As can be inferred from the description of the surface chemistry of silica, one of the major adsorption applications of silica is the adsorption of polar molecules (see Chapter 6) [16]. On the other hand, many practical catalysts consist of one or several active components deposited on a high surface area sup- port. In heterogeneous catalysis, transition metal nanoparticles are supported on different substrates and utilized as catalysts for different reactions, such as hydrogenations and enantioselective synthesis of organic compounds [163], oxidations and epoxidations [164], and reduction and decomposition [151]. For example, a porous silica xerogel is a good support for Co in the Fischer–Tropsch catalysts for the diesel fuel conversion of syngas [165]. The surface decoration of partially agglomerated amor- phous silica nanospheres with SnOx nanocrystals of diameter 3–6nm to produce extremely small, tin oxide nanostructures on a silica nanosurface to produce improved catalysts was as well demonstrated [166]. Besides, in various organic syntheses, catalytic hydrogenation is carried out in a liquid phase using a metal, such as Pd, Pt, or Rh supported, in silica as the catalyst [167–170].