Thermal Expansion of Metal–Organic Framework Crystal–Glass Composites

Metal-organic framework crystal-glass composites (MOF CGCs) are a class of materials comprising a crystalline framework embedded within a MOF glass matrix. Here, we investigate the thermal expansion behavior of three MOF CGCs, incorporating two flexible (MIL-53(Al) and MIL-118) and one rigid (UL-MOF-1) MOF within a ZIF-62 glass matrix. Specifically, variable-temperature powder X-ray diffraction data and thermo-mechanical analysis show the suppression of thermal expansivity in each of these three crystalline MOFs when suspended within a ZIF-62 glass matrix. In particular, for the two flexible frameworks, the average volumetric thermal expansion (β) was found to be near-zero in the crystal-glass composite. These results provide a route to engineering thermal expansivity in stimuli-responsive MOF glass composites.