Au nanoparticles confined in hybrid shells of silica nanospheres for solvent-free aerobic cyclohexane oxidation

Gold nanoparticles (NPs) confined in hybrid shells of organic linker-assisted silica nanospheres (GOS) have been prepared through a facile approach using organic amino functional groups covalently bound to shells of silica nanospheres for anchoring AuCl4 (-). Due to the hydrolysis of urea, the gold precursor was in situ reduced in the hybrid shells of silica nanospheres under desired alkaline and temperature conditions. Organic functional groups (-SiCH2CH2CH2NHCH2CH2NH2) were introduced into shells of silica nanospheres via a co-condensation of tetraethyl orthosilicate and 3-(2-aminoethylamino)propyl dimethoxymethylsilane. The results indicate that Au NPs with < 2 nm diameters were highly dispersed and well confined in the hybrid shells of silica nanospheres through the anchorage of organic functional groups under condensation process. The obtained GOS catalyst exhibited efficient catalytic activity for solvent-free catalytic oxidation of cyclohexane with 94.8% selectivity to cyclohexanone and cyclohexanol (KA oil) and adipic acid under 150 A degrees C, 1.5 MPa O-2 for 3 h.