Photosensitized Modification And Photocatalytic Properties Of Binuclear Metal Complexes

Due to the increasing global demand for sustainable energy and the environmental impact caused by fossil fuel consumption,the development of alternative energy sources has become an urgent issue.One effective approach to address these issues is photocatalysis,which converts solar energy into chemical energy.Therefore,designing and developing efficient photocatalysts is critical.Among these,molecular catalysts have garnered attention due to their high metal utilization rate,clear and adjustable structure,and feasibility for exploring the catalytic mechanism.Molecular catalysts decorated by photosensitive groups present a better prospect in photocatalysis compared to physical mixtures of molecular catalysts and photosensitizers.In this thesis,the research focuses on connecting molecular catalysts with different photosensitive materials to prepare a series of composite photocatalysts with high activity in photocatalytic hydrogen evolution and CO₂reduction reactions.The specific research contents are as follows:1.Via the Schiff base reaction,the binuclear cobalt complex（Co₂L）or mononuclear cobalt complex（Co L）（L=3,5-di（2-pyridyl）-4-amino-1,2,4-triazole）were decorated with organic photosensitive group 1-pyrenecarboxaldehyde.Pyrene binuclear cobalt complex（Pyrene-Co₂L）and pyrene molecular cobalt complex（Pyrene-Co L）are successfully synthesized.Both complexes possess photocatalytic activity for hydrogen evolution without the need of additional photosensitizer.The activity of Pyrene-Co₂L is 4.8 times higher than that of Pyrene+Co₂L,and 4.4times higher than that of Pyrene-Co L.The mechanism study reveal that Pyrene-Co₂L have higher charge transfer efficiency than Pyrene+Co₂L,which improves catalytic activity.Electrochemical experiments and fluorescence quenching tests are conducted to further explore the catalytic reaction path,the photosensitive group in Pyrene-Co₂L is photoexcited to form an excited photosensitive group（Pyrene*）,and then the electrons are transferred to the Co ^IIcenter,and the low-valence Co ^Icenter reduces the adsorbed H₂O to H₂.2.Via the electrostatic interaction,the binuclear copper complex（Cu₂L₁,Cu₂L₁={Cu₂（CH₃）₂C[CH₂N=CH（1-Br-4-OH-3,5-C₆H₃）CH=NCH₂]₂C（CH₃）₂}（Cl O₄）₂）are supported on the surface of the photosensitive Cs Pb Br₃quantum dots,i.e.,Cs Pb Br₃-Cu₂L₁,which realizes the photocatalytic reduction of CO₂to CH₃OH.Under visible light irradiation（λ≥400 nm）,Cs Pb Br₃-Cu₂L₁catalyst exhibits good photocatalytic CO₂reduction activity,and the CH₃OH yield reaches 24.37μmol g^-1within 4 h.Mechanism studies show that the transfer of photogenerated electrons from Cs Pb Br₃to Cu₂L₁is effectively promoted through electrostatic attraction,and the visible light catalytic CO₂reduction ability can be improved.