Synthesis of chiral conjugated microporous polymer composite membrane and improvements in permeability and selectivity during enantioselective permeation

Abstract

Three kinds of chiral conjugated microporous polymer composite membranes with porous silica as the support layer (CCMP/SiO2) were successfully prepared by surface-initiated Sonogashira-Hagihara polymerization for the first time. The skin layer thickness and morphology of the CCMP/SiO2 composite membrane were controlled by optimizing the concentration of monomers and solvents during polymerization. The obtained CCMP/SiO2 composite membranes showed high thermal stability and solvent stability. Racemates of phenylalanine (Phe) and tryptophan (Trp) were enantioselectively separated through CCMP/SiO2 composite membranes. The permeability and enantioselectivity were 2.07 × 10−5 m2/h and 94.1 %ee, respectively, for the (D,L)-Phe aqueous solution, and 1.17 × 10−5 m2/h and 84.9 %ee for (D,L)-Trp aqueous solution, respectively. The permeability of the CCMP/SiO2 composite membrane was more than 1000 times higher than that of the one-dimensional polymer chiral separation membrane when the selectivity was higher than 80 %ee. The excellent enantiomeric resolution performance of the CCMP/SiO2 composite membrane may be caused by the high content of micropores supported by the three-dimensional fully conjugated rigid framework and the presence of chiral moieties within the microporous polymers. As a result, highly enantioselective chiral conjugated microporous polymer composite membranes with extremely high permeability have been obtained.