The　development　of　high-performance　hydrogen　separation　membranes　is　a　crucial　step　in　the　advancement　of　sustainable　energy　technologies　and　the　achievement　of　carbon　neutrality.　In　this　study,　zeolitic　imidazolate　framework-8　(ZIF-8)　membranes　with　an　ultra-high　selectivity　for　hydrogen　over　carbon　dioxide　were　successfully　synthesised　on　polydopamine/3-aminopropyltriethoxysilane　(PDA/APTES)　modified　Al2O3　supports.　The　interfacial　layer　exhibited　excellent　adhesion　and　a　high　density　of　functional　groups,　which　served　as　nucleation　sites　for　the　growth　of　ZIF-8　crystals.　The　resulting　membranes　exhibited　a　dense　and　defect-free　structure,　achieved　through　an　optimised　12　h　in-situ　growth　process.　The　membranes　exhibited　excellent　gas　separation　performance,　with　hydrogen(H2)　permeance　reaching　14　×　10−7　mol·Pa−1·m−2·s−1　and　ideal　selectivities　of　20.3,　22.1,　and　26.8　for　H2/CO2,　H2/N2　and　H2/CH4,　respectively,　at　25　°C　and　0.2　MPa.　In　comparison　with　the　ZIF-8　membrane　that　was　synthesised　on　a　pure　PDA　modified　layer,　the　H2　permeance　increased　by　14.8　%.　Notably,　the　selectivity　for　H2/CO2　increased　by　almost　threefold.　Moreover,　long-term　stability　tests　demonstrated　the　durability　and　robustness　of　the　ZIF-8　membranes　under　operational　conditions.　©　2025　Elsevier　Ltd