Laterally Heterogeneous Structure and Dynamics of Water and Ion inside a Nanochannel of a Covalent Organic Framework Membrane Designed for Osmotic Energy Conversion

Covalent organic framework (COF)-based membranes show great promise in the realm of osmotic energy conversion (OEC). Despite their great potential, the understanding of the structure and dynamics of water and ions within COF channels is still limited at the atomic level. To address this, we have conducted a series of all-atom molecular dynamics (MD) simulations with the focus on the structure and dynamics of water and K+ ion in a one-dimensional channel of a negatively functionalized COF membrane, known for its effectiveness in OEC. Through sophisticated analyses, we observe pronounced lateral heterogeneity in both the structure and dynamics of water and K+ ions. An increased crowding of water and K+ ions near the COF channel surface leads to significantly slowed dynamics in their vicinity. This sluggish behavior consequently impacts the overall K+ ion transport through the channel. Our findings illuminate the complex diffusive dynamics within COF channels, informing future COF membrane modifications for enhanced OEC.