Supramolecular assembly of mesoporous silicas with Gemini surfactants and microemulsion templating: Synthesis, characterization and catalysis

In 1992 researchers from Mobil demonstrated the assembly of mesoporous silicate using organic cation surfactant assemblies. These researchers were able to assemble mesoporous molecular sieves with pore sizes ranging from 2–10 nm and uniform pore size distributions from aluminosilicate and purely siliceous gels. Tanev and Pinnavaia assembled mesostructures using H-bonding interactions between electrically neutral amine surfactant micelles (S0) as the structure director and molecular silica species (I0) as the source of silica.; Kim et al extended the (S0 I0 ) using a class of diamine based surfactants called Gemini surfactants to form ultrastable lamellar mesoporous silica. The resulting mesostructures denoted as MSU-G silicas possessed unique structural characteristics such high cross-linking, exceptional thermal and hydrothermal stability, in addition to a vesicular structure. Presented here is a comprehensive study of the assembly of mesoporous silica molecular sieves using Gemini surfactants as the structure directors.; The hierarchical structures of mesostructured silicas assembled from electrically neutral Gemini surfactants of the type C_nH_2n+1 NH(CH₂)_mNH₂ with n = 10, 12, 14 and m = 3, 4 are described in this study. Different hierarchical structures are observed depending on a delicate balance between the hydrophilic interactions at the surfactant head group—silica interface and the hydrophobic interactions between the surfactant alkyl groups. AI-MSU-G derivatives prepared through in situ alumination reactions are far more efficient acid catalysts than 2% AI-MCM-41 for cumene cracking and the conversion of 2,4-di- tert-butylphenol and cinnamyl alcohol to a bulky flavan as the primary alkylation product.; A new family of mesostructured cellular foams (MSU-F) with microemulsion-templated structures has been synthesized using triblock copolymer P123 as structure-directing agents, 1,3,5-trimethylbenzene (TMB) as swelling agent and low-cost and water-soluble silicate precursors under near neutral conditions are described. The MSU-F foams consist of uniform spherical cells measuring 16–85 nm in diameter, windows with diameters of 5–40 nm and a narrow size distribution interconnecting the cells.; Mercaptopropyl-functionalized mesostructured catalysts assembled using direct assembly methods and ocatdecylamine as structure directors were converted to acidic catalysts by oxidation of thiol groups to sulfonic acid. These materials were tested for acid catalyzed esterification of glycerol with lauric acid. Conversions as high as 100% in terms of lauric acid were observed with 66% selectivity for the monoester.