| Summary: | Cr(VI) is one of the most toxic heavy metals, posing multiple threats to humans and ecosystems. Photoreduction of toxic Cr(VI) to para-toxic Cr(III) is one of the most effective ways to remove heavy metal chromium but is still challenging. Herein, Ti<sub>3</sub>C<sub>2</sub>/UiO-66-NH<sub>2</sub> composites with different ratio of Ti<sub>3</sub>C<sub>2</sub> were synthesized via an in situ solvothermal process and used for the enhanced photocatalytic removal of Cr(VI) for the first time. The UiO-66-NH<sub>2</sub> nanoparticles were dispersed on the surface and slits of accordion-like Ti<sub>3</sub>C<sub>2</sub> homogeneously. A strong interfacial interaction between Ti<sub>3</sub>C<sub>2</sub> and UiO-66-NH<sub>2</sub> was formed, which was indicated by the XPS. The Fermi level of the MXene cocatalyst is lower than UiO-66-NH<sub>2</sub>; thus, Ti<sub>3</sub>C<sub>2</sub> can serve as the electron sink and accumulate photogenerated electrons from UiO-66-NH<sub>2</sub> on its surface. A depletion layer was also formed due to the different Fermi levels of UiO-66-NH<sub>2</sub> and Ti<sub>3</sub>C<sub>2</sub>, which prevents electrons from flowing back to UiO-66-NH. The strong interfacial interaction and formed depletion layer are beneficial for the following charge transfer from UiO-66-NH<sub>2</sub> to Ti<sub>3</sub>C<sub>2</sub> after light irradiation and for suppressing the photogenerated charge recombination. With suitable band positions and enhanced charge separation ability, Ti<sub>3</sub>C<sub>2</sub>/UiO-66-NH<sub>2</sub> composites exhibited better photoreduction efficiency of Cr<sub>2</sub>O<sub>7</sub><sup>2−</sup> than pure Ti<sub>3</sub>C<sub>2</sub> and UiO-66-NH<sub>2</sub>, with optimized samples reaching 100% in 40 min. The photoreduction kinetics of Cr<sub>2</sub>O<sub>7</sub><sup>2−</sup> by 2-T/U was also studied, with a photoreduction rate of 0.0871 min<sup>−1</sup>, which is about 2.6 times higher than that of the pure UiO-66-NH. This research provides a new type of efficient and environmentally friendly photocatalysts for the photoreduction of Cr<sub>2</sub>O<sub>7</sub><sup>2−</sup>.
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