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Natural Abundance O-17 DNP NMR Provides Precise O-H Distances and Insights into the Bronsted Acidity of Heterogeneous Catalysts

TitleNatural Abundance O-17 DNP NMR Provides Precise O-H Distances and Insights into the Bronsted Acidity of Heterogeneous Catalysts
Publication TypeJournal Article
Year of Publication2017
AuthorsPerras, FA, Wang, ZR, Naik, P, Slowing, II, Pruski, M
JournalAngewandte Chemie-International Edition
Volume56
Pagination9165-9169
Date Published07
Type of ArticleArticle
ISBN Number1433-7851
Accession NumberWOS:000424260200042
KeywordsBronsted acidity, chemistry, dynamic nuclear polarization, dynamic nuclear-polarization, gamma-alumina, Heterogeneous catalysis, natural-abundance O-17, oxides, silica, sites, solid-state nmr, solid-state NMR spectroscopy, Spectroscopy, surface, zeolites, zero-point
Abstract

Heterogeneous Bronsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Bronsted acid sites can be directly observed at natural abundance by O-17 DNP surfaceenhanced 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. Experiments performed on materials impregnated with pyridine also allow for the direct detection of intermolecular hydrogen bonding interactions through the lengthening of O-H bonds.

DOI10.1002/anie.201704032
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