Copolymerization with 2,4,6-Triaminopyrimidine for the Rolling-up the Layer Structure, Tunable Electronic Properties, and Photocatalysis of g-C₃N₄

Abstract

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.

A review on g-C3N4 for photocatalytic water splitting and CO2 reduction

“…Different from the heteroatom dopants with limited extension in the absorption, the subtle modifications of g-C 3 N 4 networks by molecular "dopants" always give rise to the markedly enhanced absorption in the visible light range [89][90][91][92][93][94][95][96][97][98]. Crystalline g-C 3 N 4 has a layered structure similar to graphite.…”

“…Since the first case of barbituric acid (BAA) was used as the molecular dopants to modify the network of g-C 3 N 4 [89], the heteromolecule doping has received a lot of interest in engineering the electronic structure of g-C 3 N 4 , as listed in Table 1 [90][91][92][93][94][95][96][97]. By far, several -electron conjugated aromatic molecules, including 3-aminothiophene-2-carbonitrile (ATCN) [91], 4-amino-2,6-dihydroxypyrimidine (ADHP) [92], 3-minothiophene-2-carbonitrile (MTCN) [93], 2,4-diamino-6-phenyl-1,3,5-triazine (DMPT) [94], 2,4,6-triaminopyrimidine (TAP) [96], 2,6-diaminopyridine (DAP) [97], have been demonstrated as efficient heteromolecular dopants that enhanced the electron conjugated system of g-C 3 N 4 , as listed in Table 1. Notably, these incorporated electron conjugated aromatic molecules can evidently red-shift the absorption edge of g-C 3 N 4 to over 550 nm, and lead to enhanced photocatalytic activity.…”

Condensed and low-defected graphitic carbon nitride with enhanced photocatalytic hydrogen evolution under visible light irradiation

“…However, due to the high exciton binding energy of polymer, C 3 N 4 shows just moderate activity and low quantum efficiency during the water splitting process. To improve its photocatalytic efficiency, great efforts have been made on modification of C 3 N 4 , including chemical structure adjustment and nanostructure design, such as fabricating pore structure [10,11], doping with heteroatoms (C, B, S) [12][13][14], coupling with other semiconductors [15,16], controlling morphology [17,18], and copolymerizing with 6 organic molecules [19,20], etc. As a result of these strategies, the photocatalytic activity for H 2 evolution of C 3 N 4 has been much improved.…”

Enhanced photocatalytic H2 evolution over CdS/Au/g-C3N4 composite photocatalyst under visible-light irradiation

“…Graphitic carbon nitride (g-C 3 N 4 ), a typical metal-free photocatalyst, has been attracting considerable attention in hydrogen production, 3,[20][21][22] decomposition of organic pollutants, 23 gas pollutant removal, 24 and CO 2 photoreduction 25,26 under visible-light irradiation. Therefore, g-C 3 N 4 could be a remarkable candidate for building Z-scheme photocatalytic systems.…”