A Visible Light Responsive Bi2S3/MIL-53(Fe) Heterojunction with Enhanced Photocatalytic Activity for Degradation of Tetracycline

Metal-organic frameworks (MOFs), as a new type of crystal materials, are considered a kind of promising photocatalysts. In this work, a novel Bi2S3/MIL-53(Fe) heterojunction photocatalyst was successfully prepared via a facile two-step method (hydrothermal and water bath). The characterization means, including XRD, SEM-EDS, FT-IR, XPS, PL, and UV-Vis, were employed to analyze the structural and morphological properties of Bi2S3/ MIL-53(Fe). The photocatalytic performance of Bi2S3, MIL-53(Fe), and Bi2S3/MIL-53(Fe) was evaluated by the removal efficiency of the photocatalytic degradation of tetracycline (TC, 10 mg/L) under visible light irradiation (& lambda; > 420 nm). The results show that the photocatalyst BSM-10 (the mass ratio of Bi2S3 to MIL-53(Fe) is 10:90) exhibits improved photocatalytic performance compared to Bi2S3 and MIL-53(Fe), showing the optimum photocatalytic activity (the degradation efficiency of TC is 90.9% within 120 min), and the corresponding first-order reaction rate constant is about 3 and 2 times higher than that of MIL-53(Fe) and Bi2S3, respectively. The improvement in photocatalytic activity is attributable to the efficacious separation of photogenerated electronhole pairs and significant acceleration of charge transfer rate. Based on the free radical trapping experiment and ESR test results, combined with the band structure of MIL-53 (Fe) and Bi2S3, we speculate that a heterojunction is formed between MIL-53 (Fe) and Bi2S3, and the proposed Z scheme mechanism can well explain the enhanced catalytic activity of BSM-10. The Bi2S3/MIL-53 (Fe) heterojunction photocatalyst synthesized in this work has potential application value for removing the typical pollutant tetracycline from water.