Molecular Origins of Lithium-Ion Transport in the Anionic Metal–Organic Framework SU-102
Year: 2026
Type: preprint
Abstract: Metal–organic framework (MOF) quasi-solid electrolytes offer chemically tunable environments for ion transport, but the molecular roles of framework coordination and confined solvent remain unclear. Here, we combined solid-state nuclear magnetic resonance (ssNMR) measurements with molecular dynamics simulations to determine the Li+ transport mechanism in propylene carbonate-filled SU-102. Variable-temperature direct-and cross-polarization 7Li ssNMR reveal two distinct Li+ populations with different local tumbling dynamics. Our simulations identified Zr-associated, linkerassociated, and fully PC-solvated Li+ coordination environments. We found that Zrassociated sites provide the strongest thermodynamic stabilization, whereas the sitepersistence function decays more rapidly for linker-associated Li+ over the simulated interval. The linker-associated state exhibits the largest trial-weighted displacement, and linker-to-linker hopping is the most frequent classified event under the sampled fields, followed by Zr-to-Zr hopping. Chemical color-diffusion nonequilibrium molecular dynamics yielded an ionic conductivity of 1.34 ± 0.48 mS cm−1, the same order of magnitude as the experimental value of 0.52 mS cm−1. Together, our results support a picture in which PC-assisted hopping between linker sites contributes more strongly than vehicular diffusion of fully solvated ions under the simulated conditions. These findings identify the balance between ion–framework stabilization and facile site-to-site exchange as a key design principle for reticular quasi-solid electrolytes.
Source: ChemRxiv
Institutions: University of California San Diego, Princeton University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204794478