HOFs structured CN template enables the dual regulation of Cu–O and Cu–N active sites in porous Cu-g-CN for synergistic photo-Fenton process

Photo-Fenton catalysis with strong oxidation potential and cyclic stability represents a promising technique for addressing the escalating environmental challenges. However, the photo-Fenton activity using Fe/Cu doped graphitic carbon nitride (g-CN) catalysts is significantly hindered by the limited reaction interface and non-tunable surface-active sites. Herein, we present a novel CN polymer type hydrogen bonded organic framework (CN-HOFs) template derived Cu-g-CN (Cu/CH-g-CN) based hybriding catalyst (CN-HOFs/Cu/CH-g-CN), which process greatly optimized surface features for high-performance photo-Fenton reaction with exceptional durability in a broad pH range of 3–11. Importantly, the distinctive porous structure of CN-HOFs template offers not only high specific surface area, but also the possibility to regulate Cu active sites. The coexistence of Cu–O and Cu–N active sites is identified by XPS, which facilitates the separation and migration of photogenerated charges, expediting the redox cycle. The synergistic photo-Fenton reaction boosted by the porous CN-HOFs structure and the dual Cu active sites (Cu–O and Cu–N) was verified by degradation activity of tetracycline. Under visible light irradiation at a concentration of 20 mg/L, the degradation efficiency reaches nearly 100% within 20 min, with exceptional cycling stability. Further investigations have revealed that the Cu–O active site is conducive to the adsorption of organic pollutants, while the Cu–N active site promotes electron transfer, accelerates the cyclic conversion of Cu+ and Cu2+. The dual copper active site is beneficial for the generation of hydroxyl radicals and the stable operation of the catalyst, resulting in significant photo-Fenton activity. This work underscores the importance of regulating the nanoscale morphology and electronic structure of photofunctional catalysts, not only to increase the active sites for photo-Fenton reactions but also to facilitate charge transfer and the cycling of active metal ions, thereby improving the sustainability of heterogeneous photo-Fenton process.