Fluorinated ZnFeIII Hollow Metal–Organic Framework as a 19F NMR Probe for Highly Sensitive and Selective Detection of Hydrogen Sulfide

Hydrogen sulfide (H 2 S) is considered as a highly toxic environmental pollutant and an important signal transmitter in physiological processes, and the selective and reliable detection of H 2 S is of great concern and remains challenging. Herein, we report a smart sensitive "off-on" 19 F NMR sensor for H 2 S by partially introducing a fluorinated ligand to construct a hollow dual metal-organic framework (MOF) nanosystem, F-ZnFe III hMOF, in which the fluorinated ligand acts as the 19 F signal source but is initially quenched due to the strong paramagnetic relaxation enhancement (PRE) effect from neighboring Fe 3+ nodes. Upon exposure to sulfide ions, reduction of Fe 3+ to Fe 2+ is specifically triggered, which attenuates PRE efficiency, thus turning on the 19 F NMR signal. The unique hollow MOF architecture benefits the mobility of 19 F atoms, thereby improving the response sensitivity. Meanwhile, the desirable H 2 S-sorption feature and appropriate redox potential of Fe 3+ /Fe 2+ account for the favorable selectivity. The increase in the 19 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 H 2 S in complex matrixes such as biological and foodstuff samples.