| abstract |
A neutral templating route to mesoporous molecular sieves based on H-bonding and self-assembly between neutral primary amine or diamine surfactants (S DEG ) and neutral inorganic precursors (I DEG ) has been used to prepare hexagonal and lamellar mesoporous silicas with site isolated transition metal centers. This templating approach allows for the preparation of hexagonal or hexagonal-like mesoporous oxidation catalysts with large framework wall thickness of at least about 17 ANGSTROM , small elementary particle size (</=400 ANGSTROM ), and unique combinations of framework-confined mesopores and textural mesopores while at the same time providing for facile recovery of the neutral template by simple solvent extraction. The templating of neutral metallosilicate precursors (I DEG ) with neutral diamine surfactants (S DEG -S DEG ) affords thermally stable pillared lamellar metallosilicates exhibiting complementary framework-confined microporosity and textural mesoporosity while at the same time also providing for template recovery by solvent extraction. In addition, a hexagonal transition metal-substituted catalysts, analogous to MCM-41, have been prepared using the mediated S+X-I+ templating pathway (Pathway 3) and mild reaction conditions. These new mesoporous metallosilicate molecular sieves exhibit exceptional catalytic activity for peroxide hydroxylation of benzene and oxidation of substituted aromatics with kinetic diameters that are too large (larger than 6 ANGSTROM ) to access the pore structure of the conventional microporous transition metal-substituted molecular sieves such as titano- and vanadosilicates. |