A visible light responsive Bi2S3/MIL-53(Fe) heterojunction with enhanced photocatalytic activity for degradation of tetracycline

Abstract

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 (λ > 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 electron-hole 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.