Covalent organic frameworks (COFs) are a class of promising photocatalysts for conversing light energy into chemical energy. Based on the tunable building blocks, COFs can be well-designed as photocatalyst for mediating reversible addition-fragmentation chain-transfer (RAFT) polymerization. Herein, 1,3,6,8-tetrakis(4-formylphenyl)pyrene (TFPPy) and 2,2″-bipyridine-5,5″-diamine (Bpy) are chosen to construct imine-based TFPPy-Bpy-COFs for catalyzing RAFT polymerization of methacrylates under white light irradiation. The well-defined polymers with precise molecular weight and narrow molecular weight distribution are obtained. The switch on/off light experiments suggest excellent temporal control toward RAFT polymerization system and the chain-extension reaction indicates high chain-end fidelity of macro-initiators. Mechanism study clarifies that the electron transfer between excited state of TFPPy-Bpy-COFs and RAFT agent can form living radicals to mediate polymerization. This methodology provides a novel platform for reversible-deactivation radical polymerization using COFs as heterogeneous catalysts.

中文翻译：

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高结晶度共价有机骨架可见光调控多相催化PET-RAFT

共价有机骨架（COFs）是一类有前途的光催化剂，用于将光能转化为化学能。基于可调结构单元，COFs 可以很好地设计为光催化剂，用于介导可逆加成-断裂链转移 (RAFT) 聚合。在此，选择 1,3,6,8-四（4-甲酰基苯基）芘（TFPPy）和 2,2”-联吡啶-5,5”-二胺（Bpy）构建基于亚胺的 TFPPy-Bpy-COFs在白光照射下催化甲基丙烯酸酯的 RAFT 聚合。获得了具有精确分子量和窄分子量分布的明确定义的聚合物。开/关灯实验表明对 RAFT 聚合系统具有出色的时间控制，链延长反应表明大分子引发剂的链端保真度高。机理研究表明，TFPPy-Bpy-COFs 的激发态与 RAFT 试剂之间的电子转移可以形成活性自由基来介导聚合。该方法为使用 COF 作为非均相催化剂的可逆失活自由基聚合提供了一个新平台。