The　synthesis　of　ethyl　methyl　carbonate　(EMC)　is　of　paramount　importance　for　the　lithium-ion　battery　industry　as　electrolytes.　Herein,　we　present　a　series　of　swellable　poly(ionic　liquid)s　(PILs)　functionalized　with　phenol　anions,　aiming　at　inducing　effective　catalysis　in　EMC　production　through　the　transesterification　of　ethanol　(EtOH)　and　dimethyl　carbonate　(DMC).　The　obtained　PILs　catalysts　exhibit　remarkable　EMC　yields　of　57.0%　and　selectivity　of　86.7%,　coupled　with　robustness　and　facile　reusability　under　mild　conditions.　By　establishing　a　correlation　between　the　swelling　degree　of　PILs　and　the　yield　of　EMC,　and　by　a　theoretical　calculation　on　the　energy　and　electrostatic　potential　changes　of　[CPIL-Tr]1[PhO]　during　its　reaction　with　EtOH　and　DMC,　we　show　that　these　impressive　catalytic　performances　arise　from　efficient　proton　dissociation　of　EtOH　by　phenol　anion　and　accelerated　transportation　of　reactants　by　swelling　cationic　backbone.　This　research　endeavors　to　provide　an　appealing　platform　for　the　industrial-scale　production　of　EMC.