(90j) Correlating Ion Solvation and Conductivity in Porous Aromatic Frameworks

Porous aromatic frameworks are a recently developed class of materials that demonstrate exceptional promise as single-ion conducting electrolytes. However, a limited understanding of the factors governing ion diffusion in PAFs hinders the rational design of these materials. This current work aims to address this lack of fundamental knowledge by implementing a variety of NMR techniques to elucidate the solvation structure and dynamics of cations in each of these frameworks. Towards this goal, I previously developed synthetic routes for a variety of PAFs and systematically varied one of several critical framework parameters in order to develop relationships between systematic structural changes and bulk ionic conductivity. In this work, ⁷Li, ¹H, and ¹⁹F solid-state NMR spectra provide a picture of the local cation environment; relaxation measurements and pulsed-field gradient NMR provide insight into local cation dynamics and permit the calculation of bulk diffusion coefficients. NMR results are compared with electrochemical impedance data to correlate alterations in framework structure with changes in bulk ionic conductivity. Ultimately, these structure/property relationships informed the design of future materials with improved properties for battery applications, some of which will be presented.