A Hydrophilic Mixed Lanthanide Metal-Organic Framework Monitoring H₂O in D₂O

Lanthanide metal-organic framework (Ln-MOF) luminescent sensors monitoring the H₂O content in D₂O are still rare. We designed and built a hydrophilic mixed Ln-MOF (Eu_0.4Tb_0.6-MOF) monitoring the H₂O content in D₂O. By designing a ligand and controlling the synthesis method, we achieved a balance between the structural stability and sensing capacity. When the H₂O content ranges from 0 to 100%, the photoluminescence color of Eu_0.4Tb_0.6-MOF can change from yellow to green, which can be observed by the naked eye. The mechanism is that the photoluminescence intensity of Eu³⁺ decreases faster than that of Tb³⁺ when the H₂O content increases. The sensing mechanism was studied further by transient fluorescence spectrometry.