Synthesis, Structure, and Photoluminescence of Color-Tunable and White-Light-Emitting Lanthanide Metal-Organic Open Frameworks Composed of AlMo(OH)O Polyanion and Nicotinate.

A series of isostructural compounds Na(HL)(CHCOO)Ln(Al(OH)MoO)(HO)·10HO [L = nicotinate; Ln = Eu (1), Tb (2)] and Na(HL)(CHCOO)EuTbLa(AlMo(OH)O)(HO)·10HO (3-8, L = nicotinate), wherein Anderson-type polyanions AlMo(OH)O as basic inorganic building blocks are connected by Eu(CHCOO)(HL)(HO)] and [Na(HO)] cations, resulting in formation of three-dimensional lanthanide metal-organic open frameworks, were synthesized successfully with AlCl·6HO, NaMoO·2HO, nicotinic acid, and lanthanide nitrates as starting materials. The compounds were characterized by UV-vis, IR, elemental analysis, powder XRD, and TG-DTA measurements. The single-crystal structures of compounds 1 and 2 show that the two compounds display three-dimensional open frameworks with 1D channels along the b and c axes. Investigation of the energy transfer mechanism indicated that the organic nicotinate ligand can transfer energy efficiently to Tb rather than Eu. The influence of the POM moiety on the fluorescence of the compounds is also studied. Compounds 1-8 exhibit tunable luminescence color, and emitting of white light was realized through adjusting the molar ratio of Eu:Tb:La within the compounds.