Pebax® MH 1657 (Pebax)-based blend membranes with different polyether-amine (PEA) loadings were designed and fabricated for efficient CO 2 separation. The CO 2 separation performance of Pebax/PEA blend membranes was greatly improved in comparison with that of pure membranes. This was mainly because the introduced PEA tailored the physical and chemical microenvironments in blend membranes. Specifically, PEA was a liquid-like additive, which was beneficial to reduce the mass transfer resistance of gases and increase CO 2 permeability. Meanwhile, PEA contained amino groups that acted as mobile carriers to tailor the chemical microenvironment in blend membranes. The mobile carriers preferentially reacted reversibly with CO 2 molecules, facilitating CO 2 transport in membranes. Compared with CO 2 /CH 4 separation performance of pure Pebax membrane, CO 2 permeability and CO 2 /CH 4 separation factor of Pebax/PEA-3 increased by 144.8% and 29.4%, respectively. This study suggests that PEA is a promising membrane material for tailoring the physical and chemical microenvironments in blend membranes for efficient CO 2 separation.