Fluorinated ZnFe Hollow Metal-Organic Framework as a F NMR Probe for Highly Sensitive and Selective Detection of Hydrogen Sulfide.

Hydrogen sulfide (HS) is considered as a highly toxic environmental pollutant and an important signal transmitter in physiological processes, and the selective and reliable detection of HS is of great concern and remains challenging. Herein, we report a smart sensitive "off-on" F NMR sensor for HS by partially introducing a fluorinated ligand to construct a hollow dual metal-organic framework (MOF) nanosystem, F-ZnFe hMOF, in which the fluorinated ligand acts as the F signal source but is initially quenched due to the strong paramagnetic relaxation enhancement (PRE) effect from neighboring Fe nodes. Upon exposure to sulfide ions, reduction of Fe to Fe is specifically triggered, which attenuates PRE efficiency, thus turning on the F NMR signal. The unique hollow MOF architecture benefits the mobility of F atoms, thereby improving the response sensitivity. Meanwhile, the desirable HS-sorption feature and appropriate redox potential of Fe/Fe account for the favorable selectivity. The increase in the F signal is linear with the concentration of sulfide in the range of 20 to 150 μM with a detection limit of 2.8 μM. The probe is well demonstrated by analyzing HS in complex matrixes such as biological and foodstuff samples.