Engineering Interfacial Low-Coordinated Mg_3C²⁺-O_3C^2– Lewis Acid–Base Pairs on MgO for Cycloaddition of CO₂ with Epoxides

Abstract

Activation of CO2 faces great challenges due to its high chemical inertness. Herein, we constructed interfacial low-coordinated Mg3C2+-O3C2– Lewis acid–base pairs on highly defective MgO by modulating the local coordination environment of the central Mg species for effective CO2 activation. Through various in situ techniques, significantly enhanced CO2 adsorption strength and capacity (∼80%) were detected qualitatively on the low-coordinated Mg3C2+-O3C2– pairs, where O3C2– and Mg3C2+ function as Lewis base and acid sites, respectively. The MgO catalysts with rich Mg3C2+-O3C2– Lewis acid–base pairs delivered 6.18 times higher activity compared to commercial MgO catalysts for propylene epoxide cycloaddition with CO2 in the absence of solvent and cocatalyst. Also, the selectivity of propylene carbonate reached 99.3%. The MgO catalysts were also demonstrated successfully for cycloaddition between CO2 and various epoxides. This work paves the way for the rational construction of active sites in oxide catalysts for CO2 activation.