Iron-based　catalysts　have　been　widely　studied　for　the　oxidation　of　H2S　into　elemental　S.　However,　the　prevention　of　iron　sites　from　deactivation　remains　a　big　challenge.　Herein,　a　facile　copolymerization　strategy　is　proposed　for　the　construction　of　isolated　Fe　sites　confined　in　polymeric　carbon　nitride　(CN)　(Fe-CNNχ).　The　as-prepared　Fe-CNNχ　catalysts　possess　unique　2D　structure　as　well　as　electronic　property,　resulting　in　enlarged　exposure　of　active　sites　and　enhancement　of　redox　performance.　Combining　systematic　characterizations　with　density　functional　theory　calculation,　it is　disclosed　that　the　isolated　Fe　atoms　prefer　to　occupy　four-coordinate　doping　configurations　(Fe–N4).　Such　Fe–N4　centers　favor　the　adsorption　and　activation　of　O2　and　H2S.　As　a　consequence,　Fe-CNNχ　exhibit　excellent　catalytic　activity　for　the　catalytic　oxidation　of　H2S　to　S.　More　importantly,　the　Fe-CNNχ　catalysts　are　resistant　to　water　and　sulfur　poisoning,　exhibiting　outstanding　catalytic　stability　(over　270　h　of　continuous　operation),　better　than　most　of　the　reported　catalysts.　©　2020　Wiley-VCH　GmbH