Gold Nanoparticles Embedded in Poly(2,6-dimethyl-1,4-phenylene) Oxide Matrix: A Selective and Reusable Catalyst for Nitroarene Reduction via Polymer-Controlled Reaction Pathway

Gold nanoparticles (AuNPs) supported by a polymer matrix of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were investigated as a catalyst for the selective reduction of nitroarenes (NAs) to aniline derivatives (ANs), using sodium borohydride (NaBH4) as a reductant. A systematic investigation of reaction parameters, including temperature, solvent, and NaBH4 concentration, revealed a strong influence on both catalytic activity and product selectivity. Under optimised conditions (80 °C for 60 min using a [Nitrobenzene]/[Au] molar ratio of 510), the AuNPs-PPO catalyst achieved quantitative conversion and excellent selectivity toward aniline (AN) (>99%), with turnover frequencies (TOF) up to 510 h−1. Methanol (CH3OH) was identified as the optimal solvent, while lower reductant concentrations led to the formation of intermediates such as azobenzene (AB), azoxybenzene (AOB), and hydrazobenzene (HB), providing insight into the reaction pathway. The catalyst exhibited remarkable recyclability over multiple runs without significant loss of activity or structural changes, as confirmed by Wide-angle X-ray diffraction (WAXD) analysis. Furthermore, the catalytic system proved effective for a range of substituted nitroarenes (SNAs), demonstrating broad substrate scope and functional group tolerance. These results highlight the potential of AuNPs-PPO as a versatile, selective, and sustainable platform for the reduction of NAs under mild and environmentally benign conditions.