MOF Ceramic‐Like Membrane With High Proton Conduction and Tunable Transparency

ABSTRACT The industrial deployment of metal‐organic frameworks (MOFs) is hindered by their particulate morphology, while the fabrication of macroscopic architectures—particularly continuous membranes remain a major challenge. Traditional approaches, such as matrix blending, vitrification, or substrate‐supported deposition, often sacrifice MOF loading amount, crystallinity, porosity, or mechanical integrity. Here, we present a breakthrough strategy based on OH‐bridging (i.e., using metal─OH‐metal bonds to connect nanoparticles) for fabricating MOF ceramic‐like membrane, which endows the membranes with pure MOF composition, ordered porous structure, and self‐supporting capability. The prepared membrane demonstrates remarkable proton conduction and humidity‐responsive optical transparency, which stems from its compact grain boundary structure and the strong grain boundary‐water interactions. This OH‐bridging strategy overcomes a critical challenge in metal‐organic frameworks: the inability to process powdered MOFs into freestanding, crystalline porous membranes, which is beneficial for bridging the gap between nanoscale design and macroscopic functional systems.