Pressure-induced metallicity and piezoreductive transition of metal-centres in conductive 2-dimensional metal–organic frameworks

Abstract

Due to their generally poor conductivity, metal–organic frameworks (MOFs) have been limited in electrical applications. The highest performing materials are two-dimensionally connected Ni₃(hexaiminotriphenylene)₂ and Ni₃(hexaiminobenzene)₂; both feature experimental conductivities exceeding 500 S m⁻¹. From theory, both are predicted to be bulk metals but the former is known to be a semiconductor within a single monolayer. In this work we explore structural deformation as a route to augmenting the electronic properties of these two high performing materials. We show that, under hydrostatic negative pressure, metallicity can be installed in the Ni₃(hexaiminotriphenylene)₂ monolayer. Further, we predict a unique piezoreduction of metal ions and induced-magnetization in Ni₃(hexaiminobenzene)₂ due to the shift in energy of metal–ligand bonding and antibonding orbitals. These observations aid in our understanding of how MOFs conduct electricity and may also be used as a design principle in future MOF technologies.