Ag(I)-grafted UiO-67 to enhance the photochemical efficiency under visible light for highly efficient photocatalytic reduction of Cr(VI) and degradation of reactive blue 13

Abstract

As a new kind of organic-inorganic hybrid semiconductor materials, MOFs have come into focus as photocatalysts for decontamination of Cr(VI) oxates and reactive dyes from contaminated water. However, although most Zr-MOFs exhibit hydrolytic stability, they absorb almost only ultraviolet light. Assembly of MOFs with both hydrolytic stability and high visible light responsiveness thus has become a most feasible avenue recently. Here, composite of Ag@UiO-67 was intentionally designed by modifying the classical Zr-MOF of UiO-67 with highly photosensitive Ag+ ions. Results suggested that compared with pristine UiO-67, Ag@UiO-67 displays significantly narrowed band gap (Eg) value, sufficiently negative conduction band (CB) potential, suitable valence band (VB) potential and significantly improved charge transfer efficiency. Notably, the Eg value of 2.09 eV gives Ag@UiO-67 excellent ability of visible photocatalytic reduction of Cr(VI) and degradation of Reactive dark blue K-R (RB13), with reduction and degradation efficiencies of 91.37 % within 140 min (k = 0.024 min−1) and 92.63 % within 160 min (k = 0.016 min−1), respectively, which are 5.6 and 6.9 times of as synthesized UiO-67. Moreover, photocatalytic mechanism studies reveal that ·O2– plays key roles in bleaching RB13 and photogenerated species with sufficient negative potential can effectively reduce Cr(VI). And Ag@UiO-67 can utilize visible light more efficiently to accelerate the charge transfer rate. This work provides a feasible avenue to tailor the visible light sensitivity and band structure of classic Zr-MOFs, for eliminating inorganic and organic contaminants such as Cr(VI) ions and dye of RB13.