The gas separation properties of the corresponding ion gel formed by the self-assembly of PS-PIL-PS in the ionic liquid 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl)amide (EMIM) was reported. The polymer was synthesized through a two-step reversible addition-fragmentation chain transfer (RAFT) polymerization, followed by two functionalization steps to introduce ionic liquid functional groups. By using ion gel, the real selectivity of polymeric as separation membranes is found to be almost the same as the ideal selectivity. The performance of the PIL gel lies above the upper bound for CO 2/N2 and very close to the upper bound for CO 2/CH4. The ion gel is found to achieve a liquid-like permeability in a solid-state material, and by incorporating a PIL as the mid-block, the selectivity is increased.