Membrane separations are considered to be sustainable technologies because of their relatively low energy consumption. However, the fabrication of membranes is yet to turn green. Thin film composite (TFC) membranes...

Porous membranes of recycled poly­(ethylene terephthalate) (PET) were prepared by nonsolvent-induced phase separation (NIPS) and evaluated for the first time for the filtration in high temperature solvents and other harsh environments. The PET was recycled from commercial water bottles. The morphology, pore size, and pore density were optimized by varying the composition of the polymer concentration in the casting solution, the solvent, and the nonsolvent bath in conditions of controlled humidity and temperature. Poly­(ethylene glycol) (PEG) of 0.2 and 1 kg mol–1 was used as an additive and pore inducing agent. The filtration performance of the membranes was tested under different solvents and temperatures. The obtained PET membranes were successfully applied for ultrafiltration with a MWCO of 40 kg mol–1 in dimethylformamide (DMF) at temperatures up to 100 °C. PET membranes were found to be resistant to a wide variety of solvents as well as in chlorine and acid medium. They could be used as porous support for thin-film composite membranes and for different applications requiring high chemical and heat resistance.

Polymeric membranes are highly advantageous over their ceramic counterparts in terms of the simplicity of the manufacturing process, cost and scalability. Their main disadvantages are low stability at temperatures above 200 ˚C, and in organic solvents. We report for the first time porous polymeric membranes manufactured from poly(oxindolebiphenylylene) (POXI), a polymer with thermal stability as high as 500 ˚C in oxidative conditions. The membranes were prepared by solution casting and phase inversion by immersion in water. The asymmetric porous morphology was characterized by scanning electronic microscopy. The pristine membranes are stable in alcohols, acetone, acetonitrile and hexane, as well as in aqueous solutions with pH between 0 and 14. The membrane stability was extended for application in other organic solvents by crosslinking, using various dibromides, and the efficiency of the different crosslinkers was evaluated by thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). POXI crosslinked membranes are stable up to 329 ˚C in oxidative conditions and showed organic solvent resistance in polar aprotic solvents with 99% rejection of Red Direct 80 in DMF at 70 ˚C. With this development, the application of polymeric membranes could be extended to high temperature and harsh environments, fields currently dominated by ceramic membranes.

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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.