Photocatalytic properties of MOF-derived ZnO/C, Ag/ZnO/C porous composite materials

Two photocatalytic materials, ZnO/C and Ag/ZnO/C, were synthesized by high temperature heat-treatment and wet-chemical methods using a typical metal-organic framework (MOF-5) as precursor. The samples were characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), X-ray energy dispersive spectroscope (EDS), and UV-Vis diffuse reflection spectroscope (UV-Vis DRS), respectively. After heat-treatment under nitrogen, the initial morphology of MOF-5 is mostly retained. As a result, relatively high surface area up to 390 m²/g of ZnO/C and 232 m²/g of Ag/ZnO/C are realized. The size of Ag particles loaded on Ag/ZnO/C is about 30 nm. The photocatalytic efficiencies of both ZnO/C and Ag/ZnO/C composites on photo-degradation of methylene blue (MB) are higher than that of commercial TiO₂ powder (Degussa P25). Ag/ZnO/C possesses even higher photocatalytic ability, repeatability and stability than does ZnO/C. The results strongly suggest that high temperature heat-treatment of the MOF properly followed by moderate silver doping is a facile way to improve the photocatalytic properties.