Constructing a composite interface on in situ grown MOF scaffolds for efficient separation of D,L-amino acids via chiral ligand-exchange capillary electrochromatography

The inherently low phase ratio and limited surface capacity of open-tubular capillary electrochromatography (OT-CEC) significantly restrict its efficiency in enantioseparation. To overcome this limitation, we developed a rigid-flexible composite interface strategy to construct a high-efficiency chiral ligand-exchange CEC (CLE-CEC) column. A uniform nanocrystalline UiO-66-NH 2 layer was in situ grown on the capillary inner wall to serve as a high-surface-area rigid scaffold, followed by the covalent immobilization of L-arginine (L-Arg) as a flexible chiral ligand. This composite architecture combines the structural stability of metal-organic frameworks (MOFs) with the stereochemical selectivity of amino acid ligands. The dense MOF scaffold effectively increases the specific surface area and ligand loading capacity of the stationary phase, thereby facilitating efficient Zn(II)-mediated ternary complexation for chiral recognition. Validating this design, the UiO-66-NH-L-Arg@capillary column achieved baseline separation for seven pairs of Dns-D,L-AAs, with resolution factors reaching up to 2.56. The column exhibited satisfactory repeatability and good operational stability. Furthermore, the practicability of this method was demonstrated by its successful application in the kinetic monitoring of L-alanine dehydrogenase, providing a robust micro-separation tool for precise bioanalysis.