Carboxymethyl cellulose supported ionic liquid as a heterogeneous catalyst for the cycloaddition of CO2 to cyclic carbonate

• Ionic liquid (IL) and Lewis acid were loaded on HCMC through co-impregnation.
• Electrostatic interaction and hydrogen bond are key for IL immobilization.
• The HCMC-supported material can be utilized as a heterogeneous catalyst.
• The catalyst was efficient for cycloaddition of CO2 to cyclic carbonate.
• The catalytic stability was excellent in the continuous fixed-bed flow reactor.

The non-toxic biologic material carboxymethyl cellulose (CMC) supported imidazolium-based ionic liquids (ILs), coupling with a series of Lewis acids has been prepared and used as heterogeneous catalysts for the cycloaddition of CO2 to cyclic carbonate. The as-synthesized catalysts have been characterized by FT-IR, XRD, TGA, SEM etc. Especially, the protonated CMC (HCMC) supporting both the hydroxyl group functionalized IL (1-hydroxypropyl-3-n-butylimidazolium chloride, HBimCl) and NbCl5 (HBimCl-NbCl5/HCMC) exhibited the best catalytic performance. It was indicated that HBimCl on HBimCl-NbCl5/HCMC catalyst was highly leaching-resistant even if it was immobilized through non-covalent interaction. The IL and Lewis acid exhibited strong synergistic effects for the cycloaddition reaction. Additionally, the HBimCl-NbCl5/HCMC catalyst exhibited a high activity and excellent selectivity for a wide scope of substrates under optimum conditions and also it was further extended to application in the continuous fixed-bed flow reactor and showed an excellent catalytic stability. No loss of catalytic activity was observed even after 120 h on stream.

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