Preparation of MOF NPs and pMOF MSs
To
illuminate the concept of improving separation performance of MMMs by
incorporating pMOF MSs, we employed NH2-UiO-66 as filler
and PSF as matrix. As one of the most studied MOFs materials,
NH2-UiO-66,47,48 constructed by the
coordination between
Zr6O4(OH)4 centers and
NH2-BDC linkers, has excellent chemical stability and
good adsorption capacity for CO2.49PSF with cost-effective and thermally stable features possesses great
potential in fabrication of high-performance
membranes.50,51 Figure 1 showed the synthesis
procedures of the MOF NPs and MSs. The NH2-UiO-66 MSs
were obtained by the simple one-pot synthesis via introducing PSF in
precursor solutions, while the NH2-UiO-66 NPs were
prepared without polymer additives. On account of solubility, the
polymer was added with concentration of 6.0 wt/v% in precursor
solutions, because the dissolutions of polymers and precursors
influenced each other. As shown in SEM images (Figure 2a), the
NH2-UiO-66 NPs without polymer additives possessed
well-defined octahedral structure, with the size of 150˗200 nm. For the
polymer-embedded pMOF MSs, the obvious different spherical structure
appeared (Figure 2b,c). The size of pMOF microspheres was about 1˗2 μm,
which was much larger than that of the MOF NPs. During the
crystallization process of MOFs, the added polymer chains in precursor
solution prompted the assemblage of the nuclei and the intergrowth of
crystals, thereby leading to the formation of large polycrystalline
spherical structures.52,53 Moreover, it was noticeable
that the prepared pMOF MSs possessed relatively rough surface, which
might be beneficial to improve the interfacial interaction between MSs
and matrixes due to the enlarged contacting area.