Nanoscale Organization of Thiol and Arylsulfonic Acid on Silica Leads to a Highly Active and Selective Bifunctional, Heterogeneous Catalyst Eric L. Margelefsky, † Anissa Bendje ´ riou, ‡ Ryan K. Zeidan, † Ve ´ ronique Dufaud,* ,‡ and Mark E. Davis* ,† DiVision of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, and Laboratoire de Chimie, Ecole Normale Supe ´rieure de Lyon, 46 allee d’Italie, 69364 Lyon cedex 07, France Received May 30, 2008; E-mail: mdavis@cheme.caltech.edu; vdufaud@ens-lyon.fr Abstract: Ordered mesoporous silicas functionalized with alkylsulfonic acid and thiol group pairs have been shown to catalyze the synthesis of bisphenols from the condensation of phenol and various ketones, with activity and selectivity highly dependent on the distance between the acid and thiol. Here, a new route to thiol/sulfonic acid paired catalysts is reported. A bis-silane precursor molecule containing both a disulfide and a sulfonate ester bond is grafted onto the surface of ordered mesoporous silica, SBA-15, followed by simultaneous disulfide reduction and sulfonate ester hydrolysis. The resulting catalyst, containing organized pairs of arylsulfonic acid and thiol groups, is significantly more active than the alkylsulfonic acid/thiol paired catalyst in the synthesis of bisphenol A and Z, and this increase in activity does not lead to a loss of regioselectivity. The paired catalyst has activity similar to that of a randomly bifunctionalized arylsulfonic acid/thiol catalyst in the bisphenol A reaction but exhibits greater activity and selectivity than the randomly bifunctionalized catalyst in the bisphenol Z reaction. Introduction Organic-inorganic hybrid materials represent an attractive class of solids that allows for molecular-level fine-tuning of catalytic materials. 1 Of current interest in the design and synthesis of solid catalysts is the creation of materials that contain multiple types of active centers. 2 These functionalities may be used to perform several steps in a reaction sequence or work in a cooperative manner to alter the characteristics (rates, selectivities) of a single reaction. Logically, cooperative behavior between functional groups should depend on the control of the distance between the reactive groups in order to optimize the catalysis for a particular reaction. We have been developing positioned monofunctional and bifunctional catalytic materials where the functional groups are present in a highly ordered fashion at predefined distances. The synthetic route to these materials involves the integration of incipient functional groups, in a protected form, positioned around a central spacer during the synthesis of the solid. When the spacer is removed by deprotection, one is left with the positioned functional group pair. 2g One reaction where cooperative, heterogeneous catalysis has been established is the synthesis of bisphenols. Bisphenols, such as bisphenol A (BPA) and bisphenol Z (BPZ), are important industrial feedstocks, especially as monomers in polycarbonate materials and epoxy resins. They are synthesized by the acid- catalyzed condensation between a ketone and phenol, yielding the desired p,p′ isomer and a byproduct, the o,p’ isomer (Scheme 1). The addition of thiols as a cocatalyst is known to improve both the rate of reaction and the selectivity to the desired isomer. 3,4 Mineral acids can be used to catalyze the bisphenol conden- sation reaction, but solid acid catalysts such as polymeric ion- exchange resins are typically used for commercial bisphenol A production due to their recyclability. Thiols have been either added as a homogeneous feed additive 4 or bound to the resin surface by ion-pairing. 5 Several solid catalysts bearing both acid and thiol groups covalently attached to a solid support have been reported. Thiols have been covalently tethered to polymeric resins containing sulfonic acid groups, 6,7 and polysiloxane catalysts containing randomly organized alkylsulfonic acid and alkylthiol groups have also been reported to have good catalytic † California Institute of Technology. ‡ Ecole Normale Supe ´rieure de Lyon. (1) Wight, A. P.; Davis, M. E Chem. ReV. 2002, 102, 3589–3613, and references therein. 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Published on Web 09/13/2008 10.1021/ja804082m CCC: $40.75  2008 American Chemical Society 13442 9 J. AM. CHEM. SOC. 2008, 130, 13442–13449