Dual-spacing-channel graphene oxide membranes with multiple hydrophilic domains give high permeance and high rejection in organic solvent nanofiltration.

Graphene oxide (GO) liquid crystals are of great interest for membrane preparation. Vacuum filtration has been frequently adopted as small-scale manufacturing method. The main challenge is to obtain thin and robust layers with high permeation and selectivity by methods that could be applied in large scale. GO liquid crystals are mostly formed by dispersion in water. For the first time, we demonstrate that GO can form lyotropic liquid crystalline nematic phase dispersions in protic ionic liquid and be fabricated as membranes for nanofiltration. The well-balanced electrostatic interaction between ionic liquid and GO promotes and stabilizes the alignment of GO nanosheets even when concentrations as low as 9 mg GO /mL are used, providing the ideal rheology for the dispersion casting and membrane preparation. Robust membranes with GO layers as thick as 1 m with high permeance (37 L m-2 h-1 bar-1) and 99.9 % rejection of dyes with molecular weight 697 g/mol were obtained. We confirmed the liquid crystal formation by the detection of birefringence and the rheological behavior and explained the liquid crystal formation as an interplay between hydrogen bonding and electrostatic interactions.

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The direct synthesis of oriented, defect-free nanocrystal metal-organic framework (MOF) films is a challenging step toward their applications in advanced technologies, such as optics, sensing, and membrane-based separations. Here, we propose a one-step, in-situ growth approach to synthesize oriented zeolitic imidazolate framework-L (ZIF-L) membranes by using an isoporous film as the support. The high metal-binding efficiency, as well as the ordered pore structure, given by the polymeric isoporous support, promote the preferred nucleation and rapid growth of vertically aligned ZIF-L nanocrystals to construct dense membranes. Vertically aligned nanochannels between the inter-lattice of ZIF-L are therefore formed through the polycrystalline membrane. The membrane exhibited a high H 2 permeance, 1635 GPU (1 GPU= 1 × 10 @1 cm 3 (STP)/cm 2 s cmHg), and H 2 /C 3 H 8 selectivity of 516, when targeting hydrogen separation from hydrocarbon in a steam reforming process. The membrane can be further used in organic solvents nanofiltrations, with a methanol permeance of 38.7 L m @, h @< bar @< , and >90% rejection of organic dye molecules. Furthermore, by taking advantage of the anisotropic pore structure, the ZIF-L membrane could be further hydrolyzed to produce ultrathin ZIF-L nanosheets with a thickness ~5 nm, which provides a facile platform to synthesize two-dimensional MOFs nanosheets.

Graphene Oxide (GO) membranes are well-known materials for water purification, owing to their unique molecular transport and sieving properties. However, one of the factors that limit their use in aqueous and organic solution for the application in the industry and water treatment plants is the tendency to swell, forming an enlarged interlayer spacing, disintegrating its structure. Here we report stable ethylenediamine-crosslinked GO membranes, which can efficiently permeate water and organic solvents and filter organic solutions containing molecular dyes. The prepared membranes with 150 nm thickness demonstrated high permeance for water and organic solvents and exhibited >95% rejection for small organic dyes dissolved in methanol. A dead-end filtration device was used to estimate the performance of the membranes, confirming a pure water