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Title: Natural Abundance 17O DNP NMR Provides Precise O$-$H Distances and Insights into the Brønsted Acidity of Heterogeneous Catalysts

Authors:
ORCiD logo [1];  [1];  [1]; ORCiD logo [1]; ORCiD logo [1]
  1. U.S. DOE Ames Laboratory, and Department of Chemistry, Iowa State University, Ames IA 50011 USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1374913
Grant/Contract Number:
AC02-07CH11358; FY2015-MPRU-0812
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Angewandte Chemie
Additional Journal Information:
Journal Volume: 129; Journal Issue: 31; Related Information: CHORUS Timestamp: 2017-11-10 06:52:14; Journal ID: ISSN 0044-8249
Publisher:
German Chemical Society
Country of Publication:
Germany
Language:
English

Citation Formats

Perras, Frédéric A., Wang, Zhuoran, Naik, Pranjali, Slowing, Igor I., and Pruski, Marek. Natural Abundance 17O DNP NMR Provides Precise O$-$H Distances and Insights into the Brønsted Acidity of Heterogeneous Catalysts. Germany: N. p., 2017. Web. doi:10.1002/ange.201704032.
Perras, Frédéric A., Wang, Zhuoran, Naik, Pranjali, Slowing, Igor I., & Pruski, Marek. Natural Abundance 17O DNP NMR Provides Precise O$-$H Distances and Insights into the Brønsted Acidity of Heterogeneous Catalysts. Germany. doi:10.1002/ange.201704032.
Perras, Frédéric A., Wang, Zhuoran, Naik, Pranjali, Slowing, Igor I., and Pruski, Marek. Fri . "Natural Abundance 17O DNP NMR Provides Precise O$-$H Distances and Insights into the Brønsted Acidity of Heterogeneous Catalysts". Germany. doi:10.1002/ange.201704032.
@article{osti_1374913,
title = {Natural Abundance 17O DNP NMR Provides Precise O$-$H Distances and Insights into the Brønsted Acidity of Heterogeneous Catalysts},
author = {Perras, Frédéric A. and Wang, Zhuoran and Naik, Pranjali and Slowing, Igor I. and Pruski, Marek},
abstractNote = {},
doi = {10.1002/ange.201704032},
journal = {Angewandte Chemie},
number = 31,
volume = 129,
place = {Germany},
year = {Fri May 12 00:00:00 EDT 2017},
month = {Fri May 12 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on June 6, 2018
Publisher's Accepted Manuscript

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  • Heterogeneous Brønsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Brønsted acid sites can be directly observed at natural abundance by 17O DNP surface-enhanced NMR spectroscopy (SENS). We additionally show that the O–H bond length in these catalysts can be measured with sub-picometer precision, to enable a direct structural gauge of the lability of protons in a given material, which is correlated with the pH of the zero point of charge of the material. As a result, experiments performed on materials impregnated with pyridine also allow for the direct detection ofmore » intermolecular hydrogen bonding interactions through the lengthening of O–H bonds.« less
  • Due to its extremely low natural abundance and quadrupolar nature, the 17O nuclide is very rarely used for spectroscopic investigation of solids by NMR without isotope enrichment. Additionally, the applicability of dynamic nuclear polarization (DNP), which leads to sensitivity enhancements of 2 orders of magnitude, to 17O is wrought with challenges due to the lack of spin diffusion and low polarization transfer efficiency from 1H. Here, we demonstrate new DNP-based measurements that extend 17O solid-state NMR beyond its current capabilities. The use of the PRESTO technique instead of conventional 1H– 17O cross-polarization greatly improves the sensitivity and enables the facilemore » measurement of undistorted line shapes and two-dimensional 1H– 17O HETCOR NMR spectra as well as accurate internuclear distance measurements at natural abundance. This was applied for distinguishing hydrogen-bonded and lone 17O sites on the surface of silica gel; the one-dimensional spectrum of which could not be used to extract such detail. As a result, this greatly enhanced sensitivity has enabled, for the first time, the detection of surface hydroxyl sites on mesoporous silica at natural abundance, thereby extending the concept of DNP surface-enhanced NMR spectroscopy to the 17O nuclide.« less
  • Dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy is increasingly being used as a tool for the atomic-level characterization of surface sites. DNP surface-enhanced SSNMR spectroscopy of materials has, however, been limited to studying relatively receptive nuclei, and the particularly rare 17O nuclide, which is of great interest for materials science, has not been utilized. We demonstrate that advanced 17O SSNMR experiments can be performed on surface species at natural isotopic abundance using DNP. We use 17O DNP surface-enhanced 2D SSNMR to measure 17O{ 1H} HETCOR spectra as well as dipolar oscillations on a series of thermally treatedmore » mesoporous silica nanoparticle samples having different pore diameters. These experiments allow for a nonintrusive and unambiguous characterization of hydrogen bonding and dynamics at the surface of the material; no other single experiment can give such details about the interactions at the surface. Lastly, our data show that, upon drying, strongly hydrogen-bonded surface silanols, whose motions are greatly restricted by the interaction when compared to lone silanols, are selectively dehydroxylated.« less
  • Here, we report that spatial (<1 nm) proximity between different molecules in solid bulk materials and, for the first time, different moieties on the surface of a catalyst, can be established without isotope enrichment by means of homonuclear CHHC solid-state nuclear magnetic resonance experiment. This 13C– 13C correlation measurement, which hitherto was not possible for natural-abundance solids, was enabled by the use of dynamic nuclear polarization. Importantly, it allows the study of long-range correlations in a variety of materials with high resolution.