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.
Keywords: copolymerization; g-C3N4; nitrogen substitution; photocatalysis; tubular configuration.