Hollow terbium metal-organic-framework spheres: preparation and their performance in Fe 3+ detection.

Hollow metal-organic framework (MOF) micro/nanostructures have been attracting a great amount of research interest in recent years. However, the synthesis of hollow metal-organic frameworks (MOFs) is a great challenge. In this paper, by using 1,3,5-benzenetricarboxylic acid (H 3 BTC) as the organic ligand and 2,5-thiophenedicarboxylic acid (H 2 TDC) as the competitive ligand and protective agent, hollow terbium MOFs (Tb-MOFs) spheres were synthesized by a one-pot solvothermal method. By comparing the morphology of Tb-MOFs in the presence and absence of H 2 TDC, it is found that H 2 TDC plays a key role in the formation of the hollow spherical structure. Single crystal analyses and element analysis confirm that H 2 TDC is not involved in the coordination with Tb 3+ . Interestingly, Tb-MOFs can be used as the luminescent probes for Fe 3+ recognition in aqueous and N , N -dimethylformamide (DMF) solutions. In aqueous solution, the quenching constant ( K SV ) is 5.8 × 10 -4 M -1 , and the limit of detection (LOD) is 2.05 μM. In DMF, the K SV and LOD are 9.5 × 10 -4 M -1 and 0.80 μM, respectively. The sensing mechanism is that the excitation energy absorption of Fe 3+ ions reduces the energy transfer efficiency from the ligand to Tb 3+ ions.