Nitrogen-deficient porous g-C₃N₄ derived from an HMTA-regulated supramolecular precursor for enhanced photocatalytic H₂ evolution

Precursor structure engineering is a fundamental strategy for regulating the physicochemical properties of g-C₃N₄, which can promote the development of efficient photocatalysts. Herein, hexamethylenetetramine (HMTA) with a stable three-dimensional cage-like spatial configuration, was successfully incorporated into a melamine-cyanuric acid supramolecular complex via a hydrothermal method. Furthermore, a novel N-defect-rich porous g-C₃N₄ was obtained through thermal pyrolysis of this HMTA-regulated supramolecular precursor. The presence of N defects and the resulting midgap states which were proved to be induced by HMTA-regulated precursor structure engineering could effectively enhance the light absorption and promote the separation of photogenerated carriers of g-C₃N₄. As a result, the HMTA-regulated g-C₃N₄ exhibited an enhanced H₂-evolution activity of 2.77 mmol g⁻¹ h⁻¹, which was 5.8 times that of pristine g-C₃N₄. This work proposes a molecular-level structure engineering strategy of g-C₃N₄ by rationally incorporating functional molecules into the precursor, offering valuable insights for developing highly efficient photocatalysts.