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Metal-organic frameworks (MOFs) have emerged as porous solids of a superior type for the fabrication of membranes. However, it is still challenging to prepare a uniformly dispersed robust MOF hybrid membrane. Herein, we propose a simple and powerful strategy, namely, coordination-driven in situ self-assembly, for the fabrication of MOF hybrid membranes. On the basis of the coordination interactions between metal ions and ligands and/or the functional groups of the organic polymer, this method was confirmed to be feasible for the production of a stable membrane with greatly improved MOF-particle dispersion in and compatibility with the polymer, thus providing outstanding separation ability. As an experimental proof of concept, a high-quality ZIF-8/PSS membrane was fabricated that showed excellent performance in the nanofiltration and separation of dyes from water.

This paper is concerned with the self-assembly of polyelectrolyte multilayer membranes (PEMMs) by using dynamic layer-by-layer (LBL) adsorption technique for pervaporation separation of water/alcohol mixtures. The polyacrylonitrile (PAN) ultrafiltration membrane used as a support was firstly hydrolyzed with alkaline solutions followed by alternatively depositing polyethyleneimine (PEI) and polyacrylic acid (PAA) under a pressure of 0.1 MPa. The PEI-ethanol solution and PEI-aqueous solution were used to investigate the effects of solvents on the assembly process. It was found that both separation factor and permeate flux were improved remarkably by replacing PEI aqueous solution with PEI-ethanol solution. Because only a few composite bilayers were needed to achieve a good capability in the dynamic LBL process, the hydrolysis degrees of PAN support membrane would strongly affect the pervaporation membrane performances. It was also noted that the exposure of membranes to low pH after hydrolysis would not benefit for the assembly. Further studies were conducted to investigate the effects of alkali species on the PAN hydrolysis and pervaporation performances of PEMMs. The contribution of alkali species on the pervaporation performance was in the order of KOH > NaOH > LiOH. Finally, the performances of PEI/PAA multilayer membranes assembled on the hydrolyzed PAN support were evaluated with a relatively wide range of feed temperature and concentration. The PEMMs obtained with only 2.5 bilayers had a separation factor of 604 and a permeate flux of 314 g/m 2 h (70 • C) for pervaporation of 95 wt% ethanol-water mixture.

No abstract

The ability to obtain a maximum loading of inorganic nanoparticles while maintaining uniform dispersion in the polymer is the key to the fabrication of mixed-matrix membranes with high pervaporation performance in bioalcohol recovery from aqueous solution. Herein, we report the simultaneous spray self-assembly of a zeolitic imidazolate framework (ZIF)-polymer suspension and a cross-linker/catalyst solution as a method for the fabrication of a well-dispersed ZIF-8-PDMS nanohybrid membrane with an extremely high loading. The ZIF-8-PDMS membrane showed excellent biobutanol-permselective pervaporation performance. When the ZIF-8 loading was increased to 40 wt%, the total flux and separation factor could reach 4846.2 g m(-2) h(-1) and 81.6, respectively, in the recovery of n-butanol from 1.0 wt% aqueous solution (80 °C). This new method is expected to have serious implications for the preparation of defect-free mixed-matrix membranes for many applications.