In　this　study,　the　coupling　agent　polydopamine/polyethyleneimine　(PDA/PEI)　was　utilized　to　modify　the　surface　of　an　α-Al2O3　support.　Owing　to　the　cross-linking　characteristics　of　the　–NH2　and　–OH　functional　groups　with　Zn2+　ions　on　the　support　by　the　coupling　agent,　a　continuous　and　dense　2D-zeolitic　imidazolate　framework-8　(ZIF-8)　membrane　was　induced　and　regulated.　The　hydrogen　(H2)　separation　performance,　mechanism　and　preparation　optimization　of　the　ZIF-8　membrane　grown　on　the　modified　layer　of　PDA/PEI　were　investigated.　The　results　indicated　that　a　ZIF-8　membrane　with　an　approximate　thickness　of　12　μm　formed　on　a　Zn2+@PDA/PEI-modified　α-Al2O3　support.　The　H2　permeance　of　the　ZIF-8　membrane　was　3.02　×　10–7　mol·Pa−1·m−2·s−1　at　25　°C　and　0.15　MPa,　with　ideal　selectivities　of　12,　51,　and　59　for　H2/CO2,　H2/N2,　and　H2/CH4,　respectively.　Notably,　these　values　significantly　exceeded　the　Robeson　upper　limits.　The　primary　mechanism　of　zinc　ion　complexation　in　the　PDA/PEI　codeposit　layer　involves　the　formation　of　complexes　between　the　O　and　N　atoms　on　the　layer　and　Zn2+,　and　a　significant　number　of　imines　(NH=)　can　be　employed　to　chelate　Zn2+　and　facilitate　the　formation　of　Zn　=N　compounds.　This　facilitated　the　heterogeneous　nucleation　of　ZIF-8　on　the　support　surface,　resulting　in　the　synthesis　of　continuous　ZIF-8　membranes　with　ultrahigh　H2/N2　and　H2/CH4　selectivity　and　excellent　intergrowth.　©　2025　Elsevier　B.V.