Acid red 14 (AR14) is a widely used azo dye that belongs to a major family of commercial dyes employed extensively in the textile industry. The present study aimed to investigate the photocatalytic discoloration of AR14 using a visible-light-responsive catalyst. The composite catalyst was synthesized by integrating thermally modified MIL- 101 (M-MIL) integrated into bismuth oxide. Thermal modification of MIL-101 produced octahedral α-Fe2O3 particles with a size of 1–2 µm, which were incorporated into bismuth oxyiodide (BiOI) featuring a nanosheet structure. BiOI@M-MIL composite exhibited an enhanced photocatalytic activity. The bandgap energy, Eg, of BiOI was reduced from 1.95 eV to 1.73 eV in the composite. Photocatalytic reactions were performed under visiblelight irradiation using a 5 W cold LED lamp. The AR14 discoloration tests demonstrated that BiOI@M-MIL was 1.81-fold more efficient compared to pristine BiOI. Key parameters affecting AR14 discoloration —such as catalyst dosage, pH, dye concentration, and contact time, were investigated. The composite achieved almost a complete dye removal efficiency of 94.26% under experimental conditions. Radical trapping tests highlighted the crucial role of superoxide radicals, ????ଶ.ି, in the dye discoloration process. BiOI@M-MIL takes advantage of simultaneous adsorption and photocatalysis with the highest adsorption capacity of 45.32 mg g−1 and 32.2 mg g−1, based on Sips and Langmuir models, respectively. The catalyst also showed good reusability and ~14% loss in removal efficiency after five consecutive cycles. In conclusion, the BiOI@M-MIL composite demonstrates excellent photocatalytic performance, combining low energy consumption with material stability, making it a promising candidate for AR14 discolorati

Keywords