Disclosed are membranes and methods for making the same, which membranes provide improved permeability, stability, and cost-effective manufacturability, for separating CO2 from gas streams such as flue gas streams. High CO2 permeation flux is achieved by immobilizing an ultra-thin, optionally catalyzed fluid layer onto a meso-porous modification layer on a thin, porous inorganic substrate such as a porous metallic substrate. The CO2-selective liquid fluid blocks non-selective pores, and allows for selective absorption of CO2 from gas mixtures such as flue gas mixtures and subsequent transport to the permeation side of the membrane. Carbon dioxide permeance levels are in the order of 1.0×10−6 mol/(m2sPa) or better. Methods for making such membranes allow commercial scale membrane manufacturing at highly cost-effective rates when compared to conventional commercial-scale CO2 separation processes and equipment for the same and such membranes are operable on an industrial use scale.