Facile fabrication of flower-like NH2-UIO-66/BiOCl Z-scheme heterojunctions with largely improved photocatalytic performance for removal of tetracycline under solar irradiation

A novel Z-scheme 3D flower-like NH2-UIO-66/BiOCl composite was fabricated by a facile solvothermal method. The structural characterization results demonstrate that NH2-UIO-66 is embedded on the smooth surface of the flower-like BiOCl, forming a tight contact interface. As a visible light collector, NH2-UIO-66 expands the optical absorption range of BiOCl, which is confirmed by the UV-Vis diffuse reflectance spectra (DRS). By combining UV-Vis DRS, Mott-Schottky (MS) plots and VB-XPS, a well-matched band structure between NH2-UIO-66 and BiOCl is obtained. Photoelectrochemical characterizations indicate that the synergistic effect between NH2-UIO-66 and BiOCl interfaces facilitates the separation and transfer of photogenerated electron-hole pairs. In the case of photocatalytic performance experiments, the removal efficiency of the prepared NU66/BOC composites for TC-HCl was higher than either NH2-UIO-66 or BiOCl under simulated solar irradiation. NU66/BOC-20 exhibited the best performance with Kapp value (0.01269 min−1), which is 84 and 3 times more than the pristine NH2-UIO-66 (0.00015 min−1) and BiOCl (0.00410 min−1), respectively. In addition, NU66/BOC-20 composite demonstrates remarkable stability with a TC-HCl removal rate of 83% in the third cycle. The radical quenching experiments indicate that the primary active species is superoxide radicals (·O2−) while holes (h+) play a role to some extent. Based on the above experimental results and in-situ irradiated XPS, Z-scheme was proposed to explain the electron transfer pathway in the photocatalytic process.