Tethering Dual Hydroxyls into Mesoporous Poly(ionic liquid)s for Chemical Fixation of CO2 at Ambient Conditions: A Combined Experimental and Theoretical Study

Vicinal dual hydroxyl functional mesoporous poly­(ionic liquid)­s with large surface area and high ionic liquid (IL) content were synthesized through the copolymerization of epoxy-containing IL monomers and divinylbenzene, followed by ring opening in water. They acted as recyclable heterogeneous organocatalysts in the cycloaddition of a series of epoxides with CO2 under mild conditions (down to ambient conditions). The catalyst can be lightly recovered and reused with stable activity. The remarkable performance was attributable to the abundant mesoporosity and the synergistic effect of vicinal dual hydroxyls as hydrogen-bonding donors and halogen anions as nucleophiles. Density functional theory calculation, comprising the structural optimization, the energetic profile, and the charge and energy decomposition analysis by the combination of the extended transition state energy decomposition scheme with the natural orbitals for chemical valence approach, was performed to afford insight, indicating that the vicinal dual hydroxyls accelerated the reaction by providing a strong hydrogen-bonding effect and enhancing the leaving ability of the halogen anions.