Mixed matrix membranes (MMMs) attract great attention due to their outstanding gas separation performance. The compatibility between the fillers and the polymer matrix is one of the key points for the preparation of high-performance MMMs. In this work, MMMs consisting of metal-organic frameworks (MOFs) of amine-modified Cu-BTC (NH2-Cu-BTC; BTC = 1,3,5-benzenetricarboxylic acid) and submicrometer-sized amine-modified Cu-BTC (sub-NH2-Cu-BTC) incorporated into a Pebax-1657 polymer were fabricated for the gas separation. The SEM image and Fourier transform infrared spectroscopy (FTIR) spectra showed an increase in the surface roughness of MOFs and the presence of amino groups on the surface of Cu-BTC after the amination modification, and a decrease in the size of MOFs crystals after the submicrometer-sized aminated modification. Gas adsorption analysis indicated that NH2-Cu-BTC and sub-NH2-Cu-BTC had a higher gas adsorption capacity for CO2 compared to the unmodified Cu-BTC. The scanning electron microscopy (SEM) image showed that NH2-Cu-BTC and sub-NH2-Cu-BTC, especially sub-NH2-Cu-BTC, had a better compatibility with a polyether-block-amide (Pebax) matrix in the MMMs. The gas separation performance indicated that the Pebax/sub-NH2-Cu-BTC MMMs evidently improved the CO2/N2 and CO2/CH4 selectivity at the expense of a slight CO2 permeability. The results reveal that modified MOF-filled MMMs possess great potential for applications in the CO2 separation field.
The interfacial properties within
a composite structure of membranes
play a vital role in the separation properties and application performances.
Building an interlayer can facilitate the formation of a highly selective
layer as well as improve the interfacial properties of the composite
membrane. However, it is difficult for a nanomaterial-based interlayer
to increase the flux and retention of nanofiltration membranes simultaneously.
Here, we report a nanofiltration membrane with a hybrid dimensional
titania interlayer that exhibits excellent separation performance.
The interlayer, composed of Fe-doped titania nanosheets and titania
nanoparticles, helps the formation of an ultrathin (∼30 nm
thick) and defect-free polyamide selective layer with an ideal nanostructure.
The hybrid dimensional interlayer endows the membrane with a superior
permeability and alleviates flux decline. In addition, the rigid interlayer
framework on a PVDF support drastically improves the pressure resistance
of nanofiltration membranes and shows negligible flux loss up to 1.5
MPa of pressure.
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