Strategies for the Control of Porosity around Organic Active Sites in Inorganic Matrices

Abstract

The functionalization of inert supports with catalytic sites has been utilized for the preparation of solid catalysts for decades. Recently, there has been a surge in the use of silane chemistry to functionalize the surfaces of porous silica materials to create high surface area, catalytically active solids. Silica-organic hybrid materials have been prepared with acidic, basic, oxidizing and reducing catalytic sites, with most attention directed at creating new or unique molecular sites on the silica surface. Whereas the molecular structure of the active site can be of paramount importance in homogeneous catalysts, in heterogeneous catalysts both the structure of the active site and the porosity around the active site are of extreme importance, since reactant and product diffusion can strongly influence catalytic function. Here, strategies for the control of porosity around organic active sites in silica hosts are discussed.