Ultrathin cyclodextrin-based nanofiltration membrane with tunable microporosity for antibiotic desalination

Nanofiltration (NF) membranes play a crucial role in ion separation and antibiotic purification due to their energy efficiency and environment-friendliness. However, conventional polymeric membranes are susceptible to the “trade-off” between permeability and selectivity due to the lack of intrinsically rigid micropores. Herein, the amino-cyclodextrins (amino-CDs) with different cavity sizes were synthesized and employed as the building block to construct 15-nm-thick nanofilms. The rational incorporation of macrocycles with well-defined and tunable cavity into nanofilm enabled a significant enhancement of water permeance and a precise manipulation of molecular weight cut-off of the membranes. Thanks to the significant difference of inherent energy barrier for passage of ions through CD cavity, the CD-incorporated membranes achieved a high Cl⁻/SO₄²⁻ selectivity of 87. In addition, the CD-regulated membranes showed an excellent antibiotic desalination performance, out-performing the state-of-the-art membranes for antibiotic purification. This work provides a gateway to the development of nanofiltration membranes with precise molecular sieving for antibiotic desalination.