The preparation of membranes with high selectivity based on specific chemical properties such as size and charge would impact the efficiency of the world’s energy supply, the production of clean water, and many other separation technologies. We report a flexible synthetic protocol for preparing highly ordered two-dimensional nanoporous polymeric materials (termed covalent organic frameworks or COFs) that allow for placing virtually any function group within the nanopores. We demonstrate that membranes, fabricated with this new family of materials with carboxylated pore walls, are very water permeable, as well as highly charged and size selective.

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Over the past decade, substantial progress has been made in the chemical processing (chiral enrichment, length sorting, handedness selectivity, and filling substance) of single-wall carbon nanotubes (SWCNTs). Recently, it was shown that large, horizontally-aligned films can be created out of post-processed SWCNT solutions. Here, we use machine-vision automation and parallelization to simultaneously produce globally-aligned SWCNT films using pressure-driven filtration. Feedback control enables filtration to occur with a constant flow rate that not only improves the nematic ordering of the SWCNT films, but also provides the ability to align a wide range of SWCNT types and on a variety of nanoporous membranes using the same filtration parameters. Using polarized optical spectroscopic techniques, we show that meniscus combing produces a two-dimensional radial SWCNT alignment on one side of the film. After we flatten the meniscus through silanation, spatially-resolved nematicity maps on both sides of the SWCNT film reveal global alignment across the entire structure. From experiments changing ionic strength and membrane tribocharging, we provide evidence that the SWCNT alignment mechanism stems from an interplay of intertube interactions and ordered membrane charging. This work opens up the possibility of creating globally-aligned SWCNT film structures for a new-generation of nanotube electronics and optical control elements. KeywordsNematic ordering, 1D crystals, single-wall carbon nanotubes Significant interest in one-dimensional (1D) nanocrystals (NCs) follows from their highly anisotropic properties of electrical and thermal transport, optical absorption, radiative emis-sion, and conduction. Typically, physical attributes observed in these NCs are significantly enhanced along the extended 1D crystal axis relative to the short axes, the latter often 1 arXiv:1907.09499v1 [cond-mat.mes-hall]

We report a new synthetic protocol for preparing highly ordered two-dimensional nanoporous covalent organic frameworks (2D-COFs) based on a quinoxaline backbone. The quinoxaline framework represents a new type of COF that enables postsynthetic modification by placing two different chemical functionalities within the nanopores including layer-to-layer cross-linking. We also demonstrate that membranes fabricated using this new 2D-COF perform highly selective separations resulting in dramatic performance enhancement post cross-linking.

The well-known reaction of amines with anhydrides to produce highly stable imide moieties has been extended to the synthesis of two dimensional polyimide-linked covalent organic frameworks (2D-COFs) by others. We...