MOF-Derived ZnFe/NC Bimetallic Catalyst with Tunable Residual Zn for Enhanced Photocatalytic Persulfate Activation for Organic Pollutants Degradation

Tuning residual Zn content represented a promising strategy to overcome iron aggregation and metal leaching defects of MOF-derived Fe/NC persulfate activators. Herein, ZnFe/NC bimetallic catalysts with tunable Fe/Zn ratios were synthesized via reduction-passivation pyrolysis of Fe-ZIF-8. Regulating residual Zn via reduction time suppressed Fe sintering and optimized Fe0, Fe-Nx, and graphitic-N active sites. ZnFe/NC–4 (4 h reduction, Fe/Zn ratio = 3.08) exhibited the optimal persulfate activation performance, achieving complete rhodamine B (RhB) removal within 20 min and 71.61% mineralization under visible-light irradiation (300 W Xe lamp, 0.96 W/cm2). This was 1.21 and 1.87 times higher than that of the dark catalyst group and catalyst-free blank group, respectively. Meanwhile, only 6.37% cumulative Fe leaching was detected after three cycles, verifying that residual Zn effectively anchored Fe species within the carbon framework. The coupling effect of residual-Zn-tuned dual active sites and visible-light-assisted persulfate activation promoted charge separation and interfacial electron transfer, generating singlet oxygen (1O2) for RhB mineralization with reduced ecological risk. This present work provided a facile strategy to construct high-efficiency MOF-derived bimetallic activators for refractory organic wastewater treatment.