Photocatalytic Carbon Dioxide Reduction Properties Of Dinuclear Molecular Complexes And Their Derived/Composite Materials

The over-exploitation and utilization of fossil energy have caused serious energy and environmental problems.Using solar energy to drive the reduction of carbon dioxide（CO₂）into carbon-based fuel is an ideal solution to these problems.Therefore,the development of CO₂ reduction photocatalyst has become a hot research topic in recent years.Among them,metal complexes catalysts have attracted much attention because of its clear structure and adjustable structure.Compared with mononuclear metal catalysts,the synergistic effect between metals in dinuclear metal catalysts can significantly enhance the catalytic performance.However,there are relatively few reports on the photocatalytic CO₂ reduction of dinuclear metal catalysts.Furthermore,to improve the practical application of metal complexes catalysts,it is of great significance to construct the derived/composite materials based on dinuclear metal complexes to realize the heterophase of metal complexes catalysts.Based on this,the following research was carried out in this dissertation:1.Based on crown macrocycle ligand,dinuclear Co K complex catalyst was synthesized by coordination and employed as photocatalytic CO₂ reduction catalyst.In the acetonitrile and H₂O（v/v=3:2）solution,the TON value of CO was up to12220,about 3 times than that of the correspond mononuclear Co catalyst.The experimental results indicate that Co（III）is the active center in the dinuclear metal catalyst,and the presence of K（I）improved the adsorption of CO₂,thereby enhancing the catalytic performance.2.By using template co-pyrolysis strategy,dinuclear cobalt（II）cryptate as the template to co-pyrolysis with urea,a single-atom cobalt supported amino-rich carbon nitride material was successfully obtained.This material exhibited outstanding performance in the photocatalytic reduction of CO₂.Acetonitrile and H₂O（v/v=4:1）solvent as reaction medium,TEOA as sacrificial agent,the CO production rate could reach 263.5μmol·g^–1·h^–1,which is order of magnitude higher than that of the conventional prepared g-C₃N₄.The experimental characterization reveals there were the hydrogen bonds between the organic ligand and urea,which promoted the formation of amino groups during the thermal polymerization of urea to form carbon nitride.And the Co-based NH_x-rich carbon nitride was obtained.The increase of amino group content not only optimize the light adsorption,but also improve the capacity of CO₂ capture and the separation of photo-generated electron and hole,all of which are in favor of boosting the photocatalytic activity of CO₂ reduction property.3.Via electrostatic interaction,electropositive dinuclear cobalt（II）cryptate（DMC）was adsorpted into the anionic pore of conductive MOF（c MOF）,and photosensitive perovskite（PVK）quantum dots were spin-coated on the surface of c MOF.A[DMC@c MOF]-PVK composite film was prepared as catalyst.In the gas-solid system with water as sacrificial agent,the highest CO yield of the composite film could up to 100.3μmol·g^–1·h^–1.The controlled experiments and in situ characterization reveal the formation of heterogeneous structures and the mechanism of synergistic catalysis.Conductive MOF,as an electron transport medium,promoted the separation of photoexcited electrons and holes,thus optimizing the photocatalytic activity.The preparation strategy of these r composite materials has opened up a new way for the development of dinuclear metal catalysts.