Synthesis and characterization of Ni@UiO-66 Metal-Organic Framework for fluorescence detection of heavy metal ions in the aqueous phase

The toxicity of clean fresh water has become a major concern in the 21st century. The pollution of fresh and marine water bodies via anthropogenic activities introduces fatal chemicals like heavy metal ions into the environment causing disastrous impacts on human life as well as floral-faunal biota. Hence, it is crucial to develop a nanomaterial that can probe on these lethal heavy metal ions feasibly as well as with low detection limits. Metal-Organic Frameworks are frequently employed in optics as fluorescence sensors for detecting heavy metal ions. Therefore, in this study, Ni(II) was doped into the UiO-66 network, and the fluorescent characteristics of the obtained MOF structure were observed. The morphological characterizations were conducted via PXRD and SEM while the optical tests based on fluorescent spectroscopy were given more attention. The as synthesized MOF i.e., Ni@UiO-66 gave excellent fluorescent detection exhibiting “Turn-Off” for Hg(II) and Fe(III), while “Turn On” for Cr(VI), and Al(III) analytes. In aqueous phase, the lowest detection limit values of 7.98 x 10−7 M for Hg(II) ions is observed. The former's sensing mechanism was attributed to the inner filter effect (IFE), while the latter's mechanism could potentially be linked to the chelation-enhanced fluorescent (CHEF) effect. These findings imply that the Ni@UiO-66 metal-organic framework has the potential to be used for the detection for minute quantities of Hg(II), Al(III), Cr(VI), and Fe(III) ions.