Upcycling eggshell waste into sustainable and portable chiral membranes for the physical separation and electrocatalytic deracemization of enantiomers

The preparative separation and synthetic deracemization of enantiomers are conventionally dominated by resource-intensive chromatographic methods and chemically wasteful asymmetric syntheses, posing significant challenges to Green Chemistry principles. Herein, we present a highly sustainable, electrically switchable chiral bio-hybrid device, achieved by upcycling globally abundant avian eggshell biomineral waste (CaCO3). Exploiting the raw, heterogeneously sized microparticles as a binder-free, hierarchically porous structural scaffold, we engineered a “structural multiplier” that drastically amplifies the stereospecific interactions of an electrodeposited inherently chiral oligomer. Integrated into a miniaturized, solvent-efficient continuous-flow setup operating with microliter volumes and green extraction media (heptane), the bio-hybrid interface completely transcends conventional physical filtration. We demonstrate that by simply tuning the externally applied DC bias, the membrane's operational logic toward carvone enantiomers is dynamically inverted. At a moderate anodic bias (0.7 V), it acts as a passive thermodynamic affinity filter, while at 1.3 V, it rigidifies into an absolute steric gatekeeper. Most remarkably, poised at an intermediate hyper-reactive regime (1.1 V), the system operates as a solid-state electrocatalytic reactor capable of actively breaking racemic equilibriums. Through an iterative, multi-pass continuous-flow process, the membrane actively interconverted the unfavoured enantiomer into the favoured antipode, upgrading a strict 50 : 50 racemic mixture to an exceptional >99% enantiomeric excess (ee) using solely localized electrical perturbation. This work seamlessly merges zero-cost biomineral valorization with advanced molecular electrochemistry, offering a low-energy, reagent-free paradigm that bridges green enantioseparation and sustainable asymmetric synthesis.