Heavy metal ions constitute a class of non-biodegradable pollutants affecting the global environment. As a result, there is an ever-increasing need to identify and constantly monitor these chemical species. Towards this end, analytical techniques based on luminescence are attracting an increasing interest due to their high sensitivity and their ability to be incorporated into portable devices for in-field use. Luminescent MOFs show great potential as sensory materials because they possess highly regular porous structures able to host various chemical species which may induce changes in their emission characteristics, thereby generating a detection signal. In this contribution, we describe a microporous fluorescent ZrIV MOF (Zr-1) of the UiO-66 family, based on bridging ligand bearing uncoordinated carboxylate moieties. Fluorescence studies on the MOF and on a model compound revealed that Zr-1 exhibits exceptional ability for real-time detection of Cu2+ ions in ppb levels in drinking water. Furthermore, Cu2+ sensing studies in the presence of several competitive cations indicated that the performance of our MOF is not influenced by the presence of coexistent cations. Batch sorption studies have shown that Zr-1 exhibits exceptional sorption capacity, while the sorption equilibrium is reached in the first minute, allowing the efficient removal of Cu2+ ions from water. Moreover, we demonstrate that Zr-1 can be easily regenerated with no loss of its crystallinity.

Selective recognition of Cu2+ ion in aqueous media by a fluorescent ZrIV metal-organic framework containing uncoordinated carboxylate moieties

ACS Fall 2021

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