A fluorescence analysis model for assessing the water stability of porphyrinic metal−organic frameworks

Porphyrinic metal−organic frameworks (PMOFs) are a type of emerging porous material with potential applications in catalysis, biomedicine, and sensing. Despite their plentiful advantages, the applications of many PMOFs are ultimately limited by their water stability. The water stability of PMOFs is influenced by the coordination interactions between metal nodes and water molecules. In this work, based on the excellent photoluminescent properties of magnesium porphyrins, the interactions between water molecules and PMOFs with 15 metal nodes were studied and assessed by the fluorescence method. First, the ligand-to-metal charge transfer (LMCT) effect of these PMOFs was investigated. Subsequently, according to the fluorescence intensity and kinetic performance of PMOFs in ethanol with different water contents, a model for the water stability of PMOFs was established, and PMOFs were classified into three categories: water stable, relatively stable, and unstable. Finally, the water-sensitive magnesium node PMOF (MgTCPP-Mg) can serve as an excellent fluorescent probe for highly sensitive detection of trace water in organic media, particularly methanol, with detection limits as low as 0.0093% (v/v). The establishment of this evaluation method and model helps researchers choose the appropriate PMOFs according to their needs.