Turn-on and Ratiometric Luminescent Sensing of Hydrogen Sulfide Based on Metal–Organic Frameworks

The sensing of hydrogen sulfide (H2S) has become a long-time challenging task. In this work, we developed a general strategy for sensing of H2S utilizing postsynthetic modification of a nano metal-organic frameworks (MOF) UiO-66-(COOH)2 with Eu3+ and Cu2+ ions. The nano MOF Eu3+/Cu2+@UiO-66-(COOH)2 displays the characteristic Eu3+ sharp emissions and the broad ligand-centered (LC) emission simultaneously. Because H2S can strongly increase the fluorescence of Eu3+ and quench the broad LC emission through its superior affinity for Cu2+ ions, the MOF Eu3+/Cu2+@UiO-66-(COOH)2 exhibits highly sensitive turn-on sensing of H2S over other environmentally and biologically relevant species under physiological conditions. Furthermore, this approach for fluorescent turn-on sensing of H2S is expected to extend to other water-stable MOFs containing uncoordinated -COOH.