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Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity. The obtained image involves structural information transferred up to 2.1 Å, allowing the resolution of individual atomic columns of Zn and organic linkers in the framework. Furthermore, TEM reveals important local structural features of ZIF-8 crystals that cannot be identified by diffraction techniques, including armchair-type surface terminations and coherent interfaces between assembled crystals. These observations allow us to understand how ZIF-8 crystals self-assemble and the subsequent influence of interfacial cavities on mass transport of guest molecules.

2D metal–organic frameworks are attractive filler in mixed matrix membranes (MMMs) due to the high aspect ratio and contact opportunity at the filler–polymer interface. However, their alignment in polymer matrix remains a challenge to fully play their functions. Herein, to our best knowledge, for the first time, the facile synthesis of KAUST‐7‐NH2 (KAUST, King University of Science and Technology) nanoplate is reported with 1D channels with an aspect ratio greater than 30. The nanoplates are incorporated and aligned in the 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride‐2,4‐diaminomesitylene (6FDA‐DAM) polymer matrix under the shear force with a filler loading up to 50 wt%. The large difference in adsorption abilities between CO2 and CH4 from the (001)‐oriented KAUST‐7‐NH2 nanoplate‐based MMMs and the favorable interaction at the filler–polymer interface contribute to the excellent CO2/CH4 separation performance. The resultant membranes show CO2/CH4 selectivity with 66.2% enhancement (surpassed 2008 Robeson upper bound), antiplasticization up to 17 bar, and long‐term stability up to 240 h indicating its good potential for natural gas treatment. [ABSTRACT FROM AUTHOR]

High-performance mixed matrix membranes (MMMs) were developed to assist in controlling global warming by capturing carbon dioxide (CO2) from moist flue gas. However, the separation performance of MMMs has always been limited by gas permeability and long-term operating stability under humid conditions. ZIF-302 is a novel chabazite (CHA) topology structure with hydrophobic ligand. Herein, uniform ZIF-302 nanocrystals were doped into the P84 polymer matrix to synthesize different content of defect-free ZIF-302/P84 MMMs for CO2/N2 separation. A significant combination of gas permeability and separation factors was found in MMMs with a ZIF-302 packing load of 30 wt%. The gas permeability of CO2 and the separation factor of CO2/N2 were significantly increased to 5.2 Barrers and 46, respectively, which breaks the trade-off between permeability and selectivity of the polymer membrane. In addition, the long-term operation stability showed that the separation performance of ZIF-302/P84 MMMs for CO2/N2 was maintained more than 30 h at 3 bar and 60 °C. The main characteristics of the MMMs prepared in this paper include the combination of favorable structural stability under humid conditions and unaffected CO2/N2 gas separation performance. [ABSTRACT FROM AUTHOR]