Dual Emission in a Ligand and Metal Co-Doped Lanthanide-Organic Framework: Color Tuning and Temperature Dependent Luminescence

In this study, we report the luminescence color tuning in the lanthanide metal-organic framework (LnMOF) ([La(bpdc)Cl(DMF)] (1); bpdc(2−) = [1,1′-biphenyl]-4,4′-dicarboxylate, DMF = N,N-dimethylformamide) by introducing dual emission properties in a La(3+) MOF scaffold through doping with the blue fluorescent 2,2′-diamino-[1,1′-biphenyl]-4,4′-dicarboxylate (dabpdc(2−)) and the red emissive Eu(3+). With a careful adjustment of the relative doping levels of the lanthanide ions and bridging ligands, the color of the luminescence was modulated, while at the same time the photophysical characteristics of the two chromophores were retained. In addition, the photophysical properties of the parent MOF (1) and its doped counterparts with various dabpdc(2−)/bpdc(2−) and Eu(3+)/La(3+) ratios and the photoinduced energy transfer pathways that are possible within these materials are discussed. Finally, the temperature dependence study on the emission profile of a doped analogue containing 10% dabpdc(2−) and 2.5% Eu(3+) (7) is presented, highlighting the potential of this family of materials to behave as temperature sensors.