Spectroscopic Signatures of Internal Hydrogen Bonds of Brønsted‐Acid Sites in the Zeolite H‐MFI

Autor: Henning Windeck, Fabian Berger, Joachim Sauer
Rok vydání: 2023
Předmět:
Zdroj: Angewandte Chemie
Angewandte Chemie International Edition
ISSN: 1521-3773
1433-7851
Popis: The location of Brønsted-acid sites (bridging OH groups, b-OH) at different crystallographic positions of zeolite catalysts influences their reactivity due to varying confinement. Selecting the most stable b-OH conformers at each of the 12 T-sites (T=Si/Al) of H-MFI, a representative set of 26 conformers is obtained which includes free b-OH groups pointing into the empty pore space and b-OH groups forming H-bonds across five- or six-membered rings of TO4 tetrahedra. Chemically accurate coupled-cluster-quality calculations for periodic models show that the strength of internal H-bonds and, hence, the OH bond length vary substantially with the framework position. For 11 of the 19 H-bonded b-OH groups examined, our predictions fall into the full width at half maximum range of the experimental signals at 3250±175 cm−1 and 7.0±1.4 ppm which supports previously debated assignments of these signals to H-bonded b-OH sites. Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659 Fonds der Chemischen Industrie http://dx.doi.org/10.13039/100018992 OP VVV Excellent Research Teams Studienstiftung des Deutschen Volkes http://dx.doi.org/10.13039/501100004350 North German Supercomputing Alliance (HLRN)
Databáze: OpenAIRE
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