The Design, Synthesis Of Metalloporphyrin Catalysts And Their Applications In The Reaction Of Carbon Dioxide And Epoxides

Carbon dioxide(CO2), emitted as a waste and greenhouse gas from a myriad of metabolism of living organisms and industrial processes, is a renewable, ubiquitous, non-toxic, inexpensive, infinite C1 resource and increasingly viewed as an important feedstock for chemical processes. Thus, chemical ?xation of CO2 is a very attractive subject, which would positively affect environmental issue and satisfy growing human demand for raw materials. Although CO2 is thermodynamically stable, some progresses have been achieved over the last decades. One potentially useful strategy is the 100% atom-economical coupling reaction of epoxides and CO2 to synthesis of five-membered cyclic carbonates or polycarbonates. Both cyclic and polymeric products have important industrial applications: cyclic carbonates can be used as aprotic polar solvents, electrolytes for lithium batteries, fuel additives, synthetic intermediates and materials for engineering plastics; polycarbonates are highly valuable polymeric materials, which possess outstanding properties, including impact resistance, and optical properties, especially biodegradation.Various heterogeneous and homogeneous catalyst systems were developed for cycloaddition and copolymerization reaction of epoxides and CO2, in which, the biomimetic metalloporphyrin catalysts have received much interesting in light of showing high activities and their unique frameworks that was facile to be functionalized. In order to understanding the relationship between their structures and catalytic abilities, we have designed and synthesized some series metalloporphyrin catalysts, and investigated their performance in the reaction of carbon dioxide and epoxides:Chapter 1: An overview of the carbon dioxide resources, cyclic carbonates, polycarbonates, metalloporphyrins and the catalytic progress of the reaction of epoxides and CO2.Chapter 2: Six tetraalkylammonium functionalized porphyrin zinc complexes have been designed, prepared and well-characterized by NMR, MS and elemental analysis. They were applied as efficient bifunctional catalysts to the cycloaddition of epoxides and carbon dioxide without additive and organic solvent yielding cyclic carbonates. It has been found that both the structure of porphyrin complex cations and the anion moieties would strongly affect their catalytic performance. The catalysts J-m4 B have been demonstrated excellent activities under optimized conditions, and it was versatile for the cycloaddition of CO2 to various terminal epoxides in satisfying yields with excellent selectivities. Phenoxypropylene carbonate can be able to be obtained in large-scale or under atmosphere pressure of CO2. Moreover, a plausible mechanism involving Lewis acid-base synergistic catalysis has been proposed according to our experimental results.Chapter 3: A series of innovative bisimidazole-functionalized porphyrin cobalt(III) complexes have been devised, synthesized and well-characterized. These homogeneous catalysts were applied to the cycloaddition of epoxides and carbon dioxide without organic solvent and co-catalyst. It was found that the performance of the catalysts deeply relies on their structural features. The alkoxyl chain length of the linkage and the imidazole position relative to the phenyl rings of porphyrin evidently affects the catalyst activities. The catalysts of J-m8 and J-o6 demonstrated excellent activity under optimal reaction conditions. Synchronously, a preliminary kinetic investigation of this reaction was carried out using three catalysts and illustrated the activation energies of cyclic carbonate formation. Furthermore, a tri-synergistic catalytic mechanism has been carefully proposed in light of the features of the new catalysts and experimental results.Chapter 4: Some C2v(Cs)-porphyrin cobalt complexes have been devised, synthesized and well-characterized. They were utilized as ef?cient catalysts in combination with dimethylaminopyridine(DMAP) for the alternating copolymerization of propylene oxide(PO) and CO2. The effects of reaction conditions are investigated systematically. The axial counterions and the substituents of these metalloporphyrins exhibited distinct infection on the catalytic activity and selectivity. The C2v-catalyst [5,15-diphenylporphyrin]cobalt(III) chloride(1d) has demonstrated excellent reactivity and selectivity under optimized conditions because of its minimum steric barriers at the central metal ion of porphyrin skeleton.Chapter 5: To illustrate the operational mechanism between copolymerization and cycloaddition reaction of PO and CO2, preliminary kinetic investigations of this reaction were achieved by using two catalyst systems illustrating the activation energies of copolymerization and cycloaddition reaction, respectively. According to our experimental results, a competition mechanism between the polymerization and cycloaddition has been carefully proposed.Chapter 6: Conclusion and prospective.