Facilitated charge separation in non-covalent NiO–UPDI donor–acceptor composite for efficient photocatalytic degradation of ciprofloxacin

Efficient charge separation remains a central challenge in achieving the deep mineralization of organic pollutants via photocatalysis. Herein, we report a nickel oxide isintegrated with urea-perylene diimide (NiO–UPDI) photocatalyst with a donor–acceptor (D–A) structure, constructed through solvothermal precipitation, in which NiO is integrated with UPDI via non-covalent coordination. Under visible-light irradiation, the optimized NiO–UPDI (20 wt.%) achieves a ciprofloxacin degradation rate of 0.553 h⁻¹, exceeding those of UPDI and bulk g-C₃N₄ by factors of 6.21 and 7.18, respectively. The enhanced photocatalytic performance originates from the NiO-induced D–A configuration, which creates an unsymmetric electron distribution that strengthens intermolecular dipoles, yielding a 5.5-fold higher internal electric field and markedly improved charge separation. Photogenerated electrons (e⁻) migrate from NiO to UPDI, while photogenerated holes (h⁺) transfer to the catalyst surface, enabling synergistic oxidation and degradation. This study provides fundamental insights into the rational design of non-covalent D–A photocatalysts for achieving superior photocatalytic performance through efficient charge separation.