Silica-based, cubic mesostructures: Synthesis, characterization and relevance for catalysis

We review the formation mechanism, synthetic history and catalytic applicat ions of the cubic phases of mesoporous silica. MCM-48 and SBA-1, analogous to surfactant lyotropic liquid crystal phases, possess a three-dimensional pore array, a 15-30 Angstrom pore aperture and a narrow pore size distribut ion. Evidence for intermediate range order within the silicate walls based on PAS-FTIR spectra will be discussed. Isomorphic heteroatom substitution o f aluminum and a number of transition metals has been achieved by both hydr othermal and post-synthetic methods in order to modify the surface activity of these materials. Modified materials containing fully oxidized, early tr ansition metals were found to be catalytically active for photocatalytic re duction of CO2 with water as well as peroxidative oxidation and halogenatio n of large organic substrates.