Optimized design of BiVO4/NH2-MIL-53(Fe) heterostructure for enhanced photocatalytic degradation of methylene blue and ciprofloxacin under visible light

Visible-light-driven type II BiVO4/NH2-MIL-53(Fe) (BNMF) heterostructure have been synthesized by a facile stepwise hydrothermal method. Specifically, four BNMF heterostructures with different material ratios (BNMF-10, BNMF-20, BNMF-30, and BNMF-40) have been obtained by adjusting the amount of NH2-MIL-53(Fe) (10, 20, 30, or 40 mg) on the BiVO4-based photocatalyst. The BNMF-30 sample exhibited enhanced photocatalytic activity under visible light, degrading 90.2% of methylene blue in 180 min and 80.8% of ciprofloxacin in 120 min. The apparent rate constants for methylene blue and ciprofloxacin degradation over BNMF-30 were 2.8 and 1.4 times higher than those over pure BiVO4. The enhanced photocatalytic activity of BNMF-30 can be mainly ascribed to the formation of a tight joint interface between BiVO4 and NH2-MIL-53(Fe), which not only facilitates the separation of photo-induced charge carriers, but also extends the light absorption range. Meanwhile, the NH2-MIL-53(Fe) component facilitates the adsorption of pollutants, expediting the interfacial oxidation–reduction kinetics. Moreover, superior stability of the BNMF-30 photocatalyst was observed over repeated cycles. Furthermore, ·OH, ·O2‾, and h+ have been identified as the main active radicals through trapping experiments, providing a mechanism for the enhanced catalytic performance.