Mesostructured Bifunctional ZnBr2/g‐C3N4 Catalysts Towards Efficient Cocatalyst‐Free Cycloaddition of CO2 to Propylene Carbonate

Abstract Catalytic cycloaddition of CO 2 with propylene oxide (PO) is a sustainable pathway for the synthesis of propylene carbonate (PC), and the design of efficient heterogeneous catalysts is a hot research topic in both C1 chemistry and functional materials. In this work, graphitic carbon nitride (g‐C 3 N 4 ) materials were prepared using urea (U) and melamine (M) as precursors through one‐step thermal condensation and then applied as catalyst supports for ZnBr 2 . As heterogeneous catalysts, the synthesized composites (ZnBr 2 /g‐C 3 N 4 ‐MU) exhibited higher activity in the cycloaddition reaction of CO 2 to PC than ZnBr 2 /g‐C 3 N 4 ‐M and ZnBr 2 /g‐C 3 N 4 ‐U. The preparation temperature of ZnBr 2 /g‐C 3 N 4 ‐MU could affect the distributions of nitrogen species and acidic strength, which thus determined the final catalytic activity. More importantly, the loading of ZnBr 2 not only introduced acidic sites but also enhanced the strength of alkaline sites of g‐C 3 N 4 ‐MU, enabling ZnBr 2 /g‐C 3 N 4 ‐MU materials as acid–base bifunctional catalysts in cycloaddition of CO 2 with PO.