A facilitated-transport enantio-separation mechanism was proposed in this study and verified with an enantio-selective thin film composite membrane. The polysulfone membrane substrate was first fabricated at the optimized conditions, and the chiral selector alpha-CD was then incorporated into the selective layer by mixing with the MPD monomer for interfacial polymerization. Racemic tryptophan was employed as the model selectant, and inversed enantio-selectivities, 1.55 and 0.6 were observed from two different operation mode driven by concentration gradient and pressure gradient, respectively. The facilitated-transport separation mechanism was demonstrated by the concentration driven mode. The effects of other influencing factors including racemic feed concentration, alpha-CD concentration and pressure were also investigated. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.