Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO2 and Epoxides: From High Pressure and Temperature to Ambient Conditions

Organophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO2 and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6-Tris[tri(1-pyrrolidinyl)-iminophosphorane]-1,3,5-triazine (C3N3-Py-P-3) with a relatively low basicity (pK(a)=26.5 in CD3CN) and a bulky molecular size (phi=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO2 and cyclohexene oxide (CHO), and produced CO2-based polycarbonates (CO2-PCs) with high molar masses (M-n up to 275.5 kDa) at 1 MPa of CO2 and 80 degrees C. Surprisingly, this binary catalytic system achieved efficient CO2/CHO copolymerization with TOF up to 95 h(-1) at 1 atm pressure and room temperature.

Automated summary

Organophosphazenes combined with triethylborane were used as binary organocatalysts for the copolymerization of CO2 and epoxides, showing high activity and selectivity dependent on the nature of phosphazenes. 2,4,6-Tris[tri(1-pyrrolidinyl)-iminophosphorane]-1,3,5-triazine exhibited unprecedented efficiency in producing CO2-based polycarbonates at 1 MPa of CO2 and room temperature.