Two new 3D lanthanide-organic frameworks based on rod-shaped metal-carboxylate chain SBU: Synthesis, characterization and luminescent detection of Fe3+ and S2− in aqueous solution

Abstract

The study of metal-organic frameworks (MOFs) as luminescence sensors for the detection of polluting molecules and ions are of great importance to the health of all creatures in the world. In this research field, lanthanide ions, especially for Eu3+ and Tb3+, have intrinsic advantages based on their outstanding luminescent properties. To develop smart luminescence sensors towards heavy metal ions and acid anions, two new lanthanide(III)-based MOFs: {[Ln2(btpdc)3·DMF·2H2O]·2DMF·4H2O}n (Ln ​= ​Eu (1), Tb (2), H2btpdc ​= ​benzo[b]thiophene-2,6-dicarboxylic acid) were designed and synthesized under solvothermal condition based on a dicarboxylate ligand H2btpdc. Single crystal X-ray diffraction tests show the two complexes are isostructural with three dimensional (3D) porous framework structure. Notably, both of them exhibit good chemical stability in water. Under the excitation of ultra-violet light, 1 can exhibit strong Eu3+-based red light emission in both solid state and aqueous suspension while 2 doesn't show observable luminescence emission. The luminescence sensing experiments performed on 1 reveal that it can be employed as a smart “turn-off” luminescence sensor for the detection of Fe3+ or S2− in aqueous solution with high selectivity, low detection limit, good anti-interference ability and recyclability. The obtained quenching constant Ksv and detection limits are 2.316 ​× ​104 ​M−1 and 0.26 ​μM, respectively, for Fe3+, and 1.38 ​× ​104 ​M−1 and 1.05 ​μM, respectively, for S2−.