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

Schoonheydt, Robert A.

doi:10.1016/0022-3697(89)90430-7

Cited by 41 publications

(16 citation statements)

References 52 publications

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“…40,59,69,86,[116][117][118] Fully hydrated samples have a pale blue color, and corresponding UV-Vis-NIR spectra are shown in Fig. hydrated and O 2 activated samples.…”

Section: Uv-vis-nir Spectroscopymentioning

confidence: 99%

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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“…40,59,69,86,[116][117][118] Fully hydrated samples have a pale blue color, and corresponding UV-Vis-NIR spectra are shown in Fig. hydrated and O 2 activated samples.…”

Section: Uv-vis-nir Spectroscopymentioning

confidence: 99%

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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“…[1] Cu 2 + -zeolites are, for instance, used as active catalysts for a range of reactions, such as the decomposition of nitrogen oxides, [2][3][4][5][6][7][8][9][10][11][12][13] the selective hydroxylation of methane and benzene to methanol [14][15][16][17][18][19][20] and phenol [21][22][23][24][25] respectively, and the oxidative carbonylation of alcohols. [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] Location of TMIs in zeolites and their coordination is thus established for many zeolite topologies and zeolite compositions. Indeed, Cu 2 + -zeolites are excellent probes to study the coordination chemistry of transition metal ions (TMIs), mainly with the combination of UV/Vis-NIR and EPR spectroscopy and theoretical approaches.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, Cu 2 + -zeolites are excellent probes to study the coordination chemistry of transition metal ions (TMIs), mainly with the combination of UV/Vis-NIR and EPR spectroscopy and theoretical approaches. [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50] Location of TMIs in zeolites and their coordination is thus established for many zeolite topologies and zeolite compositions. [1] Often these spectroscopic studies focused on low transition metal contents, [35][36][37][38]51] while the best catalytic results were mainly reported with high Cu 2 + loadings.…”

Section: Introductionmentioning

confidence: 99%

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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“…The coordination of Co 2+ , Ni 2+ and Cu 2+ in zeolites are exemplary studies that illustrate this point. 24,45,[56][57][58][59] For the study of the coordination of Cu 2+ to lattice oxygens in zeolites UV-VIS-NIR spectroscopy in DRS mode in combination with EPR is the preferred approach. Both techniques give complementary information on the number of oxygen atoms and their arrangement in the first coordination sphere.…”

Section: Coordination Of Tmi To Surface Oxygensmentioning

confidence: 99%

UV-VIS-NIR spectroscopy and microscopy of heterogeneous catalysts

Schoonheydt

2010

Chem. Soc. Rev.

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122

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This critical review article discusses the characterization of heterogeneous catalysts by UV-VIS-NIR spectroscopy and microscopy with special emphasis on transition metal ion containing catalysts. A review is given of the transitions, that can be observed in the UV-VIS-NIR region and the peculiarities of catalytic solids that have to be taken into account. This is followed by a short discussion of the techniques that have been developed over the years: diffuse reflectance spectroscopy, UV-VIS microscopy, in situ or operando spectroscopy, the combination of UV-VIS spectroscopy with other spectroscopic techniques, with chemometrics and with quantum chemistry. In the third part of this paper four successes of UV-VIS-NIR spectroscopy and microscopy are discussed; (1) coordination of transition metal ions to surface oxygens; (2) quantitative determination of the oxidation states of transition metal ions; (3) characterization of active sites and (4) study of the distribution of transition metal ions and carbocations in catalytic bodies, particles and crystals (104 references).

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

Cited by 41 publications

References 52 publications

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

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

Spectroscopy and Redox Chemistry of Copper in Mordenite

UV-VIS-NIR spectroscopy and microscopy of heterogeneous catalysts

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