Study On Photoactivity Of Transition Metal-oxo Clusters

Transition Metal-oxo Clusters,as an important branch of polyoxometalates?POMs?,is a kind of inorganic metal-oxo clusters.Because of the novelty and designability of the structure,Transition Metal-oxo Clusters has wide application prospects in the field of catalysis,especially in photocatalysis.At present,the main problems that limit the application of Transition Metal-oxo Clusters in photocatalysis are its poor chemical stability and narrow light absorption range,which make it difficult to generate absorption in visible and near-infrared region and thus lack of catalytic eflfect.Therefore,how to prepare metal-oxo clusters with good chemical stability and catalytic performance is the main research we focus and challenge we meet.Based on the combination of the pervious literatures and our research background,we use the metohds of carboxylic acid,phosphoric acid and sulfuric acid groups as ligand and transition metal doping to design and synthesis Transition Metal-oxo Clusters with optical activity and new-type titanium-based multidimensional materials.We analyze crystal structures by single crystal X-ray diffraction technique and study their optical activity,including photocatalysis,photovoltaic and thermal conversion,etc.Through theoretical calculation,the relationship between energy charge separation and transfer mechanism,structural design and photoactivity are domestrated,which provides new ideas and cases for the controllable design,synthesis and application of materials,especially in the field of photocatalysis.The main research results are summarized as follow:1.We report a stable and semiconductive hetero-polyoxotitanate of[Ti12Cr6O18?OOCC₆H₅?30]?denoted as POTii2Cr6?,which exhibits a pronounced photocatalytic hydrogen evolution rate,photothermal effect and photocurrent under full solar spectrum,including NIR irradiation,moreover,with high stability in both acid and base aqueous solution.Crystallinity and photocatalytic activity of POTi12Cr6 remain unchanged under cycling photocatalysis tests.This work demonstrates an approach to overcome the common restriction of low stability and limited solar absorption capability in polyoxotitanate-and TiO2-based materials.The result will open up hetero-polyoxotitanate as a novel type of semi-conductor material for full solar spectrum,especially NIR energy utilization including photothermal transformation,photocurrent response,and photocatalytic H₂ evolution.2.Two new chromium and manganese bimetallic nanoclusters:[Cr8-xMnx?OH?8-x?H₂O?x?OOCC₆H₅?16,x=1.11]?1?and[Cr4Mn4O4?OOCC6Hs?i2.3CH3CN.H₂O]?2?,have been synthesized in one-pot solvothermal reaction in this work.Under the visible irradiation,cluster 1 can produce pronounced photocurrent and exhibits significant visible-light-driven photocatalytic activity for H₂ evolution in an aqueous system.Most importantly,it exhibit ultrahigh stability in both acid and base aqueous solutions,making them excellent synthons for preparing functional material.3.After applying precise parameters control of types of precursor titanium salts,reaction temperature,proportion of template agent and the acidty of reactions system,we adopt hydrothermal synthesis,using piperazine as the template agent,sulfuric acid and phosphoric acid as ligands,to design and synthesis four different zero,one,two and three dimensional titanium-based single crystals.Meanwhile,we study the reaction conditions and structure formation of their structure-activity relationship.