Tuning Catalytic Sites in Au/Mesoporous Silica Nanocatalyst for Highly Efficient Hydrogenation of 4-Nitrophenol

Regulating the dispersion of metal nanoparticles in supported metal catalysts is crucial for enhancing the catalytic activity and selectivity for a variety of hydrogenation reactions. However, the application of these supported catalysts in achieving highly efficient catalytic hydrogenation reactions still remains ambiguous due to the difficulties associated with stability and controlling the distribution of active catalytic sites onto the support materials. Herein, we report a cost-effective methodology to obtain Au nanoparticles (Au NPs)-supported mesoporous SiO2 (Meso-Au/SiO2) catalysts with highly exposed active sites for enhancing the catalytic selectivity toward hydrogenation of 4-nitrophenol(4-NP) to 4-aminophenol (4-AP) as a model catalytic system. The results revealed that by increasing Au-metal loading in Au/meso-SiO2 catalysts, the metal dispersion and catalytic activity can be effectively tailored. At an optimum Au-loading (about 6.04 wt %), the Au/meso-SiO2 catalyst exhibited maximum catalytic activity with a rate constant (Kapp) of 0.432 min–1 and a good stability of about 40% after four cycles compared with other obtained catalysts. Importantly, the observed Kapp value is much greater compared with the commercial Au/γ-Al2O3(c) and Au/SiO2(c) catalysts under similar conditions. This facile approach enables designing highly efficiently supported catalysts with exposed active sites for maximizing catalytic activity for efficiently removing organic pollutants from aqueous solutions.