Web Release Date: August 24,
Theoretical Study of CuIY Zeolite: Structure and Electronic Properties
Laboratoire de Matériaux Catalytiques et Catalyse en Chimie Organique, UMR 5618, UMI ENSCM-CNRS, 8 rue de l'Ecole Normale, 34296 Montpellier Cedex 5, France
Departamento de Química, Centro de Investigación y de Estudios Avanzados, Av. IPN 2508, Colonia San Pedro Zacatenco 07360, México City D.F., México
Received: June 8, 2006
In Final Form: July 25, 2006
Abstract:
The structural and electronic properties of the accessible CuI site of a faujasite-type zeolite have been studied, by use of large cluster models and a density functional theory-based methodology. We demonstrate that the local ideal C3 symmetry of the CuI site II is broken. The CuI cation is bonded to the zeolite framework by one bond of about 2.26 Å and two shorter ones of 2.07 Å. We demonstrate that only one cation position exists at this site. This result is also confirmed by a molecular electrostatic potential analysis. We show that local properties at site II, as well as the global properties of the solid (frontier orbitals), do not depend on the Al and cation distribution and only slightly on the cocation nature. Taking into account the present results and well-known experimental data, we propose that specific catalytic behaviors are correlated with local response properties, such as the local acid strength or, in other reactions, specific local architecture or confinement.
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