Developing　metal-free　heterogeneous　catalysts　with　high　efficiency　for　the　elimination　of　H2S　into　eco-friendly　products　are　very　important　for　both　fundamental　catalytic　science　and　industrial　chemistry.　Herein,　we　design　a　new　modified　carbon　nitride　catalyst　engrafted　with　Br-substituted　aromatic　heterocycle　(CNU-Br)　through　a　simple　copolymerization　and　exfoliation　method.　CNU-Br　exhibits　excellent　H2S　conversion　efficiency,　high　sulfur　selectivity,　and　outstanding　stability　in　the　catalytic　desulfurization　reaction,　which　is　better　than　most　of　the　reported　catalysts.　The　experiments　and　theoretical　calculations　show　that　the　grafting　of　bromophenyl　groups　into　the　fundamental　carbon　nitride　structural　network　leads　to　pi-delocalization,　surface　modification,　as　well　as　enhances　the　basicity　of　the　structural　active　N　sites.　The　regulation　of　the　H　and　S　affinity　of　CNU-Br　that　mediate　the　facile　cleavage　of　H2S　hydrogen-sulfur　bonds　and　the　release　of　S　atoms　in　thermodynamics.　Furthermore,　the　superior　surface　area　and　mass　transfer　over　CNU-Br　accelerate　the　adsorption　and　oxidation　of　H2S　in　kinetics　compared　with　the　ordinary　carbon　nitride.