A homochiral covalent organic framework membrane for the enantioseparation and fractionation of amino acids
Ting Xu, Li Cao, Shuhao An, Xiaowei Liu, Zhen Li, Zhiping Lai
Abstract
The separation of amino acids from complex mixtures remains an essential yet multi-step, energy-intensive process. Membrane separation technology offers a more energy-efficient alternative, but its effectiveness relies on achieving highly precise molecular recognition. Here, we report a homochiral covalent organic framework (COF) membrane with ordered ultra-microporous pore structures for targeted extraction of specific enantiomer from amino acid mixtures. Benefiting from its high crystallinity and ultra-microporous chiral channels, the membrane exhibits both excellent permeability and enantioselectivity. A combination of experimental results, density functional theory calculations, and molecular dynamics simulations reveal a retarded transport mechanism, wherein stronger interactions between L-enantiomers and the homochiral pores hinder their transmembrane diffusion. We further demonstrate a two-stage cascade membrane process to simultaneously fractionate and enantioseparate amino acid mixtures, achieving near pure (99.5%) D-threonine from an eight-component protein hydrolysis complex. This study offers a promising and sustainable membrane-based solution for efficient amino acid purification. The use of membranes for the separation of complex amino acid mixtures is energy efficient but relies on achieving precise molecular recognition. Here, the authors report on a homochiral covalent organic framework membrane for the enantioseparation and fractionation of amino acids.