Nanoporous organosilicas: Periodic materials synthesized with surfactant templates in acidic media

Nanoporous organosilicas have been synthesized by the acid-catalyzed hydrolysis and condensation of bis (triethoxysilyl)ethane (BTSE) using a hydrothermal approach. Cetyltrimethylainnionium chloride (CTAC), polyoxyethylene(10) cetyl ether (Brij 56), and polyoxythylene(10) stearyl other (Brij 76) were employed as structure directors using the surfactant template method. The surfactants were extracted from the nanoscopic composite precipitates with acidified ethanol. The resulting nanoporous organosilicas have been characterized by nitrogen gas sorption, powder X-ray diffraction, and high-resolution thermogravimetric analysis. While the organosilicas synthesized with CTAC exhibit large surface areas (1000 m(2)/g) and pore volumes (1.0 cm(3)/g), they form relatively disordered matrixes as evidenced by broad pore size distributions and X-ray diffraction patterns. Brij 56 gives periodic nanoporous organosilicas with pore diameters 36-39 Angstrom. The use of brij 76 as the structure director gave better quality organosilicas, with large surface areas, sharp pore size distributions, and pore diameters of 43-45 Angstrom. X-ray diffraction patterns exhibit three well-defined peaks typical of hexagonal (p6mm) mesoporous materials. The effects of initial HCl concentrations on the chemical and structural properties of the final products are examined.