Improved enantioselective permeation in cellulose membrane-supported metal–organic framework via polyvinylpyrrolidone as the pore-forming agent

Chiral membranes have limited permeability and selective trade-off, which has been a major problem in chiral membrane separations. To address this issue, the carboxylated cellulose (CC) membranes were prepared with small pore size and low resistance substrate by regulating the amount of polyvinylpyrrolidone (PVP) and casting solution, and the CC@CuLBH composite membrane with chiral separation capability was fabricated by in situ formation of well-dispersed [Cu(L-mal)(Bipy)]·H2O (CuLBH) with the carboxyl group on the surface of CC membrane as the metal anchor points. Under the optimal conditions, the CC@CuLBH membrane showed good chiral separation ability with an ee value of 60% for R-1-(1-naphthyl)ethanol (R-NE). Compared with the CC/CuLBH membrane formed by physical blend, the CC@CuLBH membrane exhibited improved enantioselective permeation for R-NE enantiomer. Both the unique chiral microenvironment of CuLBH and the regular pore structure of CC membrane, in addition to their synergistic effects resulted in the highly permeable and enantioselectivity for the CC@CuLBH composite membrane, which broadened the preparation method of chiral membrane.