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

Abstract

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 ONDI²⁻. 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.