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

The metal- and solvent-free capture and reduction of large amounts of CO₂ 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 CO₂ capacities at room temperature and 1 bar with up to 1 g $$  g^-1 _IL . CO₂ gas reacts with the BH₄ ^- anion to give triformatoborohydride, [HB(OCHO)₃ ]^- . The reaction occurs without loss in capacity at low CO₂ concentration (6 vol % diluted with N₂ ). The thermodynamics and kinetics of the reaction were monitored by using a magnetic suspended balance. In addition, more than 1 mol $$  mol^-1 $$ is captured and reduced if air is used as a CO₂ 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 CO₂ absorber and reducer to produce alternative fuels.