Cross-linked γ-cyclodextrin metal-organic framework-a new stationary phase for the separations of benzene series and polycyclic aromatic hydrocarbons.

The cross-linked γ-cyclodextrin metal-organic framework (CL-CD-MOF) was synthesized by crosslinking γ-cyclodextrin metal-organic framework (γ-CD-MOF) with diphenyl carbonate to separate benzene series and polycyclic aromatic hydrocarbons (PAHs). The separation ability of the CL-CD-MOF packed column was assessed in both reverse-phase (RP-) and normal-phase (NP-) modes. The retention mechanisms of these compounds were discussed and confirmed by combining molecular simulations in detail. It was found that baseline separation could be obtained in RP-HPLC mode and it was superior to commercial C18 column in separating xylene isomers. The interaction between CL-CD-MOF and analytes, such as dipole-dipole interaction, π-electron transfer interaction, hydrophobic interaction, and van der Waals force, may dominate the chromatographic separation, and CL-CD-MOF column had a certain shape recognition ability. In addition, the composition of the mobile phase also had a crucial effect. Moreover, the column demonstrated satisfactory stability and repeatability (the relative standard deviations of retention time, peak height, peak area, and half peak width for six replicate separations of the tested analytes were within the ranges 0.17-1.1%, 0.96-1.9%, 0.23-1.7%, and 0.32-1.9%, respectively) and there was no significant change in the separation efficiency for at least 3 years of use. Thermodynamic characteristics indicated that the process of separations on the CL-CD-MOF column was both negative enthalpy change (ΔH) and entropy change (ΔS) controlled. The excellent performance made CL-CD-MOF a promising HPLC stationary phase material for separation and determination of benzene series and PAHs.