Abstract:

The development of efficient and stable photocatalysts is highly desired and significantly critical for the current environmental field. In this paper, a novel Ag/NH₂-MIL-125(Ti) was successfully prepared by solvothermal coupled with simple ultraviolet(UV) reduction method. The morphology, structure and optical properties of as-prepared samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), UV-Vis diffuse reflectance spectra(DRS) and X-ray photoelectron spectroscopy(XPS). The photo-reduction performance of obtained catalysts were tested on Cr(Ⅵ) removal in various conditions. Under visible light irradiation(λ≥420 nm), the catalysts dosage, heavy metal concentration, pH and hole scavenger were fully investigated to optimize the best Cr(Ⅵ) reduction parameters. The results indicate that Ag/NH₂-MIL-125(Ti) exhibits excellent adsorption and photo-reduction activities on Cr(Ⅵ), which is 3.11 times higher than that of NH₂-MIL-125(Ti). This special “sesame cakes” and heterojunction formation of Ag/NH₂-MIL-125(Ti) are attributed to enhancing Cr(Ⅵ) catalytic reduction performance. Meanwhile, through the control experiments, the main active species during the photo-reduction route were suggested and the mechanism of the Cr(Ⅵ) reduction was proposed. This study will provide theoretical and experimental guidance for the application of novel metal-organic framework(MOF) composites in the field of environmental remediation.

Key words: metal-organic framework, Ag nanoparticle, visible light photocatalysis, Cr(Ⅵ) reduction;