Gold nanoparticles supported on mesoporous silica: origin of high activity and role of Au NPs in selective oxidation of cyclohexane

Abstract

Homogeneous immobilization of gold nanoparticles (Au NPs) on mesoporous silica has been achieved by using a one-pot synthesis method in the presence of organosilane mercapto-propyl-trimethoxysilane (MPTMS). The resultant Au NPs exhibited an excellent catalytic activity in the solvent-free selective oxidation of cyclohexane using molecular oxygen. By establishing the structure-performance relationship, the origin of the high activity of mesoporous supported Au catalyst was identified to be due to the presence of low-coordinated Au (0) sites with high dispersion. Au NPs were confirmed to play a critical role in the catalytic oxidation of cyclohexane by promoting the activation of O2 molecules and accelerating the formation of surface-active oxygen species.

Stable and solubilized active Au atom clusters for selective epoxidation of cis-cyclooctene with molecular oxygen

“…Since the auto-oxidation was rather insensitive to the concentration of Au (within a factor of two for [Au] ranging from 20 to 120 ng ml −1 ), an inflated value of TOF could reach as high as 7,000 s −1 . For reactions that involve complex radical chain mechanism such as cyclohexane oxidation, often the contributions to the rate by Au catalyst and auto-oxidation are not separated but attributed entirely to Au, resulting in over-estimated values of TOFs2425.…”

Ru Nanoparticles Embedded in Cubic Mesoporous Silica SBA-1 as Highly Efficient Catalysts for Hydrogen Generation from Ammonia Borane

“…Unfortunately, agglomeration of metal NPs still takes place because of the poor electrostatic interaction between the pure mesoporous silica and the metal NPs that decrease the performance of the catalyst. The surface of the mesoporous silicas is hence altered by integrating organic functional groups, such as carboxylic acid (-COOH) [43], amino (NH 2 ) [44], and thiol (SO 3 ) [45] etc., to confine the metal NPs firmly within the support.…”

Supported Gold Nanoparticles as Reusable Catalysts for Oxidation Reactions of Industrial Significance

“…They have been used successfully in cyclohexane oxidation. Some of the supports used are carbon materials, metal oxides, metal–organic frameworks, zeolites, mesoporous and other silica‐based, materials, modified aluminas, hydroxyapatite, C 3 N 4 , and photocatalytically active materials . There is no consensus on if Au acts as a catalyst or as a promoter of the autoxidation reaction .…”