Pyrolysis of metal–organic frameworks to hierarchical porous Cu/Zn-nanoparticle@carbon materials for efficient CO2 hydrogenation

Abstract

Conversion of CO₂ to CO via hydrogenation, also known as the reverse water-gas shift (RWGS) reaction, is an important chemical process to generate CO as a platform chemical for further conversions. Metallic Cu catalyses the RWGS reaction at a temperature of 500 °C with a high initial turnover frequency, but surface structural reorganization and particle growth at the reaction temperature deleteriously reduce its activity over time. In this work, we synthesized hierarchical structures of porous Cu@C and Cu/Zn@C materials via pyrolysis of Cu-BTC Metal–Organic Frameworks (MOFs) with or without Zn doping. Carbon encapsulation protects the Cu NPs from sintering, leading to stable catalytic activity at 500 °C under which RWGS is favored. Furthermore, the final catalyst pellet size can be controlled by tuning the crystal size of MOF precursors, eliminating the step of forming catalysts for fixed bed reactor applications.