Synthesis, crystal structure, and luminescence properties of three-dimensional rare earth molybdate framework based on [LnMo₁₂] icosahedron

Two new 3D rare-earth molybdate frameworks, [Ln(H2O)(3)](3)[LnMo(12)O(42)]center dot xH(2)O, where Ln=Eu (1), Tb (2); x= 7 (1), 10.17 (2), have been synthesized by slow evaporation. Both of these rare earth molybdate frameworks have a new rare-earth-centered icosahedron [LnMo(12)O(42)] building unit, which is further connected to adjacent ones by {LnO(9)} polyhedra to form a 3D network. Photoluminescence tests reveal that 1 and 2 exhibited different emission properties, which are caused by the f-orbital energy levels of Eu3+ and Tb3+. 1 exhibited bright red emissions (CIE chromaticity coordinates: (0.66, 0.33)) corresponding to the transition from D-5(0) to F-7(J) (J=4, 3, 2, 1, 0), with high luminescent emission intensity and high quantum yield (about 60%). 2 exhibited light green emissions (CIE chromaticity coordinates: (0.34, 0.60)) corresponding to the transition from D-5(4) to F-7(J) (J=6, 5, 4, 3), with lower luminescent emission intensity and quantum yield (about 20%). Interestingly, the introduction of Tb and the presence of a large number of solvent molecules in compound 2, both lead to partial fluorescence quenching but have little effect on the fluorescence properties of 1. CCDC: 2254280, 1; 2254281, 2.