Synthesis and Characterization of Organic−Inorganic Modified Silica Hollow Nanoparticles for the Oxidation of Alcohols to Aldehydes and Ketones

We demonstrate the preparation and characterization of novel organic−inorganic hybrid palladium nanocatalyst fabricated via the covalent grafting of Pyr-ligand on chlorfunctionalized silica-hollow nanoparticles, followed by its metallation with palladium acetate for the selective oxidation of primary and secondary benzylic and aliphatic alcohols to give the corresponding carbonyl products in good yields. The reactions were carried out in ethanol in the presence of hydrogen peroxide as an oxidant at 50°C. Hollow nanoparticles can be synthesized with various materials such as organic polymer, silicates, carbon, titania, and phosphates [1]. In this work, we report on the synthesis of SiO2 hollow spheres using carbon nanospheres as templates. Acting as seeds, carbon nanospheres were then wrapped with a silica shell by the modified Stӧber method [2]. After calcination at 600 ̊C, uniform spheres with a thin shell of silica and hollow interior structures were synthesized. The synthesized substrates are in a spherical morphology and uniform size distribution. The nanostructure and properties of nanocatalyst were studied by TEM, SEM, XRD, TGA, and FT-IR characterizations.