Synthesis, Structure, and Photoluminescence of Color-Tunable and White-Light-Emitting Lanthanide Metal-Organic Open Frameworks Composed of AlMo6(OH)6O183- Polyanion and Nicotinate.

A series of isostructural compounds Na(HL)(CH3COO)Ln(Al(OH)6Mo6O18)(H2O)6·10H2O [L = nicotinate; Ln = Eu (1), Tb (2)] and Na(HL)(CH3COO)EumTbnLa1-m-n(AlMo6(OH)6O18)(H2O)6·10H2O (3-8, L = nicotinate), wherein Anderson-type polyanions AlMo6(OH)6O183- as basic inorganic building blocks are connected by Eu(CH3COO)(HL)(H2O)3]24+ and [Na2(H2O)8]2+ cations, resulting in formation of three-dimensional lanthanide metal-organic open frameworks, were synthesized successfully with AlCl3·6H2O, Na2MoO4·2H2O, 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 Tb3+ rather than Eu3+. 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.