4f/5f Molecular Framework Materials: Design,Synthesis,Structure,and Photocatalytic Activity

Uranyl complexes and Rare-earth complexes have unique structural characteristics and properties,they are widely applied in many kinds of fields.We have designed and synthesized six functional uranyl complexes and four rare-earth complexes.Wherein the uranyl complexes were synthesized by UO₂?CH3CO₂?2·2H₂O,histidine,glycine,2,2'-bipyridine,5-sulfosalicylic acid,oxalic acid,benzenesulfonic acid and adipic acid.Rare-earth complexes were synthesized by rare-earth nitrate,2,6-di?5-methyl-1H-pyrazolly-3-yl?pyridine?L11?,adipic acid,1,4-phthalic acid and succinic acid.The structure of these complexes was determined by X-Ray single crystal diffraction,and they were characterized by elemental analysis,spectroscopy and TG.There are two kinds of geometry in uranyl complexes: pentagonal bipyramid and hexagonal bipyramid.Complexes 1 and 6 were connected by covalent bond to form a 1D chain structure,while complexes 2 and 5 were linked to form a 2D layer structure.Complexes 3 and 4 were discrete structure.By the hydrogen bond interactions,complexes 7-9 were formed 3D,3D and 2D supramolecular structures,respectively.Complex 10 was connected by covalent bond to form 3D network structure.Uranyl complexes and europium complex all emit strong fluorescence,they could be used as potential luminescent material.The photocatalytic activity of the uranyl complexes were investigated by photodegradation organic dey of methylthionine chloride under visible and UV light,the results showed that complexes 1 and 2 exhibit relatively high catalytic activity.Relating the photocatalytic activity to crystal structure and uranium content of uranyl complexes,the higher uranium content will result in higher photocatalytic activity.Moreover,the organic ligand containing both nitrogen atom and oxygen atom may be in favour of photocatalytic activity comparing with oxygen-containing or nitrogen-containing organic ligand.In addition,the photocatalytic activity will decrease with the increase of the coordinaton number of uranium.Successful synthesis of these complexes provides new ideas for design and synthesis of new complexes,and this work lays a foundation for research of photoelectric,catalytic and materials.Note :his=histidine;gly=glycine;L₁₁=2,6-di?5-methyl-1H-pyrazolly-3-yl?pyridine2,2'-bipy = 2,2'-bipyridine;H₂suc=succinic acid;H₂BDC= 1,4-phthalic acid.