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Identity of two types of strong Brønsted acid sites in mazzite revealed by CO probe: IR study and periodic DFT modeling
Author(s) -
Rejmak Paweł,
Datka Jerzy,
Broclawik Ewa
Publication year - 2019
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25873
Subject(s) - redshift , density functional theory , brønsted–lowry acid–base theory , adsorption , chemistry , spectral line , infrared spectroscopy , catalysis , infrared , chemical physics , crystallography , physics , computational chemistry , astrophysics , quantum mechanics , organic chemistry , galaxy
The nature of catalytic Brønsted sites in mazzite is clarified by molecular modeling combined with spectroscopy. Density Functional Theory study for periodic models of high‐silica mazzite evidence that most stable bridging hydroxyls, noticeably binding CO probe, fall into two categories: Brønsted sites located in larger channels, characterized by higher OH frequency of bare hydroxyl with very large redshift upon CO interaction, and lower‐frequency sites located in smaller channels, showing lower redshift. This fully corresponds to two bands obtained for OH stretch in IR spectra. Very good agreement between theory and experiment found in this work not only confirms that Brønsted sites studied here belong to the strongest acid sites among known zeolites but also clarifies their identity in mazzite. Location of sites with exceptionally large red shift upon CO adsorption at 12‐T wide channel very well conforms to both intuitive expectations and predictions for other zeolites from former studies.