Title: Identification of Cu(II) coordination structures in Cu-ZSM-5, based on a DFT/ab initio assignment of the EPR spectra
Authors: Groothaert, MH ×
Pierloot, Kristine
Delabie, Annelies
Schoonheydt, Robert #
Issue Date: Jan-2003
Publisher: Royal soc chemistry
Series Title: Physical Chemistry Chemical Physics vol:5 issue:10 pages:2135-2144
Abstract: The coordination structures of Cu(II) exchanged into ZSM-5 were obtained by B3LYP-DFT geometry optimizations on cluster models, representing the cation sites. The EPR g-factors of the resulting cluster models were calculated by means of the CASPT2 method (multi-configurational perturbation theory), with the inclusion of spin-orbit coupling. In order to facilitate the confrontation of theoretical and experimental results, the EPR spectra of a selection of dehydrated Cu(II)-ZSM-5 samples are presented as well. The axially symmetric signal with g(parallel to) = 2.30-2.33, which is present over the whole range of copper loadings, is assigned to a five-fold or distorted three-fold Cu(II) coordination in site alpha, a six-ring with bridging T-site, containing 2 lattice Al's. The axially symmetric species with g(parallel to) = 2.26-2.28, present at medium copper loadings, is assigned to a square-planar Cu(II) coordination in six-rings and a square-pyramidal Cu(II) coordination in five-rings, with both rings containing only one Al and no extra-lattice oxygen (ELO). The near absence of the g(parallel to) = 2.26-2.28 signal at the highest Cu/Al ratio's is explained by the coordination of ELO to Cu(II) in these sites with one Al, yielding an EPR silent species.
ISSN: 1463-9076
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Quantum Chemistry and Physical Chemistry Section
Centre for Surface Chemistry and Catalysis
× corresponding author
# (joint) last author

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