A Study On The Synthesis And Photocatalytic Reduction CO₂ Of Cobalt Porphyrin And Its Derivative

Nowadays,the tremendous carbon dioxide emission has led to the serious environmental problem.Exploring noble-metal-free complex catalysts for CO₂ reduction have received extensive attention.Reduction CO₂ to CO is considered as one of the most effective ways to stave off environmental issues.In this work,we mainly introduce the mother porphyrin compound as a ligand and obtain seven ligands with different substituents on the porphyrin.The different ligands can be labled as L1,L2,L3,L4,L5,L6 and L7.When introduced the cheap cobalt???as the central metal,seven kinds of cobalt???porphyrin complexes of C1,C2,C3,C4,C5,C6 and C7 were synthesized.Then,we introduce the above seven complexes as the planar ligands and organophosphate as the axial ligand to successfully synthesize another seven complexes labeled as C1',C2',C3',C4',C5',C6' and C7'.The photocatalytic and spectral properties of the complexes were investigated as follows:1.The compositions and structures of the novel porphyrins and their derivatives were characterized by UV-Vis,1H-NMR,MS,XPS and X-ray single crystal diffraction.The complexes C6'were determined by XPS and the peak located at780.4 eV correspond with that of CoO?780.4 eV?in the standard card,while the peak at 796.2 eV was in accord with that of Co?NO3?2?796.3 eV?in standard card,indicating that the cobalt element in C6' is Co???.2.In the process of photocatalytic reduction of carbon dioxide to carbon monoxide,all the involved photocatalytic reactions were firstly optimized and obtained the optimum reaction conditions?photosensitizer: ruthenium pyridine,sacrifice: TEOA,solvent: CH3 CN,solvent: sacrificial v/v=2:1?.Under the optimal conditions,the cobalt porphyrin complex C4 showed the best catalytic efficiency.The TON value for C4 is 268,however,for C7,the TON was only 167 under the same conditions.In the cobalt porphyrin derivatives,C4' demonstrated the best efficiency and the related TON value is 279,Whereas,for C7,the TON value was 185.The results also showed that the electron with drawing group?-CF3?has an advantage overthe electron donative group?-CH3,-OCH3,-OH?.3.The crystal structures of complexes C2' and C3' were studied and obtained their spatial structures.The results showed that the diethyl phosphite was above the whole cobalt porphyrin structure,and formed a Co-P bond,which came from the phosphorus elements indiethyl phosphate and cobalt in porphyrin complex.4.The electrochemical tests of complexes C1 and C2 show that the introduction of electron donor groups leads to a decrease in oxidation-reduction potential.