Gold Nanoparticles Supported on Passivated Silica: Access to an Efficient Aerobic Epoxidation Catalyst and the Intrinsic Oxidation Activity of Gold

Well-defined and perfectly dispersed [(square SiO)Au(1)] surface species supported on silica have been obtained via surface organometallic chemistry and transformed upon mild reduction (H(2), 300 degrees C) into small (1.8 +/- 0.6 nm) Au particles supported on silica passivated with SiMe(3) functionalities. improved performance in liquid-phase aerobic epoxidation has been achieved, and the intrinsic activity of gold in oxidation is revealed

Methane Reacts with Heteropolyacids Chemisorbed on Silica to Produce Acetic Acid under Soft Conditions

Selective functionalization of methane at moderate temperature is of crucial economic, environmental, and scientific importance. Here, we report that methane reacts with heteropolyacids (HPAs) chemisorbed on silica to produce acetic acid under soft conditions. Specially, when chemisorbed on silica, H4SiW12O40, H3PW12O40, H4SiMo12O40, and H3PMo12O40 activate the primary C-H bond of methane at room temperature and atmospheric pressure. With these systems, acetic acid is produced directly from methane, in a single step, in the absence of Pd and without adding CO. Extensive surface characterization by solid-state NMR spectroscopy, IR spectroscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy suggests that C-H activation of methane is triggered by the protons in the HPA-silica interface with concerted reduction of the Keggin cage, leading to water formation and hydration of the interface. This is the simplest and mildest way reported to date to functionalize methane