In-Situ synthesis of ZIF-8 membranes on PDA/APTES modified alumina supports and optimization of their hydrogen separation performance

• A PDA/APTES interfacial layer enhanced membrane adhesion, uniformity, & nucleation density for ZIF-8 synthesis. • Optimized growth achieved ZIF-8 membranes with 14×10 −7 mol/(m 2 ·s·Pa) H 2 flux and H 2 CO 2 =20.3, H 2 /N 2 =22.1, H 2 /CH 4 =26.8 selectivity. • Long-term tests demonstrated stable ZIF-8 membranes for hydrogen purification and emission reduction applications. 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 Al 2 O 3 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(H 2 ) permeance reaching 14 × 10 −7 mol·Pa −1 ·m −2 ·s −1 and ideal selectivities of 20.3, 22.1, and 26.8 for H 2 /CO 2 , H 2 /N 2, and H 2 /CH 4 , 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 H 2 permeance increased by 14.8 %. Notably, the selectivity for H 2 /CO 2 increased by almost threefold. Moreover, long-term stability tests demonstrated the durability and robustness of the ZIF-8 membranes under operational conditions.