2050
Langmuir 1997, 13, 2050-2054
Infrared Study on the Dehydroxylation of C60-Loaded MCM-41 Jiesheng Chen,* Qinghua Li, Hong Ding, Wenqin Pang, and Ruren Xu Department of Chemistry, Jilin University, Changchun 130023, China Received May 21, 1996. In Final Form: January 8, 1997X The dehydroxylation behavior of two MCM-41 samples with and without C60 was monitored by infrared spectroscopy. Both samples contain isolated and hydrogen-bonded silanol groups, but with different distributions. Without C60, the hydrogen-bonded species are eliminated at elevated temperatures under vacuum whereas the isolated ones remain. Loading C60 in the MCM-41 materials greatly changes their dehydroxylation behavior. When the MCM-41:C60 weight ratio is 10:1, at about 400 °C under vacuum, the isolated silanols are reduced to a certain degree whereas the hydrogen-bonded hydroxyls become more resistant to thermal treatment by comparison with those in the parent C60-free samples. Increasing the loading amount of C60 to a MCM-41:C60 weight ratio of 10:3 results in complete removal of both isolated and hydrogen-bonded silanols, at about 350 °C. However, the two MCM-41 samples exhibit different infrared spectra at lower evacuation temperatures in the presence of C60, indicative of a discrepancy in the dehydroxylation process between them. It is postulated that during the dehydroxylation, C60 captures hydroxyls from the silanol groups of MCM-41 to form C-H and C-OH species, followed by condensation of the C-OH groups and/or combination of C-OH with C-H.
Introduction The invention of the mesoporous molecular sieves M41S1,2 has stimulated the further synthesis of a variety of new mesostructured materials3-9 through an inorganicorganic assembly route. Efforts have also been focused on the formation mechanism10-14 and application15-21 of M41S materials, especially MCM-41, a member of the M41S family which possesses a hexagonal array of mesopores with a diameter that is adjustable within the X Abstract published in Advance ACS Abstracts, February 15, 1997.
(1) Kresge, C. T.; Leonowicz, M. E.; Roth, W. J.; Vartuli, J. C.; Beck, J. S. Nature 1992, 359, 710. (2) Beck, J. S.; Vartuli, J. C.; Roth, W. J.; Leonowicz, M. E.; Kresge, C. T.; Schmitt, K. D.; Chu, C. T-W.; Olson, D. H.; Sheppard, E. W.; McCulen, S. B.; Higgins, J. B.; Schlenker, J. L. J. Am. Chem. Soc. 1992, 114, 10834. (3) Antonelli, D. M.; Ying, J. Y. Angew. Chem., Int. Ed. Engl. 1995, 34, 2014. (4) Huo, Q.; Margolese, D. I.; Ciesla, U.; Feng, P.; Gier, T. E.; Sieger, P.; Leon, R.; Petroff, P. M.; Schu¨th, F.; Stucky, G. Nature 1994, 368, 317. (5) Abe, T.; Taguchi, A.; Iwamoto, M. Chem. Mater. 1995, 7, 1429. (6) Luca, V.; MacLachlan, D. J.; Hook, J. M.; Withers, R. Chem. Mater. 1995, 7, 2220. (7) Cielse, U.; Demuth, D.; Leon, R.; Petroff, P.; Stucky, G. D.; Unger, K.; Schu¨th, F. J. Chem. Soc., Chem. Commun. 1994, 1387. (8) Hudson, M. J.; Knowles, J. A. J. Mater. Chem. 1996, 6, 89. (9) Tanev, P. T.; Pinnavaia, T. J. Science 1996, 271, 1267. (10) Huo, Q.; Margolese, D. I.; Ciesla, U.; Demuth, D. G.; Feng, P.; Gier, T. E.; Sieger, P.; Firouzi, A.; Chmelka, B. F.; Schu¨th, F.; Stucky, G. D. Chem Mater. 1994, 6, 1176. (11) Monnier, A.; Schu¨th, F.; Huo, Q.; Kumar, D.; Margolese, D. I.; Maxwell, R. S.; Stucky, G. D.; Krishnamurty, M.; Petroff, P. M.; Firouzi, A.; Janicke, M.; Chmelka, B. F. Science 1994, 261, 1299. (12) Firouzi, A.; Kumar, D.; Bull, L. M.; Besier, T.; Sieger, P.; Huo, Q.; Walker, S. A.; Zasadzinski, J. A.; Glinka, C.; Nicol, J.; Margolese, D.; Stucky, G. D.; Chmelka, B. F. Science 1995, 267, 1138. (13) Chen, C. Y.; Burkett, S. L.; Li, H. X.; Davis, M. E. Microporous Mater. 1993, 2, 27. (14) Cheng, C. F.; Luan, Z. H.; Klinowski, J. Langmuir 1995, 11, 2815. (15) Tanev, P.; Chibwe, M.; Pinnavaia, T. Nature 1994, 368, 321. (16) Blasco, T.; Camblore, M. A.; Corma, A.; Perez-Pariente, J. J. Am. Chem. Soc. 1993, 115, 11806. (17) Kloetstra, K. R.; Vanbekkum, H. J. Chem. Soc., Chem Commun. 1995, 1005. (18) Maschmeyer, T.; Rey, F.; Sankar, G.; Thomas, J. M. Nature 1995, 378, 159. (19) Corma, A.; Martinez, A.; Martinezsoria, V.; Monton, J. B. J. Catal. 1995, 153, 25. (20) Wu, C. G.; Bein, T. Chem. Mater. 1994, 6, 1109. (21) Wu, C. G.; Bein, T. Science 1994, 264, 1757.
S0743-7463(96)00502-1 CCC: $14.00
range 20-100 Å. This pore diameter is much larger than that (
