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  Local Platinum Environments in a Solid Analogue of the Molecular Periana Catalyst

Soorholtz, M., Jones, L. C., Samuelis, D., Weidenthaler, C., White, R. J., Titirici, M.-M., et al. (2016). Local Platinum Environments in a Solid Analogue of the Molecular Periana Catalyst. ACS Catalysis, 6(4), 2332-2340. doi:10.1021/acscatal.5b02305.

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 Creators:
Soorholtz, Mario1, Author           
Jones, Louis C.2, Author
Samuelis, Dominik3, Author
Weidenthaler, Claudia4, Author           
White, Robin J.5, Author
Titirici, Maria-Magdalena5, Author
Cullen, David A.6, Author
Zimmermann, Tobias7, Author           
Antonietti, Markus5, Author
Maier, Joachim5, Author
Palkovits, Regina1, 8, Author           
Chmelka, Bradley F.2, Author
Schüth, Ferdi7, Author           
Affiliations:
1Research Group Palkovits, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445615              
2Department of Chemical Engineering, University of California, Santa Barbara, California 93106-5080, United States, ou_persistent22              
3Max Planck Institute for Solid State Research, Stuttgart, D-70569, Germany, ou_persistent22              
4Research Group Weidenthaler, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1950291              
5Max Planck Institute of Colloids and Interfaces, Potsdam, D-14476, Germany, ou_persistent22              
6Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States, ou_persistent22              
7Research Department Schüth, Max-Planck-Institut für Kohlenforschung, Max Planck Society, ou_1445589              
8RWTH Aachen University, Aachen, D-52074, Germany, ou_persistent22              

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Free keywords: methane oxidation; Periana catalyst; solid analogue vs molecular catalyst; solid-state 195Pt NMR; atomic dispersion
 Abstract: Combining advantages of homogeneous and heterogeneous catalysis by incorporating active species on a solid support is often an effective strategy for improving overall catalyst performance, although the influences of the support are generally challenging to establish, especially at a molecular level. Here, we report the local compositions, and structures of platinum species incorporated into covalent triazine framework (Pt-CTF) materials, a solid analogue of the molecular Periana catalyst, Pt(bpym)Cl2, both of which are active for the selective oxidation of methane in the presence of concentrated sulfuric acid. By using a combination of solid-state 195Pt nuclear magnetic resonance (NMR) spectroscopy, aberration-corrected scanning transmission electron microscopy (AC-STEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), important similarities and differences are observed between the Pt-CTF and Periana catalysts, which are likely related to their respective macroscopic reaction properties. In particular, wide-line solid-state 195Pt NMR spectra enable direct measurement, identification, and quantification of distinct platinum species in as-synthesized and used Pt-CTF catalysts. The results indicate that locally ordered and disordered Pt sites are present in as-synthesized Pt-CTF, with the former being similar to one of the two crystallographically distinct Pt sites in crystalline Pt(bpym)Cl2. A distribution of relatively disordered Pt moieties is also present in the used catalyst, among which are the principal active sites. Similarly XAS shows good agreement between the measured data of Pt-CTF and a theoretical model based on Pt(bpym)Cl2. Analyses of the absorption spectra of Pt-CTF used for methane oxidation suggests ligand exchange, as predicted for the molecular catalyst. XPS analyses of Pt(bpym)Cl2, Pt-CTF, as well as the unmodified ligands, further corroborate platinum coordination by pyridinic N atoms. Aberration-corrected high-angle annular dark-field STEM proves that Pt atoms are distributed within Pt-CTF before and after catalysis. The overall results establish the close similarities of Pt-CTF and the molecular Periana catalyst Pt(bpym)Cl2, along with differences that account for their respective properties.

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Language(s): eng - English
 Dates: 2015-10-142016-02-162016-04-01
 Publication Status: Published in print
 Pages: 9
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1021/acscatal.5b02305
 Degree: -

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Title: ACS Catalysis
  Abbreviation : ACS Catal.
Source Genre: Journal
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Publ. Info: Washington, DC : ACS
Pages: - Volume / Issue: 6 (4) Sequence Number: - Start / End Page: 2332 - 2340 Identifier: CoNE: https://pure.mpg.de/cone/journals/resource/2155-5435