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.