Synthesis And Photocatalytic Reduction Of CO ₂ Complexes With Inexpensive Metal Complexes

For conquering forthcoming serious twin problems of global warming and energy crisis, utilization of solar energy to reduce carbon dioxide can be an ideal solution to the problems. Therefore, it is an important task for chemical research workers to prepare highly efficient photocatalysts for reduction of cobalt dioxide.In the dissertation three novel metal cobalt porphyrin compounds C1, C2, C3 were synthesized, crystal structures of two of them have been determined by X-ray diffraction analysis. In addition, copper and nickel Schiff base complexes wer also obtained. All the complexes were characterized by mass spectrometry, 1H-NMR, X-ray crystal diffraction, infrared spectroscopy, UV-vis absorption spectra. Furthermore, their photocatalytic activities for reduction of carbon dioxide into carbon oxide were investigated, some obtaned results were presented as following:1. A few visible-light driven catalytic systems using these complexes as photocatalyst, ruthenium complex as well as some small molecular organic dye as photosensitizer were established. The cobalt porphyrin compounds C1′, C2′?l>, C1, C2 exhibited goog catalytic performaces in the presence of different sacrificial electron donor such as TEA or TEOA in acetonitrile and DMF mixed solvent. The results showed that catalytic efficiency for reduction of CO₂ to CO for the cobalt porphyrin compounds without diethyl phosphite is better than that with diethyl phosphite ligand, photocatalytic reduction of carbon dioxide into carbon monoxide integral area of 7000 for C2 is the highest.2. Cobalt porphyrin compound C2 exhibits good performance for photocatalytic reduction of CO₂ performance, carbon monoxide integral area of 7000 was achieved. Whereas C1 displays relative high catalytic activity, the integral area of carbon monoxide is about 6000.3. The copper and nickel complexes with Schiff base ligand have lower efficiency for photocatalytic reduction of carbon dioxide, but exhibit high photocatalytic hydrogen-generating activity with the observed integral area of 60,000 after ligh irradiation for 8 hours.4. An investigation of photochemical properties of aqueous K3[Fe（C2O4）3] solution showed that the complex can decompose and product CO during visible-light irradiation. Introduction of ruthenium complex, CAN, rhodamine, fluorescein into the system can not enhance the efficience of the photochemical reaction.In conclusion, the reported cheap metal complexes have good solubility in organic solvent. Through these attempts, more efficient visible-light driven artificial photocatalysts for CO₂ conversion could be constructed in the future.