Stepwise removal of the copolymer template from mesopores and micropores in SBA-15

Abstract

A method for the removal of the triblock copolymer template from mesoporous silica SBA-15 in two stages has been developed. The mesopores of SBA-15 are first vacated by treatment with sulfuric acid that decomposes accessible portions of the template via ether cleavage. The concentration of the acid was found to be crucial for the decomposition of the template. The micropores of SBA-15 can then be vacated by calcination at 200 °C, a low temperature that prevents the silica matrix from shrinking, so that both the mesopores and the micropores retain their original sizes and volumes. The connectivity of the mesopores was studied by imaging the inverse platinum replicas of SBA-15 materials. The acid-treated SBA-15 materials also show less shrinkage, even when subsequently calcined at 540 °C. Compared with the template removal just by calcination, the stepwise removal of the copolymer template generates materials with wider mesopores and larger micropore volumes. Furthermore, this method opens up the possibility of functionalizing the mesopores and micropores independently, widening the field of application of copolymer-templated mesoporous silicas.