Development of novel semiconducting nanomaterials opens doors to a diverse array of reconfigurable electronics. Metal-organic frameworks (MOFs), nanoporous and crystalline materials composed of metal ions or clusters coordinated to multitopic organic linkers, are traditionally insulators due to their poor overlap of π-d orbitals. However, the introduction of redox active guest molecules into the MOF pores bridge the metal nodes of the MOF, resulting in semiconductive behavior. Infiltration of 7, 7, 8, 8-tetracyanoquinododimethane (TCNQ), a conjugated acceptor molecule, into M-MOF-74 analogues (M=Cu, Mn), results in tunable electrical conductivity through coordination of TCNQ to the subunits of the metal nodes. Scanning electron microscopy and powder x-ray diffraction showed retention of the M-MOF-74 analogue structures after TCNQ infiltration without formation of metal-based TCNQ nanowires. Absorbance spectra show charge transfer bands between TCNQ and M-MOF-74 (M=Cu, Mn). The TCNQ@Cu-MOF-74 and TCNQ@Mn-MOF-74 materials produced conductivities of up to 5.40 x10<sup>-2</sup> S/m and 5.02 x10<sup>-3</sup> S/m with activation energies of 889.9 meV and 580.7 meV, respectively. This work demonstrates the simple addition of conjugated acceptor molecules enables the creation of alternative charge transport pathways rendering insulating MOFs to exhibit exciting semiconductive properties.

From insulator to semiconductor: Effect of guest-host interactions on charge transport in metal−organic frameworks

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.