Enhancing Osmotic Energy Harvesting Through Supramolecular Design of Oxygen‐Functionalized MXene with Biomimetic Ion Channels

Abstract Reverse electrodialysis (RED) technology, relying on ion‐selective permeability membranes (ISPM), offers a direct means of harnessing osmotic energy from the salinity difference between seawater and freshwater. Critical technical challenges include limitations in ISPM's immobile charge carriers, transmembrane ionic internal resistance, and durability in water. Drawing inspiration from the subunit structure of the epithelial sodium channel (ENaC), an ISPM assembled using a supramolecular engineering strategy is introduced. This innovative approach enables the synergistic action of multiple molecular building blocks to mimic the distribution of ENaC subunit structures, strategically planning the placement of immobile charge carriers on nanofluidic channels. The design incorporates nano‐confined oxygen‐rich functionalized MXene (O‐MXene) and high‐strength polymer backbone aramid fibers to construct 3D nanofluidic channels with a high surface charge density. Enhanced by a bonding network of sodium carboxymethylcellulose, the ISPM achieved an exceptional output power density of 21.7 W m −2 and 46.0% energy conversion efficiency in a RED half‐cell system using natural seawater and river water, surpassing current technologies. This research not only advances RED technology but also provides biomimetic customization concepts for ISPM design across various applications, including flow batteries, fuel cells, and related fields.