Immobilization of β-Cyclodextrin on Silica Gel

Abstract β-Cyclodextrin (β-CyD) was covalently immobilized on silica gel by chlorination of silica gel with thionyl chloride or silicon tetrachloride, followed by the reaction of the resulting chlorinated silica gel with β-CyD in pyridine. The amounts of the immobilized β-CyD were 8×10−5 to 1.4×10−4 mol per 1 g of the β-CyD–silica gel composites. On heating, the composites did not exhibit weight decrease up to 250 °C. The β-CyD in the composites formed 1 : 1 complex with phenol in aqueous solutions, and the equilibrium constant for the dissociation of the complex was 6×10−3 mol dm−3 at 25 °C. The immobilized β-CyD exhibited catalytic activity in the cleavage of 4-nitrophenyl acetate at 25 °C, pH 8.7.