Tailoring Bifunctional Periodic Mesoporous Organosilicas for Cooperative Catalysis
Dolores Esquivel, Juan Amaro‐Gahete, Noelia Caballero‐Casero, César Jiménez‐Sanchidrián, José Rafael Ruiz, Soledad Rubio, Pascal Van Der Voort, Francisco J. Romero‐Salguero
Abstract
This paper presents a novel approach to create bifunctional periodic mesoporous organosilicas containing thiol and sulfonic acid groups (SHm/SO3Hn@PMO) by co-condensation reactions of an own designed bis-silane precursor (EtO)3Si–CH2CH(SH)–Si(OEt)3 containing thiols groups with its predecessor (EtO)3Si–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 13C (13C CP/MAS NMR) and 29Si (29Si 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.