Post-synthetic modification of a metal-organic framework with a chemodosimeter for the rapid detection of lethal cyanide via dual emission.

A new Hf(iv) based metal-organic framework with the UiO-66 (UiO = University of Oslo) topology was prepared via a standard modulated solvothermal reaction. The weakly emissive MOF material was well characterized via various analytical techniques. The parent MOF was then post-synthetically modified with a highly emissive pyrene based chemodosimeter probe without altering the parent framework structure. The incorporation of the chemodosimeter in the modified MOF material was successfully confirmed by using FT-IR and H NMR spectroscopy. The emission behaviour of the parent MOF was changed drastically with a noticeable colour change after post-synthetic modification. After modification, the MOF material showed a very selective colorimetric and fluorometric dual-emissive response towards lethal cyanide ions. A large blue shift (Δλ = 127 nm) was observed in the emission spectra which can be also visualized with the naked eye under a hand held UV lamp. The presence of a vinyl functional group in the chemodosimeter can serve as a potential nucleophilic reaction centre, which was also confirmed by the DFT calculations. The reaction based sensing mechanism of the MOF material was successfully confirmed by H NMR spectroscopy. Furthermore, to apply the modified MOF material in real life, the test strip based sensing of cyanide in drinking water was demonstrated.