Detection of H 2 S in the biological system has attracted enormous attention in recent years. In this work, a new vinyl-functionalized metal-organic framework (MOF), [(Me 2 NH 2 ) 2 ] [Eu 6 (μ 3 -OH) 8 (BDC-CH═CH 2 ) 6 (H 2 O) 6 ] (Eu-BDC-CH═CH 2 , BDC-CH═CH 2 = 2-vinylterephthalic acid), was synthesized under solvothermal conditions. The vinyl groups in the ligands can not only modulate the "antenna effect" of the ligand on Eu 3+ ions but also serve as an exposed reactive site to allow for the quantitative detection of H 2 S by Eu-BDC-CH═CH 2 . The ratiometric fluorescent probe has the advantages of water stability, acid-base stability (pH = 2-11), fast response (<2 min), high selectivity, and sensitivity (LOD = 38.4 μM). We also used Eu-BDC-CH═CH 2 to detect and analyze H 2 S in tap and lake waters, demonstrating the potential of the probe for biological and environmental applications. In addition, the MOF-based agarose hydrogel film allows for the visual detection of H 2 S via a smartphone by identifying the RGB values. The vinyl-functionalized MOF can thus be a powerful sensing platform for H 2 S.