Linear Dependence of Photoluminescence in Mixed Ln-MOFs for Color Tunability and Barcode Application

Multicolored
photoluminescence tuning in a single-phase material has invaluable
potential in display and security applications. By deliberate design
of a multifunctional antenna ligand and precise control of mixed metal
ionic compositions in lanthanide metal–organic frameworks (Ln-MOFs),
we achieved dichromatic fine-tuning among red, green, or blue primary
colors through growth of a series of isomorphous Ln-MOF crystals·solvents
of formula [LnnLn′1–n(TTP)2·H2O]­Cl3 (Ln = Ln′ = Eu, Tb, and Gd, 1–3; Ln = Eu, Ln′ = Tb, 4–8;
Ln = Gd, Ln′ = Eu, 9–11; Ln
= Gd, Ln′ = Tb, 12–14; 0 < n < 1; TTP = 1′,1″-(2,4,6-trimethylbenzene-1,3,5-triyl)­tris­(methylene)­tris­(pyridine-4­(1H)-one)). The linear dependence of the emissions were analyzed,
and the mathematical matrix models were established, which are useful
to control the synthetic conditions and to predict the color chromaticity
coordinates under varied excitation wavelengths. The potential relevance
of these multicolored photoluminescent Ln-MOFs to barcoded materials
was demonstrated.