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Cluster Models of Cu Binding and CO and NO Adsorption in Cu-Exchanged Zeolites W. F. Schneider* and K. C. Hass*
 

Summary: Cluster Models of Cu Binding and CO and NO Adsorption in Cu-Exchanged Zeolites
W. F. Schneider* and K. C. Hass*
Ford Research Laboratory, MD 3083/SRL, Dearborn, Michigan 48121-2053
R. Ramprasad and J. B. Adams
Department of Materials Science and Engineering, UniVersity of Illinois, Urbana, Illinois 61801
ReceiVed: August 1, 1995; In Final Form: October 23, 1995X
A small cluster model is proposed and used to examine the properties of bound Cu ions and their interactions
with CO and NO in Cu-exchanged zeolites, such as Cu-ZSM-5. The model uses H2O ligands to represent
the framework oxygens of the zeolite lattice that form the local coordination environment of the Cu ion.
Variations in the oxidation state of the metal center are simulated by adjusting the net charge on the clusters.
Density functional theory is used to predict the molecular and electronic structures and binding energies of
these model clusters, including Cu(H2O)x
n+, Cu(H2O)xCOn+, and Cu(H2O)xNOn+ (x ) 1-4, n ) 0-2). While
quite simplistic, this model provides considerable insight into the behavior and interactions of zeolite-bound
Cu ions. Both Cu+
and Cu2+
ions are found to bind strongly to H2O (or bridge oxygen) ligands, with Cu2+
preferring higher and Cu+ preferring lower coordination numbers. CO and NO also bind strongly to both Cu
ions. Cu2+ preferentially binds the three ligands in the order Cu2+-NO > Cu2+-OH2 > Cu2+-CO while
Cu+

  

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

 

Collections: Materials Science