Tuning polymer spreading and enhancing butanol pervaporation performance via fluorinated covalent organic framework in PDMS/PEBA membranes

While covalent organic frameworks (COFs) have been applied for enhancing membrane separation performance, their influence on membrane formation dynamics remains underexplored. In this study, a polyether block amide (PEBA) interlayer was fabricated on the polytetrafluoroethylene (PTFE) support. On this flat PEBA/PTFE surface, the spreading behavior of COFs/polydimethylsiloxane (PDMS) could be studied. The incorporation of fluorinated triformylphloroglucinol-benzenediamine (TpBD-F) COFs significantly enhanced the spreading coefficient from −2.99mN/m to −0.86mN/m on the PEBA surface, forming a thinner and more uniform separation layer. Combined with the TpBD-F's intrinsic 1.4 nm hydrophobic nanochannels, these structural refinements facilitated enhanced butanol adsorption and diffusion. The TpBD-F@PDMS-PEBA/PTFE membrane achieved a flux of 4.8 kg·m −2 ·h −1 and a separation factor of 28.1 for a 1 wt% butanol/water mixture, representing a 118% increase in flux compared to the PDMS-PEBA membrane, while maintaining stable performance over 100 h. This work provides both practical and theoretical guidance for designing COFs mixed-matrix membranes.