The encouraging improvement of polyamide nanofiltration membrane by cucurbituril-based host–guest chemistry

The considerable performance enhancement of small molecule-sieving nanofiltration membrane has been achieved by the functional combination between host–guest chemistry and interfacial polymerization (IP) for the first time in this work. First, the water-insolubility of cucurbit[6]uril (CB6) was ameliorated by constructing host–guest complex (CB6-PIP) with piperazine. Second, the incorporation of water-soluble CB6-PIP in the selective layer via IP leads to the generation of not only the enlarged conventional polyamide network tunnels but also rotaxane tunnels. Such enrichment of solvent transport tunnels contributes to an amazing pure water permeability of 15.5–25.4 Lm⁻²bar⁻¹h⁻¹, three times higher than that of traditional polyamide membranes, with a high R/MgSO₄ of 99.5–92.5%, perfect SO₄²⁻/Cl⁻ selectivity due to the electronegative contribution of CB6, as well as untapped potential in organic solvent nanofiltration. This work not only provides a fire-new strategy to design new type of NF materials but also promotes the application of CBs in many other fields.