What is the effect of Sn and Mo oxides on gold catalysts for selective oxidation of benzyl alcohol?

A foam-like mesoporous silica (MCF)-supported gold (Au) nanoparticle (NP) catalyst was prepared by a facile one-pot synthesis strategy. SnO x and MoO x were introduced as promoters by a wet impregnation method to synthesize promoted catalysts Au-SnO x /MCF and Au-MoO x /MCF, respectively. The evaluation of the prepared catalysts in benzyl alcohol oxidation shows that introduction of a low amount of SnO x (0.2 wt%) leads to a higher catalytic activity, while a relatively high amount of SnO x (1.0 wt%) exhibits a lower catalytic activity than the unpromoted Au NP catalyst. Both characterization results and density functional theory (DFT) calculations suggest that the most important effect of SnO x species on gold catalysts is the strong interaction between them which leads to electron transfer and lattice distortion of Au NPs, providing more low-coordinated Au active sites. This structural modification enhanced the chemisorption of reactants and lowered the energy barrier for the dissociation of O 2 molecules on the surface of gold catalysts, improving the catalytic performance for benzyl alcohol oxidation. However, a weaker interaction was detected between MoO x and Au NPs on catalysts Au-MoO x /MCF and no lattice modification was observed; thus no improvement in the catalytic activity for benzyl alcohol oxidation occurred on catalysts Au-MoO x /MCF. A series of SnO x and MoO x promoted gold nanoparticle catalysts were used for the aerobic oxidation of benzyl alcohol.