Efficient visible-light photocatalytic degradation of reactive blue 21 by a magnetically recoverable UiO-66-NH₂/Fe₃O₄/Ag₃PO₄ composite

The efficient removal of synthetic dyes from wastewater remains a critical challenge for sustainable water treatment. In this work, a magnetically recoverable hybrid MOF-based photocatalyst, UiO-66-NH 2 /Fe 3 O 4 /Ag 3 PO 4 , was successfully synthesized via a stepwise solvothermal strategy and evaluated for visible-light-driven degradation of Reactive Blue 21 (RB21). Unlike conventional photocatalytic systems, this study presents a novel ternary UiO-66-NH₂/Fe₃O₄/Ag₃PO₄ heterostructure for visible-light-driven degradation of Reactive Blue 21, integrating MOF-based adsorption, enhanced photocatalysis, and magnetic recovery. This synergistic design provides an efficient and recyclable platform for sustainable dye wastewater treatment. Structural and physicochemical characterizations (XRD, FTIR, SEM/EDS, TGA, DRS, and VSM) confirmed the successful formation of a well-integrated heterostructure with strong interfacial interactions. UV-Vis DRS analysis revealed that incorporation of Ag 3 PO 4 significantly narrowed the band gap from 2.96 eV for UiO-66-NH 2 /Fe 3 O 4 to 2.38 eV for the ternary composite, enhancing visible-light absorption. The photocatalyst exhibited excellent photocatalytic performance, achieving approximately 97% RB21 removal within 180 min under visible light irradiation at pH 5 using 25 mg of catalyst. The ternary composite demonstrated excellent stability and reusability over five consecutive cycles, with negligible loss in photocatalytic activity, and its inherent magnetic properties (imparted by Fe 3 O 4 ) facilitated convenient recovery and reuse. The enhanced photocatalytic performance is attributed to the synergistic effects among UiO-66-NH 2 , Fe 3 O 4 , and Ag 3 PO 4 , which promote efficient charge-carrier separation and extended visible-light harvesting. This work highlights the potential of the UiO-66-NH₂/Fe₃O₄/Ag₃PO₄ nanocomposite as an efficient, recyclable, and sustainable material for visible-light-driven treatment of dye-contaminated wastewater, with promising prospects for future environmental applications.