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Nature of Copper Active Sites in CuZSM-5: Theory and Experiment
Institute of Catalysis, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Cracow, Poland
Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060 Cracow, Poland
* Author to whom correspondence should be addressed.
Received: 11 October 2001; Accepted: 31 January 2002 / Published: 25 April 2002
Abstract: We report here a concise resume reporting the way of constructing the model of an active site composed of transition metal cation exchanged in zeolites. The main goal was to devise the model of CuZSM-5 capable of describing geometrical and electronic properties of metal sites and adsorption complexes with small molecules. The models were built up starting from simple ring structures encountered in ZSM-5 framework to fused rings’ model selected as the representative of α position for hosting the exchanged cation. Geometrical and electronic properties of the basal model, composed of the extended framework cluster with Cu+ or Cu2+ cation, and adsorption complexes with diatomic molecules were extracted from DFT calculations. The stress was put here on direct confirmation of structural changes on copper reduction/oxidation and adsorption. Electron donor/acceptor properties of the sites combined with electronic properties of adsorbed molecules led to the proposal for the mechanism of NO activation by Cu+ZSM-5: transfer of electrons from copper d orbitals to antibonding states of NO should cause large weakening of the bond, which was evidenced also by IR measurements.
Keywords: CuZSM-5; deNOx; active sites; molecular modeling; density functional theory
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Broclawik, E.; Datka, J.; Gil, B.; Kozyra, P. Nature of Copper Active Sites in CuZSM-5: Theory and Experiment. Int. J. Mol. Sci. 2002, 3, 435-444.
Broclawik E, Datka J, Gil B, Kozyra P. Nature of Copper Active Sites in CuZSM-5: Theory and Experiment. International Journal of Molecular Sciences. 2002; 3(4):435-444.
Broclawik, Ewa; Datka, Jerzy; Gil, Barbara; Kozyra, Pawel. 2002. "Nature of Copper Active Sites in CuZSM-5: Theory and Experiment." Int. J. Mol. Sci. 3, no. 4: 435-444.