Abstract
Here we demonstrate for the first time a novel nanosieve approach for tuning the size, shape, dispersion and the quantity of the gallium oxide nanoparticles inside a mesoporous silica support with a three dimensional porous structure, high surface area, and large pore volume (KIT-6). It was found that the size and shape of the gallium oxide nanoparticles in the pore channels of the KIT-6 can be controlled by simply tuning the pore diameter of the support. The obtained gallium oxide/KIT-6 nanocomposites with different gallium oxide contents have been characterized by several characterization techniques such as powder XRD, SAXS, nitrogen adsorption, UV-Vis, FT-IR, HRSEM and HRTEM. XRD, HRTEM and nitrogen adsorption results reveal that the mesostructural order of the KIT-6 materials was not affected even after the encapsulation of ca. 30 wt% gallium oxide nanoparticles. UV-Vis results reveal that bandgap of the materials can be controlled by simply changing the concentration of the gallium oxide or varying the pore diameter of the support. The above catalytic materials have been also successfully employed for the benzylation of benzene and other aromatic compounds. The role of the pore diameter of the support, the loading of the metal oxide nanoparticles and other reaction parameters affecting the activity of the catalysts has been clearly demonstrated. It has been found that gallium oxide supported KIT-6 materials are highly stable and active, and show superior performance over other metal substituted mesoporous and zeolite materials with a high substrate conversion and a high product selectivity in the alkylation of benzene under the optimized reaction conditions.