Ultrathin Mesoporous Nanosheet‐Nanoconfined Low‐Crystallinity Framework Membranes for Ultrafast and Highly Selective Hydrogen Separation

Abstract Membrane processes are energy‐saving and promising for the purification of hydrogen, which is critical to clean energy supply and carbon capture. Developing high‐performance separation membranes is of great scientific and practical interest. In this study, a concept of using mesoporous graphene oxide (MGO) nanosheets to guide nanoconfined growth of low‐crystallinity metal‐organic framework (LCM) membranes for precise gas sieving is reported. By utilization of nanowire‐electrochemical perforation and oxidation for GO, the MGO nanosheets are reconstructed with in‐plane mesopores and abundant reactive groups and can provide nanoconfinement effects of limiting reaction region, offering anchoring sites, changing precursor diffusion, and squeezing crystallization, for in situ growth of amorphous LCM layers between adjacent mesoporous nanosheets. Benefiting from ultrathin, defect‐free, low‐crystallinity, and robust properties, combined with reduced tortuosity of MGO and adjusted transport pathways of LCM, the MGO/LCM membranes exhibit substantially enhanced long‐term stability, moisture resistance, and separation capability, with high H 2 /CO 2 selectivity of 104 and ultrafast H 2 permeance of ≈4000 gas permeation units, which can surpass those of most state‐of‐the‐art membranes.