The Synthesis, Structure And Photocatalytic Activity Of The Uranyl Complexes Containing Oxygen Or Nitogen Ligands

The uranyl complexes constructed from organic ligands containing oxygen atom or/andnitrogen atom were synthesized, and their crystal structures and photocatalytic activity werealso been studied in detail to discuss the effect of the structure of uranyl complexes on theirphotocatalytic activity preliminarily. The amino-acetic acid,2,6-pyridinedicarboxylic acid,pyromellitic acid and2,2’-bipyridine were used as organic ligand through hydrothermalsynthesis and solvent evaporation method of combining the synthesized four uranylcomplexes, the formula as shown in the following table:[（UO₂）₂（μ2-O）（μ3-OH）（μ3-OH₂）（H₂NCH₂COO）]·1.5H₂O1[UO₂（2,6-pdc）H₂O]·NH（CH₃）₂·1.5H₂O2[（UO₂）₂（μ3-OH₂）(H₂C₁₀O₈)][（CH₃）₂NH]₂·2H₂O3UO₂（CH₃COO）₂（2,2’-bipy）4Note:2,6-H₂pdc=2,6-pyridine dicarboxylic acid;2,2’-bipy=2,2’-bipyridineThe synthesized uranyl complexes were charactered by IR, X-ray single crystal diffraction,ICP, TG and powder XRD etc. X-ray single crystal structure analysis showed that complex1is a2-D wave-like layer through edge-share of pentagonal bipyramid polyhedron constructedfrom uranyl ions in same coordination enviorment; complexe2is a discrete structure with adistorted pentagonal bipyramidal geometry constructed from the coordiantion of centraluranium with nitrogen atom and oxygen atom of2,6-pdc; complex3is2-D planar structureconstructed from uranium cluster with four nuclear linked by pyromellitic acid ligands;complexes4is also a discrete structure with a twist the hexagonal bipyramidal geometryformed by the coordiantion of central uranium with nitrogen atom of2,2-bdy. The results offluorescence spectra showed that uranyl complexs2,3and4emit strong fluorescence.The photocatalytic activity of the uranyl complexes are investigated by photodegradationorganic dye of Rhodamine B （RhB） under ultraviolet light in contrast with commercialtitanium dioxide （P-25）. The photodegradation results showed that complexes1and2exhibitvery high catalytic activity, higher than that of P-25, However, the catalytic activity ofcomplexes3and4for photodegradation of RhB is far less than that of P-25Relating thephotocatalytic activity to crystal structure and uranium content of four uranl complexes, the photocatalytic activity will decrease with the increase of the coordination number of uranium.When the coordination number of uranium is equal, the higher uranium content will result inhigher photocatalytic activity. Besides, the photocatalytic activity may have some relevanceto the organic ligands in uranyl complexes. The organic ligand containing both nitrogen atomand oxygen atom may be in favour of photocatalytic activity comparing withoxygen-containing or nitrogen-containing organic ligand. The preliminary investigation of thecorrelation between photocatalytic activity and crystal structure of uranyl complexes willprovide a reference basis for the design of efficient photocatalyst of uranyl complexes.