Zwitterionic Covalent Organic Frameworks as Catalysts for Hierarchical Reduction of CO with Amine and Hydrosilane.

Controllable hierarchical reduction of carbon dioxide (CO) to selectively afford versatile chemicals with specific carbon oxidation state is important but still remains a huge challenge to be realized. Here, we report new zwitterionic covalent organic frameworks ([BE] -TD-COFs), prepared by introducing betaine groups (BE) onto the channel walls of presynthesized frameworks via pore surface engineering methodology, as the heterogeneous organocatalysts for CO reduction. The adjustable density of immobilized BE groups as well as good preservation of crystallinity and porosity inherited from their parent COFs endow [BE] -TD-COFs with highly ordered catalytic site distribution and one-dimensional mass transport pathway in favor of catalysis.