Zeolite-stabilized trinuclear Zn1Cu2 sites catalyze CO2 hydrogenation to methanol

Abstract

CuZn-based catalysts like Cu/ZnO/Al₂O₃ have been extensively investigated for CO₂ hydrogenation to methanol, while the active sites and underlying mechanism are hotly debated due to the ultra-high CuZn loadings and the structural complexity thereof. We report herein that zeolite-stabilized trinuclear Zn₁Cu₂ sites can efficiently catalyze the selective hydrogenation of CO₂ to methanol, surpassing the performance of the benchmark CuZn-based catalyst, although the CuZn loading is over an order of magnitude lower. Both experimental evidence and theoretical calculations reveal the formate pathway of CO₂ hydrogenation with the involvement of the Cu²⁺-Cu^δ+-Cu²⁺ redox cycle. Zn ions incorporated into the zeolite framework play an essential role in stabilizing cationic Cu species against overreduction to less active metallic Cu during the reaction. Our results provide new insights into the chemistry of CO₂ stepwise hydrogenation to methanol, which are useful for the rational design of catalysts.