Investigation of the Sensing Properties of Lanthanoid Metal-Organic Frameworks (Ln-MOFs) with Terephthalic Acid.

The solvothermal synthesis of LnCl 3 . nH 2 O with terephthalic acid (benzene-1,4-dicarboxylic acid, H 2 BDC) produced metal-organic frameworks (LnBDC), [Ln 2 (BDC) 3 (H 2 O) 4 ] ∞ , where Ln = Sm, Eu, Tb, and Dy. The materials obtained were characterized by a number of physico-chemical techniques. The influence of the ionic radius of the lanthanides on the microstructural characteristics of the Ln-MOFs was evaluated by performing Rietveld refinement. The MOFs obtained were tested as fluorescent sensors for numerous cations and anions in water. The highly luminescent EuBDC and TbBDC demonstrated multi-responsive luminescence sensing functions to detect Ag(I), Fe(III), Cr(III), and Cr(VI), which are essential for their environmental applications. By applying the non-linear Stern-Volmer equation, the fluorescent quenching mechanism was determined. The stability of the obtained materials in water in a wide pH range (acidity pH = 4 and alkalinity pH = 9 solutions) was confirmed.