The usage of isoporous polystyrene-block-poly(4-vinylpyridine) diblock copolymer (PS-b-P4VP) membranes as matrix material for ionic liquids (ILs) for gas separation tasks is reported and compared to an anodic alumina membrane. The compatibility of membrane components was investigated by means of porometry, tensiometry and contact angle measurement. The CO2 gas diffusivity and solubility was determined by direct observation using a “time-lag” facility and a magnetic suspension balance. Overall liquid membranes supported by PS-b-P4VP achieved remarkably good results especially in combination with 1-ethyl-3-methylimidazolium dicyanoamide (EMIM DCA) ionic liquid and are showing the way to attractive research and application opportunities.