Novel hydroxyl-functionalized ionic liquids as efficient catalysts for the conversion of CO2 into cyclic carbonates under metal/halogen/cocatalyst/solvent-free conditions†
Abstract
The development of sustainable catalysts for the conversion of carbon dioxide into value-added chemicals is an effective way to alleviate environmental problems. The design of catalysts with excellent catalytic activities that are able to efficiently convert CO2 under mild conditions is very important. The novel, single-component, metal-free functionalized ionic liquids ([N2,2,2,2OH][BA], [N2,2,2,2OH][SA], [N2,2,2,2OH][OAc], [N2,2,2,2OH][GA], [N2,2,2,2][BA]) were synthesized using a simple method, and were further used as efficient catalysts for the catalytic conversion of CO2 into cyclic carbonates without any solvent and co-catalyst. These ionic liquids exhibited outstanding catalytic activity for the conversion of CO2 and various epoxides to cyclic carbonates. A mechanism for the synergistic effects of cations and anions in functionalized ionic liquids was also proposed. The catalytic activity of [N2,2,2,2][BA] without any OH functional groups was clearly lower than that of [N2,2,2,2OH][BA]. The relationship between the higher catalytic reactivity and the OH functional group presence was shown.