Homochiral Eu³⁺@MOF Composite for the Enantioselective Detection and Separation of (<i>R</i>/<i>S</i>)-Ornidazole

Abstract

The development of homochiral materials for the enantioselective detection and separation of chiral drugs is in high demand for the pharmaceutical industry. Herein, an anionic homochiral metal-organic framework (HMOF) with <i>in situ</i> generated [Me₂NH₂]⁺ counterions, {[Me₂NH₂]₂[Zn₂(d-L)₂(HCO₂)(OH)]·5H₂O}_<i>n</i> (HMOF-<b>1</b>), was synthesized using a d-camphorate-derived enantiopure dicarboxylate ligand, 4,4'-[[(1<i>R</i>,3<i>S</i>)-1,2,2-trimethylcyclopentane-1,3-dicarbonyl]bis(azanediyl)]dibenzoic acid (d-H₂L) via a simple solvothermal method. Interestingly, HMOF-<b>1</b> could be used as a parent framework to encapsulate Eu³⁺ cations via an ion-exchange process, yielding an Eu³⁺@HMOF-<b>1</b> composite with dual-luminescent centers. The obtained Eu³⁺@HMOF-<b>1</b> has high chemical stability and good luminescence stability in water. Importantly, Eu³⁺@HMOF-<b>1</b> exhibits enhanced enantioselectivity and sensitivity in the detection of an important chiral nitroimidazole antibiotic, (<i>R</i>/<i>S</i>)-ornidazole (ONZ) in comparison to HMOF-<b>1</b> under the same aqueous conditions. The enantiomeric excess (ee) value of the ONZ enantiomers can be accurately determined by the ratio of dual emission from the ligand and Eu³⁺. In addition, Eu³⁺@HMOF-<b>1</b> shows the enantioselective separation of racemic ONZ enantiomers with an ee value of 86.6%. This work provides a simple strategy for the preparation of Ln^III-incorporated HMOF composite materials for the simultaneous enantioselective detection and separation of chiral drugs.