Performance of organic–inorganic hybrid catalysts based on Ia-3d mesoporous silica

The cubic Ia-3d mesoporous silica with ordered large pores was synthesized from tetraethoxysilane (TEOS) and a small amount of 3-mercaptopropyltorimetoxysilane (MPTS) as the silica sources under the acidic conditions by using triblock copolymer P123 (EO20PO70EO20) as a surfactant. After removal of the surfactant by the solvent extraction method, mercaptopropyl (MP) group (–CH2CH2CH2SH) remained inside pores with a slight loss. The pore diameter of this mesoporous silica was about 5 nm. After converting the MP group to sulfopropyl (SP) group (–CH2CH2CH2SO3H) by the oxidation with H2O2, the amount of organic group was significantly reduced. However, it was possible to introduce additional organic groups by post-synthetic grafting. It was also possible to graft both MP and SP groups at the same time, and cooperative effect was observed in the acid-catalyzed condensation reaction of phenol with acetone. More organics were immobilized to the multi-dimensional cubic Ia-3d structure than the one-dimensional 2d-hexagonal structure. The catalyst having both SH and SO3H groups showed much higher selectivity for bisphenol A than Amberlyst 15 and Nafion SAC-13, which could be explained by the SH group-assisted mechanism.