Spectroscopic Study of the Surface Coordination of Divalent Copper on Dehydrated a Zeolites

Packet, Dirk; Schoonheydt, Robert A.

doi:10.1016/s0167-2991(09)61139-3

Cited by 5 publications

(4 citation statements)

References 15 publications

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“…5 Nevertheless, we tentatively assume that species H is closely related with the hydrated species reported by Narayana and Kevan. [4][5][6] The EPR parameters of species D (g z ) 2.389, A z ) 0.0139 cm -1 ) agree with those of the copper species in fully dehydrated samples, 5,6,8-10 and especially well with those of Schoonheydt (g z ) 2.386, A z ) 0.0140 cm -1 ) 8 and Pierloot et al (g z ) 2.38, A z ) 0.0139 cm -1 ). 10 X-ray diffraction studies of highly loaded and dehydrated Cu/ NaA samples showed that Cu 2+ was located predominantly at the center of the plane of the six-ring (site II), coordinated to three O(3) atoms in the ring; 3 see Figure 5.…”

Section: Discussionmentioning

confidence: 99%

“…5,6,[8][9][10] On the basis of the absence of deuterium modulation from D 2 O and a weak interaction between Cu 2+ and adsorbed ethylene (C 2 D 4 ) in the ESEEM studies, 5, 23 Kevan's group suggested that Cu 2+ was located at site II′ displaced 0.12 nm from the six-ring plane into the cage and coordinated to three O(3) atoms. 11,23 On the other hand, Schoonheydt located Cu 2+ in the dehydrated species at site II on the basis of the diffuse reflectance spectrum.…”

Section: Discussionmentioning

confidence: 99%

“…3 Several groups have studied this system using EPR and ESEEM (electron spin-echo envelope modulation) techniques. [4][5][6][7][8][9][10] EPR studies have identified three copper(II) species in Cu/NaA. [4][5][6] In freshly prepared and in rehydrated samples, there is only one copper species.…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6][7][8][9][10] EPR studies have identified three copper(II) species in Cu/NaA. [4][5][6] In freshly prepared and in rehydrated samples, there is only one copper species. When this sample is partially dehydrated, either by evacuation at room temperature or by drying in air at 110°C, another species appears with reversed g values (g | < g ⊥ ).…”

Section: Introductionmentioning

confidence: 99%

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Observation of Single-Crystal-Type EPR Spectra from Monolayers of Copper-Exchanged Zeolite Na-A Crystals Assembled on Glass Plates

Lee

et al. 2003

J. Phys. Chem. B

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Single-crystal-type EPR spectra were observed for microcrystals of copper(II)-exchanged zeolite Na-A assembled on glass plates when the magnetic field was perpendicular to the glass surface. Two copper species (H and D) were identified both in the powder sample and in the assembled crystals. The g z direction of species H is parallel to [001] of the cubic crystal, while that of species D is tilted 9°away from [001]. Previously, other authors assumed the g z directions of the two corresponding species to be parallel to [111]. On the basis of the g z directions, we suggest that Cu 2+ in species H is displaced 0.149 nm along [111] from the six-ring plane into the cage and octahedrally coordinated to three zeolite oxygen atoms in the six-ring plane and three water molecules. The g z direction of Cu 2+ in species D is not compatible with site II in the six-ring plane. Species D is probably a trigonal complex with Cu 2+ displaced into the cage and coordinated to three zeolite oxygen atoms.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Observation of Single-Crystal-Type EPR Spectra from Monolayers of Copper-Exchanged Zeolite Na-A Crystals Assembled on Glass Plates

Lee

et al. 2003

J. Phys. Chem. B

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Spectroscopy and Redox Chemistry of Copper in Mordenite

et al. 2014

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Copper-containing zeolites, such as mordenite (MOR), have recently gained increased attention as a consequence of their catalytic potential. While the preferred copper loadings in these catalytic studies are generally high, the literature lacks appropriate spectroscopic and structural information on such Cu-rich zeolite samples. Higher copper loadings increase the complexity of the copper identity and their location in the zeolite host, but they also provide the opportunity to create novel Cu sites, which are perhaps energetically less favorable, but possibly more reactive and more suitable for catalysis. In order to address the different role of each Cu site in catalysis, we here report a combined electron paramagnetic resonance (EPR), UV/Vis-NIR and temperature-programmed reduction (TPR) study on highly copper-loaded MOR. Highly resolved diffuse reflectance (DR) spectra of the CuMOR samples were obtained due to the increased copper loading, allowing the differentiation of two isolated mononuclear Cu(2+) sites and the unambiguous correlation with extensively reported features in the EPR spectrum. Ligand field theory is applied together with earlier suggested theoretical calculations to determine their coordination chemistry and location within the zeolite matrix, and the theoretical analysis further allowed us to define factors governing their redox behavior. In addition to monomeric species, an EPR-silent, possibly dimeric, copper site is present in accordance with its charge transfer absorption feature at 22200 cm(-1), and quantified with TPR. Its full description and true location in MOR is currently being investigated.

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Combined ESR-DRS spectroscopies of transition metal ions and metal ion clusters in zeolites

Schoonheydt

1989

Journal of Physics and Chemistry of Solids

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Spectroscopic Study of the Surface Coordination of Divalent Copper on Dehydrated a Zeolites

Cited by 5 publications

References 15 publications

Observation of Single-Crystal-Type EPR Spectra from Monolayers of Copper-Exchanged Zeolite Na-A Crystals Assembled on Glass Plates

Observation of Single-Crystal-Type EPR Spectra from Monolayers of Copper-Exchanged Zeolite Na-A Crystals Assembled on Glass Plates

Spectroscopy and Redox Chemistry of Copper in Mordenite

Combined ESR-DRS spectroscopies of transition metal ions and metal ion clusters in zeolites

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