Water-Triggered Structural Transformation in a Silver Chalcogenolate Cluster-Based MOF (SCC-MOF) Enables Visually...

Monitoring trace water is vital for chemical processes and moisture-sensitive materials, but conventional electrical humidity sensors require complex instrumentation and lack intuitive visual readout. Luminescent metal-organic frameworks (MOFs) offer optically driven water sensing; however, most existing systems still rely on traditional node-linker structures, whereas cluster-assembled frameworks may have potential due to their multisite existence and remain largely unexplored. Here, we introduce a silver chalcogenolate cluster-based framework (SCC-MOF), Ag₁₂-TCNB 3D-3D ( TCNB, 1,2,4,5-tetracyanobenzene) that exhibits a striking orange-to-yellow luminescence transition upon water exposure, enabling rapid, naked-eye detection within relative humidity (RH) <1.26%. The atomically precise Ag₁₂ cluster node (Ag₁₂-TCNB 0D), bridged by the electron-deficient TCNB linker, forms a 2D network that achieve coordination with water molecules (Ag₁₂-TCNB 2D-H₂O). Single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD) reveal that water induces lattice displacement and perturbs the cluster-centered excited states, a conclusion further supported by electronic structure calculations. This work establishes cluster-based MOFs as a promising platform for optically readable water-vapor sensing.