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Task-Specific Synthesis of 3D Porous Carbon Nitride from Cycloaddition Reaction and Sequential Self-Assembly Strategy towards Photocatalytic Hydrogen Evolution.

Carbon nitride has drawn widespread attention as a low-cost alternative to metal-based materials in the field of photocatalysis. However, the traditionally synthesized carbon nitrides always suffer a bulky architecture, which limits their intrinsic activities. Here, a cycloaddition reaction is proposed to synthesize triazine-based precursor with implanted sodium and cyano groups, which are mostly retained in the resulting carbon nitride after following polymerization. Incorporated sodium and cyano defects can not only tune the band structure of the carbon nitride but also provide more additive active sites. The optimized properties enable it an adorable photocatalytic hydrogen evolution rate of 1070 μmol h-1 g-1, varying by almost an order of magnitude from the pristine carbon nitride (79 μmol h-1 g-1). Moreover, a sequential self-assembly strategy has been adopted to further improve its architecture. As a consequence, a 3D porous carbon nitride microtube cluster is constructed, indicating abundant exposed active sites and faster carriers' separation. The corresponding photocatalytic hydrogen evolution rate is 1681 μmol h-1 g-1. It is very competitive compared with the reported pure carbon nitride photocatalysts. Briefly, this new approach may offer the opportunities to fabricate task-specific carbon and nitrogen based materials from molecular level.