UiO-66 with confined dyes for adsorption and visible-light photocatalytic reduction of aqueous Cr(VI)

Abstract

• Dye molecules confined in MOFs for continuous and stable photosensitization in a photocatalytic reaction. • Photocatalytic reduction of Cr(VI) in water at neutral pH without any sacrificial reagent. • Adjustment on surface electrostatic properties of UiO-66 by dye confinement and loading of Pt nanoparticles. • A simple and feasible method to enhance the visible-light photocatalytic ability of a MOF. Dye sensitization is an important method to improve the visible-light response of a photocatalyst. In order to obtain stable dye-sensitized MOF photocatalysts, UiO-66 with confined rhodamine B (RhB) and eosin Y (EY) dye were prepared by simply adding dyes in the synthetic process in this work. In comparison with pristine UiO-66, the obtained RhB@UiO-66 and EY@UiO-66 can not only adsorb Cr(VI) from water more effectively, but also enhance the photocatalytic reduction of Cr(VI) to Cr(III) at a neutral pH under visible-light without adding any sacrificial agent. Thus, they both achieved an overall Cr(VI) removal rate of about 99%. The loading of Pt nanoparticles can further improve the photocatalytic abilities of RhB@UiO-66 and EY@UiO-66. The highest photocatalytic removal rate of Cr(VI) over Pt/RhB@UiO-66 is 66.4%. The confinement of the dyes and the loading of Pt nanoparticles largely changed the surface electrostatic properties of UiO-66. The adsorption process of Cr(VI) was therefore affected. Meanwhile, Pt nanoparticles greatly improved the utilization efficiency of photogenerated electrons.