Construction of polymeric carbon nitride and dibenzothiophene dioxide-based intramolecular donor-acceptor conjugated copolymers for photocatalytic H evolution.

Polymeric carbon nitride (g-CN) has succeeded as a striking visible-light photocatalyst for solar-to-hydrogen energy conversion, owing to its economical attribute and high stability. However, due to the lack of sufficient solar-light absorption and rapid photo-generated carrier recombination, the photocatalytic activity of raw g-CN is still unsatisfactory. Herein, new intramolecular g-CN-based donor-acceptor (D-A) conjugated copolymers have been readily synthesized by a nucleophilic substitution/condensation reaction between urea and 3,7-dihydroxydibenzo[,]thiophene 5,5-dioxide (SO), which is strategically used to improve the photocatalytic hydrogen evolution performance. The experimental results demonstrate that CNSO- not only improves light utilization, but also accelerates the spatial separation efficiency of the photogenerated electron-hole pairs and increases the wettability with the introduction of SO. In addition, the adsorption energy barrier of CNSO- to H* has a significant reduction theoretical calculation. As expected, the CNSO-20 realizes the best photocatalytic H evolution activity of 251 μmol h (50 mg photocatalyst, almost 8.5 times higher than that of pure CN) with an apparent quantum yield of 10.16% at 420 nm, which surpasses most strategies for the organic molecular copolymerization of carbon nitride. Therefore, this strategy opens up a novel avenue to develop highly efficient g-CN based photocatalysts for hydrogen production.