Efficient Photocatalytic Degradation of Tetracycline under Visible Light by an All-Solid-State Z-Scheme Ag3PO4/MIL-101(Cr) Heterostructure with Metallic Ag as a Charge Transmission Bridge

The Z-type Ag/Ag3PO4/MIL-101(Cr) heterojunction photocatalyst (referred to as AAM-x) was successfully prepared by a simple in situ precipitation method. The photocatalytic activity of the AAM-x samples was evaluated using a common tetracycline (TC) antibiotic. All AAM-x materials are more effective in removing TC than Ag3PO4 and MIL-101(Cr). Among them, AAM-3 exhibited efficient photodegradation efficiency and excellent structural stability, and the removal rate of TC (20 mg L–1) by AAM-3 (0.5 g L–1) under 60 min of visible light was 97.9%. The effects of photocatalyst dosage, pH, and inorganic anions were also systematically investigated. According to the X-ray photoelectron spectroscopy analysis, metallic silver particles appeared on the surface of the Ag3PO4/MIL-101(Cr) mixture during the catalyst synthesis. The results of photoluminescence spectra, photocurrent response, EIS, and fluorescence lifetime showed that AAM-3 has a high photogenic charge separation efficiency. An all-solid-state Z-type heterojunction mechanism including Ag3PO4, metallic Ag, and MIL-101(Cr) is proposed to rationalize the excellent photocatalytic performance and photostability of AAM-x composites and to explain the effect of metallic Ag acting as a charge transfer bridge. The TC intermediates were identified using liquid chromatography–mass spectrometry and possible routes of TC degradation were also discussed. This work provides a viable idea for removing antibiotics by an Ag3PO4/MOF-based heterogeneous structured photocatalyst.