The adsorption and enantioselective properties of threonine-based Zn-MOF composite supported on agar biomass aerogel.

The adsorption activity and enantioselectivity of a novel chiral metal-organic framework based on zinc and a ligand obtained by condensation of threonine and 4-pyridine carbaldehyde (Zn-MOF), as well as its composite with agar (AG/Zn-MOF-0.4), were estimated by inverse gas chromatography. Specific retention volumes (Vg, mL/g) and thermodynamic characteristics of adsorption for different classes of organic substances were calculated from chromatographic experiment. Enantioselectivity was studied with respect to α-pinenes and limonenes, by Vg and adsorption isotherms analysis. A composite material (AG/Zn-MOF-0.4) had more polar surfaces than its parent MOF (Zn-MOF) due to strong interactions with agar. Adsorption analysis showed that the molecules interact with the surface only by specific parts (e.g., a benzene ring or hydroxyl group). Both studied samples also demonstrated enantioselectivity, preferentially adsorbing L-α-pinene. AG/Zn-MOF-0.4 has also shown the ability to recognizing limonene enantiomers. The enantioselectivity coefficients α were higher on AG/Zn-MOF-0.4 than on Zn-MOF or pure agar aerogel. So the combination of chiral MOF with agar created a synergistic effect, enhancing chiral recognition and adsorption activity. This approach is promising for developing advanced chiral adsorbents.