This study investigates the synergistic photocatalytic activity of mixed bismuth oxyhalides (BiOI and BiOCl) and the critical role of iron doping in enhancing the Cr(VI) reduction. By employing FeCl3 as both a chloride source and iron dopant precursor, we achieved in situ Fe3+ incorporation into bismuth oxyhalides (BiOX; X = Cl/I) during a one-pot coprecipitation synthesis at room temperature. The resulting iron-doped BiOX formed flower-like particles integrated with NH2-UiO-66, a zirconium-based metal-organic framework (MOF), creating a Z-scheme heterojunction composite. The NH2-UiO-66/Fe-BiOX composite exhibited exceptional visible-light-driven Cr(VI) reduction, achieving 98% efficiency within 30 min (pH 2, 100 W LED). This performance surpasses that of the NH2-UiO-66/BiOI reference system (82% efficiency), highlighting the dual role of iron doping and mixed oxyhalide phases in promoting charge separation and suppressing recombination. Mechanistic studies revealed that photogenerated electrons and superoxide radicals (•O2-) act as primary reductants, with the Fe3+/Fe2+ redox cycle enhancing •O2- generation via efficient electron transfer.
Jalilian et al. (Thu,) studied this question.