Catalytic coupling of CO2 and epoxides with metal substituted Keggin based Hybrid Materials

• Published in: Journal of organometallic chemistry 2024-09, Vol.1017, p.123280, Article 123280
• Main Authors: Jan, Rehana, Ghosh, Tapan Kumar, Shaikh, Rafik Rajjak, Bhagavathy, S., Shakeela, K., Rao, G. Ranga
• Format: Article
• Language: English
• Subjects: CO2 coupling; Cyclic carbonates; Epoxides; Hybrid materials; Keggin; Polyoxometalates; Tetrabutylammonium cations
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2024.123280

•Hybrid materials of Co, Cu and Ni substituted Keggin catalysts for CO2 conversion.•Highly efficient cycloaddition of CO2 with epoxides towards cyclic carbonates.•Solvent-free reactions under ambient conditions with 100 % selectivity.•Column-free purification of products and waste minimisation.•Easily recoverable and reusable catalysts. Three hybrid catalytic materials are synthesised using transition metal (CoII, NiII, CuII) substituted lacunary Keggin polyoxometalates and tetrabutylammonium cations (TBA-TMSPOMs) and used for atom-economic cycloaddition of carbon dioxide to various epoxides producing cyclic carbonates under ambient conditions. These hybrid materials have been characterised by powder XRD, TGA, SEM, TEM, FTIR and 31P NMR. A rapid and effective method towards quantitative conversion of aliphatic, cyclic, and aromatic epoxides to their respective cyclic carbonates under solvent-free conditions is described. The percentage conversion of various epoxides into their respective cyclic carbonates is confirmed by 1H NMR and gas chromatography. Of all the cyclcoaddition reactions studied, the epichlorohydrin shows nearly 100% selectivity with turnover frequency of 244 h−1. Among the three hybrid catalysts, ∼0.12 mol% of TBA-PWCo is adequate to achieve highest catalytic efficiency with over 95% conversion in 4 h at RT. This catalyst is recyclable and reusable up to five cycles without significant loss in activity. [Display omitted]