Immobilization of Chlorosulfonyl-Calix[4]arene onto the surface of silica gel through the directly estrification

► Chemically bonded 25,26,27,28-tetrakis[chlorosulfonyl]calix[4]arene to silica gel through the directly estrification. ► Sample characterization with elemental analysis, FTIR-spectroscopy, SEM, EDAX, XRD, TGA, 29Si CP/MAS spectroscopy and acid-base titration. ► Successful incorporation of organic group via covalent bond.