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

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, C 12 TA−PMO, C 16 TA−PMO, and C 18 TA−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 29 Si and 13 C CP MAS NMR experiments that the organic−inorganic moiety (−Si−CH 2 −CH 2 −Si−) is the basic structural unit in the films. The pore diameter and the surface area of the surfactant-extracted PMO films, e.g., C 12 TA−, C 16 TA−, and C 18 TA−PMO films, obtained from the N 2 sorption isotherms were to be determined to be 24.3, 26.4, and 32.8 Å and 890.3, 917.7, and 811.0 m 2 g - 1, respectively.