Thermal stability of ZIF-8 under oxidative and inert environments: A practical perspective on using ZIF-8 as a catalyst support

Abstract

Zeolite imidazole framework-8 (ZIF-8), a representative member of the ZIF class, is a new microporous material considered to have strong potential for use in many important industrial applications, such as hydrogen purification and storage and catalyst support for carbon monoxide oxidation. In this work, we evaluate the applicability of ZIF-8 as a catalyst (support) by reporting its thermal stability under various gaseous environments. The thermal stability tests indicate that ZIF-8 exhibits its highest stability under an inert environment, followed by an oxidative environment, and exhibits the worst stability in a steam atmosphere. The results of thermogravimetric analysis (TGA) clearly suggest that the stability of the ZIF-8 structure depends strongly on the gas-phase environment as well as on its exposure time. Hydrogen reduction and CO oxidation of Au/ZIF-8 was performed to verify the structural stability of the framework under common preparation and application conditions used for supported metal catalysts. In summary, ZIF-8 is suitable for use as a catalyst support at low temperatures (below 300°C) under an inert environment. Progressive modification of the ZIF-8 structure, however, is still possible during long-term operation, including reactions or catalyst preparation or pretreatment. This work is indicative of the limitations of ZIF-8 as a catalyst support from a practical point of view.