Synthesis And Catalytic Performance Of The Metal-doped Titanium Oxygen Clusters Based On Salicylate Acid

Titanium dioxide(TiO₂)has been discovered,and widely used in the field of photocatalytic due to its properties of high-activity,low-cost,etc..However,Ti O₂'s single structure character and ultraviolet light response ability has limited its functionalization modifications and utilization in sunlight.Although the function of Ti O₂can be modified and improved by strategies such as metal/non-metal ion modification,surface photosensitive and semiconductor composites,the structure information of such materials is still unclear.The above problems can be effectively solved by converting nano-titanium dioxide into a titanium oxygen clusters(TOCs):firstly,the structural information of the titanium oxygen cluster can be obtained by single crystal technology;secondly,the modification of the organic ligands and the doping of d-/f-block metals can effectively regulate the band gap of titanium oxygen clusters,enhance the absorption of the visible sunlight and ultimately increase the photocatalytic activity.Therefore,this thesis focuses on the above mentioned two aspects:on one hand,by modification of functional group of the ligand and doping of transition metal(Cd/Ag)to the modify the structure and the band gap of the TOCs,which can change the related absorption spectrum,electrochemical nature and catalytic activity;on the other hand,by exploring the applications in photocatalytic fields and bifunctional catalysis after metal doping and ligand modifications.The specific works are as follows:(1)Synthesis of a series of cadmium doped{Cd₂Ti₁₀}clusters and the related studies of photoelectric catalytic water decomposition properties.Using anioacid as ligand,a series of cadmium doped{Cd₂Ti₁₀}clusters were successfully synthesized.The structures of seven clusters were determined by X-ray single crystal diffractometer and characterized by IR,TGA,mass spectrometry and solid ultraviolet spectroscopy.The results show that the doping of cadmium and the modifying the functional group on salicylic acid can effectively change absorption spectrum and photoelectric response activity of these clusters.We additionally studied these clusters as a photocatalyst of water oxidation.The experimental results show that the corresponding TON and TOF of{F^-Cd₂Ti₁₀}are 518.55 and 172.85 h^-1,respectively,which has the highest catalytic activity among the cluster series.The undoped cluster{Me-Ti₁₂}shows the least catalytic activity,of which the TON and TOF are 192.5 and 94.1 h^-1,respectively.All Cd-doped TOCs exhibit excellent stability and catalytic activity in water oxidation experiment.(2)The construction of Ti/Ag bimetal coordination polymer based on salicylic acid ligand as a dual function catalyst.In this research we used salicylic acid as a carboxylic acid ligand and nobel mental-silver as a doped mental to obtain three Ti/Ag bimetal coordination polymers:{Ti Ag₂},{Ti₄Ag₉}and{Ti₄Ag₈}.Each{Ti Ag₂}unit contains two silver ions,a titanium ion,three salicylic acid molecules and two acetonitrile molecules.The silver ions bridge two structural units to build one-dimensional chain structure.Alternatively,when reaction solution which yielded{Ti Ag₂}was filtered and heated in oven for one day,a core-shell type{Ti₄Ag₉}was obtained.The{Ti₄Ag₉}consist of a{Ag₈}core surrounded by a{Ag-CH₃CN}molecule and four{Ti(Sal)₃}^2-species.If the ratio of silver acetate was reduced and the reaction time was extended to 72 h,a yellow long crystal{Ti₄Ag₈}could be obtained.The structure of{Ti₄Ag₈}is very similar to{Ti₄Ag₉},except that the{Ag-CH₃CN}molecule is not directly connected.According to preview study,{Ti₄Ag₉}and{Ti₄Ag₈}have potentional monatomic catalytic activity.However,the yield and reproducibility are too poor.Consquently,the two polymers were only partially characterized.{Ti Ag₂}is the first reported one-dimensional titanium silver coordination polymer.Because of its unique structure,study of dual function catalyst of{Ti Ag₂}has been carried out.In oxidation properties,{Ti Ag₂}was able to oxidize sulfide into sulfoxide,an intermediate commonly used in industry and has excellent conversion rate and stability.In reduction properties,{Ti Ag₂}can convert greenhouse gas CO₂into CO with high Faraday efficiency FE_CO=90.3%and stability.This work provides feasibility and new ideas for titanium silver coordination polymer as bifunctional catalyst.