25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

Surface Structure Determination of Heterogeneous Catalysts by DNP SENS

27 Aug 2019, 12:30
30m
Lecture Hall C (Henry Ford Building)

Lecture Hall C

Henry Ford Building

Talk Materials applications Materials

Speaker

Ribal Jabbour (High-Field NMR Center, Université de Lyon, FRE 2034, CNRS/ENS Lyon/ UCB Lyon1)

Description

Dynamic Nuclear Polarization (DNP) is one of the promising approaches to overcome the sensitivity limitations of solid-state NMR, and has recently emerged as a powerful technique to amplify the NMR signals of surface species.1 We have recently demonstrated that the three-dimensional (3D) structure of a model organometallic platinum complex anchored on an amorphous silica can be fully determined by combining DNP Surface enhanced NMR spectroscopy (DNP SENS) with EXAFS data.2 Here we extend this approach to determine the surface structure of a catalyst containing iridium (Ir) N-heterocyclic carbene (NHC) active sites grafted onto a silica surface.3 We will first present the 3D structure of the NHC precursor, obtained from 10 internuclear distances, measured from REDOR experiments. This NHC precursor is partially converted into a Ag-NHC intermediate and then to the final Ir-NHC complex, which results in a mixture of different surface species. We will then demonstrate strategies to overcome this challenge, and get access to targeted structural insights on a surface containing multiple well-defined sites. In particular, the implementation of selective REDOR allowed the measurement of several non-ambiguous, long-range 29Si-{13C} distances. They clearly indicate that the structure of the Ag-NHC and Ir-NHC differs from that of the precursor, but also from the Pt complex determined previously. The NMR and EXAFS data point towards the presence of residual organic ligands coordinating the metal center. Establishing fine relationships between the structure and activity of a catalyst is essential in order to develop systems with improved efficiency.

  1. Berruyer, P. et al, eMagRes. 2018, 7, 93–104.
  2. Berruyer, P. et al, J. Am. Chem. Soc. 2017, 139, 849–855.
  3. Romanenko, I. et al, Angew. Chemie Int. Ed. 2015, 54, 12937–12941.

Primary authors

Ribal Jabbour (High-Field NMR Center, Université de Lyon, FRE 2034, CNRS/ENS Lyon/ UCB Lyon1) Dr Pierrick Berruyer (Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut des Sciences et Ingénierie Chimiques) Dr David Gajan (High-Field NMR Center, Université de Lyon, FRE 2034, CNRS/ENS Lyon/ UCB Lyon1) Dr Marc Renom-Carrasco (Université de Lyon, Institut de Chimie de Lyon, LC2P2, UMR 5265 CNRS-CPE Lyon-UCBL, CPE Lyon) Dr Moreno Lelli (Magnetic Resonance Center (CERM), University of Florence) Prof. Christophe Copéret (ETH Zürich, Department of Chemistry and Applied Biosciences) Prof. Lyndon Emsley (Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut des Sciences et Ingénierie Chimiques) Dr Chloé Thieuleux (Université de Lyon, Institut de Chimie de Lyon, LC2P2, UMR 5265 CNRS-CPE Lyon-UCBL, CPE Lyon) Dr Anne Lesage (High-Field NMR Center, Université de Lyon, FRE 2034, CNRS/ENS Lyon/ UCB Lyon1 )

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