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Polycrystalline metal–organic framework (MOF) layers hold great promise as molecular sieve membranes for efficient gas separation. Nevertheless, the high crystallinity tends to cause inter‐crystalline defects/cracks in the nearby crystals, which makes crystalline porous materials face a great challenge in the fabrication of defect‐free membranes. Herein, for the first time, we demonstrate the balance between crystallinity and film formation of MOF membrane through a facile in situ modulation strategy. Monocarboxylic acid was introduced as a modulator to regulate the crystallinity via competitive complexation and thus concomitantly control the film‐forming state during membrane growth. Through adjusting the ratio of modulator acid/linker acid, an appropriate balance between this structural "trade‐off" was achieved. The resulting MOF membrane with moderate crystallinity and coherent morphology exhibits molecular sieving for H2/CO2 separation with selectivity up to 82.5. [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]

For the separation of ethane from ethylene, it remains challenging to target both high C2H6 adsorption and selectivity in a C2H6‐selective material. Herein, we report a reversible solid‐state transformation in a labile hydrogen‐bonded organic framework to generate a new rod‐packing desolvated framework (ZJU‐HOF‐1) with suitable cavity spaces and functional surfaces to optimally interact with C2H6. ZJU‐HOF‐1 thus exhibits simultaneously high C2H6 uptake (88 cm3 g−1 at 0.5 bar and 298 K) and C2H6/C2H4 selectivity (2.25), which are significantly higher than those of most top‐performing materials. Theoretical calculations revealed that the cage‐like cavities and functional sites synergistically "match" better with C2H6 to provide stronger multipoint interactions with C2H6 than C2H4. In combination with its high stability and ultralow water uptake, this material can efficiently capture C2H6 from 50/50 C2H6/C2H4 mixtures in ambient conditions under 60 % RH, providing a record polymer‐grade C2H4 productivity of 0.98 mmol g−1. [ABSTRACT FROM AUTHOR]