Spectroscopic evidence of SBA-15 mesoporous solids functionalization

Abstract In order to enhance the acid properties of mesoporous materials, the functionalization of the SBA-15 silica surface with arene-sulfonic acid groups has been adopted via a one-step synthesis procedure. The structures of the sulfonic acid surface-functionalized mesoporous silica were studied and identified by using nitrogen adsorption, X-ray diffraction (XRD), FT-IR, TEM, CP/MAS 29 Si and 13 C NMR, and hyperpolarized 129 Xe NMR techniques. The number of acid groups was determined by ammonia adsorption and catalytic properties were also studied in liquid phase. The structure of the obtained materials showed hexagonal mesoscopic order, possessed large surface areas with a heterogeneous distribution of sulfonic functions within the pore of the mesoporous solid. The anchoring of acid groups has been proved by 29 Si, 13 C CP-MAS-NMR measurements and using the recent technique of hyperpolarized 129 Xe NMR. The number of acid groups is directly proportional to the functionalization ratio. Moreover, these acidified solids display interesting catalytic properties for the esterification of acetic acid with ethanol.