Fast synthesis of Cu@zeolitic imidazolate framework-8 (ZIF-8) derived Cu/ZnO catalysts via a facile mechanical grinding method for CO2 hydrogenation to methanol

Abstract

Direct conversion of CO₂ with renewable H₂ to produce methanol provides a promising way for CO₂ utilization and H₂ storage. Cu/ZnO catalysts are active, but their activities depend on the preparation methods. Here, we reported a facile mechanical grinding method for the fast synthesis of Cu@zeolitic imidazolate framework-8 (ZIF-8) derived Cu/ZnO catalysts applied in CO₂ hydrogenation to methanol. The confinement in ZIF-8 cages led to the formation of metal oxide particles with controlled crystallite sizes after pyrolysis in air. ZnO derived from ZIF-8 with ultrahigh specific surface area offered high CuO dispersion, obtaining higher Cu⁰ surface area and smaller Cu crystallite size after reduction. The effects of the Cu/(Cu + Zn) molar ratio and alcohol types during catalyst preparation on the textural properties of final catalysts were systemically studied. The resultant catalyst exhibited high activity with STY of methanol up to 128.7 g kg_cat⁻¹ h⁻¹ at 200 °C, much higher than that of catalysts prepared by the conventional impregnation and coprecipitation methods and commercial Cu/ZnO. The present work offers an efficient method for optimizing Cu/ZnO catalysts for CO₂ hydrogenation to methanol.