A Rod-like BiO Photocatalyst Derived from Bi-Based MOFs for the Efficient Adsorption and Catalytic Reduction of Cr(VI).

Heavy metal ion pollution poses a serious threat to the natural environment and human health. Photoreduction through Bi-based photocatalysts is regarded as an advanced green technology for solving environmental problems. However, their photocatalytic activity is limited by the rapid recombination of photogenerated e and h pairs and a low photo-quantum efficiency. In this work, an optimal precursor of Bi-based MOFs was identified by using different solvents, and rod-like BiO materials were derived by in situ oxidation of Bi atoms in the precursor. The adsorption and photocatalytic reduction efficiency of the prepared BiO materials for Cr(VI) were evaluated under visible light irradiation. The results showed that the prepared materials had a large specific surface area and enhanced visible light absorption. BiO(DMF/MeOH-3)-400 had a large specific surface area and many active adsorption sites, and it had the highest adsorption of Cr(VI) (49.13%) among the materials. BiO(DMF/MeOH-3)-400 also had the highest photocatalytic reduction efficiency, and it achieved 100% removal of 10 mg·L Cr(VI) within 90 min under light. In addition, the material showed remarkable stability after three consecutive photocatalytic cycles. The enhanced photocatalytic performance was mainly attributed to the fast separation of electron-hole pairs and efficient electron transfer in the MOF-derived materials, which was confirmed by electrochemical tests and PL spectroscopy. Reactive species trapping experiments confirmed that electrons were the main active substances; accordingly, a possible photocatalytic mechanism was proposed. In conclusion, this work provides a new perspective for designing novel photocatalysts that can facilitate the removal of Cr(VI) from water.