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Nanofiltration (NF) membranes as high selective separators are appealing for molecular sieving, which still remains a great challenge for the mixed dyes with same charge. In this study, cellulose acetate (CA) membranes were firstly aminated by ethylene imine polymer (PEI), and then the thin film of metal organic frameworks (MOFs) were constructed onto aminated CA membrane through forward-diffusion, slow crystallization and in situ growth of FeCo-Prussian blue (FeCo-PB) crystallization layers. The designed PB@CA composite NF membrane shows an ideal rejection for Congo red (CR)/methyl orange (MO) mixture solution, with 99.7%±0.2% for CR and 33.5%±2% for MO. In addition, the composite NF membrane demonstrated good efficiency for photocatalytic degradation of organic fouling (permeability recovery ratio was up to 92%) due to the active FeCo-PB micro-cubes. Thus, this work provides a practical strategy to prepare MOFs mediated thin film composite nanofiltration membrane for precise molecular sieving and catalytic antifouling performances. [ABSTRACT FROM AUTHOR]

A supercritical carbon dioxide (ScCO) assisted phase inversion was developed to produce microporous poly(vinylidene fluoride) (PVDF) membranes whose morphology characteristics arise from both liquid-liquid demixing and solid-liquid demixing (crystallization). This result was confirmed by Fourier transform infrared spectroscopy (FTIR), from which both α and β crystals were found. As revealed by contact angle experiment, the PVDF membranes prepared via ScCO assisted phase inversion were more hydrophobic compared with the control membrane produced via conventional immersion-precipitation technique. In particular, the sample with 15 wt% PVDF prepared at 45 °C and 13 MPa exhibited a contact angle of 142°, which was mainly caused by the multilevel micro- and nano-structure. The effects of polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP) and lithium chloride (LiCl) on the structures and crystal form were investigated. PVP promoted the formation of α phase crystal form, while PEG boosts the evolution of β phase. LiCl restrained the crystallization degree of PVDF membrane under ScCO. [ABSTRACT FROM AUTHOR]