Molybdate ionic liquids as halide-free catalysts for CO2 fixation into epoxides

Herein we describe the syntheses of a series of molybdate and polyoxomolybdate ionic liquids (ILs), their full spectroscopic characterisation (FT-IR, 1H-, 13C-, 31P-, and 95Mo-NMR and ICP-MS), a comparison of their properties, and their applications as bifunctional catalysts for CO2 insertion into e...

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Bibliographic Details
Published in:Green chemistry : an international journal and green chemistry resource : GC 2023-06, Vol.25 (12), p.4849-4860
Main Authors: Bragato, Nicola, Perosa, Alvise, Selva, Maurizio, Fiorani, Giulia, Calmanti, Roberto
Format: Article
Language:English
Subjects:
Anion exchange
Anion exchanging
Carbon dioxide
Carbon dioxide fixation
Catalysts
Epoxides
Green chemistry
Hexanes
Ionic liquids
Ions
Molybdate
NMR
Nuclear magnetic resonance
Recyclability
Substrates
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Summary:Herein we describe the syntheses of a series of molybdate and polyoxomolybdate ionic liquids (ILs), their full spectroscopic characterisation (FT-IR, 1H-, 13C-, 31P-, and 95Mo-NMR and ICP-MS), a comparison of their properties, and their applications as bifunctional catalysts for CO2 insertion into epoxides. The synthetic procedures to obtain ILs rely on anion exchange and acid–base reactions, including an innovative route for the synthesis of molybdate ionic liquids (Mo-ILs) using a halide-free organic IL precursor. The use of Mo-ILs as catalysts for CO2 fixation was investigated using 1,2-epoxyhexane as a model substrate. In the presence of 2.5 mol% of tetrabutylammonium molybdate, hexane carbonate was obtained in up to 86% yield at T = 120 °C, p0(CO2) = 30 bar in t = 9 h, under solventless conditions and without any added halide co-catalysts. The substrate scope was broadened to other 12 terminal and internal epoxides; moreover, the reaction was scaled up to 2 g of the substrate and catalyst recyclability was demonstrated up to 5 recycles.
ISSN:1463-9262
1463-9270
DOI:10.1039/d2gc04475g