A Homochiral Poly(2-oxazoline)-based Membrane for Efficient Enantioselective Separation.

Chiral separation membranes have shown great potential for the efficient separation of racemic mixtures into enantiopure components for many applications, such as in the food and pharmaceutical industries; however, scalable fabrication of membranes with both high enantioselectivity and flux remains a challenge. Herein, enantiopure S-poly(2,4-dimethyl-2-oxazoline) (S-PdMeOx) macromonomers were synthesized and used to prepare a new type of enantioselective membrane consisting of a chiral S-PdMeOx network scaffolded by graphene oxide (GO) nanosheets. The S-PdMeOx-based membrane showed a near-quantitative enantiomeric excess (ee) (98.3±1.7 %) of S-(-)-limonene over R-(+)-limonene and a flux of 0.32 mmol m-2 h-1 . This work demonstrates the potential of homochiral poly(2,4-disubstituted-2-oxazoline)s in chiral discrimination and provides a new route to the development of highly efficient enantioselective membranes using synthetic homochiral polymer networks.

Homochiral MOF-Polymer Mixed Matrix Membranes for Efficient Separation of Chiral Molecules.

Homochiral metal-organic framework (MOF) membranes have been recently reported for chiral separations. However, only a few high-quality homochiral polycrystalline MOF membranes have been fabricated due to the difficulty in crystallization of a chiral MOF layer without defects on porous substrates. Alternatively, mixed matrix membranes (MMMs), which combine potential advantages of MOFs and polymers, have been widely demonstrated for gas separation and water purification. Here we report novel homochiral MOF-polymer MMMs for efficient chiral separation. Homochirality was successfully incorporated into achiral MIL-53-NH2 nanocrystals by post-synthetic modification with amino acids, such as l-histidine (l-His) and l-glutamic acid (l-Glu). The MIL-53-NH-l-His and MIL-53-NH-l-Glu nanocrystals were then embedded into polyethersulfone (PES) matrix to form homochiral MMMs, which exhibited excellent enantioselectivity for racemic 1-phenylethanol with the highest enantiomeric excess value up to 100 %. This work, as an example, demonstrates the feasibility of fabricating diverse large-scale homochiral MOF-based MMMs for chiral separation.