Nano-confined g-C3N4 in mesoporous SiO2 with improved quantum size effect and tunable structure for photocatalytic tetracycline antibiotic degradation

Abstract Mesoporous materials offer attractive routes for designing photocatalysts with nano-confined structures, high activities, and recyclability. Here we take the core-shell and mesoporous SiO2 nanoparticles as the template for the in situ synthesis of nano-confined g-C3N4 with controllable structures and quantum size effects by varying the precursor species and concentrations. Results indicate that decrease the cyanamide, the precursor, concentration will improve the specific surface area, adsorption ability, and quantum size effect of the final photocatalysts. Cyanamide aqueous solution with a weight ratio of 50.0 wt% results in the most active photocatalyst containing 31.17 wt% of the confined g-C3N4 with a tetracycline degradation rate of 6.63 times higher than that of the cyanamide-derived bulk g-C3N4(C) under the xenon lamp irradiation. Replacing the cyanamide with urea can further improve the photocatalytic activity even the more active SiCN(U10) contains only 12.47 wt% of the confined g-C3N4. The improved photocatalytic activity is resulted from the synergistic effects of the high adsorption ability, low aggregation, enhanced quantum size effect, and more exposed active sites. The present study gives new sight on improving the aqueous phase recyclability of the few-layered and high-reactive g–C3N4–based photocatalysts, and may promote its industrial application process.