In Situ Growth of Ti3C2/UiO-66-NH2 Composites for Photoreduction of Cr(VI)

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, Ti3C2/UiO-66-NH2 composites with different ratio of Ti3C2 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-NH2 nanoparticles were dispersed on the surface and slits of accordion-like Ti3C2 homogeneously. A strong interfacial interaction between Ti3C2 and UiO-66-NH2 was formed, which was indicated by the XPS. The Fermi level of the MXene cocatalyst is lower than UiO-66-NH2; thus, Ti3C2 can serve as the electron sink and accumulate photogenerated electrons from UiO-66-NH2 on its surface. A depletion layer was also formed due to the different Fermi levels of UiO-66-NH2 and Ti3C2, 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-NH2 to Ti3C2 after light irradiation and for suppressing the photogenerated charge recombination. With suitable band positions and enhanced charge separation ability, Ti3C2/UiO-66-NH2 composites exhibited better photoreduction efficiency of Cr2O72- than pure Ti3C2 and UiO-66-NH2, with optimized samples reaching 100% in 40 min. The photoreduction kinetics of Cr2O72- by 2-T/U was also studied, with a photoreduction rate of 0.0871 min(-1), 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 Cr2O72-.

Automated summary

Ti3C2/UiO-66-NH2 composites with different ratios of Ti3C2 were synthesized via an in situ solvothermal process and used for the enhanced photocatalytic removal of Cr(VI) for the first time. The strong interfacial interaction between Ti3C2 and UiO-66-NH2 and the formed depletion layer are beneficial for efficient charge transfer and suppressing charge recombination. The Ti3C2/UiO-66-NH2 composites exhibited better photoreduction efficiency of Cr2O72- than pure Ti3C2 and UiO-66-NH2, with optimized samples reaching 100% in 40 min.