Selective gas separation has application in terrestrial and spaced-based technologies. In a recent program funded by NASA, we investigated the use of an electrochemically modulated transport mechanism to effectively separate and concentrate CO2 from a mixed-phase stream of reactants. Electrochemically modulated facilitated transport is accomplished through a redox carrier which alternately binds and releases CO2 based on cell potential. Our work demonstrates this mechanism in a supported ionic liquid membrane electrochemical device. Ionic liquids are advantageous electrolytes in this system due to their wide liquidus range, nearly zero vapor pressure, and wide electrochemical windows. Covering a broad range of gas/liquid flow regimes, our results show that this process can effectively separate CO2 from pure gas to pure liquid. In addition, the results demonstrate not only separation but concentration of CO2 as well. In a two-phase flow experiment this process concentrated the catholyte (input) CO2 concentration from 150 ppm to over 1100 ppm in the anolyte (output), with the ratio of CO2 to N2 going from 0.0015 to 0.12. The effectiveness of this process is shown to be largely dependent on the applied cell voltage, solubility of the redox carrier in the ionic liquid, and the ionic conductivity of the membrane, which is itself influenced by the reactant state.