An electrochemical methodology for the cyclic CO2 “catch and release”. The role of the electrogenerated N-heterocyclic carbene in BMIm-BF4

• The cathodic reduction of BMIm-BF4 yields the corresponding NHC.
• NHC reacts with CO2 yielding the NHC-CO2 adduct, which is stabilized by BMIm-BF4.
• CO2 is released heating to 120 °C the NHC-CO2 adduct, thus regenerating NHC.
• The CO2 “catch and release” cycle is repeated 10 times.
• 3.94 mol of CO2 are sequestrated per Faraday consumed.

According to the property of N-heterocyclic carbenes (NHCs) to yield NHC-CO2 adducts, a solution of NHCs in the parent room temperature ionic liquid (RTIL) as solvent may act as a system able to catch and release carbon dioxide cyclically and in mild conditions. The system has been set up and analyzed via simple electrochemical methodologies. NHCs have been generated by electrolysis of BMIm-BF4 (as solvent and parent of NHC) in the absence of any base and organic solvent. CO2 has been caught and released in every cycle by bubbling of CO2 in the system at 60 °C, heating and stirring at 120 °C, and subsequently cooling down to 60 °C. In a single series of 10 cycles, performed as a preliminary control, the system is able to catch and release 4 mol of CO2 per Faraday consumed in the electrolysis.

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