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Concurrent regulation of crystallographic orientation and thickness of zirconium metal–organic framework (Zr‐MOF) membranes is challenging but promising for their performance enhancement. In this study, we pioneered the fabrication of uniform triangular‐shaped, 40 nm thick UiO‐66 nanosheet (NS) seeds by employing an anisotropic etching strategy. Through innovating confined counter‐diffusion‐assisted epitaxial growth, highly (111)‐oriented 165 nm‐thick UiO‐66 membrane was prepared. The significant reduction in thickness and diffusion barrier in the framework endowed the membrane with unprecedented CO2 permeance (2070 GPU) as well as high CO2/N2 selectivity (35.4), which surpassed the performance limits of state‐of‐the‐art polycrystalline MOF membranes. In addition, highly (111)‐oriented 180 nm‐thick NH2‐UiO‐66 membrane showing superb H2/CO2 separation performance with H2 permeance of 1230 GPU and H2/CO2 selectivity of 41.3, was prepared with the above synthetic procedure. [ABSTRACT FROM AUTHOR]

Metal‐organic framework (MOF), which possesses stable framework structure constructed by highly connected metal‐oxo cluster nodes and organic linkers, has shown great promise in gas storage, adsorption, and separation, owing to the high surface areas, tunable pore aperture, and rich functional groups. In this review article, we summarized recent progress made in synthesizing high‐valence MOF (e. g. UiO‐66, MIL‐125, PCN‐22, and MIP‐207) with metal‐oxo cluster as metal source. Of particular note, recent breakthroughs in the preparation of UiO‐66 and MIL‐125 membranes with the corresponding Zr6‐oxo and Ti8‐oxo cluster sources (e. g. Zr6O4(OH)4(OAc)12 and Ti8O8(OOCR)16 clusters) possessing superior separation performance were highlighted. In the end, an outlook on the preparation of versatile high‐valence MOF membranes with the corresponding metal‐oxo clusters as metal sources was highlighted. [ABSTRACT FROM AUTHOR]

Although having shown great promise for efficient gas separation, relevant study of Ti‐MOF membranes remains very scarce, owing to limited Ti source types and uncertain factors which dominate the separation properties. In this work, we pioneered the use of the Ti8(μ2‐O)8(OOCC6H5)16 cluster as the Ti source of MIL‐125 membranes, which led to lower reaction temperature and higher missing‐linker number within the framework and therefore, enhanced CO2/N2 adsorption selectivity. The MIL‐125 membrane prepared by combining single‐mode microwave heating with tertiary growth displayed an ideal CO2/N2 selectivity of 38.7, which ranked the highest among all pristine pure MOF membranes measured under comparable conditions. In addition, the ideal H2/N2 and H2/CH4 selectivity was as high as 64.9 and 40.7, thus showing great promise for versatile utility in gas separation. [ABSTRACT FROM AUTHOR]

Concurrent manipulation of orientation and thickness of MOF membranes has become a reliable approach for improving their separation performances. In terms of oriented seeded growth, oriented deposition of MOF nanosheets during seeding process and sealing all intergranular gaps with no discernible increase in membrane thickness during secondary growth have become indispensable. In this study, we pioneered the fabrication of uniform hexagonal-shaped, 20–40 nm thick MIL-96 nanosheets through solvent composition optimization (V H2O /V FA = 1/2). Subsequently, spin coating was employed for c -oriented deposition of uniform MIL-96 seed layer, during which the addition of PVP in the suspension was found to be critical for obtaining qualified seed layer. Finally, well-intergrown, highly c -oriented ultrathin MIL-96 membrane was prepared upon employing NMF as the solvent during secondary growth. Gas permeation results implied that prepared MIL-96 membrane exhibited superior gas separation performance compared with that of a -& b -oriented counterpart. [Display omitted] • Uniform 20–40 nm thick MIL-96 nanosheets were synthesized via solvent optimization. • Solvent type affected preferred orientation and thickness of the MIL-96 membrane. • c -Oriented ultrathin MIL-96 membrane showed superior H 2 /CO 2 separation performance. [ABSTRACT FROM AUTHOR]