Gold nanoparticles stabilized in a novel periodic mesoporous organosilica of SBA-15 for styrene epoxidation

The stabilization of gold nanoparticles (GNPs) by disulfide groups linked to imidazolium chloride units in a periodic mesoporous organosilica of SBA-15 and their catalytic performances in the epoxidation of styrene were investigated. The mesoporous organosilica (PMO-SBA-15) was synthesized via a one-pot condensation process involving the assembly of ionic liquid silsesquioxane organic precursor containing disulfide group and tetraethoxysilane (TEOS) in the presence of P123 (EO₂₀PO₇₀EO₂₀). Aqueous chloroaurate ions were in situ reduced by the silanol groups presented on the channel surface of the mesoporous organosilica to form GNPs that were subsequently captured by disulfide group to obtain Au-containing mesoporous organosilica (Au-PMO-SBA-15). The PMO-SBA-15 and Au-PMO-SBA-15 were characterized by XRD, ²⁹Si MAS-NMR, FT-IR, UV–vis, TEM and N₂ adsorption–desorption measurements. It was found that both PMO-SBA-15 and Au-PMO-SBA-15 had the typical characteristics of mesoporous SBA-15, and that the GNPs entrapped into the channels of Au-PMO-SBA-15 possessed mean size of ca. 1.8 nm. The Au-PMO-SBA-15 was used as a catalyst in the epoxidation of styrene. 95% of styrene conversion and 75% of selectivity to styrene epoxide were obtained over the novel Au-PMO-SBA-15 catalyst, which were higher than that over the reported nano-Au catalysts. Furthermore, the Au-PMO-SBA-15 could be conveniently recovered for recycled use without significant loss of catalytic activity and selectivity.