Tailoring Bifunctional Periodic Mesoporous Organosilicas for Cooperative Catalysis

This paper presents a novel approach to create bifunctional periodic mesoporous organosilicas containing thiol and sulfonic acid groups (SHm/SO(3)Hn@PMO) by co-condensation reactions of an own designed bis-silane precursor (EtO)(3)Si-CH2CH(SH)-Si(OEt)(3) containing thiols groups with its predecessor (EtO)(3)Si-CH2CH(SCOCH3)-Si(OEt)(3). This bifunctional strategy involves the in situ oxidation of thiol to sulfonic acid groups during the formation of the mesostructure followed by the hydrolysis of the -SCOCH3 to -SH groups during the subsequent surfactant extraction process. The good structural ordering and mesoporosity of the bifunctional materials were confirmed by powder X-ray diffraction (PXRD) and nitrogen adsorption-desorption measurements, respectively. The successful incorporation of dual functionality in the pore walls was confirmed by elemental analysis, X-ray electron spectroscopy (XPS), and solid-state nuclear magnetic resonance of C-13 (C-13 CP/MAS NMR) and Si-29 (Si-29 NMR) measurements. The existence of cooperative effect between both functional groups was evaluated in the bisphenol A formation. The catalytic data showed that the bifunctional materials present a better selectivity to the p,p'-isomer of bisphenol A compared to materials containing only one functionality, reaching the optimal value in the material with a thiol/sulfonic acid ratio of 1:1.