Benzene-silica with hexagonal and cubic ordered mesostructures synthesized in the presence of block copolymers and weak acid catalysts

Highly ordered mesoporous benzene-silicas with 2D hexagonal (p6mm) and 3D cubic (Im3m) symmetry were prepared using weaker acids than hydrochloric acid in the presence of Pluronic P123 and F127 triblock copolymer templates. The resulting ordered mesostructures of 1,4-bis(triethoxysilyl)benzene (BTEB) were well-organized when iron(III) chloride hexahydrate (weak Brönsted acid with K _a = 6.3 × 10 ^-3) was employed; 2D hexagonal structure was obtained at the concentration exceeding 0.064 M (pH ≤1.76) and 3D cubic structure was obtained at the concentration about 0.112 M (pH ≤1.63). The specific surface areas and pore diameters of the hexagonal benzene-silicas studied were in the range from 707 to 966 m ² g ^-1 and from 7.5 to 8.2 nm, respectively; the corresponding values for cubic benzene-silicas were 514-604 m ² g ^-1 and 8.5-9.0 nm, respectively. Also, type IV nitrogen adsorption-desorption isotherms and very narrow pore size distributions were obtained for these materials, which are similar to those for mesoporous benzene-silica prepared in the presence of strong hydrochloric acid.