Extra-thin composite nanofiltration membranes tuned by γ-cyclodextrins containing amphipathic cavities for efficient separation of magnesium/lithium ions

•The amphipathic cavity of γ-CDs enhanced the surface hydrophilicity and the water flux of the nanofiltration membrane.•The cavity size of γ-CDs also effectively screened magnesium and lithium ions to a certain extent.•The γ-CDs made the diffusion rate of the water phase monomers during the interfacial polymerization reaction decelerated.