Combining zeolite with MOF glass to construct crystal-glass composite membranes for improved hydrogen separation

Metal-organic framework glasses (MOF-a_g), formed through melt-quenching crystalline MOFs, have emerged as promising membrane materials owing to their processability and retained porosity. While MOF-a_g membranes exhibit exceptional sieving selectivity, their compromised permeability has driven the development of crystal-glass composite (CGC) membranes, where crystalline porous fillers are embedded in MOF-a_g matrices. Nevertheless, the high-temperature melt-quenching process poses a significant challenge to the thermal stability of porous fillers, inducing structural degradation of thermally labile fillers and severely compromising gas permeability. In this study, we report the rational design of FAU-type zeolite-embedded ZIF-62-a_g composite membranes to improve hydrogen separation performance. The optimized 20-FAU-ZIF-62-a_g CGC membrane (20 ​wt% zeolite filler loading) exhibits the H₂ permeability of 2516 Barrer and H₂/CH₄ selectivity of 52.4 for single-gas permeation, representing 179 ​% and 45 ​% improvements over the pristine ZIF-62-a_g membrane. The zeolite incorporation not only improves porosity but also enhances mechanical strength, evidenced by the enhanced Young's modulus (85 ​%) and hardness (55 ​%). Further processing with an alternative zeolite filler (MFI-type zeolite) or an alternative MOF-a_g matrix (TIF-4) validates the universality of zeolite-MOF-a_g CGC membranes in improving performance. This study provides a versatile platform for fabricating robust MOF-a_g-based membranes with improved separation performance.