Atypical supramolecular self-assembly derived graphitic carbon nitride with n → π* electron transition capable of efficient visible light hydrogen production

Graphitic carbon nitride (g-C₃N₄) photocatalysts have attracted considerable attention due to its suitable electronic structure and remarkable visible light absorption ability. However, the application of g-C₃N₄ is still hindered by its low specific surface area, lack of active sites and low photogenerated charge carriers transport rates. Herein, we report the synthesis of a distorted g-C₃N₄ (ACCN) with high visible light activity by atypical supramolecular self-assembly of cyanuric acid and protonated melamine. The twisted heptazine ring structure enables the lone pair of electrons on the N atoms to be excited under visible light, which broadens the utilization of visible light, with the absorption edge of the UV–visible spectrum red-shifted to 650 nm. Besides, the atomic defects in the heptazine ring induce shallow energy level defects, which can trap photogenerated electrons and reduce the recombination rate of photogenerated carriers. The broadened light absorption and the presence of shallow energy level defects synergistically improve the photocatalytic hydrogen evolution rate up to 7460 µmol g^-1h⁻¹, which is 53 times higher than that of the bulk g-C₃N₄. Our work proposes that an unconventional supramolecular self-assembly enables efficient n → π* electronic transitions in g-C₃N₄ photocatalyst, which offers a novel insight into developing efficient photocatalysts.