Preparation and Photocatalytic Reduction Performance of Cr(VI) by NH2-MIL-101(Fe, Co) Composite Catalyst

This study employed a solvothermal method to prepare an NH 2 -MIL-101(Fe, Co) bimetallic organic framework composite catalyst aimed at enhancing the photocatalytic reduction performance of Cr(VI). The experimental results show that introducing Co into the single-metal NH 2 -MIL-101(Fe) does not alter the material's octahedral structure. However, the bimetallic synergistic effect shifts the light absorption range to the red end of the spectrum, reduces the bandgap, and significantly improves carrier separation efficiency. Under visible light irradiation, the NH 2 -MIL-101(Fe, 0.15Co) catalyst exhibited outstanding photocatalytic performance, achieving a reduction efficiency of 94.7% for Cr(VI) within 40 minutes and 100% within 50 minutes, with a reaction rate constant 4.7 times that of the single-metal NH 2 -MIL-101(Fe). Free radical capture experiments further revealed that ·O 2 - is the key active species in the Cr(VI) reduction process, while photo-generated holes in the valence band can oxidise OH - to ·OH, synergistically participating in the reaction. Additionally, cyclic stability experiments showed that the catalyst maintained 85.8% reduction efficiency after five cycles, demonstrating excellent stability and practical application potential.