Microporous Composite Nanofiltration Membrane With Intrinsic Microporosity for Water Treatment

ABSTRACT Novel polymers of intrinsic microporosity (PIMs) exhibit rigidity and non‐planar structures, which make them promising for constructing high‐permeability separation materials. However, the intrinsic hydrophobicity of PIMs limits their application in separation membranes for aqueous systems. Herein, we report an in situ interfacial polymerization strategy utilizing a catechol‐functionalized PIM monomer in conjunction with dopamine (DA) to fabricate a thin‐film composite (TFC) nanofiltration membrane with intrinsic microporosity. In this process, the aqueous‐phase monomer, 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl‐1,1′spirobiindan (TTSBI), modulated the pore size distribution, which facilitated water transport and enhanced permeance, while DA improved hydrophilicity and adhesion. Furthermore, the steric hindrance imparted by the contorted structure of TTSBI interfered with the self‐polymerization and assembly behavior of DA, inhibiting the formation of larger aggregates and consequently reducing structural defects within the composite layer. The resulting composite membrane exhibits a narrow pore size distribution (0.3–0.4 nm), high Vitamin B 12 (VB 12 ) rejection rate (92.5%), and outstanding permeance (4.6 L m −2 h −1 bar −1 ). Moreover, long‐term testing demonstrated excellent stability, with only a 4.4% decline in rejection after 96 h. This work provides valuable insights for the fabrication of high‐performance nanofiltration membranes for water treatment.