Dual functional MOF as a selective fluorescent naked-eye detector and effective sorbent for mercury ion

Zn(II) based metal organic framework, Zn-2(BDC)(2)(TzTz)(2) containing thiazolo[5,4-d]thiazole functional group with strong mercury chelating site was purposefully designed and assembled via the solvothermal procedure. Structural characterizations were fully performed through FT-IR spectroscopy, UV-Vis spectroscopy, powder X-ray diffraction (PXRD) and single crystal X-ray crystallography analysis. This MOF exhibits binary functions, as a rapid naked eye colorimetric and fluorescent probe as well as an effective sorbent toward mercury ions. Having such an exceptional removal capacity, 1428 mg g(-1), and quick response time as fast as 3 min, means Zn-2(BDC)(2)(TzTz)(2) is an inimitable sorbent toward mercury. Moreover, upon the adsorption of Hg the color of sorbent changes from light cream to fluorescent yellow showing the interaction between the sulfur atom of the thiazole and Hg2+ ions. Although Zn-2(BDC)(2)(TzTz)(2) can adsorb significant amounts of Pb2+ with removal capacity of 434 mg g(-1), neither remarkable uptake of competing metal ions is observed even in the presence of several interferences, such as Pb2+, Cr3+, Cd2+, Cu2+ and Co2+ at equal concentrations of Hg2+ nor was an obvious visible color change seen toward other tested ions. Zn-2(BDC)(2)(TzTz)(2) is further shown to be fully regenerable over several cycles. This work is the first example of a functionalized MOF with high affinity and rapid uptake capacity towards mercury contaminants and simultaneous visible color change in the presence of this ion.