Borocarbonitride　(BCN)　materials　are　newly　developed　metal-free　catalytic　materials　exhibiting　high　selectivity　in　oxidative　dehydrogenation　(ODH)　of　alkanes.　However,　the　in-depth　understandings　on　the　role　of　boron　(B)　dopants　and　the　intrinsic　activities　of　–C=O　and　–B–OH　still　remain　unknown.　Herein,　we　report　a　series　of　BCN　materials　with　regulable　B　content　and　surface　oxygen　functional　groups　via　self-assembly　and　pyrolysis　of　guanine　and　boric　acid.　We　found　that　the　B/C　ratio　is　the　key　parameter　to　determine　the　activity　of　ODH　and　product　distribution.　Among　them,　the　high　ethylbenzene　conversion　(∼57%)　and　styrene　selectivity　(∼83%)　are　achieved　in　ODH　for　B1CN.　The　styrene　selectivity　can　be　improved　by　increasing　of　B/C　ratio　and　this　value　reaches　near　100%　for　B5CN.　Structural　characterizations　and　kinetic　measurements　indicate　that　–C=O　and　–B–OH　dual　sites　on　BCN　are　real　active　sites　of　ODH　reaction.　The　intrinsic　activity　of　–C=O　(5.556　×　10−4　s−1)　is　found　to　be　23.7　times　higher　than　–B–OH　(0.234　×　10−4　s−1)　site.　More　importantly,　we　reveal　that　the　deep　oxidation　to　undesirable　CO2　occurs　on　–C=O　rather　than　–B–OH　site,　and　B　dopant　in　BCN　materials　can　reduce　the　nucleophilicity　of　–C=O　site　to　eliminate　the　CO2　emission.　Overall,　the　present　work　provides　a　new　insight　on　the　structure–function　relationship　of　the　BCN　catalytic　systems.　©　2023　Science　Press　and　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences