Application Of Pt（Ⅱ） Complexes In Photocatalytic Reduction Of CO₂

Currently,in the process of prioritizing the high-quality development of the economy in China,the significant increase in CO2 emissions from industrial production and daily activities will seriously affect our ecological environment and living comfort,and exacerbate the energy shortage crisis.Therefore,the research on the resource treatment of carbon dioxide is particularly important,and is a technical problem that needs to be urgently addressed.In recent researchs,the catalytic systems containing metal complexes have been effectively used to catalytically reduce CO2 to energy substances such as CO,methane,or chemical raw materials such as formates.Among them,metal complexes based on platinum group metals such as Ru,Ir,Os,Rh,and Pd are usually used as homogeneous photosensitizers or catalysts for the photocatalytic reduction of CO2,but the selectivity of reduction products is not high and the system is unstable.However,there are few reports on the application of cyclometalated Pt（Ⅱ）complexes（referred to as Pt（Ⅱ）complexes）in homogeneous photocatalytic reduction of CO2 systems.From the research literature of other types of metal complexes of the platinum group,it is feasible to apply Pt（Ⅱ）complexes with long phosphorescence lifetime to the system of homogeneous photocatalytic reduction of carbon dioxide.First,five dinuclear platinum（II）complexes（Pt1-Pt5）composed of cyclometallic organic ligands and chloride ion bridges were synthesized,and their photoelectrochemical properties were studied.The photocatalytic system constructed by the Pt（Ⅱ）complexes,and theoretical calculations and mechanism speculations were carried out.It was found that the system composed of platinum（II）complex and catalyst[Co（TPA）]²⁺can better catalyze the reduction of carbon dioxide,and the TON of the product CO in the system participated by Pt3 reached 1672,and the selectivity reached 87%.The TON of the product CO in the system participated by Pt4 is 147（7.36μmol）,and the selectivity is as high as 99%.In addition,Pt1-Pt5 itself also has a certain catalytic ability.Combining all our detection results on Pt1-Pt5,it is found that Pt1-Pt5 has the function of"photosensitivity+catalysis"in the system of catalytic reduction of CO2.but overall,it is more suitable as a photosensitizer in the photocatalytic reduction of CO2 system.Subsequently,based on the highly selective complex Pt4,we conducted further research,designed novel organic ligands,and obtained three novel Pt（Ⅱ）complexes,Pt6-Pt8.We found that the Pt6-Pt8 all have microsecond-level excited-state lifetimes,especially Pt6,which has a high lifetime of 31.88μs and a CO production selectivity of over 95%in the photocatalytic reduction of CO2.In terms of production,the CO production in the reaction involving Pt6-Pt8,compared with that of Pt4,increased by more than 30μmol.The synthesis route of Pt6 is to break the chlorine bridge in Pt4 and connect it with dimethyl sulfoxide molecule,indicating that in the photocatalytic reaction,Pt6 can better transfer energy to the catalyst and sacrificial electron donors in the system than Pt4.Pt7 and Pt8 introduce a butyl-carbazole group on the thienyl group,which enhances the conjugation structure of the Pt7 and Pt8 molecules,increases their light absorption ability at around 460 nm,and improves their solubility.In conclusion,It is feasible of the molecular structure design of Pt6-Pt8.