A stable lanthanum hydroxamate metal-organic framework with radical character and electrical conductivity

Metal-organic frameworks with hydroxamate linkers are an emerging new class of stable porous crystalline materials. Due to the difficulty in controlling reversible formation of strong metal-hydroxamate bonds and the limitation of available hydroxamate ligands, hydroxamate MOFs are rarely reported and their applications are underexplored. Herein, we report on a lanthanum MOF, La-ONDI, containing the redox-active hydroxamate ligand ONDI^2-. Due to the presence of strong coordinative bonds of chelating hydroxamate groups to metal nodes, La-ONDI not only displays high framework stability in aqueous solutions ranging from pH 3 to pH 13, but also exhibits good structural integrity in common organic solvents and harsh reagents. In addition, La-ONDI shows paramagnetic behaviour due to the presence of unpaired electrons. The amount of unpaired electrons can be modified by the reducing environment during synthesis. Although without π-π interactions between neighbouring ligands, La-ONDI still exhibits good electrically conductive performance with the conductivity reaching 10^-6 S cm^-1.