0D/3D coupling of g-C3N4 QDs/hierarchical macro-mesoporous CuO-SiO2 for high-efficiency norfloxacin removal in photo-Fenton-like processes

Highlights: • g-C₃N₄ QDs incorporated hierarchical porous CuO-SiO₂ was successfully prepared. • The catalyst exhibited excellent photo-Fenton activity for degradation of NOR. • g-C₃N₄ QDs accelerated the reduction of Cu²⁺ to Cu⁺ and enhanced the light absorption. • Hierarchical pores increased the surface area and improved the mass transfer. • ¹O₂ was discovered to be an active specie in the Cu-based heterogeneous photo-Fenton system. Photo-Fenton process is an advanced oxidation technology, which is used to eliminate organic pollutants in environmental pollution. In this paper, g-C₃N₄ quantum dots incorporated hierarchical macro-mesoporous CuO-SiO₂ (MM SC-QDs) composite was successfully fabricated by a dual-template method combined with polystyrene sphere (PS) crystal and copolymer F127. With the presence of H₂O₂, MM SC-QDs exhibited excellent degradation performance against the antibiotic pollutant norfloxacin (NOR) under visible-light assisted heterogeneous Fenton process at neutral condition, which was 27 times higher than that of the Bulk CuO-SiO₂. Interconnected macropores, together with abundant mesopores effectively expand specific surface area and improve mass transfer. In addition, the g-C₃N₄ QDs served as the separation center for photogenerated charges, promoting the separation and migration of the charge carriers. Wherein, the long-lived photogenerated electrons were effectively separated and transferred to the surface of CuO-SiO₂, which accelerated the reduction rate of Cu²⁺ to Cu⁺, enhancing the photo-Fenton-like catalytic activity. This stable, efficient, and environmentally friendly Cu-based heterogeneous photo-Fenton-like catalyst is expected to become an effective implementation in organic pollution removal. Meanwhile, this paper proves that Cu-based materials can activate H₂O₂ to generate singlet oxygen (¹O₂) for the degradation of organic pollutants. The transformation mechanism of ¹O₂ was clarified, which is helpful to better understand the Fenton-like reaction process of Cu-based materials.