Covalent Organic Framework Membranes with Spatially Aligned Ionic Sites Achieve Record Thermo‐Osmotic Output Power Density

Abstract

The advancement of nanofluidic membranes is critical for mimicking bioelectrogenic ion‐channel mechanisms and boosting output power density, essential for sustainable energy applications. The energy conversion efficiency of these devices significantly relies on the ion conductivity and permselectivity of the membranes. Membranes with aligned one‐dimentional (1D) pores, high pore density, and organized dangling ionic groups are theorized to offer superior ion permeability and selectivity, yet these configurations remain significantly underexplored. Herein, the successful fabrication of oriented ionic covalent organic framework (COF) membranes is presented. These membranes exhibit precisely aligned cationic and anionic sites within their pore channels, achieved through post‐synthetic modification using click chemistry, which shows high ion permselectivity and conductivity. When incorporated into full‐cell thermo‐osmotic generators, these membranes deliver an impressive output power density of 195 W m−‍2 under a 50‐fold salinity gradient (NaCl: 0.01 m ‖ 0.5 m ‖ 0.01 m) along with a 35 K temperature differential. This power output substantially increases 2.41 times to 471 W m−2 when the salinity gradient is enhanced tenfold, surpassing the performance of existing nanofluidic membranes under similar conditions and thus offering a promising avenue for enhancing efficiency in energy and resource utilization.