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[Cu_2O]^(2+) active site formation in Cu-ZSM-5: geometric and electronic structure requirements for N_2O activation

Tsai, Ming-Li and Hadt, Ryan G. and Vanelderen, Pieter and Sels, Bert F. and Schoonheydt, Robert A. and Solomon, Edward I. (2014) [Cu_2O]^(2+) active site formation in Cu-ZSM-5: geometric and electronic structure requirements for N_2O activation. Journal of the American Chemical Society, 136 (9). pp. 3522-3529. ISSN 0002-7863. doi:10.1021/ja4113808.

[img] PDF (Full listing of authors for ref 44; calculated [Cu2O]2+ and binuclear CuI DFT models for the other 9 possible pairs; schematic representations of η1-N2O binding modes for sites 7 and site4; spin densities, Mulliken charges, and Mayer bond order analys...) - Supplemental Material
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Understanding the formation mechanism of the [Cu_2O]^(2+) active site in Cu-ZSM-5 is important for the design of efficient catalysts to selectively convert methane to methanol and related value-added chemicals and for N_2O decomposition. Spectroscopically validated DFT calculations are used here to evaluate the thermodynamic and kinetic requirements for formation of [Cu_2O](2+) active sites from the reaction between binuclear Cu(I) sites and N_2O in the 10-membered rings Cu-ZSM-5. Thermodynamically, the most stable Cu^I center prefers bidentate coordination with a close to linear bite angle. This binuclear Cu^I site reacts with N_2O to generate the experimentally observed [Cu_2O]^(2+) site. Kinetically, the reaction coordinate was evaluated for two representative binuclear Cu^I sites. When the Cu-Cu distance is sufficiently short (<4.2 Å), N_2O can bind in a "bridged" μ-1,1-O fashion and the oxo-transfer reaction is calculated to proceed with a low activation energy barrier (2 kcal/mol). This is in good agreement with the experimental E_a for N_2O activation (2.5 ± 0.5 kcal/mol). However, when the Cu-Cu distance is long (>5.0 Å), N_2O binds in a "terminal" η^1-O fashion to a single Cu^I site of the dimer and the resulting E_a for N_2O activation is significantly higher (16 kcal/mol). Therefore, bridging N_2O between two Cu^I centers is necessary for its efficient two-electron activation in [Cu_2O]^(2+) active site formation. In nature, this N_2O reduction reaction is catalyzed by a tetranuclear Cu_Z cluster that has a higher E_a. The lower E_a for Cu-ZSM-5 is attributed to the larger thermodynamic driving force resulting from formation of strong Cu^(II)-oxo bonds in the ZSM-5 framework.

Item Type:Article
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URLURL TypeDescription Information
Hadt, Ryan G.0000-0001-6026-1358
Solomon, Edward I.0000-0003-0291-3199
Alternate Title:[Cu2O]2+ active site formation in Cu-ZSM-5: geometric and electronic structure requirements for N2O activation
Additional Information:© 2014 American Chemical Society. Received: November 7, 2013. Published: February 13, 2014. This work was supported by National Science Foundation Grant CHE-0948211 (to E.I.S.) and funded within the framework of FWO (G.0596.11), IAP (Belspo), ERIC, Methusalem (long-term structural funding by the Flemish Government) projects. We acknowledge Mrs. Esther Johnston for carefully reading the manuscript. M.-L.T. received support from the Postdoctoral Research Abroad Program sponsored by the National Science Council, Taiwan (R.O.C.), and R.G.H. acknowledges a Gerhard Casper Stanford Graduate Fellowship and Achievement Rewards for College Scientists (ARCS) Foundation. The authors declare no competing financial interest.
Funding AgencyGrant Number
Fonds Wetenschappelijk Onderzoek (FWO)G.0596.11
Belgian Federal Science Policy Office (BELSPO)UNSPECIFIED
National Science Council (Taipei)UNSPECIFIED
Stanford UniversityUNSPECIFIED
Issue or Number:9
Record Number:CaltechAUTHORS:20180612-145030835
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Official Citation:[Cu2O]2+ Active Site Formation in Cu–ZSM-5: Geometric and Electronic Structure Requirements for N2O Activation Ming-Li Tsai, Ryan G. Hadt, Pieter Vanelderen, Bert F. Sels, Robert A. Schoonheydt, and Edward I. Solomon Journal of the American Chemical Society 2014 136 (9), 3522-3529 DOI: 10.1021/ja4113808
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87027
Deposited By: George Porter
Deposited On:12 Jun 2018 22:06
Last Modified:15 Nov 2021 20:44

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