A visible-light-active ellagic acid-based titanium-oxo cluster for room temperature chemiresistive sensing

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In this study, we synthesized a visible-light active titanium-oxo cluster (TOC), [(CH₃)₂NH₂]⁺₂·[Ti₄L₂(OiPr)₁₀]²⁻ (1, H₄L= Ellagic acid) based on ellagic acid. The molecular structure of 1 was determined using single-crystal X-ray diffraction, revealing a cyclodextrin-like (CD-like) tetramer formed by four (Ti4) clusters and dimethylamine cations. Due to effective ligand-to-metal charge transfer (LMCT), 1 exhibited good visible light absorption and photocurrent response, as confirmed by UV-Vis spectroscopy and photoelectric testing. Structurally, the large number of uncoordinated oxygen sites in 1 can be used not only as assembly sites but also as active sites for NO₂ detection. Moreover, 1 exhibit high NO₂ response and excellent selectivity under visible light irradiation at room temperature. This research marks the first exploration of TOCs in gas sensing applications, expanding its potential beyond traditional uses.