Enantiomeric analysis of chiral phenyl aromatic compounds by coated capillary electrochromatography based on a MOF-on-MOF stationary phase.

Chiral phenyl aromatic compounds (CPACs) are widely used in drug development, food/cosmetic production, and other organic synthesis processes, and their different enantiomers have distinct physiological activities and application differences. A double-layer metal-organic framework composite (MOF-on-MOF) was obtained by in situ synthesis of chiral metal-organic framework (CMOM-3S) on the surface of an iron-based metal-organic framework (NH2-MIL-101(Fe)). According to our investigation, MOF-on-MOF composite was for the first time applied to the stationary phase of capillary electrochromatography (CEC), and enantioseparations of eight CPACs were accomplished. Compared with single CMOM-3S, the enantioseparation performance of the coated capillary columns based on NH2-MIL-101(Fe)@CMOM-3S was improved by 34.07 ~ 720.0%. The R-/S-mandelic acid in actual sample (apricot leaves) was detected by the newly CEC system to be 0.0118 mg mL-1 and 0.0523 mg mL-1, respectively. The spike recoveries were 96.60 ~ 104.7%, indicating its good stability and accuracy. In addition, the selective adsorption capacity of MOF-on-MOF composites was verified by adsorption experiments.