Boosted photocatalytic Cr(VI) reduction over Z-scheme MIL-53(Fe)/Bi12O17Cl2 composites under white light

Series MIL-53(Fe)/Bi12O17Cl2 (MBx) composites were constructed via facile ball-milling treatment of the MIL-53(Fe) octahedrons and Bi12O17Cl2 nanosheets. The addition of a specific quality of Bi12O17Cl2 was in favor of strengthening the transfer ability of photo-generated charge carriers in the composites, thereby further enhancing the photocatalytic performance. Being compared with pristine MIL-53(Fe) and Bi12O17Cl2, the MBx composites exhibited superior white-light-driven Cr(VI) photoreduction performance. The optimal MB100 photocatalyst displayed the best photocatalytic activity, in which 99.2% Cr(VI) can be eliminated within 90 min under white light illumination. Under the identical reaction conditions, it achieved 42.9% and 76.5% higher improvements as those of pure MIL-53(Fe) and Bi12O17Cl2. More than that, the MB100 also demonstrated good stability even after four cycles of testing experiments. At last, the corresponding reaction mechanism was clarified based on the electrochemical analysis and electron spin resonance (ESR) data. Such heterogeneous photocatalyst design strategy based on Fe-MOFs and bismuth-rich bismuth oxyhalides might provide new insights for treating Cr-containing wastewater.