Alternating copolymerization of CO2 and propylene oxide catalyzed by C2v-porphyrin cobalt: Selectivity control and a kinetic study

• New and efficient C2v-porphyrin cobalt catalysts were designed and synthesized for the PO/CO2 copolymerization.
• Catalysts demonstrated excellent reactivity and selectively.
• Detailed macro-kinetic investigations were carried out by two catalyst systems.
• A competition mechanism was firstly proposed.

Some C2v (Cs)-porphyrin cobalt complexes have been devised, synthesized and utilized as efficient catalysts in combination with dimethylaminopyridine for the alternating copolymerization of propylene oxide and carbon dioxide. The C2v-catalyst [5,15-diphenylporphyrin]cobalt(III) chloride (1d) has demonstrated excellent reactivity and selectivity under optimized conditions. The axial counterions and the substituents of these metalloporphyrins exhibited distinct infection on the catalytic activity and selectivity. Synchronously, preliminary kinetic investigations of this reaction were achieved by using two catalyst systems illustrating the activation energies of copolymerization and coupling reaction, respectively. A competition mechanism between the polymerization and cycloaddition of propylene oxide and CO2 has been carefully proposed according to our experimental results.

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