UiO-67-Typed Zr-MOFs Modified with Chiral Amine Alcohol Pendants for Adsorption Separation of Chiral Aromatic Alcohol Enantiomers

Robust UiO-67-typed Zr-HMOFs <b>1</b> and <b>2</b> (HMOFs = homochiral metal-organic frameworks) functionalized with isomeric chiral amine alcohol pendants, which have the same topology, but the relative positions between hydrogen-bonding sites and chiral carbons are different, were synthesized as adsorption platforms for the enantioseparation of 1-phenylethanol, 1-phenyl-2-propanol, and 2-phenyl-1-propanol. Both materials exhibited effective enantioseparation performance for the aforementioned alcohols. Particularly, <b>2</b> achieved an enantiomeric excess (ee) value of 96.4% for 1-phenylethanol, while <b>1</b> exhibited an exceptionally high ee value of 99.6% for 2-phenyl-1-propanol, ranking among the highest ee values reported for HMOFs. Based on the experimental results and host-guest structure analysis, it can be inferred that the higher the similarity of groups directly bonded to the chiral carbon in Zr-HMOFs and substrate, the better the performance of enantioseparation. Replacing the chiral ligand in material <b>1</b> with an achiral ligand with the same skeleton, four <b>1</b>@<i>x</i> % (<i>x</i> % being the molar percentage of chiral ligand used during synthesis) materials were synthesized to explore the impact of the framework's pore size and chiral active site concentration on enantiomeric separation performance. The results showed that <b>1</b>@50% had the highest adsorption capacity and ee value for 1-phenylethanol, which were 47.7 mg g^-1 and 98.6%, respectively.