Carbon　nitride　(CN)　materials　have　been　employed　as　catalysts　in　many　scientific　fields.　Moreover,　highly　crystalline　CN　as　an　ideal　model　material　for　key　problems　in　catalytic　reaction　research　has　received　a　lot　of　attention.　Herein,　the　Li+　incorporated　highly　crystalline　poly(triazine　imide)　(PTI–Li+)　with　a　well-defined　structure　is　successfully　fabricated　through　the　ionothermal　method.　The　atomically　dispersed　Li　in　the　PTI–Li+　serve　as　the　active　sites　in　the　selective　catalytic　oxidation　of　H2S,　and　the　interaction　between　Li　ions　and　PTI–Li+　framework　extends　electron　delocalization　and　modulate　electronic　band　structure　resulting　in　improved　O2　and　H2S　adsorption　and　activation　ability.　Consequently,　PTI–Li+　shows　excellent　selective　catalytic　desulfurization　activity　and　durability.　This　work　not　only　designs　an　efficient　desulfurization　catalyst　but　also　demonstrates　the　role　of　these　atomically　dispersed　Li　ions　in　PTI–Li+　during　the　catalytic　reaction,　enlightening　the　deeper　understanding　and　wider　application　of　carbon　nitride　materials.　©　2023　Wiley-VCH　GmbH.