Aiming at investigating the effect of the polymer molecular weight (M-w) on the physical and gas permeation properties of poly(ionic liquid)-ionic liquid (PIL-IL) composites, this work focuses on membranes based on variable M-w pyrrolidinium-PILs having [C(CN)(3)](-) as counter-anion and different amounts (20, 40 and 60 wt%) of free [C(2)mim][C(CN)(3)] IL. Although all the prepared composite materials have high thermal stability (T-onset > 556 K) for post-combustion CO2 separation, the evaluation of the film forming ability shows that it is not possible to obtain free standing PIL-IL membranes using the Low M-w PIL (average < 100 kDa). The formed Medium M-w (average 200 - 350 kDa) and High M-w (average 400 - 500 kDa) PIL-IL membranes present similar mechanical properties in terms of Young ' s modulus, tensile strength and elongation at break. The gas permeabilities and diffusivities are dependent on the M-w of the PIL used. The Medium M-w PIL-IL membranes display higher CO2 permeabilities (14.6 - 542 Barrer) than those (8.0-439 Barrer) observed for High M-w PIL-IL composites. Despite the M-w of the PIL used, the incorporation of high free IL contents increases both CO2 permeability and CO2/N-2 permselectivity. Consequently, the finest CO2/N-2 separation performances, overcoming the 2008 upper bound in the Robeson plot, were obtained for the High and Medium M-w PIL-60 IL composites, respectively, with CO2 permeabilities of 439 and 542 Barrer and CO2/N-2 permselectivities of 64.4 and 54.0.