Interfacial engineering of ZIF-8 polycrystalline membranes via 2D MOF nanosheets for hydrogen purification

Zeolitic imidazolate framework-8 (ZIF-8) membranes are promising for hydrogen purification due to their molecular-sieving capability, yet fabricating compact and defect-free crystalline layer remains challenging by conventional heterogeneous nucleation. Herein, we propose an interfacial engineering strategy using a porous 2D Co-MOF nanosheet seed layer to enable secondary growth of high-performance ZIF-8 membranes. Ultrathin Co-MOF nanosheets (∼2 nm) with mesoporous structures were synthesized via a water-assisted solvothermal method, assembled into a uniform seed layer on α-Al 2 O 3 , and activated by 2-methylimidazole vapor to enhance intergrowth of ZIF-8 polycrystalline layer. The optimized membrane achieves a H 2 permeance up to 6.0 × 10 −7  mol m −2  s −1 ·Pa −1 (∼1800 GPU) with an ideal H 2 /CO 2 selectivity of 13.38, surpassing the 2008 Robeson upper bound. Crucially, it maintains stable separation performance for an equimolar H 2 /CO 2 mixture over 100 h​, with no detectable decay in permeance or selectivity. This work offers a scalable route to robust MOF membranes for industrial hydrogen recovery.