Efficient Photoluminescence via Metal-Ligand Alteration in a New MOFs Family

Here, we introduce a family of metal-organic frameworks (MOFs) whose photoluminescence is tunable through metal and organic ligand substitutions. The compounds in this family are composed of In, In-Eu, or Eu metal centers and organic ligand chromophores. Systematic variations in the metal and organic components resulted in materials with emissions ranging from white to red. The single-component white-light emitter material is made of In, 4,4',4-s-triazine-2,4,6-triyl-tribenzoic acid (TTB) and oxalic acid. Red-emitting MOFs composed of Eu metal centers and TTB ligands have a room temperature quantum yield (QY) of 50% and a 48% QY at 150 degrees C due to reversible thermal quenching. This is the highest quantum yield measured at elevated temperatures reported for this class of materials. The materials are thermally stable, retaining their high QY after heating at 150 degrees C for several hours. These thermal quenching/stability studies show the potential use of MOFs in devices that operate at elevated temperatures, such as white-light-emitting diodes for solid-state lighting. This is a unique study that correlates the QY, thermal quenching, and thermal stability of MOFs with structural properties.