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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. https://resolver.caltech.edu/CaltechAUTHORS:20180612-145030835

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Abstract

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
Related URLs:
URLURL TypeDescription
https://doi.org/10.1021/ja4113808DOIArticle
https://pubs.acs.org/doi/suppl/10.1021/ja4113808PublisherSupporting Information
ORCID:
AuthorORCID
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.
Funders:
Funding AgencyGrant Number
NSFCHE-0948211
Fonds Wetenschappelijk Onderzoek (FWO)G.0596.11
Belgian Federal Science Policy Office (BELSPO)UNSPECIFIED
National Science Council (Taipei)UNSPECIFIED
Stanford UniversityUNSPECIFIED
ARCS FoundationUNSPECIFIED
Issue or Number:9
Record Number:CaltechAUTHORS:20180612-145030835
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180612-145030835
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
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:12 Jun 2018 22:06
Last Modified:03 Oct 2019 19:51

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