CO2 adsorption isotherms of the composites were collected to study if the addition of ZIF-8 into the glass matrix results in a higher porosity. The results confirm that porosity from ZIF-8 could be imbued within the glasses (Table and Fig. ) Surprisingly, given that one might expect composite samples to possess a lower accessible porosity compared to physical mixtures (given the dense nature of the glass preventing the ingress of guest molecules), the differences between the physical mixtures and the composites were not substantial (Fig. ). This trend is likely due to the presence of microscale voids in the composites between domains.