Immobilizing glycopyranose on mesoporous silica via "click-chemistry" for borate adsorption

Mesoporous silica materials carrying organic modifications show promising properties for their potential use in chromatography, drug delivery or catalytic applications. In this work, we highlight the possibility of specifically removing borate ions from aqueous solution by sugar-functionalized pores of MCM-41-type mesoporous silica. In order to achieve this functionalization, a click-chemistry approach was applied. The azide-functionalized carbohydrate glycopyranose was covalently attached to the acetylene-functionalized pores of mesoporous silica by using the copper-(I)-catalyzed azide-alkyne cycloaddition. The covalent binding of the sugar to the silica surface was confirmed with solid state NMR, Raman- and infrared spectroscopies. The stepwise changes in pore volume derived from nitrogen sorption experiments are consistent with the successive filling of the pore volume with the functional groups and the sugar moieties. Additionally, thermogravimetric analysis is used to determine the amount of bound sugar molecules. The glycopyranose-grafted mesoporous silica showed a significant adsorption of borate from aqueous solution. (C) 2010 Elsevier Inc. All rights reserved.