Poly(ionic liquid)s with unique adsorption-swelling ability toward epoxides for efficient atmospheric CO2 conversion under cocatalyst-/metal-/solvent-free conditions

Developing a simple and efficient heterogeneous catalyst for the cycloaddition of epoxides with CO2 under atmospheric pressure and cocatalyst-/metal-/solvent-free conditions remains a great challenge. Herein, poly(ionic liquid)s (P-[VRIm]Br-crosslinker-x) with unique adsorption-swelling ability toward epoxides are designed and facilely synthesized via free radical polymerization in water. The adsorption-swelling of epoxides by P-[VRIm]Br-crosslinker-x is controllable, reversible, and widespread, resulting from the strong interactions between the poly(ionic liquid)s and epoxide molecules, especially the hydrogenbonding interaction. Superior CO2 cycloaddition is realized in the P-[VRIm]Br-crosslinker-x catalyst through the adsorption-swelling effect. Specifically, P-[VC6Im]Br-C8-5% with 54.1 mmol g(-1) adsorptionswelling ability toward styrene oxide achieves 89.3% yield and >99% selectivity in the cycloaddition of styrene oxide with CO2 to styrene carbonate under mild conditions (1 atm, 80 degrees C) without cocatalyst/ metal/solvent consumption. Moreover, P-[VC6Im]Br-C8-5% can be easily recovered by deswelling, and shows good reusability and stability after five cycles for a total of 180 h. The adsorption-swelling property of P-[VRIm]Br-crosslinker-x to epoxides not only prompts the active centers to be fully exposed to the reactants but also induces the enrichment of epoxides during the whole catalytic process, thus accelerating the CO2 cycloaddition reaction rate. This work furnishes new insights for improving the activity of CO2 cycloaddition and would guide the design of efficient poly(ionic liquid) catalysts for atmospheric CO2 conversion.

Automated summary

In this study, a poly(ionic liquid) catalyst with unique adsorption-swelling ability towards epoxides was synthesized through free radical polymerization. The catalyst showed superior CO2 cycloaddition performance under atmospheric pressure and cocatalyst-/metal-/solvent-free conditions. The adsorption-swelling property of the catalyst was controllable, reversible, and widespread, allowing for efficient and selective reaction. The catalyst also exhibited good reusability and stability after multiple cycles. This work provides new insights for improving CO2 cycloaddition activity and guides the design of efficient poly(ionic liquid) catalysts for atmospheric CO2 conversion.