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

Ma, Kai; Liu, Fan; Ma, Hui-Na; Li, Hai-Yang; Zang, Shuang-Quan; Mak, Thomas C W · Adv Mater · 2026

basic_science · Level V

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Abstract

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), Ag<sub>12</sub>-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 Ag<sub>12</sub> cluster node (Ag<sub>12</sub>-TCNB 0D), bridged by the electron-deficient TCNB linker, forms a 2D network that achieve coordination with water molecules (Ag<sub>12</sub>-TCNB 2D-H<sub>2</sub>O). 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.