Visible-light-driven photocatalytic degradation of ofloxacin by g-C3N4/NH2-MIL-88B(Fe) heterostructure: Mechanisms, DFT calculation, degradation pathway and toxicity evolution

In this study, g-C3N4/NH2-MIL-88B(Fe) (MCN-x) heterostructures were successfully prepared using a facile solvothermal method. MCN-x composites exhibit excellent degradation performance toward ofloxacin in aqueous solution under visible light (λ > 420 nm). The photodegradation rate of ofloxacin by MCN-60 under visible light reaches 96.5% in 150 min, and the apparent first-order kinetics rate constant reaches 0.0217 min−1, 3.7 and 4.7 times that of pristine g-C3N4 and NH2-MIL-88(Fe), respectively. This decent photocatalytic performance is principally attributed that the introduction of g-C3N4 can notably promote the separation of photogenerated electron-hole pairs. Besides, the photocatalytic efficiency and structure of the MCN-60 composite basically show no change after three reuse cycles. Furthermore, trapping experiments and ESR analyses confirm that the O2– radical has a more dominant role than OH and holes (h+). The ofloxacin degradation mechanism and pathway are predicted by density functional theory (DFT) calculations and an intermediate analysis. Quantitative structure–activity relationship (QSAR) predictions reveal that the ofloxacin photocatalytic degradation process can reduce toxicity in a step-by-step manner. MOF-based materials have been confirmed to show high potential for practical application in removing emerging pollutants from wastewater.