Z-scheme heterojunction BiOBr/MIL-100(Fe) visible photocatalytic-permonosulfate degradation of AO7.

Abstract

Metal-organic frameworks (MOFs) have garnered significant interest in the field of photocatalysis. In this study, Z-scheme heterojunction BM-x composites consisting of bismuth bromide oxide (BiOBr) and iron-based metal-organic backbone (MIL-100(Fe)) were successfully synthesized using ethylene glycol as a solvent. The composites were characterized using various techniques. BM-x exhibit abundant functional groups, large specific surface areas, and narrow band gap energy, thus provide numerous active sites for catalytic reactions and respond well to visible light. Notably, BM-7 displays remarkable catalytic activity in a visible light-activated permonosulfate (PMS) system and achieves a degradation rate of 99.02% over 100 mg/L gold orange II (AO7) within 60 min. The effects of BM-7 and PMS addition, initial AO7 concentration, initial pH, inorganic anions, and humic acid on the degradation system were investigated. The proposed mechanism of the Z-scheme heterojunction in the BM-7 photocatalyst demonstrates effective photoelectron transfer from the BiOBr conduction band to the MIL-100(Fe) valence band, resulting in excellent catalytic activity. Radical burst experiments identified ¹O₂, h⁺, and ·O₂^- as the main active substances. BM-7 has high stability and reusability, with a degradation rate reduction of only 14.48% after three recycles. These findings provide valuable insights into using persulfate combined with visible light.