Chiral functionalization of nanotubular hyper-crosslinked polymer membranes with high performance for enantioselective separation

High-performance enantioseparation membranes have the great practical value in racemic mixture separation, since conventional chiral membranes often encounter a severe permeability/enantioselectivity trade-off, which remarkably restricts their large-scale applications. This work aimed to fabricate the retarded transport membrane that has great potential to alleviate the trade-off using the chiral hyper-crosslinked polymer (CHCP) nanotube. Here, a series of CHCP-based membranes (CHCPMs) was prepared via vacuum-assisted filtration, in which the chiral recognition unit ( D -phenylalanine, D -Phe) was incorporated into the main skeleton of nanotubular HCPs via a co-crosslinking method. Results show that CHCPMs display a 2–4 orders of magnitude improvement in flux as compared to traditional enantioseparation membranes and an approximately 1 order of magnitude increase in flux relative to GO-based analogues ones, accompanied by the outstanding enantioselectivity; as the nanotube-based membranes, such amine-modified CHCPMs exhibit a ca. 37% and 23% improvement in enantioselectivity and flux, respectively, compared to the hydroxyl-modified CHCPM reported in our previous work under the same conditions. Moreover, CHCPMs follow a retarded transport mechanism, further supported by density functional theory calculation methods. The amine group introduced within the nanoconfinement space can activate the non-stereoselective interaction, which plays a critical role in enhancing enantioselectivity. Our findings highlight the demand for considering the more subtle molecular structure design and modification when optimizing a particular functional property of enantioseparation membranes