Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance 119Sn Precursors

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• 作者：William R. Gunther ; Vladimir K. Michaelis ; Marc A. Caporini ; Robert G. Griffin ; Yuriy Rom谩n-Leshkov
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：April 30, 2014
• 年：2014
• 卷：136
• 期：17
• 页码：6219-6222
• 全文大小：258K
• 年卷期：v.136,no.17(April 30, 2014)
• ISSN：1520-5126

文摘

The catalytic activity of tin-containing zeolites, such as Sn-Beta, is critically dependent on the successful incorporation of the tin metal center into the zeolite framework. However, synchrotron-based techniques or solid-state nuclear magnetic resonance (ssNMR) of samples enriched with ¹¹⁹Sn isotopes are the only reliable methods to verify framework incorporation. This work demonstrates, for the first time, the use of dynamic nuclear polarization (DNP) NMR for characterizing zeolites containing 2 wt % of natural abundance Sn without the need for ¹¹⁹Sn isotopic enrichment. The biradicals TOTAPOL, bTbK, bCTbK, and SPIROPOL functioned effectively as polarizing sources, and the solvent enabled proper transfer of spin polarization from the radical鈥檚 unpaired electrons to the target nuclei. Using bCTbK led to an enhancement (蔚) of 75, allowing the characterization of natural-abundance ¹¹⁹Sn-Beta with excellent signal-to-noise ratios in <24 h. Without DNP, no ¹¹⁹Sn resonances were detected after 10 days of continuous analysis.