Engineering nanochannels in mixed‐matrix membranes using F‐anchored Aluminum‐ MOF nanoparticles for isomer separation

Abstract Robust aluminum‐based metal–organic framework (Al‐MOF) nanoparticles with ordered nanochannels represent promising fillers for mixed‐matrix membranes (MMMs) toward challenging liquid separations. Achieving both high separation factor and permeation flux, however, requires not only precise pore engineering but also reliable interfacial compatibility under complex feed conditions. Herein, we demonstrate that fluoroalkylsilane (FAS) coating concurrently enhances the processability of Al‐MOF (CAU‐23) nanoparticles in PIM‐1 and tunes their pore apertures. Through this synergy, the FAS‐anchored CAU‐23 (FCAU‐23) evolve from passive fillers into active nanochannel directors, establishing efficient, low‐resistance pathways for linear n‐hexane (n‐C6) while selectively discriminating against branched isomers. The optimized 1‐FCAU‐23‐10/PIM‐1 MMM achieves a record n‐C6 permeation flux of 1.45 kg m −2 h −1 with a separation factor (SF) of 5.1 in binary feeds. More importantly, it maintains robust performance under quinary feeds, yielding permeants enriched in linear n‐C6 and mono‐branched species (88 wt.%). This work highlights filler/interface engineering as a route to robust isomer separations.