Novel Multi-Nuclear Silver Photocatalytic Complexes And Their Photodegradation Of Organic Pollutants

With the development of industry,organic pollutants are widely found in water,and these toxic and harmful pollutants are difficult to self-degradation in the natural environment.Photocatalytic technology is a new type of water treatment technology emerged in the 1970 s.This method has many outstanding advantages such as high efficiency,simple process,nontoxic product and complete degradation of organic pollutants,etc.It showed a strong advantage in the degradation of organic pollutants,especially in the refractory organic dyes.At present,the most studied photocatalyst is TiO₂,which can only respond to ultraviolet light because of its bandgap width of 3.2 eV.Therefore,it is still an important issue to develop a new type of photocatalyst response in the visible light.Silver base complexes were synthesized from silver ions and organic ligands compounds,because most silver compounds showed the strong absorption to visible light,the research on the degradation of organic pollutants by silver-based complexes as photocatalysts is also supported by more and more people's concern.A total of 14 silver complexes were synthesized:Ag?L₁OH??L₂?·H₂O?1?,[Ag?pyz??Hnpth?]·H₂O?2?,Ag?dpyz?_2/2?Hntph??3?,Ag?4,4'-bipy??Hntph??4?,Ag?bpe??Hnpth??5?,[Ag?pyz??Hntph?]·2H₂O?6?,Ag?tpyz?_2/2?Hntph??7?,Ag?epyz?_2/2?Hntph??8?,[Ag₂?dtrz?₂?Hntph?₂]?9?,Ag?epyz?_0.5?Hnpth??10?,Ag₄?H₂O?₂?npth?₂?11?,[Ag₂?dtrz?₂?pht?]·5H₂O?12?,[Ag₂?dtrz?₂?dpt?]·5H₂O?13?,Ag₄?epyz?₂?npth?₂?14?(L₁=1H-imidazole-1-sulfinic acid,L₂=1H-imidazole,H₂npth=3-nitrophthalic acid,H₂ntph=nitroterephthalic acid,H₂pht=terephthalic acid,H₂dpt=2-hydroxy terephthalic acid,pyz=pyrazine,dpyz=2,5-dimethylpyrazine,tpyz=trimethylpyrazine,epyz=tetramethylpyrazine,dtrz=3,5-dimethyl-4H-1,2,4-triazol-4-amine,4,4'-bipy=4,4'-pyridine,bpe=1,3-bis?4-pyridinyl?ethylene.Among them,1-5 are mononuclear silver complexes,6-10 are binuclear silver complexes,11-13 are tetranuclear complexes and 14 is octa-nuclear silver complex.We carried out experiments on the photocatalytic degradation of Rhodamine B in these 14 complexes under UV and visible light and discussed the effect of different nuclei on the photocatalytic activity.Among the 5 mononuclear silver complexes,except for the complex 5,complexes 1-4 had different degradation effects on rhodamine B under ultraviolet light.When the light source was visible light simulated by LED lamp,within 7 hours,the complexes 2,3,4 for rhodamine B degradation efficiency were 64%,73%,50%.Complexes 6-10 are binuclear silver complexes,among them,complexes 6-9 have good degradation activity of rhodamine B under ultraviolet light.In 3.5 hours,complex 6 can degrade 63%rhodamine B.However,the complex 7 showed a better degradation of rhodamine B under ultraviolet light,and this dye could be completely degraded in100 minutes.The degradation efficiency of rhodamine B by complex 8 and complex 9 at 3.5 h was78%and 90%,respectively.Under visible light,it is regrettable that the complex 7 has no effect on the degradation of rhodamine B,while the degradation rates of the complexes 6,8 and 9 on rhodamine B in 7 h are 78%,94%and 91%,respectively.For the tetranuclear and octa-nuclear silver complexes,we found no significant degradation of rhodamine B in both UV and visible light through photocatalytic experiments.The above photocatalytic results show that silver-based complexes with visible light degradation of organic pollutants activity,is a potential visible light catalyst.