Spectroscopic and Electronic Structural Studies of the Cu(III)<sub>2</sub>Bis-μ-oxo Core and Its Relation to the Side-On Peroxo-Bridged Dimer

Henson, Mark J.; Mukherjee, Pulakesh; Root, David E.; Stack, T. Daniel P.; Solomon, Edward I.

doi:10.1021/ja9918425

Cited by 179 publications

(225 citation statements)

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“…This copper-related Raman band has been assigned to a bis-m-oxo dicopper(III) complex. [32] This assignment is supported by DFT calculations (591 cm À1 ; Figure S3). The CuÀOÀ Cu angle of 1108 matches well with the predictions by the Schoonheydt group.…”

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confidence: 61%

Effect of the Nature and Location of Copper Species on the Catalytic Nitric Oxide Selective Catalytic Reduction Performance of the Copper/SSZ‐13 Zeolite

et al. 2013

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. (2014). Effect of the nature and location of copper species on catalytic nitric oxide selective catalytic reduction performance of the copper/SSZ-13 zeolite. ChemCatChem, 6(2), 634-639. DOI: 10.1002/cctc.201300775 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. [b] Guanna Li, [a, b] Zhaochi Feng, [a] Emiel J. M. Hensen,* [b] and Can Li*[a] IntroductionThe selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia (NH 3 -SCR) is an efficient way for NO x abatement. [1][2][3] Copper-containing zeolites are one of the most active catalyst systems for the related reactions. [3][4][5][6][7][8] The most extensive studies have been performed on Cu/ZSM-5 and Cu/ BEA zeolites. Cu/BEA demonstrates excellent activity with better hydrothermal stability than does Cu/ZSM-5. [7,[9][10][11] The ion-exchanged copper-containing SSZ-13 zeolite, based on the small-pore chabazite (CHA) zeolite topology, recently demonstrated higher activity and selectivity to N 2 over a wide temperature range and better hydrothermal stability than did Cu/ ZSM-5 and Cu/BEA zeolites. [12][13][14][15][16][17] Typically, the catalytic SCR performance of the copper-containing zeolite greatly depends on the location and nature of copper species. The existence of various types of copper species in the zeolite has been proposed: Cu 2 + and Cu + monomers, [CuÀOÀCu] 2 + dimers, and CuO x clusters. [17][18][19] Isolated Cu 2 + species are usually postulated as the active sites in the SCR reaction. [20][21][22] The preparation method strongly affects the nature and speciation of the copper phase. In general, monomeric copper ions located at the cation-exchange sites dominate in ion-exchanged samples, with the fraction of [CuÀOÀ Cu] 2 + dimers typically becoming more important with increasing Cu content. [18] In contrast, precipitation usually results in the formation of a separate CuO phase located at the external zeolite surface. [17][18][19] Lobo et al. suggested that Cu 2 + ions are located in the six-membered rings of the CHA structure. [23] Combining extended X-ray absorption fine structure and in situ UV/Vis spectroscopy, Beale et al. proposed that isolated mononuclear Cu 2 + species slightly shifted toward the edge of the six-membered rings.[20] Kwak et al. reported that the location of ...

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Effect of the Nature and Location of Copper Species on the Catalytic Nitric Oxide Selective Catalytic Reduction Performance of the Copper/SSZ‐13 Zeolite

et al. 2013

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“…Thus, EXAFS cannot provide structural information for this core. A bis( -oxo)dicopper(III) complex is characterized by an intense isotope-sensitive stretch Ϸ600 cm Ϫ1 in its rR spectrum (10,11 (18,19). Fig.…”

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confidence: 99%

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Woertink

Smeets

Groothaert

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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597

653

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Driven by the depletion of crude oil, the direct oxidation of methane to methanol has been of considerable interest. Promising low-temperature activity of an oxygen-activated zeolite, Cu-ZSM-5, has recently been reported in this selective oxidation and the active site in this reaction correlates with an absorption feature at 22,700 cm ؊1 . In the present study, this absorption band is used to selectively resonance enhance Raman vibrations of this active site. 18 O2 labeling experiments allow definitive assignment of the observed vibrations and exclude all previously characterized copper-oxygen species for the active site. In combination with DFT and normal coordinate analysis calculations, the oxygen activated Cu core is uniquely defined as a bent mono-( -oxo)dicupric site. Spectroscopically validated electronic structure calculations show polarization of the low-lying singly-occupied molecular orbital of the [Cu 2O] 2؉ core, which is directed into the zeolite channel, upon approach of CH 4. This induces significant oxyl character into the bridging O atom leading to a low transition state energy consistent with experiment and explains why the bent mono-( -oxo)dicupric core is highly activated for H atom abstraction from CH 4. The oxygen intermediate of Cu-ZSM-5 is now the most well defined species active in the methane monooxygenase reaction. density functional theory ͉ dicopper(II)-oxo ͉ oxygen activation ͉ resonance Raman spectroscopy ͉ zeolite

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“…[18][19][20] However, HT explains our data insufficiently because neither the above-mentioned splitting into two maxima nor the fast decrease is derived correctly (Figure 2c, blue curve). To model two sharp maxima, a simultaneous resonance with two or more excited electronic states needs to be considered, as suggested by Morris and Woodruff.…”

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“…[1, 14,18] Close to these energies, resonant Raman spectra at eleven excitation wavelengths have been collected by using several lasers and a spectrometer specially optimised for the UV region (see Figure S2 in the Supporting Information). [17] The wavelength-dependent Raman spectra of [ 2 ]I 2 show strong vibrational excitations that we have assigned to the bending vibration of the copper-oxygen core at ñ = 114.3 cm À1 and at integer multiples of this excitation ( Figure 2a).…”

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confidence: 99%

“…D n is the distortion parameter of the excited state. [18,23] c am and c bn are the initial and final vibrational levels of the electronic state a with vibrational quantum number m and of the electronic state b with vibrational quantum number n. Here, L nÀm m (S) are the associated Laguerre polynomials. In addition to the ground state with m = 0, the m = 1 excited state is also thermally occupied.…”

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Stabilisation of a Highly Reactive Bis(μ‐oxo)dicopper(III) Species at Room Temperature by Electronic and Steric Constraint of an Unconventional Nitrogen Donor Ligand

Herres‐Pawlis

Binder

Eich

et al. 2009

Chemistry A European J

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Spectroscopic and Electronic Structural Studies of the Cu(III)₂Bis-μ-oxo Core and Its Relation to the Side-On Peroxo-Bridged Dimer

Cited by 179 publications

References 60 publications

Effect of the Nature and Location of Copper Species on the Catalytic Nitric Oxide Selective Catalytic Reduction Performance of the Copper/SSZ‐13 Zeolite

Effect of the Nature and Location of Copper Species on the Catalytic Nitric Oxide Selective Catalytic Reduction Performance of the Copper/SSZ‐13 Zeolite

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Stabilisation of a Highly Reactive Bis(μ‐oxo)dicopper(III) Species at Room Temperature by Electronic and Steric Constraint of an Unconventional Nitrogen Donor Ligand

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Spectroscopic and Electronic Structural Studies of the Cu(III)2Bis-μ-oxo Core and Its Relation to the Side-On Peroxo-Bridged Dimer

Cited by 179 publications

References 60 publications

Effect of the Nature and Location of Copper Species on the Catalytic Nitric Oxide Selective Catalytic Reduction Performance of the Copper/SSZ‐13 Zeolite

Effect of the Nature and Location of Copper Species on the Catalytic Nitric Oxide Selective Catalytic Reduction Performance of the Copper/SSZ‐13 Zeolite

A [Cu 2 O] 2+ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol

Stabilisation of a Highly Reactive Bis(μ‐oxo)dicopper(III) Species at Room Temperature by Electronic and Steric Constraint of an Unconventional Nitrogen Donor Ligand

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Spectroscopic and Electronic Structural Studies of the Cu(III)₂Bis-μ-oxo Core and Its Relation to the Side-On Peroxo-Bridged Dimer

A [Cu ₂ O] ²⁺ core in Cu-ZSM-5, the active site in the oxidation of methane to methanol