Highly microporous monodisperse silica spheres synthesized by the Stöber process

Abstract

Silica spheres that are prepared by the Stöber process are usually considered non-porous. Here we report on a slightly modified synthesis protocol that allows preparation of microporous Stöber particles. Successive treatment with water and alcohol at room temperature results in substantial reorganization of the silica within the Stöber particles. Hydrolysis of alkoxy groups as well as condensation and re-esterification of silanol groups upon re-immersion in alcohol are crucial for that process. As the result of the silica reorganization, micropore channels are formed within the particles. After a final washing with water to remove all alkoxy groups from the particles, pure microporous silica spheres are obtained. The total pore volumes of these materials are comparable to those of zeolitic materials.