Synthesis of Periodic Mesoporous Phenylenesilica under Acidic Conditions with Novel Molecular Order in the Pore Walls Wenhui Wang, † Wuzong Zhou, ‡ and Abdelhamid Sayari* ,† Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5, and School of Chemistry, University of St. Andrews, St. Andrews, Fife, United Kingdom KY16 9ST Received August 31, 2003 Revised Manuscript Received November 6, 2003 Periodic mesoporous organosilicates are one of the latest innovations in the field of ordered mesoporous materials. 1,2 Similarly to their silica counterparts, they are prepared in the presence of amphiphile supramo- lecular templates using bridged silsesquioxane mol- ecules, (R′O) 3 Si-R-Si(OR′) 3 , as precursors. Through proper design of the organic linker R, such materials offer unique opportunities for controlling their surface and chemical properties at the molecular level. This is in addition to the inherent advantages of periodic mesoporous materials such as their high surface area and narrow pore size distribution (PSD). In a recent development, Inagaki et al. 3 showed that using 1,4-bis- (triethoxysilyl)benzene under basic conditions in the presence of octadecyltrimethylammonium chloride af- fords a material which exhibits both long- and short- range order. In addition to the periodic system of 4.5- nm-diameter hexagonally packed cylindrical pores, the pore walls exhibited also a structural periodicity with a spacing of 0.76 nm along the channel direction due to the π-π stacking of bridging phenylene groups. Using similar preparation conditions, Bion et al. 4 synthesized phenyl-bridged organosilicas with comparable order using alkyltrimethylammonium surfactants with 14, 16, and 18 carbon atom alkyl chains. Similar molecular- scale periodicity with 1.16-nm spacing occurred also within the pore walls of biphenylene-bridged meso- porous organosilica. 5 However, prepared under acidic conditions using the triblock copolymer Pluronic P123 as the structure-directing agent, phenylene-bridged organosilica showed little evidence of molecular order within the pore walls. 6 Periodic mesoporous organosili- cates with aryl groups such as tolyl, xylyl, and dimeth- oxyphenyl prepared under acidic conditions in the presence of cetylpyridinium chloride also gave indication of arylsilica ordering in the channel walls. 7 Oligomeric surfactants such as nonionic alkyl poly- (oxyethylene) surfactants C n H 2n+1 (OCH 2 CH 2 ) 10 OH, de- noted C n OE m , proved to be excellent supramolecular templates for the synthesis of highly ordered meso- porous silicas 8 and ethanesilicas 9 under acidic condi- tions. The purpose of the current investigation is to extend this synthetic approach to phenylenesilica and to check if there is any structural ordering of the aromatic rings within the channel walls. Phenylene-bridged mesoporous materials were syn- thesized using 1,4-bis(triethoxysilyl)benzene (BTEB) as precursor in the presence of oligomeric surfactants Brij 56 (C 16 EO 10 ) and Brij 76 (C 18 EO 10 ) under acidic condi- tions. BTEB was prepared and purified according to the literature. 10 In a typical synthesis of mesoporous phe- nylenesilica, 2 g of surfactant was dissolved in 10 g of distilled water and 50 g of 2 M hydrochloric acid. After 30 min of stirring at 50 °C, BTEB (4.225 g) was added to the solution and then stirred for 20 h at 50 °C. The molar composition of the reaction mixture was BTEB: Brij 76:HCl:H 2 O ) 1:0.27:7.7:53. A white precipitate was recovered by filtration, washed thoroughly with water, and dried. The surfactant was removed by two consecu- tive solvent extractions using 150 mL of ethanol and 2 g of concentrated HCl for 1 g of sample at 50 °C for 5 h. XRD patterns (Figure 1) of the surfactant-free mate- rials revealed a strong peak at 2θ ) ca. 1.7° and two * Corresponding author: E-mail: abdel.sayari@science.uottawa.ca. Tel.: (613) 562 5483. Fax: (613) 562 5170. † University of Ottawa. ‡ University of St. Andrews. (1) Stein, A.; Melde, B. J.; Schroden, R. C. Adv. Mater. 2000, 12, 1403. (2) Sayari, A.; Hamoudi, S. Chem. Mater. 2001, 13, 3151. (3) Inagaki, S.; Guan, S.; Ohsuna, T.; Terasaki, O. Nature 2002, 406, 304. (4) Bion, N.; Ferreira, P.; Anabela, V.; Gonc ¸ alves, I. S.; Rocha, J. J. Mater. Chem. 2003, 13, 1910. (5) Yang, Q.; Kapoor, M. P.; Inagaki, S. J. Am. Chem. Soc. 2002, 124, 9694. (6) Goto, Y.; Inagaki, S. Chem. Commun. 2002, 2410. (7) Temtsin, G.; Asefa, T.; Bittner, S.; Ozin, G. A. J. Mater. Chem. 2001, 11, 3202. (8) (a) Zhao, D.; Huo, Q.; Feng, J.; Chmelka, B. F.; Stucky, G. D. J. Am. Chem. Soc. 1998, 120, 6024. (b) Kim, J. M.; Sakamoto, Y.; Hwang, Y. K.; Kwon, Y.-U.; Terasaki, O.; Park, S.-E.; Stucky, G. D. J. Phys. Chem. B 2002, 106, 2552. (9) Sayari, A.; Yang, Y. Chem. Commun. 2002, 2582. (10) Shea, K. J.; Loy, D. A.; Webster, O. J. Am. Chem. Soc. 1992, 114, 6700. Figure 1. XRD patterns for phenylene-bridged mesoporous organosilica (after extraction) prepared in the presence of (a) Brij 76 and (b) Brij 56. 4886 Chem. Mater. 2003, 15, 4886-4889 10.1021/cm034809x CCC: $25.00 © 2003 American Chemical Society Published on Web 12/02/2003