Gold nanocatalysts represent a new generation of catalysts for the reduction of nitroarenes to aminoarenes using H2. However, activated carbon has been seldom used for gold deposition. Here a coordination-assisted self-assembly approach is adopted for the intercalation of monodispersed gold nanoparticles inside ordered mesoporous carbon frameworks. An almost complete conversion of benzyl alcohol to benzoic acid is achieved within 60 min over the 9 nm-Au/C catalyst under 90 °C and 1 MPa. A reduction of gold particle size from 9 to 3.4 nm in the catalyst leads to a high activity toward the selective oxidation of benzyl alcohol to benzyl acid and toward the reduction of p-nitrophenol to p-aminophenol at a low temperature of 0 °C. The electronic modification of the d-orbitals of small particles is extremely important for chemisorption of O2 at atmosphere pressure and low temperatures. Thermally reduced 2.8 nm Au nanocatalysts were highly active and selective, reaching an initial reaction rate of 12.7 and 6.5 min-1 to convert p-CNB and 4-NP using H2 as a reducing agent, respectively. The simultaneous thermal reduction of gold nanoparticles and pyrolysis of the matrix may facilitate the involvement of gold inside the carbon matrix, the modification of carbon atoms on the gold surface, and the reconstruction of the surface induced by CO adsorption. The generation of low-coordinated gold atoms possibly reduces the H2 dissociation barrier, and can therefore significantly improve the hydrogenation activity. In addition, the encapsulation of gold nanoparticles inside carbon matrix enhances the stability.

Ordered mesoporous carbon confined gold nanocatalyst

2019 Spring National Meeting

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