Donor-n-acceptor conjugated microporous polymers for photocatalytic organic conversion with photogenerated carrier separation ability by an embedded electric field along the molecular chain

Photogenerated electron-hole pairs in conjugated microporous polymers (CMPs) recombine easily, thus donoracceptor (D -A) structure was reported to promote the separation of photogenerated carriers, while the inevitable relationship behind them has not been established. Herein, a series of D-n-A type CMPs (Dz-B-CMP, Pz-BCMP, and Py-B-CMP) were designed and constructed from carbazole (donor) and six-membered nitrogenous ring (acceptor). The photocatalytic performance of the prepared CMPs was evaluated in the reaction between ophenylenediamine and benzaldehyde. Satisfactorily, Py-B-CMP exhibited the excellent photocatalytic activity with benzimidazole yield of 95.5%, and a wide range of substrate adaptability and outstanding recycling stability. Further theoretical calculations demonstrated that the excellent activity of Py-B-CMP was attributed to the built-in electric field along the molecular chain. This endowed Py-B-CMP with a powerful driving force for the separation and migration of photogenerated carriers, resulting in a remarkable photocatalytic performance. Additionally, a possible photocatalytic synthesis mechanism of benzimidazole was proposed.