In this work, the high-performance semi-interpenetrating polymer network (semi-IPN) membranes are prepared by incorporating a self-crosslinkable comb copolymer into the matrix of Pebax. The comb copolymer, poly(glycidyl methacrylate-g-polypropyleneglycol)-co-poly (oxyethylenemethacrylate) (PGP-POEM) is synthesized via one-pot free-radical polymerization followed by epoxide-amine self-crosslinking reaction without any treatment. The high performance (CO₂ permeability of 236.6 Barrer and CO₂/N₂ selectivity of 38.8) is achieved by the semi-IPN membrane containing 40 wt% PGP-POEM. Through this work, the applicability of the semi-IPN membrane based on a self-crosslinkable comb copolymer to CO₂ capture is exhibited.