Multifunctional Ln–MOF Luminescent Probe for Efficient Sensing of Fe³⁺, Ce³⁺, and Acetone

A new series of five three-dimensional Ln(III) metal-organic frameworks (MOFs) formulated as [Ln₄(μ₆-L)₂(μ-HCOO)(μ₃-OH)₃(μ₃-O)(DMF)₂(H₂O)₄] n {Ln³⁺ = Tb³⁺ (1), Eu³⁺ (2), Gd³⁺ (3), Dy³⁺ (4), and Er³⁺ (5)} was successfully obtained via a solvothermal reaction between the corresponding lanthanide(III) nitrates and 2-(6-carboxypyridin-3-yl)terephthalic acid (H₃L). All of the obtained compounds were fully characterized, and their structures were established by single-crystal X-ray diffraction. All products are isostructural and possess porous 3D networks of the fluorite topological type, which are driven by the cubane-like [Ln₄(μ₃-OH)₃(μ₃-O)(μ-HCOO)]⁶⁺ blocks and μ₆-L³⁻ spacers. Luminescent and sensing properties of 1-5 were investigated in detail, revealing a unique capability of Tb-MOF (1) for sensing acetone and metal(III) cations (Fe³⁺ or Ce³⁺) with high efficiency and selectivity. Apart from a facile recyclability after sensing experiments, the obtained Tb-MOF material features a remarkable stability in a diversity of environments such as common solvents, aqueous solutions of metal ions, and solutions with a broad pH range from 4 to 11. In addition, compound 1 represents a very rare example of the versatile Ln-MOF probe capable of sensing Ce³⁺ or Fe³⁺ cations or acetone molecules.