Copolymerization with 2,4,6-triaminopyrimidine for the rolling-up the layer structure, tunable electronic properties, and photocatalysis of g-C₃N₄

Copolymerization with 2,4,6-triaminopyrimidine (TAP) is developed for precise substitution of one nitrogen with carbon atom in the triazine ring of polymeric g-C₃N₄. Direct incorporation of C₄N₂ ring from TAP into the network retains the structural features of g-C₃N₄, but induces the rolling-up of g-C₃N₄ sheets into tubular configuration. The band gap energy is narrowed from 2.7 to 2.4 eV by a negative shift of valence band of the g-C₃N₄ photocatalyst, which enhances charge-carrier migration and separation, leading to higher photocatalytic activity for NO gas pollutant removal. It is attributed to the decrease of the π-deficiency and the generation of imbalanced electron density in π-electron conjugated units of g-C₃N₄ by TAP incorporation. This work provides a significant technique for precise control of heteroatom in the framework of g-C₃N₄ to finely adjust its intrinsic electronic properties and its photocatalytic properties.