Functionalized a-Al2O3 supported gold catalyst for photocatalytic oxidative esterification of benzyl alcohol with methanol to corresponding esters

Alpha-alumina (& alpha;-Al2O3) is traditionally considered to be unsuitable as a support for high performance gold based catalysts because of its small specific surface area. Herein, a highly active & alpha;-Al2O3-supported nearly sub-nanometer Au particles photocatalyst for oxidative esterification of benzyl alcohol under visible-light irradiation in a mild condition was synthesized via the electronic interaction between gold precursor and a layer of 3-aminopropyltriethoxysilane (APTES) pre-grafted on the & alpha;-Al2O3 called as functionalized & alpha;-Al2O3. APTES could serve as a linker to strongly anchor Au nanoparticles (NPs) to & alpha;-Al2O3 surface, leading to nearly sub-nanometer Au particles (1.8 & PLUSMN; 0.1 nm). The enhanced metal-support interaction reinforces the interaction of plasmonic hot holes of Au NPs and intermediate molecules, which promote the rate-limiting step of C-H bond cleavage and facilitate the activation of oxygen molecules due to the increased electron cloud density around Au NPs. Meanwhile, & alpha;-Al2O3 support can play a synergistic role because of the reactant adsorption can be improved by the acid-base pairs contained.