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Bimetallic Co/Al nanoparticles in an ionic liquid: synthesis and application in alkyne hydrogenation

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Abstract

Herein, we report the microwave-induced decomposition of various organometallic cobalt and aluminum precursors in an ionic liquid (IL), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIm]NTf2), resulting in Co/Al nanoalloys with different molar Co/Al ratios. The dual-source precursor system of dicobalt octacarbonyl (Co2(CO)8) and pentamethylcyclopentadienyl aluminum ([AlCp*]4) in [BMIm]NTf2 afforded CoAl nanoparticles (CoAl-NPs) with a molar Co/Al ratio of 1 : 1. Their size and size distribution were determined via transmission electron microscopy (TEM) to be an average diameter of 3.0 ± 0.5 nm. Furthermore, the dual-source precursor system of cobalt amidinate ([Co(iPr2-MeAMD)2]) and aluminum amidinate [Me2Al(iPr2-MeAMD)] in molar ratios of 1 : 1 and 3 : 1 resulted in CoAl- and Co3Al-NPs with an average diameter of 3 ± 1 and 2.0 ± 0.2 nm, respectively. All the obtained materials were characterized via TEM, energy dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), together with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and (high-resolution) X-ray photoelectron spectroscopy ((HR-)XPS). Phase-pure Co/Al-NPs were not obtained since the concomitant formation of Co-NPs and Al2O3 occurred in this wet-chemical synthesis. The as-prepared Co/Al nanoalloys were evaluated as catalysts in the hydrogenation of phenylacetylene under mild conditions (2 bar H2, 30 °C in THF). In comparison to the monometallic Co-NPs, the Co/Al-NPs showed a significantly higher catalytic hydrogenation activity. The Co- and Co/Al-NPs were also active under harsher reaction conditions (80 bar H2, 80 °C) without the addition of the activating co-catalyst DIBAL-H.

Graphical abstract: Bimetallic Co/Al nanoparticles in an ionic liquid: synthesis and application in alkyne hydrogenation

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Publication details

The article was received on 12 Jul 2019, accepted on 23 Sep 2019 and first published on 26 Sep 2019


Article type: Paper
DOI: 10.1039/C9NJ03622A
New J. Chem., 2019, Advance Article

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    Bimetallic Co/Al nanoparticles in an ionic liquid: synthesis and application in alkyne hydrogenation

    L. Schmolke, B. J. Gregori, B. Giesen, A. Schmitz, J. Barthel, L. Staiger, R. A. Fischer, A. Jacobi von Wangelin and C. Janiak, New J. Chem., 2019, Advance Article , DOI: 10.1039/C9NJ03622A

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