Research On Photocatalytic Hydrogen Production System Based On Metal-Organic Tetrahedral

The energy crisis and environmental pollution problems have made anxious demand for clean and efficient energy.The rich and efficient solar energy has attracted people's attention.Converting solar energy into chemical energy is also a focus of research.Photocatalytic decomposition of water to produce hydrogen has become a hotspot of research.Considering hydrogen sulfide and water molecules have similar structure,we can photocatalytic decompose hydrogen sulfide to produce hydrogen and elemental sulfur,which solved the pollution problem of hydrogen sulphide,also produced clean energy hydrogen,at the same time generated industrial sulfur resource,which also has broad application prospects.Metal-organic polyhedron has clear structure,rigid frame,confined space and plenty of host-guest properties,which gives a variety of excellent function,making it extremely widespread applicated in some fields such as molecular recognition and selectively catalytic reaction.The study on basic structure and catalytic function of metal complexes are always the frontier of coordination chemistry.The cavity structure formed by the specific configuration can be used to simulate the microenvironment of the enzyme catalysis.The process of host-guest inclusion is similar to the substrate identification process in enzymatic reaction.After forming the inclusion of the host and guest,the distance between the substrate molecule and the catalytic activity center is shortened,and the electron transfer between the molecules is transferred to the quasi-molecule electron transfer,thus improving the transmission efficiency.Therefore,this paper is based on the three-arm structure of triphenylamine,designed two new surface oriented ligands,assembled metal-organic tetrahedron structure,using the internal cavity to encapsulate organic photosensitizer,constructed a supramolecular system,regulating the pathway of electron transfer between the photosensitizer and catalyst,which can improve the efficiency and stability of photocatalytic hydrogen production system.This work consists of two parts:First,using self-assembly interaction between the three-arm bidentate chelating ligand triphenylamine and transition metal Co(?)ion to build the Co-TFT which is electrically neutral metal-organic tetrahedron structure.The two rigidly separated NS chelators of each ligand coordinate with three different metal centers,whereas four metal centers occupy the vertical positions of the tetrahedron.This kind of coordination model makes the whole system with proper redox potential and fine stability.The tetrahedral structure can encapsulate the photosensitizer fluorescein molecules through the ?-? function.To study the properties of photocatalytic decomposition of hydrogen sulphide under mild condition,we put sodium sulfide solution,tetrahedral catalyst encapsulated fluorescein molecules together through the optimized reaction conditions,high efficiency can be achieved through visible light catalytic decomposition of hydrogen sulfide.Thus the total decomposition process of hydrogen sulfide under visible light is realized.Second,choosing three-arm and face oriented triphenylamine ligand and 1H-imidazole-4-carbaldehyde with redox active Fe(II)to build the metal-organic tetrahedron cage structure by using the method of subcomponent self-assembly.The fluorescein molecules can be encapsulated by tetrahedral structure,and then a three-component photolysis hydrogenation system is constructed with the electronic sacrificial triethylamine.The photocatalytic conversion rate(TON)of the catalyst was 2197.This system changed the pathway of electron transfer,improved the electron transfer rate and catalytic efficiency between photosensitizer and catalyst,which provides a new way of thinking for the preparation of a highly efficient and stable water splitting catalytic system.