(129g) Effect of Acid Gas Interactions on the Structure and Porosity of ZIF-8
In this study, the stability of a model ZIF material (ZIF-8) under SO2 exposure in dry, humid, and aqueous environments was investigated in detail. To determine structural and textural changes, pXRD and N2 physisorption were conducted before and after exposure. Furthermore, techniques such as EDX, XPS and FTIR were used to study the mechanistic aspects of these changes. ZIF-8 was found to be stable after prolonged exposure in both dry and aqueous SO2 environments and also in the presence of humid air without SO2. However interactions with ppm concentrations of SO2 in the presence of high relative humidity led to its irreversible structural degradation over time as evinced by substantial losses in crystallinity, BET surface areas and pore volumes. EDX analysis showed a significant presence of S even after reactivation of the exposed ZIF-8. FTIR studies revealed the presence of S-O vibrations and the protonation of the nitrogen in the imidazole ring, suggesting cleavage of the metal-linker bond. A mechanism of ZIF-8 degradation combining the synergistic effects of SO2 and humidity is proposed, which advances the present understanding of the stability of ZIF materials towards acid gas exposure.