Polyphenols-Stabilized Black Titanium-Oxo Cluster: Crystal Structure, DFT Calculations, and Photothermal Conversion

The controlled synthesis of fully stable titanium-oxo clusters (TOCs) through organic ligands to obtain products with high stability and excellent light-absorption properties remains a major challenge. In this study, we report the syntheses of a polyphenols-stabilized functionalized TOCs via an in situ solvothermal strategy, formulated as [Ti8(IV)(μ3-O)4(μ2-O)2(HTBA)8(H2O)4] (Ti8-a), (H4TBA = 2,3,4-Trihydroxybenzoic acid). Interestingly, Ti8-a exhibits a striking black color, classifying it among black TOCs, and possesses an ultralow optical band gap of 1.3 eV. Owing to the comprehensive shielding by the rich intramolecular supramolecular interactions and polyphenol ligands, Ti8-a exhibits excellent stability across various media and environments, including exposure to air and immersion in different solvents. Therefore, Ti8-a was tested for its photoelectric response performance and photothermal conversion capability because of its extremely low optical band gap and excellent stability. The experimental results show that Ti8-a exhibits excellent photoresponse and photoconversion capabilities. The photothermal conversion efficiency can reach 62.24%, and it can rapidly heat the temperature of N,N-dimethylformamide (DMF) to 88.2 °C.