Al2O3 anchored silver and gold nanoparticles as accessible, stable, and re-usable catalysts

Nanoparticles of silver and gold have become widely researched as homogeneous catalysts for organic transformations. Silver systems have shown promising activity but are often hindered by their instability and difficulty in recycling. In this work we present nanoparticles of silver and gold, colloidally stabilized on aluminum oxide, and their performance as re-useable catalysts for the reduction of 4-nitrophenol. Compared with more standard citrate stabilized catalyst nanoparticles (k = 0.71 and 0.17 min−1 for Ag and Au respectively), the aluminum oxide stabilized systems are significantly more active (k = 1.82 and 0.63 min−1 for Ag and Au respectively) due to increased surface site availability. Importantly, Al2O3 supported silver nanoparticles exhibit excellent activity/re-usability as redox catalysts that are stable across a surprising variation of reaction media, including halide salts. [Display omitted]