Catalytic degradation of organic pollutants in water under visible light by BiOCl@NH2-MIL-125(Ti–Zr) composite photocatalyst

The pollutant degradation by visible light response photocatalysis is one of the most effective and environmentally friendly strategies, which eagerly expects the highly efficient catalysis. In this study, to incorporate the merits of BiOCl and NH2-MIL-125(Ti–Zr), and exploited their synergistic effect, a series of BiOCl@NH2-MIL-125(Ti–Zr) heterostructures with different NH2-MIL-125(Ti–Zr) contents were fabricated by solvothermal method. The characterization of BiOCl@NH2-MIL-125(Ti–Zr) was performed by XRD, SEM, FTIR, EIS, DRS, and PL. The results showed that NH2-MIL-125(Ti–Zr) bimetallic MOF is highly dispersed on the surface of BiOCl. Compared with the single photocatalyst NH2-MIL-125(Ti-Zr) and BiOCl, the composite photocatalyst BiOCl@NH2-MIL-125(Ti–Zr) demonstrated superior visible light photocatalytic activity. The enhanced performance is ascribed to the improved electron transfer efficiency by NH2-MIL-125(Ti–Zr) bimetallic organic framework and the high dispersion of BiOCl, as well as the formation of heterojunction structure between BiOCl and NH2-MIL-125(Ti–Zr), which separates the photogenerated electron–hole pairs effectively. The optimal content of NH2-MIL-125(Ti–Zr) was 40 wt%, and photocatalytic degradation rate of acid red B(ARB) was up to 89% in 270 min under visible light irradiation. The photocatalytic mechanism was also studied. The results showed that photogenerated hole (h+) and superoxide radical (·O2−) are the main active substances in photocatalytic degradation. After four repeated tests, the composite photocatalyst still has an excellent photocatalytic effect, indicating its high stability and repeatability. This work provides a new idea for the further photocatalytic degradation of pollutants in water.