Aromatic Ring-Coordinated g-C₃N₄ Nanotubes for Enhanced Photocatalytic H₂ Evolution

As one of the most promising metal-free photocatalysts for renewable H₂ evolution, graphitic carbon nitride (g-C₃N₄) has attracted notable attention. Regulating its morphology and electronic structure is crucial for enhancing its performance. In this work, aromatic small molecules and melamine were hydrothermally cotreated to form a novel supramolecular precursor, which was subsequently calcined to obtain a π–π conjugated structure of g-C₃N₄ photocatalyst. The introduction of benzene-ring structures expanded the conjugated system and promoted the excitation of π electrons, thereby broadening the light-absorption range of g-C₃N₄. The synergism of bromine and chlorine provided abundant active sites for g-C₃N₄, greatly promoted the migration of photogenerated charge carriers, and reduced the recombination probability, thus improving in photocatalytic performance. Therefore, the g-C₃N₄ photocatalyst obtained from 2-bromo-5-chlorobenzoic acid-derived supramolecular precursor exhibited a visible-light (λ ≥ 400 nm) photocatalytic H₂ evolution activity of 839.8 μmol/(h g), which was about three times that of the unmodified g-C₃N₄. This work offers a novel perspective for g-C₃N₄ application in the field of photocatalysis and expands the utilization of aromatic small molecules in photocatalysts modification.