Benzodithiophene-4,8-dione-Based Conjugated Microporous Polymers for Efficient Visible-light Photocatalytic Hydrogen Evolution from Water

Conjugated microporous polymers (CMPs) have received intensive attention in photocatalytic hydrogen evolution due to their tunable structure, strong visible light absorption, and porous characteristics. In this study, a star unit in organic photovoltaics, namely, benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD), has been used to construct CMPs. Three CMPs (PH-BDD, TPhT-BDD, and TPdT-BDD) based on BDD as an acceptor, benzene, and thiophene-phenyl-thiophene with and without N-substitution as donor units are designed and synthesized for photocatalytic hydrogen evolution from water. The thermal stability, optical properties, porous structures, and photocatalytic performances were also systematically investigated. CMPs with thiophene bridge and N-substitution not only exhibited broad visible-light absorption due to the extended conjugation but also provided the binding sites for Pt because of the introduction of pyridine in the polymer backbone. Consequently, TPdT-BDD with both thiophene bridge and N-substitution showed the best photocatalytic performances with a hydrogen evolution rate of 3385 μmol g–1 h–1.