Free-Standing and Oriented Periodic Mesoporous Organosilica Films with Variable Pore Size at the Air−Water Interface

Abstract

Free-standing and oriented periodic mesoporous organosilica (PMO) films with variable pore size have been synthesized at the air−water interface using cationic alkyltrimethylammonium surfactants (alkyl chain length from 12 to 18 carbon atoms) as the structure-directing agents and 1,2-bis(triethoxysilyl)ethane as the organosilica precursor. After hydrothermal reaction at 95 °C for 8 h, C12TA−PMO, C16TA−PMO, and C18TA−PMO films grown at the air−water interface have a uniform thickness of ∼350, ∼670, and ∼400 nm, respectively. From the XRD patterns and TEM images, PMO films with hexagonal symmetry were identified. It was confirmed by 29Si and 13C CP MAS NMR experiments that the organic−inorganic moiety (−Si−CH2−CH2−Si−) is the basic structural unit in the films. The pore diameter and the surface area of the surfactant-extracted PMO films, e.g., C12TA−, C16TA−, and C18TA−PMO films, obtained from the N2 sorption isotherms were to be determined to be 24.3, 26.4, and 32.8 A and 890.3, 917.7, and 811.0 m2 g-1, re...