The Design And Synthesis Of The Efficient Metal Catalyst Systems For The Chemical Fixation Of Carbon Dioxide

As one of the most abundant, cheap and available C1resource, carbon dioxide,which is also a kind of well-known greenhouse gas, has a negative impact on themankind living environment. But at the same time, as an important natural resourceand industrial gas, carbon dioxide also can benefit mankind in many ways, such asfood, chemical industry, machinery, medicine, transportation, oil exploitation and soon. Thus, the fixation of carbon dioxide was one of the necessary measures for bothmitigating greenhouse effect and utilizing carbon dioxide.The cycloaddition reaction between carbon dioxide and epoxides to yield cycliccarbonates was one of the most common reactions for carbon dioxide chemicalfixation, which is benefit to atom economy and green chemistry. Besides, the product,cyclic carbonate has widely potential uses in industry. In this study, two differentmetal composite catalyst systems, Ni(PPh3)2(Naphthyl)Cl/PPh3/Zn/n-Bu4NBr andZnCl2/PPh3/n-Bu4NBr, were employed in this coupling reaction. Both two catalystsystems were shown to catalyze the coupling of CO2and PO to generate PC in perfectyields (92.60%and93.4%, respectively) and selectivities (>99%) in milder condition(3MPa,5h,130oC) without any organic solvents. Moreover, the two catalystsystems were also proved to be applicable to other terminal epoxides, and a reactionmechanism has been proposed, which plausibly explained the reaction results.The synthesis and characterization by1H NMR,13C NMR, FT-IR, elementalanalysis and single-crystal X-ray diffraction patterns of a series of metal tetradentateSchiff base complexes was also described herein. The series of complexes, along withLewis base such as n-Bu4NI, had been demonstrated to be highly active and versatilecatalysts for coupling reaction of CO2and PC to generate PC (the PC yield99.7%)only in mild conditions (110oC,5h,2MPa) without any organic solvents. Like themetal catalyst system mentioned above, this binary catalyst system was also proved tobe applicable to other terminal epoxides. In addition, the catalyst was also could bereused five times with only minor loss in the catalyst activity, and acoordination-insertion mechanism was proposed for this catalyst system.