Cobalt Porphyrin Complexes In The Design, Synthesis And Catalytic Co < Sub > 2 < / Sub > And Epoxy Cyclohexane Copolymerization Behavior Research

Carbon dioxide is an atmospheric green house gas that contributes to globalwarming, thereby it is important to utilize or immobilize carbon dioxide. Thecopolymerization of carbon dioxide and epoxides to produce polycarbonate has beenintensively studied as one of the most promising processes for CO₂utilization.However designing a novel catalyst with high activity and high selectivity is still achallenge．In the present study, a series of Cobalt porphyrin complex were synthesized, andtheir structures were characterized by1HNMR and UV-vis. The catalysts were the usedto catalyze the copolymerization of the CO₂and cyclohexene oxide （CHO）, and theproducts were characterized by1HNMR、GPC. The catalytic efficiency of the differentligands, X﹣and cocatalyst for the copolymerization was compared, while the optimalconditions, such as temperitures, press, time, solvent and molar ratio.It was found that porphyrin cobalt chloride derivatives showed a high selectivityfor the copolymerization of CO₂and cyclohexene oxide,with the product selectivityand structure selectivity almost reaching100%. The effects of ligands on thepolymerization were also investigated and it was found that4-methoxy phenylporphyrin cobalt chloride （T（p-OCH₃）PPCoCl） exhibited the highest activity with aTOF of163h^-1. The Mnof PCHC could be as high as4.91×104g/mol. Meanwhile, itwas found that the anions of the catalyst affected catalytic activity and Mnof theproduct such as Cl－, Br－,OAc－. The results indicated that the catalyst with Cl－wasmost active. we found that the catalytic activity increased with the nucleophilicity ofanion. The cocatalyst also had a great impact on the polymerization, the catalyticactivity was only8h^-1in the absence of cocatalyst and low in the presence of excessivecocatalyst. The optimal ratio of catalyst and cocatalyst was found to be1:1resulting inthe highest catalytic activity of32h^-1.The effects of experimental conditions such as temperature, time, pressure,solvents on the polymerization are discussed.The polymerization activity shows a lowlevel of10h^-1 at40C. At100C, the product was transformed into cyclohexenecarbonate. The time was also crucial to the polymerization, for the conversion ofmonomer can be only14%within1h, however,when the time is prolonged,thedepolymerization rate also goes up and the molecular weight of product decreases from2.32×104g/mol to1.60×104g/mol by the time from6h to24h,and the optimal timeof polymerization is proved to be6h;The pressure mainly effects on the molecularweight of PCHC, and the number-average molecular weight reaches the peak at the pressure of7MPa;The solvents are another influential factor,and it is found that littleproduct is formed in chlorideform and N,N-DMF,and the catalytic activity can be only8h-1in tolune,with0.65×10⁴g/mol number-average molecular weight of PCHC.Whileusing methelene dichloride as solvent, the catalytic activity can be145h^-1,and thenumber-average molecular weight can be as high as3.75×10⁴g/mol.