Poly　(ethylene　oxide)　(PEO)　membranes　are　attractive　for　CO2　capture　due　to　the　particular　dipolar-quadrupolar　interaction　between　EO　units　and　CO(2　)molecules,　which　offer　high　CO2/N-2　selectivity.　However,　the　low　CO2　permeability　of　PEO　membranes　hampers　their　practical　applications.　Herein,　a　simple　solvothermal　annealing　approach　was　proposed　to　enhance　the　flexibility　of　PEO　chains　via　＇activating＇　the　disengagement　and　rearrangement　of　side　chains,　which　is　essential　for　boosting　the　gas　permeability.　The　effects　of　solvothermal　annealing　temperature,　time,　and　solvent　on　the　CO2/N-2　separation　performance　were　comprehensively　investigated.　The　mechanism　for　the　performance　enhancement　was　proposed:　a　＂highway　＂　for　gas　transportation　was　built　up　by　the　released　flexible　side　chains,　which　were　confirmed　by　the　mechanical　and　Li　ion　conductivity　characterizations.　The　optimized　PEO　membrane　offers　a　superior　CO2　permeability　of　1294　Barrer,　a　high　CO2/N-2　selectivity　of　50,　and　110-h　long-term　running　stability,　being　beyond　the　2008　Robeson＇s　upper　bound　line　and　promoting　the　practical　application　of　PEO　membranes　in　CO2　capture　by　reducing　the　cost.