4756 Chem. Mater. 2009, 21, 4756–4758 DOI:10.1021/cm902522b
Cation Cross-Linked Ionic Liquids as Anion-Exchange Materials Je Seung Lee,† Huimin Luo,‡ Gary A. Baker,† and Sheng Dai*,† †
Chemical Sciences Division and and ‡Nuclear Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 Received August 25, 2009 Revised Manuscript Received September 16, 2009
Recently, we introduced a new polymerization system that allows for the formation of porous carbon materials through an ionothermal cyclotrimerization of taskspecific ionic liquids (TSILs) containing nitrile groups without requiring any Lewis acid catalyst.1 Using this approach, highly porous carbon materials with high thermal and chemical stabilities could be facilely prepared with tailored pore structures. The intermediate polymer structure for the carbonization reaction was proposed to consist of triazine-based frameworks derived from the trimerization reaction of nitrile groups in the TSIL cations. A similar trimerization reaction was also conjectured by Kuhn et al. to rationalize the formation of their triazine-based neutral frameworks from pressurized pyrolysis of benzene nitrile under ZnCl2 catalysis.2,3 One of the key differences between our intermediate triazine-based frameworks derived from TSILs1 and those derived from neutral organic molecules2-4 lies in the charged nature of our planar triazine-based intermediate frameworks. As shown in Figure 1, the putative triazine-based frameworks of the former system are positively charged while the latter polymer systems carry neutral molecular frameworks. Accordingly, our intermediate polymers derived from TSILs prior to carbonization under high-temperature conditions should exhibit anion-exchange capabilities. In this communication, we would like to report on a novel class of anion-exchange polymers based on cation crosslinked ionic liquids (CCLILs) and disclose our preliminary investigation into their anion-exchange capabilities. *Corresponding author. E-mail:
[email protected].
(1) Lee, J. S.; Wang, X. Q.; Luo, H. M.; Baker, G. A.; Dai, S. J. Am. Chem. Soc. 2009, 131, 4596. (2) Kuhn, P.; Forget, A.; Su, D. S.; Thomas, A.; Antonietti, M. J. Am. Chem. Soc. 2008, 130, 13333. (3) Thomas, A.; Kuhn, P.; Weber, J.; Titirici, M. M.; Antonietti, M. Macromol. Rapid Commun. 2009, 30, 221. (4) Shin, Y.; Wang, C.; Englehard, M.; Fryxell, G. E. Microporous Mesoporous Mater. 2009, 123, 345. (5) (a) Carter, T. G.; Yantasee, W.; Sangvanich, T.; Fryxell, G. E.; Johnson, D. W.; Addleman, R. S. Chem. Commun. 2008, 5583. (b) Marsh, S. F. Solvent Extr. Ion Exch. 1989, 7, 889. (c) Barr, M. E.; Jarvinen, G. D.; Moody, E. W.; Vaughn, R.; Silks, L. A.; Bartsch, R. A. Sep. Sci. Technol. 2002, 37, 1065. (d) Gu, B. H.; Brown, G. M.; Bonnesen, P. V.; Liang, L. Y.; Moyer, B. A.; Ober, R.; Alexandratos, S. D. Environ. Sci. Technol. 2000, 34, 1075.
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Organic polymer anion-exchange resins, including quaternary ammonium resins, are one class of sorbents most widely used to recover anions from various process wastes.5 However, these organic polymer anion-exchange resins have several drawbacks, such as limited thermal and chemical stabilities.6,7 ILs typically consist of asymmetric cations and anions,8,9 which have relatively low melting points (
