Self-assembly approach toward polymeric carbon nitrides with regulated heptazine structure and surface groups for improving the photocatalytic performance

Polymeric carbon nitrides (PCNs) are important metal-free photocatalysts due to their unique conjugated structures. However, the activity of PCNs is low due to its complex microstructure and lack of active surface functional groups. The activity of PCNs can be improved by fine control of the microstructure and chemical modification of active heptazine. Herein, a self-assembly method was proposed to synthesize PCNs with adjustable microstructure and composition from benzoic acid and melamine. The addition of benzoic acid not only controlled the morphology, heptazine structure and band structure, but also introduced hydroxyl and carboxyl groups. The introduction of polar groups promoted the formation of singlet oxygen and superoxide anion, and enhanced the photocatalytic activity of selective oxidation of benzylamine; the regulation of heptazine units enhanced the separation and mobility of charge carriers, promoting the activity of hydrogen evolution. Our work provides a strategy for the design of metal free photocatalysts for the selective synthesis of organic compounds and photocatalytic hydrogen production.