Fluorinated conjugated poly(benzotriazole)/g-C3N4 heterojunctions for significantly enhancing photocatalytic H2 evolution

Organic conjugated polymers employed as suspension photocatalysts for hydrogen evolution reactions have attracted the attention of researchers. However, the low charge mobility and weak interface reactive activity prohibited their further application. Herein, three new polymers with fluorene as donor and nitrogen-rich benzotriazole containing different numbers fluorine atoms as acceptor unit were successfully synthesized and further to construct the polymer heterojunctions with g-C3N4 for efficient photocatalytic hydrogen evolution. Flu DFBZ with two fluorine atoms/g-C3N4 heterojunctions achieved the highest H-2 production rate of 14.85 mmol h(-1) g(-1) with a recorded apparent quantum yield of 33.49 % at 450 nm and good photocatalytic stability. Photoelectrochemical experiments combining with density functional theory calculations further supported that fluorination accelerated the charge transfer and adsorption capacity of H-containing species on the N sites of g-C3N4. This work offers a new strategy to obtain stable and efficient photocatalysts by using fluorination strategy of polymer/g-C3N4 heterojunctions.