Periodic Mesoporous Benzene- and Thiophene-Silicas Prepared Using Aluminum Chloride as an Acid Catalyst: Effect of Aluminum Salt/Organosilane Ratio and Stirring Time

Periodic mesoporous benzene-silica and thiophene-silica with two dimensional (2D) p 6 mm symmetry were synthesized in the presence of a nonionic poly(ethylene oxide)-poly( dl -lactic acid-co-glycolic acid)-poly(ethylene oxide) (PEO-PLGA-PEO) block copolymer template using aluminum chloride hexahydrate (AlCl 3 ·6H 2 O) as an acid catalyst instead of the proton-containing hydrochloric acid (HCl). 1,4-Bis(triethoxysilyl)benzene (BTEB) and 2,5-bis(triethoxysilyl)thiophene (BTET) were used as organosilica precursors. The effect of the AlCl 3 ·6H 2 O/organosilane ratio and the stirring time was investigated to find the optimum experimental conditions. It was shown that the highly ordered 2D hexagonal mesostructures of aromatic-silicas were formed using relatively small amounts of AlCl 3 ([AlCl 3 ·6H 2 O]/[BTEB] and [AlCl 3 ·6H 2 O]/[BTET] ≥ 1) and a stirring time of about 20 h. The BET surface areas, pore volumes, and pore diameters of the benzene- and thiophene-silicas studied varied from 505 to 1215 m 2 g −1, from 0.55 to 1.62 cm 3 g −1, and from 7.55 to 9.23 nm, respectively, depending on the aluminum salt concentration and the stirring time. In the case of thiophene-silica, the optimum experimental conditions for the formation of ordered mesostructure were [AlCl 3 ·6H 2 O]/[BTET] = 1 and a stirring time of 20 h. Also, the chemistry and crystallinity of aromatic-silicas were investigated using solid-state 13 C-, 29 Si-, and 27 Al-NMR and wide-angle X-ray scattering methods.