Engineering Cu-loaded SiO₂/g-C₃N₄ photocatalysts for efficient visible-light-driven removal of organic pollutants

The efficient elimination of organic contaminants in water remains a significant challenge due to their stability and complexity, demanding advanced, affordable photocatalysts. In this study, a novel, low-cost Cu@SiO₂/g-C₃N₄ composite was synthesized via integration of rice-husk-derived mesoporous silica with g-C₃N₄ nanosheets and subsequent copper nanoparticle loading (0.5–2 wt%) by chemical reduction. The prepared nanocomposites were characterized by various techniques, confirming reasonable porosity, strong visible light absorption, and stable morphology. The optimized 2 % Cu@SiO₂/g-C₃N₄ exhibited exceptional photocatalytic activity: complete reduction of 4-nitrophenol in just 2.5 min and more than 93 % degradation of Rhodamine 6G within 70 min under visible light. Based on comprehensive characterization, the enhanced performance arises from synergies among the electron-rich g-C₃N₄ core, mesoporous SiO₂ serving as an electron mediator, and Cu nanoparticles acting as an electron reservoir, which together strongly suppress electron–hole recombination. Kinetic comparisons show up to 16-fold and 172-fold increases in reaction rates for 4-NP and Rh 6G relative to pristine g-C₃N₄, respectively. Structural and morphological integrity remained unchanged after multiple photocatalytic cycles, confirming substantial stability. This work establishes Cu@SiO₂/g-C₃N₄ as a benchmark sustainable photocatalyst with outstanding efficiency for solar-driven water purification and organic transformation.