Periodic Mesoporous Benzene−Silicas Prepared Using Boric Acid as Catalyst

Abstract

Highly ordered periodic mesoporous benzene−silicas with 2D p6mm symmetry were synthesized through sol−gel self-assembly in the presence of a nonionic poly(ethylene oxide)−poly(dl-lactic acid-co-glycolic acid)−poly(ethylene oxide) (PEO−PLGA−PEO, EO16(L29G7)EO16) triblock copolymer template using boric acid (weak Lewis acid) as a catalyst instead of strong hydrochloric acid. 1,4-Bis(triethoxysilyl)benzene (BTEB) was used as an organosilica precursor, and the reaction and aging temperatures were set at 40 and 100 °C, respectively. The molar concentration of boric acid was varied from 0.5 to 3 M to find the minimum acidity required and to check the effect of this acidic catalyst on the formation of benzene−silica mesostructures. This study shows that the ordered mesostructure of benzene−silica was observed even at 1 M concentration of boric acid ([B(OH)3]/[BTEB] = 12), and highly ordered hexagonal mesostructures were obtained at higher concentrations of this acid. Thermal stability of the benzene−silica mater...