Dual role for CO2: Pure formic acid can be obtained continuously by hydrogenation of CO2 in a single processing unit (see scheme). An immobilized ruthenium organometallic catalyst and a nonvolatile base in an ionic liquid (IL) are combined with supercritical CO2 as both reactant and extractive phase.
Wesselbaum, S., Hintermair, U., & Leitner, W. (2012). Continuous-flow hydrogenation of carbon dioxide to pure formic acid using an Integrated scCO2 process with immobilized catalyst and base. Angewandte Chemie-International Edition, 51(34), 8585-8588. https://doi.org/10.1002/anie.201203185