A europium-based MOF fluorescent probe for efficiently detecting Co2+ and CrO42−

Abstract

Cobalt is an essential trace element in the human body that is vital for metabolism in living organisms. Insufficient or excessive intake of cobalt can lead to adverse effects. We prepared a europium-based metal–organic framework (Eu-MOF), NH4[Eu(sal)4(phen)2] (abbreviated as Eu-sal, sal = salicylic acid group, phen = 1,10-phenanthroline). Fluorescence investigations revealed that Eu-sal can efficiently and selectively identify Co2+ through a fluorescence quenching effect, with a quenching efficiency K SV and limit of detection (LOD) of 2.7 × 104 M−1 and 0.37 μM, respectively. In addition, Eu-sal also shows highly selective for CrO42− (K SV: 3.6 × 104 M−1; LOD: 0.27 μM). The quenching of Eu-sal fluorescence emission by Co2+ and CrO42− ions may be caused by spectral overlap, energy transfer, and competition. Furthermore, Eu-sal has good thermal and chemical stability. These results indicate that Eu-sal is a promising fluorescence probe for highly selective detection of Co2+ and CrO42− ions.