Fe-O-Fe-bridged Porphyrin Network Membranes for Solvent-resistant Nanofiltration
s The stability of solvent-resistant nanofiltration (SRNF) membranes, such as integrally skinned asymmetric (ISA) and thin-film composite (TFC) membranes, in polar aprotic solvents must be improved if they are to meet increasingly complex industrial demands. The stability of the former membranes can be improved by forming crosslinked rigid chains, such as polybenzimidazoles and polyimides, but this requires time-consuming treatment processes. Conversely, the latter membranes are easy to fabricate but lack efficient active sites for crosslinking and structural rigidity. Herein, we present a fabrication strategy combining the characteristics of both types of membranes. We first utilize amino-functional porphyrins as polyaromatic units to form rigid polyamide networks by vacuum-assisted interfacial polymerization, simultaneously providing active sites for further crosslinking, which is accomplished by immersion in FeCl 2 /dimethyl sulfoxide (DMSO) solution to directly establish Fe-O-Fe bridges between porphyrin centers to form a stable network. The Fe-O-Fe-bridged porphyrin networks are solvent-stable in DMSO. Furthermore, they achieve outstanding molecular separation (96.2% rejection of methyl orange, 327 Da) and limited molecular-weight-cutoff change (from 360 to 420 Da) during alternating MeOH and DMSO filtration, along with long-term recovery efficiency (> 96.7% over seven days). Thus, our study provides a promising strategy for the facile development and fabrication of efficient, robust SRNF membranes.
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