This work is focused on the permeability modulation of Supported Magnetic Ionic Liquid Membranes (SMILMs) for CO2 separation, when applying an external magnetic field. Four magnetic ionic liquids (MILs) have been studied ([]P-66614][[C0Cl(4)], [P-66614][FeCl4], [P-66614][MnCl4] and [P-66614][GdCl6]) in combination with a commercial hydrophobic PVDF porous support. An experimental evaluation of the membrane permeability was carried out for CO2, N-2 and air. The influence of the magnetic field on MILs viscosity was also studied, allowing to establish the relationship between permeability and viscosity depending on the external magnetic field. An external magnetic field between 0 and 2 T increases the gas permeability for CO2, N2 and air without changing the permeability ratio and decreases MILs viscosity, depending on the MILs magnetic susceptibility. The MIL [P-66614][GdCl6] shows the maximum CO2 permeability increase (21.64%) in comparison with the result when no magnetic field is applied. The permeability and viscosity product is a constant with a different value for each SMILM studied. Experimental results confirm the potential for gas permeability modulation through supported liquid membranes by tuning the external magnetic field intensity. (C) 2012 Elsevier B.V. All rights reserved.