Three different water−alcohol cosolvent systems were used to assemble mesoporous molecular sieve silicas with wormhole framework structures (previously denoted HMS silicas) from an electrically neutral amine surfactant (S°) and a silicon alkoxide precursor (I°). The fundamental particle size and associated textural (interparticle) porosity of the disordered structures were correlated with the solubility of the surfactant in the water−alcohol cosolvents used for the S°I° assembly process. Polar cosolvents containing relatively low volume fractions of C n H2 n +1OH alcohols (n = 1−3) gave heterogeneous surfactant emulsions that assembled intergrown aggregates of small primary particles with high textural pore volumes (designated HMS−HTx). Conversely, three-dimensional, monolithic particles with little or no textural porosity (designated HMS−LTx) were formed from homogeneous surfactant solutions in lower polarity cosolvents. Aluminum substituted Al-HMS−HTx analogues with high textural porosity and improved framework accessibility also were shown to be much more efficient catalysts than Al-HMS−LTx or monolithic forms of hexagonal Al-MCM-41 for the sterically demanding condensed phase alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol. Transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies verified the textural differences between wormhole HMS and electrostatically assembled hexagonal MCM-41 and SBA-3 molecular sieves. Power law fits to the scattering data indicated a surface fractal (D s = 2.76) for HMS−HTx, consistent with rough surfaces. A second power law at lower-q indicated the formation of a mass fractal (D m = 1.83) consistent with branching of small fundamental particles. Hexagonal MCM-41 and SBA-3 silicas, on the other hand, exhibited scattering properties consistent with moderately rough surfaces (D s = 2.35 and 2.22, respectively) and large particle diameters (≫1 μm). HMS−LTx silicas showed little or no mass fractal character (D m = 2.87), and no surface fractal scattering.

gamma-Al2O3 is one of the most extensively utilized metal oxides in heterogeneous catalysis. Conventional forms of this oxide typically exhibit a surface area and pore volume less than 250 m2/g and 0.5 cm3/g, respectively. Previous efforts to prepare mesostructured forms of alumina resulted only in structurally unstable derivatives with amorphous framework walls. The present work reports mesostructured aluminas with walls made of gamma-Al2O3, denoted MSU-gamma. These materials are structurally stable and provide surface areas and pore volumes up to 370 m2/g and 1.5 cm3/g, respectively. The key to obtaining these structures is the formation of a mesostructured surfactant/boehmite precursor, denoted MSU-S/B, assembled through the hydrolysis of an aluminum cation, oligomer, or molecule in the presence of a nonionic surfactant. Mesostructured, gamma-aluminas offer the possibility of improving the catalytic efficiency of many heterogeneous catalytic processes, such as petroleum refining, petrochemical processing, and automobile exhaust control.

Very large pore hexagonal and cellular foam-like molecular sieve silicas with well cross-linked framework walls (denoted MSU-H and MSU-F, respectively), have been prepared from soluble silicate precursors under neutral pH conditions.

Wormhole HMS silica molecular sieves with average framework pore sizes in the range 2.9 to 4.1 nm were assembled from 4:1 molar mixtures of TEOS as the inorganic precursor (I o ) and dodecylamine as the structure-directing surfactant (S°) in 63:27 (v/v) water/ethanol. Increasing the assembly temperature from 25 °C to 65 °C resulted in an increase in the Horvath-Kawazoe pore size (from 2.9 to 4.1 nm). Also, the ratio of fully cross-linked (Q 4 ) to incompletely cross-linked (Q 3 ) SiO 4 sites (Q 4 /Q 3 ) increased more than 2-fold from 1.96 to 4.26 with little or no change in the framework wall thickness (∼1.0 nm). Analogous results were obtained for HMS mesostructures assembled at an I o /S°ratio of 10. Postsynthesis remodeling of as-made HMS mesostructures through digestion in hot distilled water resulted in comparable expansions in the framework pore sizes. The pore expansion process, whether achieved through an increase in the direct assembly temperature or through postsynthesis remodeling in distilled water, is consistent with a mechanism based on temperaturedependent changes in the polarity of the S°I o interface and concomitant changes in the surfactant packing parameter and self-swelling of the structure-directing micelle.