Two‐Dimensional Metal–Organic Frameworks for Proton Conduction, Sensing, and Separation

Over the past two decades, two‐dimensional (2D) materials have garnered significant attention in both academic research and real‐world applications. Among these, 2D metal–organic framework (MOF) nanosheets stand out due to their remarkable structural tunability, ultrathin layered architectures, high surface area, accessible metal nodes, soft crystallinity, and anisotropic structural arrangements. These distinctive features make 2D MOF nanosheets highly promising candidates for a variety of advanced applications, including proton‐conducting electrolytes for fuel cells, selective sensing and molecular recognition, and the separation of diverse molecules—from small organic pollutants and metal ions to large biomolecules such as DNA. Despite their considerable potential, a substantial gap remains between laboratory‐scale research and industrial‐scale implementation. This gap is primarily attributed to challenges such as limited scalability, high production costs, stability concerns, and the pronounced stacking tendency of 2D MOF nanosheets, which can diminish their unique properties. In this review, we aim to provide a comprehensive overview of recent advances in the structural understanding, synthetic strategies, nanosheet formation processes, and stacking behaviors of 2D MOF nanosheets. We further discuss their applications as proton‐conducting materials in proton‐exchange membrane fuel cells (PEMFCs), as well as their roles in sensing, recognition, and molecular separation. By elucidating the structure–property relationships, particularly the influence of secondary building units (SBUs) on nanosheet morphology and performance, we seek to bridge the gap between fundamental research and practical, industrial utilization of these promising materials.