Sulfur doped Bi-MOF with adjustable band gap for tetracycline removal under visible light

Visible light driven antibiotic degradation with metal-organic frameworks (MOFs) has been regarded as a feasible and efficient approach. Herein, Bi-based MOF (CAU-17) was synthesized and used for tetracycline (TC) removal. To enhance the photocatalytic performance, sulfur (S) element was doped on CAU-17 through solvothermal process. Characterization results verified that S element was successfully doped on CAU-17 and distributed uniformly. The introduction of S element could boost the generation of oxygen vacancies and tune the band gap of CAU-17. By optimizing the S content, the band gap energy (Eg) of CAU-17–0.02 S sample (0.02 g thiourea was added during the synthesis) reduces from 3.57 to 3.37 eV compared to pristine CAU-17. In addition, the visible light response was enhanced and the charge transfer resistance was reduced. TC removal tests demonstrated that CAU-17–0.02 S exhibited a removal efficiency of 62.9%, and the degradation rate constant is 1.44 times than that of bare CAU-17. Reactive species trapping experiment indicated h+,·OH and·O2- all promoted the degradation of TC, following the order of h+>·OH> ·O2-. Moreover, CAU-17–0.02 S presented a good reusability with slight performance loss after four cycles.