Cyano‐Cyclotrimerization Strategy for Constructing Bi‐Functional Acid‐Base Sites in Covalent Organic Frameworks for Achieving Synergistic‐Optimization of Catalytic Activity and Rapid‐Recyclability in CO₂ Cycloaddition

Abstract For the cycloaddition of CO₂ to epoxides to be a viable non‐redox CO₂ fixation pathway, it is crucial to develop active, stable, selective, metal‐free, rapidly separable, and cost‐effective catalysts. To this end, three novel catalysts are synthesized via cyano‐trimerization reactions on the cyano‐groups of the sp²‐c linked COF─CN, using two cyano‐monomers and the polymers of intrinsic microporosity (PIM‐1). Among these, the powder catalysts (COF─CN─COOH, COF─CN─NH₂), featuring acidic hydrogen‐bond donors (─COOH, ─NH₂) and basic sites (triazine ring), exhibited excellent catalytic performance in CO₂ cycloaddition reaction due to their customizable hydrogen‐bond sites, high CO₂ affinity, and stability. Notably, COF─CN─COOH achieved a catalytic yield of 99.9% with selectivity exceeding 99%. The 20%COF─CN@sPIM‐1 membrane catalyst, formed by covalent‐connection between COF─CN and PIM‐1, demonstrates good interfacial compatibility, facilitating easy recycling while maintaining excellent catalytic activity. Furthermore, density functional theory (DFT) studies on the hydrogen‐bond promoted mechanism reveal that hydrogen bond donors (HBDs) can significantly reduce the activation energy. Therefore, this work introduces a novel trimerization reaction strategy utilizing cyano‐groups on the sp²‐c linked COF as reaction sites, establishing a unique acid‐base synergistic‐catalytic system and laying the foundation for the development of a membrane catalytic system that can be rapidly separated while exhibiting high activity and stability.