Free-standing mesoporous carbon-graphitic carbon nanocomposite membranes with controllable pore size (7.3-11.3 nm) were synthesized by the "brick-and-mortar" method, carbon black (CB) as "bricks" and soft-templated phenolic resin-based mesoporous carbon (MC) as the "mortar". Immobilization of imidazolium-based room temperature ionic liquids ([C(n)mim][Tf2N], n=2, 4, and 6) in the MC-CB membranes produced a series of supported ionic liquid membranes (SILMs) that are permselective for separation of CO2-N-2 gas pair. Strong capillary forces resulting from the well-developed mesoporosity of the MC CB membranes greatly enhanced the stability of the supported ionic liquids. This enabled the SILMs to operate under transmembrane pressures as high as 1000 kPa without degrading their separation performance. This makes it possible to apply SILMs to high-pressure CO2 capture and separation processes, where high transmembrane pressure would greatly increase the permeate flux through the membranes. (C) 2014 Elsevier B.V. All rights reserved.