The Structure of Molecular and Surface Platinum Sites Determined by DNP-SENS and Fast MAS 195Pt Solid-State NMR Spectroscopy
| Autor: | Ribal Jabbour, Amrit Venkatesh, Pierrick Berruyer, Christophe Copéret, Anne Lesage, David Gajan, Aaron J. Rossini, Christopher P. Gordon, Georges Menzildjian, Jasmine Viger-Gravel, Lukas Rochlitz, Alicia Lund |
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| Rok vydání: | 2020 |
| Předmět: |
Analytical chemistry
chemistry.chemical_element General Chemistry Nuclear magnetic resonance spectroscopy 010402 general chemistry 01 natural sciences Biochemistry Catalysis 0104 chemical sciences NMR spectra database chemistry.chemical_compound Colloid and Surface Chemistry chemistry Solid-state nuclear magnetic resonance ddc:540 Magic angle spinning Platinum Spectroscopy Organometallic chemistry |
| Zdroj: | Journal of the American Chemical Society, Vol. 142, No 44 (2020) pp. 18936-18945 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/jacs.0c09101 |
| Popis: | The molecular level characterization of heterogeneous catalysts is challenging due to the low concentration of surface sites and the lack of techniques that can selectively probe the surface of a heterogeneous material. Here, we report the joint application of room temperature proton-detected NMR spectroscopy under fast magic angle spinning (MAS) and dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS), to obtain the 195Pt solid-state NMR spectra of a prototypical example of highly dispersed Pt sites (single site or single atom), here prepared via surface organometallic chemistry, by grafting [(COD)Pt(OSi(OtBu)3)2] (1, COD = 1,5-cyclooctadiene) on partially dehydroxylated silica (1@SiO2). Compound 1@SiO2 has a Pt loading of 3.7 wt %, a surface area of 200 m2/g, and a surface Pt density of around 0.6 Pt site/nm2. Fast MAS 1H{195Pt} dipolar-HMQC and S-REDOR experiments were implemented on both the molecular precursor 1 and on the surface complex 1@SiO2, providing access to 195Pt isotropic shifts and Pt–H distances, respectively. For 1@SiO2, the measured isotropic shift and width of the shift distribution constrain fits of the static wide-line DNP-enhanced 195Pt spectrum, allowing the 195Pt chemical shift tensor parameters to be determined. Overall the NMR data provide evidence for a well-defined, single-site structure of the isolated Pt sites. |
| Databáze: | OpenAIRE |
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