MXene‐Induced Selective Ion Separation in Capacitive Deionization: Bridging Fundamentals With Frontier Innovations

ABSTRACT Selective ion separation is essential for effective water treatment and resource recovery. Conventional techniques, such as adsorption, coagulation/flocculation, and membrane technologies, suffer from low selectivity, substantial cost, and high energy requirements. Alternatively, ion separation using capacitive deionization (CDI) has shown strong potential for energy efficiency, cost‐effectiveness, environmental sustainability, and selective removal. However, traditional carbon electrodes used in CDI have limitations for selective separations. MXene‐based electrodes present an attractive alternative for CDI due to their exceptional electrochemical properties. Nevertheless, MXenes are typically unstable over extended cycles, and to achieve ion selectivity, controlled interlayer spacing adjustment is required. Methods such as hybridization and functionalization can improve the selectivity properties of MXenes by tailoring their interlayer spacing. Several studies have reported the use of MXenes as CDI electrodes; however, most focus on brackish water desalination, while selective ion separation is rarely addressed. This review presents an in‐depth analysis of the role of modified MXene electrodes in advancing ion‐selective CDI technologies, exploring various strategies to achieve the desired selectivity. Moreover, it highlights critical challenges that hinder scalability and practical implementation. Finally, the review showcases the strategic roadmap for future opportunities toward next‐generation water purification and resource recovery solutions.