Size-Selective Crystallization of Homochiral Camphorate Metal–Organic Frameworks for Lanthanide Separation

Lanthanides (Ln) are a group of important
elements usually found
in nature as mixtures. Their separation is essential for technological
applications but is made challenging by their subtly different properties.
Here we report that crystallization of homochiral camphorate metal–organic
frameworks (MOFs) is highly sensitive to ionic radii of lanthanides
and can be used to selectively crystallize a lanthanide element into
predesigned MOFs. Two series of camphorate MOFs were synthesized with
acetate (Type 1 with early lanthanides La–Dy) or formate (Type
2 with late lanthanides Tb–Lu and Y) as the auxiliary ligand,
respectively. The Ln coordination environment in each type exhibits
selectivity for Ln3+ of different sizes, which could form
the basis for a new cost-effective method for Ln separation.