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 (E-g) 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)-O-center dot and(center dot)O(2)(-) all promoted the degradation of TC, following the order of h(+)>(OH)-O-center dot> O-center dot(2)-. Moreover, CAU-17-0.02 S presented a good reusability with slight performance loss after four cycles.

Automated summary

In this study, sulfur-doped Bi-based metal-organic framework material CAU-17 was synthesized and applied for photocatalytic degradation of tetracycline. The optimized CAU-17-0.02 S sample exhibited enhanced photocatalytic performance with a removal efficiency of 62.9% and a degradation rate constant 1.44 times higher than that of bare CAU-17. Reactive species trapping experiment revealed that photogenerated holes, hydroxyl radicals, and superoxide anion radicals all contributed to the degradation of tetracycline, with the photogenerated holes playing the most significant role. Moreover, CAU-17-0.02 S showed good reusability with slight performance loss after four cycles.