Donor-acceptor carbon nitride with electron-withdrawing chlorine group to promote exciton dissociation

Carbon nitride (C 3 N 4 ) is promising for photocatalytic hydrogen production , but photogenerated electrons and holes in C 3 N 4 usually tend to exist as excitons due to intrinsic Coulomb interactions making its photocatalytic activity unsatisfactory. Herein, a well-designed intramolecular C 3 N 4 -based donor-acceptor (D-A) photocatalytic system was constructed to promote exciton dissociation. Due to its good chemical compatibility with melamine and appropriate sublimation property, 2-amino-4,6-dichloropyrimidine unit was chosen as the monomer to react with melamine to construct intramolecular D-A system (CNCl x ). The hydrogen evolution rate of CNCl 0.15 is 15.3 times higher than that of bulk C 3 N 4 under visible light irradiation, with apparent quantum efficiency of 13.6% at 420 nm. The enhanced activity is attributed to introduced electron-withdrawing −Cl group as terminal group in the resulted CNCl x samples, which can build internal electric field to promote the exciton dissociation into free electron and hole. In addition, lower work function value of CNCl x samples indicates that internal electric field can help free electrons and holes transfer to the surface of CNCl x samples for photocatalytic reaction.