Donor-acceptor type conjugated porous polymers based on benzotrithiophen and triazine derivatives: Effect of linkage unit on photocatalytic water splitting

Abstract

Donor-acceptor conjugated polymers have received significant attention as the most promising photocatalysts for efficient photocatalytic hydrogen production (PHP). Nonetheless, achieving high photocatalytic PHP performance relies on molecular framework design and the judicious selection of different structural units. Herein, benzotrithiophene (BTT) and triazine derivatives were used as the basic units of organic polymers, and two conjugated porous polymers (CPPs) named as CP1 and CP2 were successfully synthesized by Stille coupling reaction. Compared with benzene as the linkage unit of triazine, it is evident that the incorporation of the thiophene unit in CP2 broadens its light response range, and promotes the generation of electrons/holes induced by light. Density functional theory (DFT) calculations and femtosecond transient absorption(fs-TA) spectroscopy reveal that CP2 effectively inhibits the photogenerated electron-hole pair recombination and promotes carrier transport. Remarkably, CP2 with Pt co-catalyst exhibited a notably superior PHP performance compared with that of CP1 polymer, which achieved an impressive hydrogen evolution rate (HER) of 21702.4 μmol/g/h, surpassing CP1 by approximately 3.7 times. This work provides a new tactic for enhancing the intrinsic PHP activity and reveals the underlying mechanism for the enhanced photocatalytic activity by regulating the different structural units of the donor-acceptor conjugated polymers.