Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy
The Lewis acidity of isolated framework metal sites in Beta zeolites was characterized with ¹⁵N isotopically labeled pyridine adsorption coupled with magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The ¹⁵N chemical shift of adsorbed pyridine was found to scale with the acid c...
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| Format: | Article |
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American Chemical Society (ACS)
2018
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| Online Access: | http://hdl.handle.net/1721.1/113314 https://orcid.org/0000-0002-6708-7660 https://orcid.org/0000-0003-1589-832X |
| _version_ | 1826189190834946048 |
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| author | Gunther, William Robert Michaelis, Vladimir K. Griffin, Robert Guy Román-Leshkov, Yuriy |
| author2 | Massachusetts Institute of Technology. Department of Chemical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Chemical Engineering Gunther, William Robert Michaelis, Vladimir K. Griffin, Robert Guy Román-Leshkov, Yuriy |
| author_sort | Gunther, William Robert |
| collection | MIT |
| description | The Lewis acidity of isolated framework metal sites in Beta zeolites was characterized with ¹⁵N isotopically labeled pyridine adsorption coupled with magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The ¹⁵N chemical shift of adsorbed pyridine was found to scale with the acid character of both Lewis (Ti, Hf, Zr, Nb, Ta, and Sn) and Brønsted (B, Ga, and Al) acidic heteroatoms. The ¹⁵N chemical shift showed a linear correlation with Mulliken electronegativity of the metal center in the order Ti < Hf < Zr < Nb < Ta < Sn < H⁺. Theoretical calculations using density functional theory (DFT) showed a strong correlation between experimental ¹⁵N chemical shift and the calculated metal-nitrogen bond dissociation energy, and revealed the importance of active site reorganization when determining adsorption strength. The relationships found between ¹⁵N pyridine chemical shift and intrinsic chemical descriptors of metal framework sites complement adsorption equilibrium data and provide a robust method to characterize, and ultimately optimize, metal-reactant binding and activation for Lewis acid zeolites. Direct ¹⁵N MAS NMR detection protocols applied to the Lewis acid-base adducts allowed the differentiation and quantification of framework metal sites in the presence of extraframework oxides, including highly quadrupolar nuclei that are not amenable for quantification with conventional NMR methods. |
| first_indexed | 2024-09-23T08:11:17Z |
| format | Article |
| id | mit-1721.1/113314 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T08:11:17Z |
| publishDate | 2018 |
| publisher | American Chemical Society (ACS) |
| record_format | dspace |
| spelling | mit-1721.1/1133142022-09-30T08:09:58Z Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy Gunther, William Robert Michaelis, Vladimir K. Griffin, Robert Guy Román-Leshkov, Yuriy Massachusetts Institute of Technology. Department of Chemical Engineering Massachusetts Institute of Technology. Department of Chemistry Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology) Gunther, William Robert Michaelis, Vladimir K. Griffin, Robert Guy Román-Leshkov, Yuriy The Lewis acidity of isolated framework metal sites in Beta zeolites was characterized with ¹⁵N isotopically labeled pyridine adsorption coupled with magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The ¹⁵N chemical shift of adsorbed pyridine was found to scale with the acid character of both Lewis (Ti, Hf, Zr, Nb, Ta, and Sn) and Brønsted (B, Ga, and Al) acidic heteroatoms. The ¹⁵N chemical shift showed a linear correlation with Mulliken electronegativity of the metal center in the order Ti < Hf < Zr < Nb < Ta < Sn < H⁺. Theoretical calculations using density functional theory (DFT) showed a strong correlation between experimental ¹⁵N chemical shift and the calculated metal-nitrogen bond dissociation energy, and revealed the importance of active site reorganization when determining adsorption strength. The relationships found between ¹⁵N pyridine chemical shift and intrinsic chemical descriptors of metal framework sites complement adsorption equilibrium data and provide a robust method to characterize, and ultimately optimize, metal-reactant binding and activation for Lewis acid zeolites. Direct ¹⁵N MAS NMR detection protocols applied to the Lewis acid-base adducts allowed the differentiation and quantification of framework metal sites in the presence of extraframework oxides, including highly quadrupolar nuclei that are not amenable for quantification with conventional NMR methods. United States. Department of Energy. Office of Basic Energy Sciences (Grant DE-SC0016214) National Institutes of Health (U.S.) (Award EB-002026) 2018-01-26T16:50:19Z 2018-01-26T16:50:19Z 2016-09 2016-08 2018-01-24T19:03:30Z Article http://purl.org/eprint/type/JournalArticle 1932-7447 1932-7455 http://hdl.handle.net/1721.1/113314 Gunther, William R., Vladimir K. Michaelis, Robert G. Griffin, and Yuriy Román-Leshkov. “Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy.” The Journal of Physical Chemistry C 120, 50 (December 2016): 28533–28544 © 2016 American Chemical Society https://orcid.org/0000-0002-6708-7660 https://orcid.org/0000-0003-1589-832X http://dx.doi.org/10.1021/ACS.JPCC.6B07811 Journal of Physical Chemistry C Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf American Chemical Society (ACS) PMC |
| spellingShingle | Gunther, William Robert Michaelis, Vladimir K. Griffin, Robert Guy Román-Leshkov, Yuriy Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy |
| title | Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy |
| title_full | Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy |
| title_fullStr | Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy |
| title_full_unstemmed | Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy |
| title_short | Interrogating the Lewis Acidity of Metal Sites in Beta Zeolites with ¹⁵N Pyridine Adsorption Coupled with MAS NMR Spectroscopy |
| title_sort | interrogating the lewis acidity of metal sites in beta zeolites with ¹⁵n pyridine adsorption coupled with mas nmr spectroscopy |
| url | http://hdl.handle.net/1721.1/113314 https://orcid.org/0000-0002-6708-7660 https://orcid.org/0000-0003-1589-832X |
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