Bimetallic Co/Al nanoparticles in an ionic liquid: synthesis and application in alkyne hydrogenation. (11th October 2019)

• Record Type: Journal Article
• Authors: Schmolke, Laura; Gregori, Bernhard J.; Giesen, Beatriz; Schmitz, Alexa; Barthel, Juri; Staiger, Lena; Fischer, Roland A.; Jacobi von Wangelin, Axel; Janiak, Christoph
• Is Part Of: New journal of chemistry. Volume 43:Number 42(2019)
• Page Start: 16583
• Page End: 16594
• Publication Date: 2019-10-11
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c9nj03622a
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : CoAl- and Co3 Al-NPs are effective catalysts for alkyne-to-alkane hydrogenation with DIBAL-H as a co-catalyst under mild conditions (2 bar H2, 30 °C). 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( i Pr2 -MeAMD)2 ]) and aluminum amidinate [Me2 Al( i Pr2 -MeAMD)] in molar ratios of 1 : 1 and 3 : 1 resulted in CoAl- and Co3 Al-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 Al2 O3 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.