Synergistic Effects in a Nitrogen-Coordinated Zinc Single-Atom Catalyst for Efficient CO2 Cycloaddition

Abstract

The valorization of CO₂ into organic carbonates through its cycloaddition to epoxides has garnered significant attention in catalysis. However, the reaction is often hindered by low selectivity, and a key challenge is the development of catalysts capable of effectively activating both CO₂ and epoxides simultaneously. In this study, we prepared and characterized a catalyst comprising isolated zinc single atoms dispersed on carbon nitride for the selective CO₂ conversion to cyclic carbonates. The monoatomic nature and homogeneous distribution of the zinc species were confirmed utilizing advanced characterization methods, including X-ray absorption spectroscopy and aberration-corrected scanning transmission electron microscopy. The catalyst activity and recyclability were validated through catalytic tests with epichlorohydrin as a model epoxydic compound, and the study scope was subsequently extended to include a wide range of functionalized epoxides. Density functional theory calculations were performed to elucidate the reaction mechanism, revealing that both CO₂ and epichlorohydrin interact with the same zinc atom in the cycloaddition process, highlighting the key role of zinc single atoms in promoting the reaction. Overall, the present study provides new insights into the design and optimization of heterogeneous catalysts for CO₂ cycloadditions, paving the way for more effective strategies in CO₂ valorization and conversion for producing valuable fine chemicals.