Triple-Wavelength-Region Luminescence Sensing Based on a Color-Tunable Emitting Lanthanide Metal Organic Framework

A series of isomorphic lanthanide metal–organic frameworks (Ln-MOFs), namely [Ln(dcbba)(DMF)2]n·H2O·0.5DMF [Ln = La (1), Eu (2) and Tb (3); H3dcbba = 4-(3, 5-dicarboxylatobenzyloxy)benzoic acid; DMF = N,N′-dimethylformamide] have been designed and synthesized by the solvothermal reactions of H3dcbba and La(NO3)3·6H2O. Single-crystal X-ray diffraction analysis reveals that the complexes 1–3 exhibit a (3,6)-connected open framework structure with binuclear [Ln2(COO)6]n secondary building units as 6-connected nodes and H3dcbba ligands as 3-connected nodes. The isostructural mixed La/Eu/Tb-dcbba (4) was obtained via the in-suit doping of different Ln3+ ions into the host framework, which is able to emit pure orange, white, and blue light when excited at 300, 305, and 350 nm, respectively. Subsequently, a novel and multifunctional sensing process was designed based on the excitation wavelength sensitive color tunable luminescent sample 4, which can detect HS– ions, THF (tetrahydrofuran), and Ag+ ions via different luminescence color change mechanisms. The remarkable color change, excellent selectivity, and high sensitivity further indicate the promise of this type of multifunctional luminescent materials for the sensing of anion, cation, and organic small molecule.