Ordered Macro–Microporous Covalent Organic Frameworks as Bifunctional Catalysts for CO2 Cycloaddition

Carbon dioxide (CO2) cycloaddition is one of the most promising approaches for reducing CO2 and achieving carbon neutrality. Bifunctional metal-free heterogeneous catalysts offer an environmentally friendly and efficient alternative to traditional unifunctional or metal-based catalysts. Here, we report a novel strategy for the preparation of a bifunctional macro–microporous covalent organic framework (COF) heterogeneous catalyst by the integration of the template-assisted method and incomplete ion-substitution method. Based on this strategy, the bifunctional and hierarchical pore macro-EB-COF:Br-H2PO4 was successfully achieved with Brønsted acidic sites and nucleophilic sites. The improved mass diffusion properties of such hierarchical frameworks, together with the synergy of two functional sites, yield macro-EB-COF:Br-H2PO4 with excellent catalytic activity and recyclability for the cycloaddition of CO2 with epoxides.