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Density Functional Theory Molecular Cluster Study of Copper Interaction with Nitric Oxide Dimer in Cu−ZSM-5 Catalysts

“…Spatial π-interaction of Two Oxygen Atoms Implements π-Conjugation of the Bonds and Stabilizes the cis Form of ONNO Dimer Table 1. spin density on the oxygen atoms: F s (O1) ) 0.6 e and F s (O2) ) 0.9 e. We believe that these results are consistent with the observation of the ESR spectrum of O -ion radicals for Cu-ZSM-5 zeolites. 22,25 The calculated geometry of model CAS is almost linear: ∠O1Cu2O2 ) 179.6°and ∠AlO2Cu2 ) 174.0°. Only ∠Cu1O1Cu2 ) 145.1°angle is smaller than 180°.…”

“…The molecular cluster (HO) 3 Al-OCu-O-Cu has a great number of possible electronic states because of the intermixing of oxygen p-orbitals and copper d-orbitals. [22][23][24][25] We found that the lowest energy state of this cluster corresponds to the S ) 1 with spin populations on the oxygen atoms [(HO) 3 …”

“…This agrees well with the observation of the ESR spectra of O -ion radicals for Cu-ZSM-5 zeolites. 22,24 All calculations, geometry optimizations, and search of a transition state (TS) were performed with the Gaussian-98 package 38 at the DFT level using the hybrid exchange-correlation functional B3LYP. 39,40 The following basis set partition scheme was employed:…”

“…[23][24][25] This conclusion agree with ESR data for isolated Cu 2+ ions. 4,6,22,25 The intensive band in 30 000-32 000 cm -1 is identified as CTB L f M corresponding to square-plain oxide clusters. 24, 25 The origin of two bands 15 000-17 000 cm -1 and 18 000-23 000 cm -1 is not known and we assume that these bands are arising from copper oxide chain structures in zeolite channels.…”

“…Stabilization of isolated Cu 2+ and Cu + ions, [4][5][6][7][8] as well as oxide CuO-and Cu 2 O-like clusters, 9,10 [22][23][24][25] in Cu-ZSM-5 has been observed by spectroscopic methods. These copper states each have been suggested to act as catalytic active sites in NO decomposition and SCR by hydrocarbons.…”