Structural Modulation of Two Luminescent Bismuth-organic Frameworks by the Mixed-ligand Synthetic Strategy

Hydrothermal reactions of Bi2O3 with pyridine-2,6-dicarboxylic acid （2,6-H2pdc） and trimesic acid （H3btc）/pyromellitic acid （H4pyr） lead to two bismuth-organic frameworks, namely, [Bi（2,6-pdc）（H2btc）（H2O）2]n （1） and [Bi2（2,6-pdc）2（H2pyr）（H2O）2]n （2）. Compound 1 crystallizes in the space group P21/c. The dimeric {Bi2} units are linked by 2,6-pdc2？ ligands to form 1D chains; Compound 2 exhibits a 2D layered structure with 44 network topology by using dimeric {Bi2} as secondary building units （SBUs）. The chains and layers in 1 and 2 are further arranged into 3D supramolecular structures via hydrogen bonding interactions. The compounds emit blue luminescence. Furthermore, the PXRD, TGA, UV-visible and IR spectra were also studied. Compounds 1, 2 represent good examples of using mixed-ligand approach to construct diversity of luminescent bismuth-organic frameworks.

Hydrothermal synthesis and luminescence properties of Eu^(3+) and Sm^(3+) codoped BiPO_4

Eu3＋/Sm3＋codoped BiPO4 phosphors were synthesized via a facile hydrothermal method with surfactant-free environment. The X-ray diffraction analysis demonstrated that the samples possessed the standard BiPO4 monoclinic structure. Scanning electron microscopy images showed that all samples composed of well-dispersed, micrometer-sized crystals with shuttle-like shape. Energy transfer from Sm3＋to Eu3＋was confirmed by the luminescence spectra and the decay processes of Sm3＋ 4G5/2→6H5/2 emission. Or-ange-red luminescence could be obtained in Eu3＋/Sm3＋codoped BiPO4 phosphors. The average lifetime of Sm3＋ 4G5/2→6H5/2 emis-sion decreased from 2.70 ms in BiPO4：0.03Sm3＋ to 2.37 ms in BiPO4：0.03Sm3＋,0.05Eu3＋. The strong and wide absorption band around 395 nm, originating from both 7F0→5L6 transition of Eu3＋and 6H5/2→4K11/2 transition of Sm3＋, endowed BiPO4：Eu3＋,Sm3＋phosphors with the potential application in the fields of near UV-excited white-light-emitting diodes.