Multisite activation of epoxides by recyclable CaI2/N-methyldiethanolamine catalyst for CO2 fixation: A facile access to cyclic carbonates under mild conditions

Abstract

The conversion of CO2 into valuable products has become the inherent part of green and sustainable chemistry. Here we demonstrated an efficient synthesis of cyclic carbonates from epoxides and CO2 under mild conditions (at 50 °C for 6 h under a CO2 atmosphere) via the use of CaI2/N-methyldiethanolamine (MDEA) system as the catalyst. The excellent conversions and selectivities for a broad range of epoxides are achieved under solvent-free conditions even at atmospheric CO2 pressure and in the presence of water. The catalyst can be simply recycled and reused without obvious loss in its activity. A plausible multisite-activation mechanism is proposed involving hydrogen bond site-assisted and Ca2+-promoted ring opening path, in combination with the activation of epoxides by iodide ion.