Framework‐Material‐Based Ion‐Selective Membranes for Salinity‐Gradient Energy Conversion

Salinity‐gradient energy (SGE), generated from the mixing of waters with different salinities, is a sustainable and widely available source of blue energy. Reverse electrodialysis (RED) is one of the most promising approaches for harvesting SGE, but its performance is largely determined by the ion‐selective membranes employed. Crystalline framework materials, particularly metal–organic frameworks (MOFs) and covalent–organic frameworks (COFs), have recently emerged as attractive membrane platforms because their well‐defined nanochannels and chemically tunable pore environments enable precise control over ion transport, while their high porosity provides abundant parallel pathways for ion conduction. These features offer unique opportunities to improve ion selectivity and permeability simultaneously, thereby alleviating the trade‐off that limits conventional membranes. This review summarizes recent progress in MOF‐ and COF‐based membranes for RED‐driven SGE conversion, with emphasis on membrane fabrication, regulation of ion transport through structural and chemical design, and strategies for improving power output. The key challenges that still hinder practical implementation, including scalable fabrication, defect control, membrane stability, and performance in realistic environments, are also discussed, together with future opportunities for advancing framework‐material‐based membranes toward efficient and durable SGEtechnologies.