Synergistic Dual-Active Sites Engineering in ZIF-Derived CoOx/B-Modified g-C3N4 for Efficient CO2 Cycloaddition Under Mild Conditions

Abstract

The carbon dioxide (CO₂) cycloaddition reaction provides an efficient route to achieve resource utilization of CO₂. However, the inherent chemical stability of CO₂ itself hinders its efficient transformation into cyclic carbonates. Herein, the CoO_x/BCN catalyst was successfully prepared by a simple deposition method. The CoO_x/BCN exhibited excellent catalytic performance in the CO₂ cycloaddition reaction synergistically catalyzed with the nucleophilic reagent KI under solvent-free and mild reaction conditions (80 °C, 0.8 MPa, 6 h). The yield of cyclic carbonate was 98% and the selectivity was 99%, which was significantly superior to CoO_x/CN catalyst (with a cyclic carbonate yield of 73.7%). Furthermore, after six cyclic reactions, CoO_x/BCN still maintained a yield of over 93%. It was found that after boron (B) was doped into graphitic carbon nitride (g-C₃N₄), the generated ─NB(OH)₂ group on CoO_x/BCN effectively activated the epoxide. Importantly, the interaction between B-doped g-C₃N₄ and CoO_x induced the generation of abundant oxygen vacancies, which provided sufficient active sites for CO₂ adsorption and activation. In addition, carbonates were identified as the main reaction intermediates by in situ DRIFTS, and the possible reaction pathways of the CoO_x/BCN catalyst were proposed. Therefore, this work provides new idea for the design of catalysts for CO₂ cycloaddition.