Abstract: A composite membrane including a porous support and a thin film layer comprising a reaction product of: i) a polymer comprising a sub-unit including a Troger's base moiety represented by Formula I: wherein L includes an arylene group substituted with at least one carboxylic acid or a corresponding salt or ester group, or a hydroxyl; and ii) a crosslinking agent selected from at least one of: a) a multifunctional epoxy compound and b) a multifunctional azide compound.