Photocatalytic Reduction Of CO₂ Based On Cheap Metal Complexes

With excessive exploitation and utilization of fossil energy,a lot of energy and ecological environment problem have been caused,The“greenhouse”CO₂,is also a potentially reservoir of carbon energy.The catalytic conversion of CO₂ into fuel compounds by solar energy optical driving have its dual significance for energy conservation and environmental protection.In this paper,three carboxylic acid complexes and two nickel complexes were synthesized with 2-propyl-4,5-imidazole dicarboxylic acid,imidazole and pyrazole as ligands and non-precious metals Ni,Mn and Fe as center ions.The five complexes were tested by spectroscopic analysis and electrochemical analysis,and used as catalysts to study the photocatalytic reduction of CO₂.Specific research results are as follows:1.Single crystal tests were conducted on the five complexes.The crystal data showed that all the four complexes except iron complexes had been reported,but the photocatalytic reduction of CO₂ was not studied,this paper is mainly to explore its nature.2.In the research experiment of photocatalytic reduction of CO₂ to CO,three carboxylic acid complexes were used as catalysts and various conditions were optimized,and the optimal photocatalytic conditions were obtained as follows:three kinds of catalyst Ni,Mn and Fe concentration of 0.001 mM,solvent and its ratio of DMF:TEOA=5:1,photosensitizer[Ru]concentration is 0.45 mM,BIH concentration is 0.029 M,with a wavelength of 460 nm blue light 12 h,the conversion number of CO calculated was 2264.8,984.1 and 1250,and the selectivity was 95.0%,86.1%and92%,respectively,for the CO₂ reduction of catalyst Ni was the best,followed by Mn and Fe.3.Similarly,an optimization experiment was carried out for the photocatalytic reduction of CO₂ using the nickel complexes N1 and N2 as cataiysts:the optimal concentrations of N1 catalyst is 0.01 mM/L,the solvent ratio is CH₃CN:H₂O=4:1,the concentration of photosensitizer[Ru]is 0.45 mM,the concentration of BIH is 0.029M,the blue light is illuminated for 8 h,the highest number of CO conversion is1400.2,the H₂ conversion number is 154.2,and the selectivity is 90%;The optimal concentration of N2 catalyst is 0.1 mM,the solvent is DMF plus water,the ratio is 3:1,photosensitizer[Ru]concentration is 0.45mm,the sacrificial agent BIH is 0.029 M,the optimal illumination time is 8 h,and the highest conversion number reached 841.2.