Electrocatalytic　semi-hydrogenation　of　acetylene　to　ethylene　has　recently　attracted　attention　as　a　process　for　removing　acetylene　from　ethylene-rich　gas　streams　due　to　its　mild　conditions　and　energy-saving　advantages.　However,　developing　catalysts　with　low　cost　and　high　selectivity　for　acetylene　semi-hydrogenation　remains　a　huge　challenge.　Here,　we　investigated　the　effect　of　hydroxyl　group　modification　on　the　acetylene　semi-hydrogenation　selectivity　of　poly(heptazine　imide)　(PHI)　supported　metal　single　atom　catalyst　under　alkaline　conditions　by　density　functional　theory　calculations.　The　results　show　that　hydroxyl　group　as　ligand　not　only　increases　the　steric　resistance　of　acetylene　adsorption,　but　also　acts　as　electron-withdrawing　group　to　delocalize　the　electrons　of　metal　atoms,　weaken　the　interaction　with　acetylene　and　subsequent　intermediates,　and　make　the　adsorption　moderate,　which　is　beneficial　to　the　desorption　of　ethylene　and　avoid　over-hydrogenation.　The　Ni-OH/PHI　and　Fe-2OH/PHI　are　capable　of　achieving　the　selective　hydrogenation　of　acetylene　to　ethylene　and　have　good　thermodynamic　stability,　which　can　be　used　as　ideal　catalysts　for　the　electrocatalytic　semi-hydrogenation　of　acetylene　to　selectively　generate　ethylene.　This　study　provides　theoretical　guidance　for　the　rational　design　of　electrocatalysts　for　the　selective　semi-hydrogenation　of　acetylene.　©　2024　Elsevier　B.V.