Here,　we　studied　Al　or　B　atom-doped　carbon　nitride　(g-C3N4　and　C2N)　as　catalysts　for　H2　activation　and　acetylene　hydrogenation　using　density　functional　theory　calculations.　The　Al　or　B　could　be　assembled　with　the　surface　N　atoms　of　carbon　nitride　to　form　diverse　frustrated　Lewis　pairs　(FLPs).　The　results　show　that　Al-N　FLPs　had　lower　barriers　of　H2　activation　in　comparison　with　B-N　FLPs.　The　heterolytic　H2　dissociation　catalyzed　by　Al-N　FLPs　led　to　the　formation　of　Al-H　and　N-H　species.　The　Al-H　species　were　highly　active　in　the　first　hydrogenation　of　acetylene　to　C2H3∗,　yielding　a　mild　barrier,　while　in　the　second　hydrogenation　step,　the　reaction　between　C2H3　and　the　H　of　N-H　species　caused　a　relatively　high　barrier.　Electronic　structure　analysis　demonstrated　the　electron　transfer　in　the　heterolytic　H2　cleavage　and　explained　the　activity　differences　in　various　FLPs.　The　results　suggest　that　Al　with　the　surface　N　of　carbon　nitride　can　act　as　an　FLP　to　catalyze　the　H2　activation　and　acetylene　hydrogenation,　thus　providing　a　new　strategy　for　the　future　development　of　noble　metal-free　hydrogenation　catalysts.　©　2021　the　Owner　Societies.