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Theoretical Study of CO and NO Vibrational Frequencies in Cu-Water Clusters and Implications for Cu-Exchanged Zeolites
 

Summary: ARTICLES
Theoretical Study of CO and NO Vibrational Frequencies in Cu-Water Clusters and
Implications for Cu-Exchanged Zeolites
R. Ramprasad, W. F. Schneider, K. C. Hass,*, and J. B. Adams,
Department of Materials Science and Engineering, UniVersity of Illinois, Urbana, Illinois 61801, and
Ford Research Laboratory, MD 3028/SRL, Dearborn, Michigan 48121-2053
ReceiVed: May 21, 1996; In Final Form: December 23, 1996X
Local spin density functional theory calculations of vibrational frequencies were performed for small Cu-
containing complexes in an effort to assess models of exchanged Cu ion sites in zeolites and to help interpret
infrared spectroscopy results. Model complexes consisted of Cun+ (n ) 0-2) ions with varying coordination
to water ligands and to more realistic fragments of zeolites. Calculated CO and NO vibrational frequencies
for Cu-bound mono- and dicarbonyl and mono- and dinitrosyl species lie in ranges consistent with
experimentally observed frequencies and confirm earlier assignments. Our results show a clear linear correlation
between bond length and frequency for both carbonyl and nitrosyl complexes. The (nominal) oxidation state
of Cu in these complexes is the most important factor in determining CO and NO frequencies and bond
lengths, with the local coordination of Cu and the presence of explicit countercharges producing secondary
effects.
I. Introduction
Cu-exchanged zeolites, particularly ZSM-5, show consider-
able promise both for the selective catalytic reduction (SCR)

  

Source: Adams, James B - Department of Chemical and Materials Engineering, Arizona State University

 

Collections: Materials Science