Preparation of mesoporous silica particles with carbon-coated pore walls: selective grafting of polyacrylonitrile onto the inner surface of a mesoporous silica particle and carbonization

Abstract

We prepared mesoporous silica particles with inner surfaces coated with carbonaceous materials. A functional mesoporous silica particle (FSP) having methoxy urethane moieties tethered to the pore wall was synthesized by the template method from tetraethoxysilane (TEOS) and an amphiphilic organotriethoxysilane bearing a thermally reversible urethane bond. The surfactant template molecules in the pores were extracted in methanol in the presence of HCl. An atom transfer radical polymerization (ATRP) initiator was selectively introduced onto the inner surface by the reaction of 2-hydroxyethyl-2-bromo-2-methylpropanoate with the methoxy urethane group. The ATRP of acrylonitrile was carried out inside the pores to yield polyacrylonitrile (PAN) grafted to the pore wall. Subsequent pyrolysis of PAN resulted in the formation of mesoporous silica particles with carbon-coated pore walls. The property changes in the inner surface were investigated by analyzing the hydrogen adsorption. Carbonized silica particles showed an improved hydrogen adsorption capacity of 1.26 wt% at 1 bar and 77 K compared to 0.46 wt% for FSP.