Metal-organic frameworks (MOFs) have garnered much attention due to their fantastic structural diversity and technological interest as component materials for gas sorption and separation based applications. One key advantage of MOFs over traditional porous solids is the potential amalgamation of disparate functionalities. Specifically, the combination of crystallinity, permanent porosity, and bulk electrical conductivity yield a truly unique set of properties not found in any other class of materials. Mastery of charge transport in porous crystals may also result in emergent technologies including gas sensing, electrocatalysis, and field gated gas sorption. However, conductive frameworks heretofore remain rare owing in part to a lack of well-founded <i>ab initio</i> design principles. In attempt to further elucidate the mechanics of conductivity and the link between charge transport and surface chemistry, the inherent porosity of MOFs may be leveraged. Through simple adaptation of a standard gas sorption analyzer, simultaneous measurement of conductivity and gas sorption is possible. Using a variety of gaseous probe molecules, both steady state isotherms of sorption and conductivity make it possible to directly determine conductance-composition profiles. Conductivities responds selectively to gas probes based not only on heat of adsorption and quantity absorbed but also on the specific host-guest interaction, as corroborated by powder neutron diffraction. Finally, time-resolved gas sorption and conductance prove that interparticle contacts are transport limiting. This was found to have the unexpected consequence of the chemresistive response being faster than compositional equilibration. More broadly this technique is capable of also characterizing ion and proton conductors, as well as dielectrics with very little to no modification in experimental design.

Interrogation of charge transport by gas sorption in metal-organic frameworks

253rd National Meeting (2017)

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