ZIF-8 and the inorganic glass were mixed in the required amounts by ball-milling to ensure sample homogeneity, and then pelletised at different pressure values: 1, 0.74, 0.5 and 0.22 GPa (see Supplementary Material, Fig. ). For successful composite formation, both the selected glass and MOF material should be thermally compatible. More precisely, the Tg value should be sufficiently below the recrystallisation temperature of the glass (Tr) and the Td of ZIF-8. Above Tg, the viscosity (ŋ) of the glass must decrease enough (log ŋ ∝ 1/T) to be able to flow around the ZIF-8 particles, resulting in a more cohesive composite with better mechanical properties.