Rational design of poly-cyclodextrin nanofibers through crosslinker chemistry and cavity size for selective...

Developing adaptable membrane materials for the selective removal of chemically diverse organic micropollutants from water remains a major challenge in advanced separation technologies. Here, we report a library of nine poly-cyclodextrin nanofibrous membranes (poly-CD NM) prepared by combining three cyclodextrins with different cavity sizes, hydroxypropyl-α-cyclodextrin (HP-α-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), and hydroxypropyl-γ-cyclodextrin (HP-γ-CD), with three crosslinking systems: neutral hexamethylene diisocyanate (HMDI), cationic polyethyleneimine/glutaraldehyde (PEI-GA), and anionic 1,2,3,4-butanetetracarboxylic acid (BTCA). This platform enables systematic evaluation of the combined effects of cyclodextrin cavity size and crosslinker chemistry on membrane performance and micropollutant removal. The membranes were evaluated using six organic micropollutants: methyl orange, methylene blue, ibuprofen, ciprofloxacin, triclosan, and bisphenol A (BPA). Crosslinker chemistry dominated the removal of charged micropollutants: BTCA-crosslinked poly-CD preferentially removed cationic species, whereas PEI-GA-based poly-CD preferentially removed anionic species, largely independent of cyclodextrin cavity size. In contrast, HMDI-crosslinked poly-CD exhibited limited removal of charged micropollutants (generally <35%, except for methyl orange, which showed substantially higher removal). At the same time, cyclodextrin cavity size became a more important factor governing the removal of neutral micropollutants. These findings demonstrate that both crosslinker chemistry and cyclodextrin cavity size can be tailored to enable the development of poly-cyclodextrin nanofibers for selective micropollutant removal.