Solvent‐ and Catalyst‐Free Carbon Dioxide Capture and Reduction to Formate with Borohydride Ionic Liquid

Abstract The metal‐ and solvent‐free capture and reduction of large amounts of CO 2 to formate under ambient conditions is achieved by combining a pyrrolidinium‐based ionic liquid with a borohydride anion. This material demonstrates one of the highest CO 2 capacities at room temperature and 1 bar with up to 1 g g −1 IL . CO 2 gas reacts with the BH 4 − anion to give triformatoborohydride, [HB(OCHO) 3 ] − . The reaction occurs without loss in capacity at low CO 2 concentration (6 vol % diluted with N 2 ). The thermodynamics and kinetics of the reaction were monitored by using a magnetic suspended balance. In addition, more than 1 mol mol −1 is captured and reduced if air is used as a CO 2 source. The product can be then treated with HCl to give formic acid and the corresponding ionic liquid chloride, which can be recycled. This ionic liquid borohydride demonstrates great potential as a CO 2 absorber and reducer to produce alternative fuels.