Hierarchically macro/mesostructured porous Au monoliths: simple synthesis, characterization and catalytic performance

Abstract

We report an efficient, highly selective and low-temperature three-dimensional hierarchically macro/ mesostructured porous gold monoliths catalyzed reaction process for one-step oxidation of benzene to phenol with hydrogen peroxide as the green oxidant. The porous catalysts were characterized before calcination by FTIR and TGA and after calcination by XRD, FESEM-EDX and BET techniques. The selectivity of phenol production from the one-step oxidation of benzene over porous gold catalysts can be enhanced by concise tuning of pore diameter and pore surface morphology. From the results obtained, it was concluded that the balance between the decomposition rate of H 2 O 2 and benzene adsorption over the catalyst surface is responsible for the outstanding catalytic performance of the three-dimensional macro/mesoporous gold monoliths. Graphical Abstract The as-synthesized series of nanoporous gold monoliths were evaluated for the first time as alternative heterogeneous catalysts for the direct catalytic oxidation of benzene to phenol at low temperature. Therefore, it is of great interest to ''switch-off'' other timeand energy-consuming reactions and promote the hydroxylation of benzene with porous Au catalysts.

Hierarchical synthesis of silver monoliths and their efficient catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol

“…Noble metal nanoparticles such as Ag, Au, and Pt have attracted immense interest because of their catalytic properties in diverse organic/inorganic reactions such as the reduction of nitroarenes, oxidation of CO to CO 2 and conversion of benzene to phenol. 1,2 Because of their high surface energy and large surface to volume ratio, nanoparticles coagulate or aggregate, change their shape, damage the surface states during catalytic reactions and lose their intrinsic activity and selectivity when they are used directly. 3 To overcome these problems, nanoparticles are encapsulated in polymers, hydrogels, porous monoliths, metal oxides, silicates, dendrimers, colloids, porous carbon and latex particles.…”