The amine functional groups in room-temperature ionic liquid (RTIL)-based epoxy-amine ion gel membranes allow for the fixed-site-carrier facilitated transport of CO2. These membranes were tested under humidified mixed-gas (CO2/N-2) feeds in order to evaluate the effects of relative humidity, CO2 partial pressure, and hydrophobicity of the added free RTIL on CO2/N-2 separation performance. Changes in relative humidity were found to have little effect on CO2/N-2 separation performance at constant CO2 partial pressure. However, comparison to dry-gas measurements showed that the presence of water vapor is necessary to observe facilitated CO2 transport in these systems. Increased CO2 permeability and CO2/N-2 selectivity were observed for these epoxy-amine ion gel membranes with decreasing CO2 partial pressure, as expected for materials operating via the fixed-site-carrier facilitated transport mechanism. The hydrophilicity of the free RTIL was found to influence CO2 transport, with a more hydrophilic RTIL able to facilitate CO2 transport at lower relative humidity. Facilitated transport enhances the CO2/N-2 separation performance of these epoxy-amine ion gel membranes and enables them to exceed the 2008 Robeson plot upper bound. (C) 2015 Elsevier B.V. All rights reserved.