Cu2+−Catechol Coordination-Enabled Chiral Fabry−Perot Interferometer for Amplifying Weak Enantioselective Interactions

Efficient transduction of weak enantioselective adsorption into amplified optical signals remains challenging in label-free chiral sensing. Herein, we report a Cu2+−catechol coordination-enabled chiral Fabry−Pérot interferometer for amplified enantioselective sensing of catechol-containing chiral molecules. The sensing interface was constructed by in situ growing an l-glutamic-acid-modified MIL-125(Ti) layer within TiO2 nanotube Fabry−Pérot cavities, providing a homochiral porous microenvironment for differential enantiomer adsorption. Using DOPA enantiomers as model analytes, their distinct adsorption behaviors induce different local refractive-index changes, which are transduced into effective optical thickness variations by reflectometric interference spectroscopy. After target capture, Cu2+ ions coordinate with the catechol groups of adsorbed DOPA molecules, increasing interfacial loading and amplifying the refractive-index perturbation within the Fabry−Pérot cavity. This coordination-assisted amplification enlarges the optical response difference between DOPA enantiomers and enables sensitive discrimination with a detection limit down to 10−8 M under both static incubation and flow-through monitoring conditions. By integrating homochiral MOF recognition, Fabry−Pérot transduction, and Cu2+−catechol coordination amplification, this work provides a low-cost, label-free strategy for amplifying chiral host−guest interactions, with potential extension to catechol-containing enantiomers.