Assembly of Large-Pore Silica Mesophases with Wormhole Framework Structures from α,ω-Diamine Porogens

Abstract

Large-pore mesoporous silicas with wormhole framework structures have been assembled through hydrogen-bonding pathways from sodium silicate or tetraethyl orthosilicate (TEOS) as the silica source and amine-terminated Jeffamine surfactants of the type H2NCH(CH3)CH2[OCH2CH(CH3)]xNH2 as the structure-directing porogen. Depending on the molecular weight of the α,ω-diamine surfactant (x ∼ 33 and 68 for Jeffamine D2000 and D4000, respectively) and the synthesis temperature (25−65 °C), the mean pore size distributions of the mesostructured silicas (denoted MSU-J) were centered between 4.9 and 14.3 nm, making these materials comparable to hexagonal SBA-15 mesostructures in average framework pore size. In addition to the BET surface areas of MSU-J silicas (408−1127 m2/g) being comparable to those of SBA-15 (630−1040 m2/g), MSU-J silicas exhibit larger pore volumes (1.37−2.29 cm3/g) than SBA-15 silicas (0.56−1.23 cm3/g) prepared in the absence of mesitylene. MSU-J wormhole mesostructures represent the largest pore sizes observed to date for a fully three-dimensional mesoporous framework assembled from a single micellar porogen. Only mesostructured micellar foam structures exhibit larger pore sizes, but the preparation of foam structures requires the use of more complex microemulsions or latex polymers as porogens.