composite polymeric transport membrane structures feature an ultra - thin polymeric membrane skin having microscopic pores therein forming an anisotropic microporous film combined with a relatively thick macroporous polymeric support substrate membrane which carries the skin . a quantity of liquid transport medium in the pores of the ultra - thin membrane skin enhances transport of one or more species of interest and wets the surface of the pores . the microscopic pores are of a size such that the vapor pressure of the liquid transport medium contained therein is reduced by an amount equal to or greater than that theoretically predicted by the kelvin effect . methods of activating the membrane with the transport mediums are also disclosed .