Fe–O–Zr in MOF for effective photo-Fenton Bisphenol A degradation: Boosting mechanism of electronic transmission

To enhance the efficiency of photogenerated electron transport in the photo-Fenton reaction, we report a Fe-doped UiO-66 containing Fe-O-Zr bonds for the photo-Fenton reaction system. The modulation changes the energy bandgap from 3.89 eV to 2.02 eV, and its absorption edge is red-shifted from the UV region to the visible range. Simultaneously, Fe-O-Zr reduces the redox internal resistance, enhances the photocurrent and catalytic process, and suppresses the compounding of photogenerated electrons and holes. These promote the valence cycling of Fe(III)/Fe(II) in the photo-Fenton reaction. Compared with UiO-66, the hydroxyl radical generation efficiency of this reaction system was increased by 5.8 times (UiO-66: 0.0009 mM/min, FeUiO-1: 0.0053 mM/min). The degradation efficiency of BPA was increased by 100.8 times (UiO-66: 0.0012 min-1, FeUiO-1: 0.121 min-1), and the removal rate of TOC also reached 69.55%. The removal rate of BPA was maintained at more than 85% through 5 cycles. The reaction system was able to maintain a removal rate more than 97% at pH:3-9. In the presence of anions, such as Cl-, SO42-, NO32- (10 mM), the degradation rates of BPA were still above 94%. The catalytic efficiency was 2.02 times higher under natural light than relative to dark conditions. It was demonstrated by EPR and inhibition experiments that the main active species in the reaction were hydroxyl radicals and vacancies. The HOMO energy level and LUMO energy level of the intermediates were analyzed, and the possible degradation pathways of the active species were speculated. Evaluation of the biological toxicity of intermediates demonstrated that the system can effectively detoxify BPA. This investigation provides a reference method to enhance the efficiency of the photo-Fenton reaction of MOFs.