The state of excessively lon-exchanged copper in mordenite: formation of tetragonal hydroxy-bridged copper ion

Kuroda, Yasushige; Kotani, Akira; Maeda, Hironobu; Moriwaki, Hisaki; Morimato, Tetsuo; Nagao, Mahiko

doi:10.1039/ft9928801583

Cited by 95 publications

(69 citation statements)

References 21 publications

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“…The XANES spectra of the dehydrated material are peculiar because the 1s f 4p pre-edge transition is a distinct well-resolved band: this fact is rather unusual for Cu(II) species where the 1s f 4p transition is observed as a shoulder of the edge in most of the cases. 11,22,27,28,[30][31][32][33] The evolution of the XANES features upon progressive outgassing is in accordance with the removal of water: (i) the decrease of white line is classically interpreted with a decrease in coordination; (ii) the red shift and increase in intensity of the 1s f 4p peak is interpreted as an increase of covalency in the ligand-copper bond. It is worth noticing that this transition is better described as a shakedown transition [1s(2)...3d(9)4p(0) L 0 ] f [1s(1)...3d(10)4p(1) L + ] where the internal electronic transition of the metal is accompanied by a ligand to metal electron transfer, 26,35,36 L 0 and L + representing the neutral and charged ligands, respectively.…”

Section: Xanes Spectroscopymentioning

confidence: 83%

Local Structure of Framework Cu(II) in HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates

et al. 2006

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XRD, UV-Vis, EXAFS, XANES, and Raman techniques have been used to study the removal of water molecules coordinated to the Cu(II) framework atoms of the novel HKUST-1 metal-organic framework. The dehydration process preserves the crystalline nature of the material, just causing a reduction of the cell volume due to the shrinking of the [Cu 2 C 4 O 8 ] cage. The removal of adsorbed H 2 O molecule makes the framework Cu(II) sites available for interaction with other probe molecules. In situ IR spectroscopy has evidenced the formation at liquid nitrogen temperature of labile Cu(II)‚‚‚CO adducts characterized by a ν(C-O) ) 2178 cm -1 and at 15 K of Cu(II)‚‚‚H 2 adducts characterized by a ν(H-H) ) 4100 cm -1 . To the best of our knowledge, we have observed for the first time a clear signal of Cu(II) carbonyl and dihydrogen complexes formed inside a crystalline microporous hosting matrix. The sinking of the oxygens of the carboxyl units, undergone by the Cu(II) framework ions in the dehydration process, is responsible for the rather low coordinative unsaturation of Cu(II). The important shielding effect of the four oxygen framework atoms is testified by the low polarization factor of the Cu(II) site probed by both CO and H 2 molecules.

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Section: Xanes Spectroscopymentioning

confidence: 83%

Local Structure of Framework Cu(II) in HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates

et al. 2006

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“…In the latter case, the copper exchange level can reach value as high as 200-400% [1,4,13]. For the over-exchanged Cu-ZSM-5, the predominant copper state corresponds to copper dimers ([Cu-O-Cu] 2+ , [10,17]), bis(-oxo) dicopper [Cu-(O) 2 -Cu] 2+ [3] and chain-like copperoxide structures [4] inside the zeolite channels and highly dispersed copper-oxide clusters on the zeolite surface [9,18,19].…”

Section: Introductionmentioning

confidence: 99%

Cu-substituted ZSM-5 catalyst: Controlling of DeNO reactivity via ion-exchange mode with copper–ammonia solution

Yashnik

Ismagilov

2015

Applied Catalysis B: Environmental

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“…After 24 h at 723 K, complete dehydration can be assumed. 22 The samples were cooled in an O 2 -stream and flushed with He. DRS spectra were recorded on a Varian Cary 5 UV-VIS-NIR spectrophotometer at room temperature.…”

Section: Methodsmentioning

confidence: 99%

The siting of Cu(II) in mordenite: a theoretical spectroscopic study

Delabie

Pierloot

Groothaert

et al. 2001

Phys. Chem. Chem. Phys.

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The siting of Cu(II) in mordenite has been studied by ab initio calculations on large cluster models, representing the cation exchange sites in mordenite. Partial geometry optimizations, based on density functional theory (DFT), were performed to obtain the structure of the coordination environment of Cu(II) at the different sites. The ligand field spectra and EPR g-tensors of these clusters were then calculated by means of multiconfigurational perturbation theory (CASPT2). The calculated results were compared with experimental information, obtained by diffuse reflectance spectroscopy (DRS) and EPR. The calculations indicate that at low exchange levels Cu(II) is coordinated to oxygen six-rings in the main channel of mordenite, in the presence of two aluminiums. At higher loadings, six-or five-rings containing only one aluminium also become occupied, where Cu(II) is coordinated as a single ion, not as (Cu-OH) þ . The calculations indicate also that in fully dehydrated mordenite, the twisted eight-ring (site A) is not occupied by Cu(II).

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The state of excessively lon-exchanged copper in mordenite: formation of tetragonal hydroxy-bridged copper ion

Cited by 95 publications

References 21 publications

Local Structure of Framework Cu(II) in HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates

Local Structure of Framework Cu(II) in HKUST-1 Metallorganic Framework: Spectroscopic Characterization upon Activation and Interaction with Adsorbates

Cu-substituted ZSM-5 catalyst: Controlling of DeNO reactivity via ion-exchange mode with copper–ammonia solution

The siting of Cu(II) in mordenite: a theoretical spectroscopic study

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