Homogeneous Polymer Membrane for Ultra‐Stable Osmotic Energy Conversion and Circular Material Lifecycle

ABSTRACT Membrane‐based osmotic energy generation provides a sustainable energy solution that harvests energy by exploiting salinity gradients. However, achieving long‐term operational stability in aqueous environments remains a critical challenge, while the recyclability of end‐of‐life membranes presents an unexplored frontier in real applications. Hydrolyzed polyacrylonitrile (HPAN) membranes present a compelling platform for this technology due to their chemically tunable functionality and intrinsic recyclability. The hydrogen bonding network structure among partially hydrolyzed hydrophilic groups and the high negative charge density of carboxylate moieties endow the HPAN membrane with exceptional cation selectivity, exceeding 0.90, and enable a record‐high power density of 112.4 W m ⁻² under synergistic high‐salt, alkaline, and thermal conditions. More importantly, these membranes demonstrate unprecedented recyclability, maintaining relatively stable power density through four closed‐loop recovery cycles within 120 days. Integrating high performance with recyclable materials establishes a transformative paradigm for next‐generation sustainable osmotic energy harvesting technologies.