Synthesis of Metal Oxide Aerogels via Epoxide-Assisted Gelation of Metal Salts

Abstract

Over the past two decades, the diversity of metal and metalloid oxide materials prepared using sol–gel techniques has increased significantly. This transformation can be attributed in part to the development of the technique known as epoxide-assisted gelation. The process utilizes organic epoxides as co-reactants for the sol–gel polymerization of simple inorganic metal salts in aqueous or alcoholic media. In this approach, the epoxide acts as a proton scavenger, which drives hydrolysis and condensation of hydrated metal species in the sol–gel reaction. This process is generalizable and applicable to the synthesis of a wide range of metal and metalloid oxide aerogels, xerogels, and nanocomposites. In addition, modification of synthetic parameters allows for control over the structure and properties of the sol–gel product. The method is particularly amenable to the synthesis of multicomponent and nanocomposite sol–gel systems with intimately mixed nanostructures. This chapter describes both the reaction mechanisms associated with epoxide-assisted gelation and an overview of materials that have been prepared using this technique.