Two Exceptionally Stable Luminescent MOFs for Selectively and Sensitively Detection of Fe3+ ions in Aqueous Solution
Excess and shortage of iron(III) from normal permissible limits will induce serious disorders, so its detection is significant but challenging. Luminescent metal-origanic framworks (LMOFs) are a class of attractive materials for the detection of Fe3+ ions. However, the improvement of hydrolytic stability, fastly, sensitivity, and selectivity of function is the key to advance application of LMOFs in aqueous environment. Herein, two hydrostabil LMOFs Zn-DTA and Cd-DTA based on the π-conjugated aromatic ligand 2,5-di(1H-imidazol-1-yl)terephthalic acid (H2DTA) were selected as highly efficient sensor for rapid, sensitive and selective detection of Fe3+ in aqueous solution. On the basis of the rigid structure and multiple coordination sites of H2DTA ligand, Zn-DTA and Cd-DTA possess brilliant stability and excellent fluorescent emission. Both of them exhibit extra selectivity (Ksv = 8400 and 6420 M-1) and high sensitivity (0.82 and 1.07 μM) for the rapid detection (less than 30 s) of Fe3+ with low usage (0.2 mg mL-1) in water. It is worth noting that compounds not only remain stable in the water for a long time but also maintain structural integrity at high temperatures. To the best of our knowledge, Zn-DTA and Cd-DTA, as two exceptionally stable MOF chemosensors used to selective detection of Fe3+, are very scarce compared to the reported Zn/Cd-MOFs. The quenching mechanism for such high selectivity can be mainly explained by the competition between the absorption of Fe3+ and the excitation of compounds. Moreover, the introduced carboxyl O atoms of Zn-DTA additionally donate their lone-pair electrons to the Fe3+ ions, leading to enhanced detection ability. Our work reveals the enormous potential of LMOFs as an appealing platform to construct sensing materials.