Regulating interface nucleus growth of CuTCPP membranes via polymer collaboration method
Supported metal–organic framework (MOF) membranes are promising candidates for energy-efficient natural gas purification, but the preparation of ultrathin MOF membranes supported by polymer substrates remains challenging. Herein, we proposed a polymer collaboration method for preparing ultrathin two-dimensional MOF membranes on polymer support layers. Cu(II) meso-tetra (4-carboxyphenyl) porphyrin (CuTCPP) membranes having thicknesses as low as <10 nm were formed in situ because of the high density of heterogeneous nucleation sites in a polyvinyl alcohol-Cu 2+ interface layer and the controlled anisotropic growth of nanocrystals enabled by a polyvinylpyrrolidone (PVP) surfactant. The prepared CuTCPP membranes showed excellent CO 2 /CH 4 separation performance, yielding a high permeance of 4560 GPU and a moderate selectivity of 31.8. Furthermore, the prepared CuTCPP membranes also displayed good CO 2 /N 2 separation performance, having a CO 2 permeance of 3200 GPU and a CO 2 /N 2 selectivity of 36. The thickness of CuTCPP membranes can be controlled by varying the concentration of metal ions in the organic interface layer. This preparation method can not only fix the active sites for membrane formation but also control the morphology of crystal growth and is applicable to membrane fabrication using other porous MOFs.
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