Supramolecular precursor-derived P-doped 3D porous g-C₃N₄ nanosheets with highly efficient rhodamine B degradation

Morphology engineering and heteroatom doping are established strategies for developing high-performance photocatalysts. In this study, phosphorus-doped three-dimensional porous g-C₃N₄ nanosheets were synthesized by calcining melamine–cyanuric acid supramolecular precursors, followed by gas-phase phosphidation using NaH₂PO₂ at 300 °C. The optimized material exhibited exceptional photocatalytic activity, achieving over 99 % Rhodamine B degradation within 40 min under visible light, significantly outperforming undoped 3D and bulk g-C₃N 4 . It also showed the highest photocurrent density and prolonged carrier lifetime, indicating enhanced charge separation. The catalyst maintained >90 % efficiency after four cycles, demonstrating remarkable stability. Mechanistic studies revealed that holes and superoxide radicals serve as the primary active species, with hydroxyl radicals also participating. The enhanced performance is attributed to the synergistic effect of P-doping—which modifies the electronic structure—and the 3D porous framework, which facilitates mass transfer and exposes active sites. This work provides a scalable route to efficient photocatalysts for environmental remediation.