Programmed synthesis of magnetic mesoporous silica nanotubes with tiny Au nanoparticles: A highly novel catalyst system

Magnetic mesoporous silica nanotubes were produced from carbon nanotubes using a well-controlled programmed synthesis method and were characterized by TEM, XRD, XPS, N₂ adsorption-desorption and VSM. The well-designed nanotubes had a large specific surface area (1017 m² g^-1), a highly open mesoporous structure (∼3.2 nm) and high magnetization (18.6 emu g^-1). Ultrafine gold nanoparticles were successfully supported on the thiol-modified nanotubes by a co-precipitation method. These unique multicomponent nanotubes showed high performance in the catalytic reduction of 4-nitrophenol (with a conversion of 99% in 6 min), and styrene epoxidation with high conversion (65%) and selectivity (58%). Interestingly, the new catalysts could be recovered by magnetic separation from the reaction mixture and could be recycled several times without any significant loss in activity. The unique nanostructure of the nanotubes resulted in a novel, stable and easy to use catalyst system for application in various industrial processes.