Interfacial Bi–O–Zn bonding induces faster charge transfer in S-scheme Bi-MOF/ZnFe2O4 heterojunction for enhanced photocatalytic tetracycline elimination

Abstract

Interfacial chemical bonding is essential for speeding up the separation and transfer of charge carriers at the heterojunction interface, thereby improving the photocatalytic activity. Herein, two-dimensional ZnFe₂O₄ nanosheets were grown in situ on Bi-MOF nanorods by a facile hydrothermal method, creating Bi-MOF/ZnFe₂O₄ heterojunctions with interfacial Bi–O–Zn bonds. The optimized sample (ZFB-2) exhibited significantly higher photocatalytic degradation efficiency of tetracycline hydrochloride (TC), which was 41.7 times and 2.0 times that of Bi-MOF and ZnFe₂O₄, respectively. Furthermore, ZFB-2 exhibited notable stability, demonstrating no obvious reduction in TC removal across five cyclic experiments, while also retaining its interfacial Bi–O–Zn bonds and morphology. The interfacial Bi–O–Zn bonds not only boosted the light absorption of ZFB-2 but also expedited the transfer of charge carriers via an S-scheme charge transfer pathway, functioning as conduits for charge transfer. It was found that h⁺ and ·O₂⁻ were the dominating active species, and the coexisting ions had a negligible effect on photocatalytic degradation of TC over ZFB-2. The potential degradation routes for tetracycline were outlined, and the toxicity of the resulting intermediates was assessed. This study offers a deep understanding of interfacial modulation of MOF-based S-scheme heterojunction photocatalysts and their enhanced performances in wastewater treatment for antibiotic removal.