A strategy to immobilize noble metal nanoparticles on silica microspheres

Abstract

A strategy to immobilize noble metal nanoparticles on silica microspheres is proposed. Following this strategy, 350 nm silica microspheres synthesized by Stöber method are initially activated with 3-(trimethoxysilyl) propyl methacrylate to anchor C C bonds on the surface of the silica microspheres. Then a thin layer of coordination polymer containing chelate ligand of β-diketone is coated on the surface of the activated silica microspheres by dispersion polymerization. The noble metal nanoparticles therefore can be immobilized on the polymer coated silica microspheres initially through coordination between the chelate ligand of β-diketone in the coating polymer and the metal precursors followed by reduction. It is found that 5.1 nm Pd, 6.1 nm Au, and 5.7 nm Ag nanoparticles can be immobilized on the polymer coated silica microspheres. The typical immobilized Pd catalyst is tested using hydrogenation of cinnamyl alcohol in water at 300 K as model reaction. The catalysis demonstrates that the immobilized Pd catalyst affords a turnover frequency of 270 h −1 with minimal leaching and it could be recycled ∼8 times without any loss of activity.