Cation-assisted　interactions　between　N-containing　heterocycles　(NHCs)　and　CO2　have　been　systematically　studied　by　using　density　functional　theory　(DFT).　For　neutral　and　anionic　(non-carbenoid)　NHCs,　the　effects　of　monovalent　cations　(i.e.,　alkali　metal　ions)　are　moderate　to　small　(the　NHC-CO2　binding　energy　change,　DBE　usually　＜　25　kJ　mol(-1)).　However,　for　NHC　carbenes,　due　to　their　strong　basicity,　the　effects　are　strong　(Delta　BE　＞　60　kJ　mol(-1))　and　the　monovalent　cations　play　a　critical　role　in　the　single　carboxylation　of　dicarbenes　with　CO2.　In　comparison,　divalent　alkali　earth　metal　cations,　due　to　both　their　smaller　sizes　and　higher　formal　charges,　exhibit　a　much　stronger　influence　(Delta　BE　＞　100　kJ　mol(-1)).　Divalent　cations　should　be　incorporated　into　next　generation　CO2　capture　reagents.　Other　aspects　including　the　reaction　potential　energy　surface　(PES),　orbital-based　analyses　of　interactions,　substitution　effects,　and　the　reactivity　descriptors　(cation　size,　reacting　N　lone　pair　orbital　energy,　etc.)　have　been　discussed　in　detail　as　well.