Tunable, Ligand-Based Emission from Inorganic-Organic Frameworks: A New Approach to Phosphors for Solid State Lighting and Other Applications

Two dense inorganic-organic frameworks were prepared using the intrinsically luminescent organic ligand 9-fluorenone-2,7-dicarboxylic acid (H2FDC) in combination with the alkaline earth metals calcium and strontium. Ca(FDC)(H2O)(2) (1) and Sr(FDC)(H2O)(5)center dot 2H(2)O (2) were prepared hydrothermally and both adopt three-dimensional framework structures. They absorb strongly between 380 and 460 nm and show broad visible emission with peaks at 503 and 526 nm, respectively. Structure 1 shows a quantum yield at room temperature of 7.8% which increases to 15% at -196 degrees C, while structure 2 shows a room temperature quantum yield of 2.8%, increasing to 3.3% at -196 degrees C.