Review on the rise of MXenes in ion-selective technologies: A decade of progress and future directions

The global transition toward a circular economy has intensified the demand for high-fidelity ion-selective separation, essential for resource recovery, water purification, and advanced energy storage. While traditional polymeric membranes often struggle with the “selectivity-permeability” trade-off, MXenes, a rapidly growing family of 2D transition metal carbides and nitrides, have emerged as a revolutionary solution. This review provides a comprehensive analysis of the progress in MXene-based technologies for ion-ion discrimination. We first evaluate synthesis and functionalization strategies, highlighting how surface terminations (-O, –OH, -F) and interlayer engineering dictate material performance. Central to this work is a deep dive into the transport mechanisms, including size exclusion, Donnan repulsion, and electrochemical intercalation, that enable precise sub-nanometer sieving. We categorize current applications across three primary platforms: laminated membranes, high-capacity adsorbents, and ion-sieving electrodes for capacitive deionization. Finally, we discuss critical challenges, such as oxidative stability and large-scale manufacturing, that must be resolved to bridge the gap between laboratory breakthroughs and industrial deployment. This review serves as a roadmap for the future design of MXene-based systems in the pursuit of sustainable ion management.