Combined Experimental and Theoretical Investigations of Heterogeneous Dual Cation Sites in Cu,M-FER Zeolites

Bulánek, Roman; Frolich, Karel; Čičmanec, Pavel; Nachtigallová, Dana; Pulido, Angeles; Nachtigall, Petr

doi:10.1021/jp200293y

Cited by 24 publications

(21 citation statements)

References 61 publications

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“…DFT method describe exactly Cu + cation locations and stretching frequencies of CO adsorption complexes in Cu(I) zeolite. The present study shows similar results of Cu + cation position to previous studies [18,30,31] from cluster to periodic model. The Cu + cation position located in MCM-22 either on the top of channel wall ring (5 or 6-membered ring) and coordinated with 3 framework oxygen atoms (type I) or on the intersection forming between supercage (12membered ring) and crossing window cage (10membered ring) (type II) or edge of sinusoidal channel and coordinated with only two framework oxygen atoms.…”

Section: Discussionsupporting

confidence: 92%

CO interaction with Cu(I)-MCM-22 zeolite: density functional theory investigation

Viet

Nachtigall

2014

Sci. Tech. Dev. J.

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MCM-22 zeolite has been widely used in many applications for catalysis and adsorption. Especially, this material exchanged with Cu+ cation (Cu(I)-MCM-22) is an active catalyst in green chemical reaction, such as decomposition of NO and N2O. The local geometry of Cu+ in vicinity of Al (III) replacement in six different Si (IV) sites and CO interaction with the most stable Cu+ in each Al site were explored using periodic density functional theory (DFT) method. The CO stretching frequencies were computed applying the ω/r scaling method in which frequencies were determined at high quantum level (couple cluster) and CO bond length calculated at DFT level. The results showed that Cu+ cation located in the channel wall position and intersection position coordinated with 3 or 2 framework oxygen atoms, respectively, before CO adsorption and Cu+ cation coordinated with 2 framework oxygen atoms after CO adsorption. The interaction energies between CO and Cu+ cation were in range - 148 to -195 kJ.mol-1 and CO frequencies exhibit two peaks at 2151 and 2159 cm-1 in good agreement with experimental data. This investigation brought us to understand the Cu+ location in MCM-22 and CO adsorption in Cu(I)-MCM-22 zeolite.

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Section: Discussionsupporting

confidence: 92%

CO interaction with Cu(I)-MCM-22 zeolite: density functional theory investigation

Viet

Nachtigall

2014

Sci. Tech. Dev. J.

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“…In the present case, we can rule out this kind of assignment because we do not see the typical IR bands due to mono-and di-nitrosyl adducts formed on Cu 2 O upon NO adsorption (vide infra Fig. 108 In the same work, CO adsorption complexes on dual cation sites were not observed in Cu-H-FER and Cu-Na-FER zeolites, 108 making it hard to associate the 2134 cm −1 band to a dual cation adsorption centre in Cu-SSZ-13; indeed M can be only H or Cu in our case. Moreover, UV-Vis spectra (vide infra Section 2.2) do not see the strong energy gap at 16 300 cm −1 of Cu 2 O.…”

Section: Papermentioning

confidence: 69%

Characterization of Cu-exchanged SSZ-13: a comparative FTIR, UV-Vis, and EPR study with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios

et al. 2013

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Cu-SSZ-13 has been characterized by different spectroscopic techniques and compared with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios and prepared by the same ion exchange procedure. On vacuum activated samples, low temperature FTIR spectroscopy allowed us to appreciate a high concentration of reduced copper centres, i.e. isolated Cu(+) ions located in different environments, able to form Cu(+)(N2), Cu(+)(CO)n (n = 1, 2, 3), and Cu(+)(NO)n (n = 1, 2) upon interaction with N2, CO and NO probe molecules, respectively. Low temperature FTIR, DRUV-Vis and EPR analysis on O2 activated samples revealed the presence of different Cu(2+) species. New data and discussion are devoted to (i) [Cu-OH](+) species likely balanced by one framework Al atom; (ii) mono(μ-oxo)dicopper [Cu2(μ-O)](2+) dimers observed in Cu-ZSM-5 and Cu-β, but not in Cu-SSZ-13. UV-Vis-NIR spectra of O2 activated samples reveal an intense and finely structured d-d quadruplet, unique to Cu-SSZ-13, which is persistent under SCR conditions. This differs from the 22,700 cm(-1) band of the mono(μ-oxo)dicopper species of the O2 activated Cu-ZSM-5, which disappears under SCR conditions. The EPR signal intensity sets Cu-β apart from the others.

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“…For the sake of comparison with other computational studies [45][46][47][48][49][50][86][87][88] where the PBE [73,74] functional was adopted, additional calculations were performed employing the PBE1PBE [75] functional. Such a modified version of the PBE functional includes a 25% of HartreeFock exchange and was chosen in order to get results comparable at the same time to those obtained by the pure PBE and by the hybrid B3LYP functionals.…”

Section: Basis Set Effects On Cu ? Coordinationmentioning

confidence: 99%

“…The main challenge related to the application of quantum mechanical calculations is to find a compromise between accuracy and computational costs, taking into account that zeolites are complex solids with large unit cells. The most simple and the most complex computational approaches are, respectively, quantum mechanical calculations on small and nonstructure-specific cluster models [36][37][38][39][40][41], or the application of quantum-mechanical methods (mostly based on planewaves DFT) to the full periodicity of the zeolite lattice [42][43][44][45][46][47][48][49][50]. Apart from the above two extreme cases, the most widely employed approaches are nowadays molecular orbital calculations which treat only a portion of the S. Morpurgo (&) Á G. Moretti Á M. Bossa Dipartimento di Chimica, Università degli Studi di Roma ''La Sapienza'', P.le Aldo Moro 5, 00185 Rome, Italy e-mail: simone.morpurgo@uniroma1.it structure (i.e., the active site for a given reaction) taking into account in a variable way the geometrical constraints imposed by the remaining part of the crystal [51,52].…”

Section: Introductionmentioning

confidence: 99%

Basis set effects on Cu(I) coordination in Cu-ZSM-5: a computational study

2012

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DFT calculations on the coordination of Cu+ to the framework oxygen atoms of Al-substituted ZSM-5 were performed by using combinations of different basis sets in order to investigate the dependence of the results on the adopted computational level. With low-end basis sets, a large basis set superposition error (BSSE) favors the coordination of Cu+ to three to four oxygen atoms of the framework, only two of which belong to the AlO4 tetrahedron corresponding to the investigated T-site. More extended basis sets considerably lower the BSSE and favor the coordination of Cu+ to only two oxygen atoms of the AlO4 tetrahedron. Upon interaction with NO, the Cu+ ion is always coordinated by two oxygen atoms of the AlO4 tetrahedron, independently of the basis set adopted and of the coordination number before NO adsorption. The shift from three-to twofold coordination caused by the Cu+-NO interaction requires a deformation energy that lowers the final adsorption energy. Such an effect is relevant with low-end basis sets, whereas it is substantially absent with more extended basis sets, which favor the twofold coordination of Cu+ even before NO adsorption. As a result, high-end basis sets increase the NO interaction energy with respect to that calculated by low-end basis sets, in agreement with experiments and suggesting a possible re-interpretation of the catalytic properties of the investigated sites. Provided suitable scale factors are employed, the N-O stretching frequencies of adsorbed nitrogen oxide calculated by sufficiently extended basis sets turned out in fair agreement with experimental findings

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Combined Experimental and Theoretical Investigations of Heterogeneous Dual Cation Sites in Cu,M-FER Zeolites

Cited by 24 publications

References 61 publications

CO interaction with Cu(I)-MCM-22 zeolite: density functional theory investigation

CO interaction with Cu(I)-MCM-22 zeolite: density functional theory investigation

Characterization of Cu-exchanged SSZ-13: a comparative FTIR, UV-Vis, and EPR study with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios

Basis set effects on Cu(I) coordination in Cu-ZSM-5: a computational study

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