Ion-ion Separations in Biomimetic Water Channels*

Demand for critical elements has increased exponentially as the implementation of batteries (Li) and solid-state devices (Nd, Tb, & Eu) have become ubiquitous. A key limiting step in the extraction of these critical elements is understanding ion-membrane interactions that result in high permselectivies. Through molecular dynamics simulations, we analyze an energy efficient and environmentally beneficial membranes for ion-ion separations that are embedded with artificial water channels. Such channels display angstrom-scale separations and tunable ion-ligand binding energies that mimic transmembrane proteins. Using the ligand-appended pillarene chemistry, we have implemented a range of techniques to evaluate ion transport and correlated the effects of channel chemistry to ion permselectivity. The combination of these techniques bridge monomer-ion interactions, which can be resolved on a very fast timescales, to ion-channel interactions that must be resolved through non-equilibrium or milestoning methods due to larger timescales.