Research On Properties Of Homogeneous Photocatalytic Reduction Of CO₂ To CO By Phenanthrene Fe Complexes

Photocatalytic reduction of CO₂ to CO,CH₄ and hydrocarbon derivatives can not only mitigate the greenhouse effect,but also realize the artificial carbon cycle efficiently,which has important scientific significance and practical prospect.Precently,photocatalytic reduction of CO₂ using solar as the energy input is the most clean way of CO₂ conversion.However,the CO₂ molecule is a linear nonpolar molecule,and the sluggish kinetics involving multiple electrons and protons transfer limit the wide-scale application of the photocatalytic reduction reaction.To combat the chemical inertness of CO₂ and the associated limits of the reaction's efficiency,most efforts have focused on exploration of promising new highly active catalytic systems.Current research on catalysts for CO₂ reduction focuses primarily on two types of catalytic material:homogeneous metal complexes and inorganic semiconductors.The homogeneous catalytic reduction of CO₂ by transition metal complexes has been extensively investigated,but there are still a lot of problems to be solved.1)The mechanism of electron transfer between the catalytic components in the catalytic process is not clear;2)The use of a large number of noble metal molecular catalysts makes consumption very high.Therefore,the development of excess metal complexes based on the earth's abundant reserves as catalysts can reduce cost and improve catalytic efficiency and selectivity.The master's thesis involves synthesis of four Fe complexes and their application for catalysts in photocatalytic CO₂ reduction,the gained results is as follows:1.Investigation of photocatalytic reduction of CO₂ by phenanthrene-Fe???complexesOne new Fe complex with 1,10-phenanthroline ligand was synthesized,its structure and composition was determined t by elemental analysis,¹H NMR,HRMS.In the presence of[Ru?bpy?₃]²⁺as photosensitizer,the effects of solvent,sacrificial agent composition,concentration of catalyst and photosensitizer,as well as illumination time on photocatalytic efficiency were performed.A highly efficient and highly selective photocatalytic reduction of CO₂ to CO was achieved.In DMF and triethanolamine?TEOA?,white light LED illumination for 2 h TON=19367,TOF=3.07 s^-1,and the CO selectivity of product was 90%.The reaction process was investigated by UV-Vis absorption spectroscopy,cyclic voltammetry,photosensitizer quenching and dynamic light scattering,empty coordination position as catalytic active sites in the reaction is proposed.In addition,the intermediates of activated CO₂ is captured by HRMS.2?Preparation of iron???complexes with poly pyridine amine derivatives and their photocatalytic properties for reduction of CO₂The Fe???complexes mentioned above were prepared,their composition was determined by elemental analysis,¹H NMR,MS.The test of catalytic activity is carried out in the same way.One of the complexes has good catalytic activity when the acetonitrile is used as a solvent.TON=206,TOF=198 h^-1,and the CO selectivity of product was up to 94%.However,the complexes containing alkane chains have not catalytic activity.This can be attributed to steric effect of ligand,the former is easy to empty coordination position by dissociation of ligand,while production of active sites for the latter is relative difficult.