Synergistically enhanced CO2 photoreduction via mesoporous silica-mediated electronic modulation and surface engineering of copper-modified graphitic carbon nitride

Abstract

The practical application of graphitic carbon nitride (g-C₃N₄) in photocatalytic CO₂ reduction is constrained by rapid charge recombination, limited active sites, and low surface area. To address these challenges synergistically, we report the rational design of a multifunctional Cu/CN@SiO₂ composite by integrating copper species with a mesoporous silica shell onto a g-C₃N₄ matrix. The introduced mesoporous SiO₂ not only significantly increases the specific surface area to enhance CO₂ physisorption but also modulates the electronic structure of the Cu through interfacial interactions, thereby promoting the separation of photogenerated charge carriers. Under visible-light irradiation, the optimized Cu/CN@SiO₂ catalyst achieves a CO production rate of 31.68 μmol g⁻¹ h⁻¹, representing a 15-fold enhancement over pristine g-C₃N₄, along with excellent cycling stability. Comprehensive characterization reveals that the mesoporous SiO₂ interface mediates directional electron transfer from g-C₃N₄ to copper species, forming electron-enriched Cu active centers, which collectively improve light harvesting, charge separation/transport, and surface reaction kinetics. This work highlights an effective integrated design strategy wherein a mesoporous silica shell functions dually as a structural promoter for gas enrichment and an electronic modulator for active sites, offering a promising pathway to overcome multiple efficiency limitations in semiconductor photocatalysis.