. In this work, we give due consideration to framework chemistry and topology to expand the phenomenon of the melting of 3D MOFs, linking crystal chemistry to framework melting temperature and kinetic fragility of the glass-forming liquids. Here we show that melting temperatures can be lowered by altering the chemistry of the crystalline MOF state, which provides a route to facilitate the melting of other MOFs. The glasses formed upon vitrification are chemically and structurally distinct from the three other existing categories of melt-quenched glasses (inorganic nonmetallic, organic, and metallic), and retain the basic metal-ligand connectivity of crystalline MOFs, which connects their mechanical properties to their starting chemical composition. The transfer of functionality from crystal to glass points toward new routes to tunable, functional hybrid glasses.

Gel-based morphological design of zirconium metal–organic frameworks

“…35,60,61 For the peaks observed below interatomic distances of 1 Å, the quality of lab-recorded total scattering data is typically insufficient to allow for a reliable interpretation. 62 The good agreement between both PDFs, as well as with previously reported PDFs for UiO-66, 35,60,61 further corroborates the successful crystallization of UiO-66 during gel formation. However, while there are no direct indications that the gels contain additional phases, their presence could not be ruled out entirely based on scattering data alone (both PDF and diffraction data), especially since the nearest-neighbour Zr–Zr and Zr–O distances in ZrO 2 are almost identical to those in UiO-66.…”

Communication: Enthalpy relaxation in a metal-organic zeolite imidazole framework (ZIF-4) glass-former

“…The sharp diffraction peaks of the ZIF-4 crystal and the broad peaks without any Bragg peaks of the amorphous ZIF-4 are consistent with the reported results. 15 The XRD curve generated by simulation is seen to coincide with the experimental one. The insets in Fig.…”

“…14,15 Upon heating, the ZIF-4 crystal collapses into a low-density amorphous phase, and then a transition to the low-density liquid (LDL) occurs, followed by the rapid transformation toward the high-density liquid (HDL). 11,13 Since the as-prepared low-density amorphous ZIF-4 by crystal collapse and the subsequent low-density liquid are not stable enough a) Electronic mail: Limin Wang@ysu.edu.cn to guarantee the experimental measurements of the transition, the high-density amorphous ZIF-4 quenched from the high-density liquid is mainly studied, showing the glass transition and subsequent recrystallization upon reheating.…”

“…The MOF-glasses are reported to be dynamically strong featured by low fragility m-indexes, 15 which expresses how rapidly the liquid dynamics such as viscosity changes with temperature at the glass transition temperature, T g . To attain a comprehensive understanding of the glass transition in MOFs, fundamental properties in kinetics and thermodynamics are necessary.…”

Theoretical prediction of the mechanical properties of zeolitic imidazolate frameworks (ZIFs)

“…11,12,[21][22][23] However, the low number of reports suggests that it is much more difficult to experimentally determine the corresponding shear modulus.…”