The effect of 5-hydroxyisophthalic acid on the transport of CO2 molecules was investigated for various polymer composite membranes for highly permeable and selective membrane. It was expected that the carboxyl groups of 5-hydroxyisophthalic acid would generate dipole-dipole interactions with CO2 molecules, allowing for increased solubility of CO2, and that the benzene rings would provide a barrier effect, resulting in decreased N-2 transport. When 5-hydroxyisophthalic acid was incorporated into a poly(ethylene oxide) (PEO) polymer matrix, the separation performance of the membrane was enhanced and the ideal selectivity of CO2 over N-2 (CO2/N-2 = 32.4) and CO2 permeability of 573 barrer were observed. The coordinative interactions in the PEO/5-hydroxyisophthalic acid composite were characterized with FT-IR and thermogravimetric analysis.