A novel ZIF-8 and ZIF-67 co-modified TiO 2 nanospheres for highly efficient degradation of methylene blue under simulated sunlight

In this work, a novel ZIF-8 and ZIF-67 co-modified TiO 2 nanospheres with highly efficient degradation of organic pollutants was synthesized successfully. The structure, morphology, and chemical components of ZIF-8-67@TiO 2 were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffractometer, infrared spectroscopy, and X-ray Photoelectron Spectroscopy. The optical properties of all samples were analyzed by UV–Visible diffuse reflectance spectroscopy diffraction. It is found that after the growth of ZIFs on the surface of TiO 2 nanospheres, the specific surface area of TiO 2 was greatly improved. The light sensitivity area of TiO 2 is extended to include both the visible and ultraviolet spectrums by loading ZIF-8 and ZIF-67 nanoparticles. In addition, the construction of Z-scheme heterojunction also improves the separation of photocarriers, and the transfer of photogenerated charges between ZIFs and TiO 2 is accelerated by the formed N–Ti–O bonds, thus extending the lifetime of photogenerated charges and enhancing the catalytic activity. The ternary ZIF-8-67@TiO 2 demonstrates excellent photocatalytic activity and photoelectrochemical performance. The corresponding first-order kinetic constant (16.56 × 10 −3 min -1 ) of ZIF-8-67@TiO 2 is 11.6 times more than that of TiO 2 (1.43 × 10 −3 min −1 ). Especially, in strong alkaline environment ( pH = 12), methylene blue can be almost completely degraded within 15 min. Furthermore, ZIF-8-67@TiO 2 exhibits the maximum photocurrent density (36.69 µA/cm 2 ), which is 15.7 times greater than that of TiO 2 (2.33 µA/cm 2 ). Therefore, the co-modified TiO 2 nanospheres with ZIF-8 and ZIF-67 can serve as a promising route to fabricate photocatalytic membranes for use in the water treatment industry.