Silver nanoparticles embedded on magnetite-coated UiO-66 microspheres for enhanced nitroarene reduction

This study explores the synthesis and catalytic properties of silver nanoparticles (AgNPs) embedded on magnetite-coated UiO-66 microspheres (Fe 3 O 4 /UiO-66(Zr)/Ag) for efficiently converting 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The inclusion of hollow Fe 3 O 4 microspheres in the composite serves a dual purpose: enhancing catalytic activity and facilitating easy magnetic recovery. Concurrently, UiO-66(Zr), with its high surface area, aids in the effective adsorption and loading of AgNPs, which act as the primary catalyst for the conversion of 4-NP to 4-AP. The combination of AgNPs, the Fe 3 O 4 microstructure, and UiO-66 properties aims to enhance catalytic performance. The investigation into the effect of various experimental parameters revealed optimal conditions for maximum catalytic activity at an initial Ag + concentration of 7.5 mM, a catalyst mass of 3 mg, pH 5, and a reaction temperature of 30 °C. Fe 3 O 4 /UiO-66/Ag exhibited superior performance with a reaction rate constant of 0.284 min −1, surpassing Fe 3 O 4 /Ag, Fe 3 O 4 /UiO-66, and Fe 3 O 4 by 2.3-fold, 83.5-fold, and 91.6-fold, respectively. The reduction mechanism involves sequential steps of adsorption, electron transfer, and synergistic interactions among catalytic components (Fe 3 O 4, UiO-66, AgNPs). Crucially, AgNPs played a pivotal role in accelerating the electron transfer process, facilitating the reduction of 4-NP to 4-AP. Remarkably, the catalyst demonstrated not only excellent stability but also impressive recyclability, maintaining a conversion rate exceeding 92 % over five consecutive reuses. Metal leaching concentrations remained well within established safety thresholds for drinking water. Overall, Fe 3 O 4 /UiO-66/Ag emerges as a highly efficient and recyclable catalyst with promising applications in environmental remediation.