Ordered Macro–Microporous Covalent Organic Frameworks as Bifunctional Catalysts for CO<sub>2</sub> Cycloaddition
Dingxuan Ma, Yuzhuang Song, Huihui Zhao, Chengzhong Yu, Yaowen Zhang, Chen Li, Kang Liu
Abstract
Carbon dioxide (CO 2 ) cycloaddition is one of the most promising approaches for reducing CO 2 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-H 2 PO 4 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-H 2 PO 4 with excellent catalytic activity and recyclability for the cycloaddition of CO 2 with epoxides.