Synthesis and Properties of a Compositional Series of MIL-53(Al) Metal-Organic Framework Crystal-Glass Composites

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 stabilisation 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 were synthesised and characterised using X-ray diffraction and nuclear magnetic resonance spectroscopy. An upper limit of MIL-53 that can be stabilised in the composite was determined. The nanostructure of the composites was probed using pair distribution function analysis and scanning transmission electron microscopy. The distribution and integrity of the crystalline component was determined, and these findings related to the MOF-CGC gas adsorption capacity in order to identify the optimal loading necessary for maximum CO₂ sorption capacity.