General synthesis of a mesoporous composite of metal oxide and silicate nanoparticles from a metal salt and laponite suspension for catalysis

A general approach is proposed for the synthesis of thermally stable and highly porous composite structures of metal oxide and silicate nanoparticles from aqueous solution of a metal salt and a suspension of Laponite clay. The formation of the mesoporous structure involves coupled processes: acid leaching of the Laponite clay sheets by acidic aqueous solution of the metal salt and polymerization of the metal hydrate species due to the high pH of the Laponite suspension. The extent of the acid leaching varies with the acidity of the metal salt solution. Moreover, introducing poly( ethylene oxide) surfactants in the synthesis significantly increases surface areas and porosity of the products. The nanocomposites obtained possess large porosity, large accessible surface area of metal oxide nanocrystals, and ion exchange capacity. They can be readily granulated, and metals can be loaded onto the solids by ion exchange and exist in highly dispersed metal nanocrystals. They have been found to be superior photocatalysts or supports for metal catalysts. The reaction mechanism of the synthesis is distinctly different from that for the synthesis of conventional pillared intercalated layered clays. This synthesis approach is an effective approach for constructing nanocomposites with a large porosity and structure and surface chemistry that can be tailored.