Silver decorated magnetic MIL-100 composite: an efficient catalyst for catalytic reduction of 4-nitrophenol

Abstract Metal–organic frameworks provide advantages as supporting material due to their three-dimensional porous structures, high stability, porous structures, and high specific surface areas. In this study, the metal–organic framework “MIL 100” was synthesized in the presence of thioglycolic acid-coated magnetic core “Fe 2 O 3 @TGA” by using iron (III) as a metal node and trimesic acid as an organic binder. After polydopamine (PDA) coating of magnetic MOF structures, silver nanoparticles “Ag” were loaded onto magnetically separable support material “Fe 2 O 3 @TGA@MIL 100@PDA@Ag” and used for catalytic reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP). The as-prepared catalysts were characterized using XRD, FT-IR, TGA, SEM, TEM, BET, and XPS techniques. TEM images confirmed that iron oxide nanoparticles between 30 and 50 nm were incorporated into the MOF structures and then modified with silver nanoparticles between 10 and 20 nm. The hybrid material, with a surface area of 148.46 m 2 /g and a pore size of 62.80 Å, showed a saturation magnetization of 7.0 emu/g, which was sufficient for separation with an external magnet. Using Fe 2 O 3 @TGA@MIL100@PDA@Ag catalyst, reduction of 4-NP to 4-AP was finished in 5, 6, and 7 min for 0.5, 1.0, and 2.0 mM 4-NP concentrations, respectively. Additionally, it was observed that the reaction proceeded slowly in a dark environment but significantly faster under illumination. As a result, the Fe 2 O 3 @TGA@MIL100@PDA@Ag catalyst exhibited high catalytic activity and stability as well as reusability.