High Catalytic Activity and Kinetic Efficiency of Pd-Loaded Amino-Functionalized Silica-Coated Magnetite Nanoparticles for Nitroarene Hydrogenation

In this study, we report the synthesis, characterization, and catalytic performance of palladium-loaded amino-functionalized silica-coated magnetite nanoparticles (APSMNPs) as efficient and magnetically recoverable catalysts for aqueous-phase hydrogenation of nitroarenes. The APSMNPs were synthesized via a continuous-flow method and surface-engineered using varying ratios of aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS). Among them, the APSMNPs with a 1:1 TEOS/APTES ratio exhibited the highest Pd(II) adsorption capacity. Upon reduction of Pd(II) to Pd(0), the resulting catalyst demonstrated exceptional activity in the hydrogenation of 4-nitrophenol and various nitroanilines under mild aqueous conditions. The catalyst followed pseudo-first-order kinetics with a high apparent rate constant (kapp = 1.500 min–1) and a turnover frequency (TOF) of 1428 h–1, indicating superior catalytic efficiency. Notably, the APSMNPs–1:1–Pd(0) catalyst maintained >95% conversion over five reuse cycles with negligible activity loss and could be easily separated by an external magnet. This work underscores the potential of structurally engineered magnetic nanocatalysts for sustainable and high-performance hydrogenation processes in green chemistry.