Facile construction of Z-scheme Fe-MOF@BiOBr/M−CN heterojunction for efficient degradation of ciprofloxacin

Abstract

A novel Fe-MOF@BiOBr/M−CN photocatalyst is synthesized via one-pot EG (ethylene glyco)-assisted solvothermal heating. The morphology, microstructure, and composition of the prepared catalysts are characterized by SEM, XRD, FTIR, and XPS. The Fe-MOF@BiOBr/M−CN photocatalyst exhibites better pollutant adsorption and degradation than pure BiOBr. After grafting iron-based metal–organic framework (Fe-MOF) and modified g-C3N4 (M−CN) species, photogenerated electrons can be transferred from BiOBr to M−CN and Fe-MOF species via interfacial charge transfer. Therefore, the separation efficiency of electrons (e−) and holes (h+) is enhanced. Fe-MOF@BiOBr/M−CN−50 can degrade approximately 93% of ciprofloxacin in 120 min under visible light illumination, which is 7.9 and 1.2 times that of pure g-C3N4 (11.8%) and BiOBr (77.4%), respectively. Furthermore, radical capturing experiments and ESR analysis reveal that h+ and ·O2− are the main reactive species in the system. A combination of DFT calculations and radical trapping experiments show that M−CN and BiOBr form a Z-type heterojunction. In addition, Fe-MOF plays a vital role as a carrier acceptor for electron transport. Finally, the degradation pathway of ciprofloxacin is revealed by gas-chromatography–mass-spectroscopy analysis. This study provides new insights into the photocatalytic degradation of pollutants in water.