Efficient photocatalytic degradation of tetracycline under visible light by Z-scheme Ag3PO4/mixed-valence MIL-88A(Fe) heterojunctions: Mechanism insight, degradation pathways and DFT calculation

Herein, Ag3PO4/mixed-valence MIL-88A(Fe) [AMM] Z-scheme heterojunctions with an in-situ-generated photo–Fenton process were successfully constructed. The optimized AMM-20 heterojunctions show the maximum rate of photocatalytic TC degradation, which is 2.5 and 6.6 times of pristine Ag3PO4 and MIL-88A(Fe). The electronic and band structures of Ag3PO4, MIL-88A(Fe), m-MIL-88A(Fe) and AMM heterojunctions were deeply investigated by both experimental and theoretical simulation. The Z-scheme transfer pathway greatly accelerates the transfer rate of charge carriers and effectively inhibits the photocorrosion, leading to the improvement of photocatalytic activity and photostability. Moreover, the adjustment of the FeII/FeIII ratio of mixed-valence MIL-88A(Fe) further enhances the photocatalytic activity of the hybrid photocatalysts, benefiting from the promotion of the efficiency of the in-situ-generated photo-Fenton process. The Z-scheme transfer route coupling with an in-situ-generated photo–Fenton process was verified by the free radical trapping experiment, in-situ XPS measurement, in-situ ESR measurement, and coumarin fluorescence analysis. The degradation pathways of TC were determined through LC-MS analysis and theoretical calculation. Furthermore, the toxicity of intermediates was evaluated by QSAR prediction.