Catalytically active gold nanoparticles confined in periodic mesoporous organosilica (PMOs) by a modified external passivation route

A modified external passivation route was performed to control the distribution of gold nanoparticles in periodic mesoporous organosilica (PMOs). The surfactants were first removed completely to ensure enough space in the mesopores. The external surface was then functionalized with n-octadecyltrimethoxysilane (C18TMS), and finally the internal surface was modified with aminopropyltrimethoxysilane (APTMS) to enhance the adsorption of (HAuCl4)− complex, followed by the reduction under hydrogen atmosphere. The external passivation aims to prevent the formation of large aggregated gold particles on the exterior surface. The aminopropyl groups at the internal surface ensure the incorporation of gold nanoparticles with a size about 5 nm inside the pore channels of PMOs. A combination of high-resolution TEM/STEM and SEM shows that the selective surface functionalization can effectively avoid the growth of large gold particles at the external surface and strictly confine the gold nanoparticles within the pore channels of PMOs. The confined gold nanoparticles in PMOs exhibit good catalytic properties in the reduction of methylene blue (MB) dye with sodium boron hydride as reducing agent.