Zr-MOFs based BiOBr/UiO-66 nanoplates with enhanced photocatalytic activity for tetracycline degradation under visible light irradiation

The concern about the removal of antibiotics and utilization of solar energy on environmental modification has motivated the development of photocatalysts. In this work, an organic-inorganic composite based on zirconium metal-organic frameworks and BiOBr/UiO-66 nanoplates was successfully synthesized by a facile in situ assembly. The BiOBr/UiO-66 nanocomposites presented distinctly enhanced photocatalytic degradation performance and mineralization ability toward the tetracycline (TC) under visible light irradiation. The maximum degradation activity was about 2.15 times higher than that of pristine BiOBr, and the 83.84% mineralization rate was obtained within 150 min, when the UiO-66 reached 8% in the mass ratio of raw materials, compared to theoretical BiOBr. According to the analysis of morphology characterization, phase structure, optical performance, and electrochemical measurements, the enhancement of the photo-generated electron-hole pair transfer and separation efficiency led to the improved photocatalytic performance of BiOBr/UiO-66. The reactive species were also tested through radical scavenging experiments, revealing that the main active radicals were superoxide radicals and holes during the degradation of TC. Additionally, a probable degradation route of TC has been proposed after high-performance liquid chromatography and LC/MS-MS analysis, and the photo-oxidative mechanism of TC degradation was further explored with the energy band structure measurement.