The interaction of NO with copper ions in ZSM5: An EPR and IR investigation

Giamello, Elio; Murphy, Damien M.; Magnacca, Giuliana; Morterra, C.; Shioya, Yasushi; Nomura, Takaiki; Anpo, Masakazu

doi:10.1016/0021-9517(92)90081-r

Cited by 312 publications

(239 citation statements)

References 13 publications

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“…These dinitrosyl complexes might be a plausible intermediate to produce N 2 O and N 2 , which was evidenced by N 2 O formation accompanying with the decrease of IR bands for dinitrosyl species [35,36]. The desorption of oxygen was not detected in this case, probably because oxygen was strongly bounded on silver surfaces and might be slowly released at high temperatures.…”

Section: No-tpd and -Tprmentioning

confidence: 83%

On the selectively catalytic reduction of NOx with methane over Ag-ZSM-5 catalysts

Shi

Cheng

et al. 2002

Applied Catalysis B: Environmental

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Section: No-tpd and -Tprmentioning

confidence: 83%

On the selectively catalytic reduction of NOx with methane over Ag-ZSM-5 catalysts

Shi

Cheng

et al. 2002

Applied Catalysis B: Environmental

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“…In this study, we consider three models of Cu(I) site in ZSM-5 interacting with NO molecule: (a) [ 4 ] -anion (T1) which is the simplest mimic for the nearest surrounding of the cation in a zeolite framework. The model (c) is composed of the fragment of ZSM-5 framework (M7 cluster cut-off the wall in the main channel) hosting Cu(I) cation and NO molecule.…”

Section: Modelsmentioning

confidence: 99%

“…On the other hand, nitric oxide (NO) is the target of paramount importance in environmental catalysis. After Iwamoto's discovery of an unusually high activity of Cu(I) zeolites in NO decomposition and its revival [1][2][3] there has been an ongoing experimental [4][5][6][7][8][9][10][11][12] and theoretical research [13][14][15][16][17][18][19][20][21][22][23] to understand the details of the mechanism of this process. Despite this tremendous effort, there are still a number of unsettled questions, including fundamental query about the nature of the bonding between various forms of copper and NO molecule.…”

Section: Introductionmentioning

confidence: 99%

“…Despite this tremendous effort, there are still a number of unsettled questions, including fundamental query about the nature of the bonding between various forms of copper and NO molecule. Following this line this study deals with the bonding of nitric oxide by Cu/MFI zeolite, showing highcatalytic activity in direct NO x decomposition [4][5][6][7], as opposed to naked Cu ? ions in gas phase that do not catalyze this reaction [22].…”

Section: Introductionmentioning

confidence: 99%

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On the nature of spin- and orbital-resolved Cu+–NO charge transfer in the gas phase and at Cu(I) sites in zeolites

et al. 2012

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Electronic factors essential for NO activation by Cu(I) sites in zeolites are investigated within spin-resolved analysis of electron transfer channels (natural orbitals for chemical valence). NOCV analysis is performed for three DFT-optimized models of Cu(I)-NO site in ZSM-5: [CuNO] ? , (T1)CuNO, and (M7)CuNO. NO as a non-innocent, openshell ligand reveals significant differences between independent deformation density components for a and b spins. Four distinct components are identified: (i) unpaired electron donation from NO p k * antibonding orbital to Cu s,d ; (ii) backdonation from copper d yz to p \ * antibonding orbital; (iii) donation from occupied p k and Cu d xz to bonding region, and (iv) donation from nitrogen lone-pair to Cu s,d . Channel (i), corresponding to one-electron bond, shows-up solely for spin majority and is effective only in the interaction of NO with naked Cu ? . Channel (ii) dominates for models b and c: it strongly activates NO bond by populating antibonding p* orbital and weakens the N-O bond in contrast to channel (i), depopulating the antibonding orbital and strengthening N-O bond. This picture perfectly agrees with IR experiment: interaction with naked Cu ? imposes small blue-shift of NO stretching frequency while it becomes strongly red-shifted for Cu(I) site in ZSM-5 due to enhanced backdonation.

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“…Despite this tremendous effort, there are still a number of unsettled questions, including the uncertainty about the nature of the reaction intermediates and about the structure of the active site; [2] either the involvement of only a single extra-framework Cu cation [3][4][5][6][7][8] or the concerted effect of two nearby Cu cations, the Cu pair, [9][10][11][12][13][14] was proposed. From the vast amount of relevant experimental data available today, it is clear that the activity of the Cu/zeolite catalysts depends on 1) zeolite topology, 2) zeolite composition (Si/Al ratio and Cu loading), and 3) Cu-exchange procedure, including the sample pretreatment.…”

mentioning

confidence: 99%

Correlation Between Catalytic Activity and Metal Cation Coordination: NO Decomposition Over Cu/Zeolites

Pulido

Nachtigall

2009

ChemCatChem

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Since Iwamoto's discovery of an unusually high activity of Cu/zeolites in NO decomposition, [1] there has been an ongoing experimental and theoretical quest to understand the details of the mechanism of this process. Despite this tremendous effort, there are still a number of unsettled questions, including the uncertainty about the nature of the reaction intermediates and about the structure of the active site; [2] either the involvement of only a single extra-framework Cu cation [3][4][5][6][7][8] or the concerted effect of two nearby Cu cations, the Cu pair, [9][10][11][12][13][14] was proposed. From the vast amount of relevant experimental data available today, it is clear that the activity of the Cu/zeolite catalysts depends on 1) zeolite topology, 2) zeolite composition (Si/Al ratio and Cu loading), and 3) Cu-exchange procedure, including the sample pretreatment. [4,6,8,12,13,15] However, the understanding of the relationship between active site structure (the metal coordination and localization) and catalytic activity is far from complete; it is our goal to increase our knowledge in this respect.The lack of direct experimental evidence about the transition-state structures and about the details of the reaction mechanism justifies the use of quantum chemistry to provide the missing details. However, a reliable description of the reactions catalyzed by transition metals in a complex environment (such as zeolites) represents a major challenge for contemporary computational chemistry since it requires the use of a model that realistically represents the active site (including its environment) and the use of a method that can consistently describe the electronic structure of the system along the reaction path (see the Methods section). Many reaction steps possibly involved in the direct NO decomposition on Cu/zeolites have been investigated previously by employing various models and methods. [16][17][18][19][20] Several reaction paths proposed in the literature have been compiled (Scheme 1) along with the reaction energies and activation barriers (where available) reported for the elementary reaction steps. Since these energies were obtained at various levels of theory using different types of models for the active site, a direct comparison should be taken with some caution. For example, the reaction energies of À107 and À173 kJ mol À1 were reported for reaction step D based on the BP86 functional (using a 1-T cluster model) and based on the B3LYP functional (using a 3-T cluster model), respectively. [16,17]

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The interaction of NO with copper ions in ZSM5: An EPR and IR investigation

Cited by 312 publications

References 13 publications

On the selectively catalytic reduction of NOx with methane over Ag-ZSM-5 catalysts

On the selectively catalytic reduction of NOx with methane over Ag-ZSM-5 catalysts

On the nature of spin- and orbital-resolved Cu+–NO charge transfer in the gas phase and at Cu(I) sites in zeolites

Correlation Between Catalytic Activity and Metal Cation Coordination: NO Decomposition Over Cu/Zeolites

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