CO2 catalyzed recycling of polyester and polycarbonate plastics†

Abstract

Recycling waste polymeric materials is essential for environmental protection and achieving carbon neutrality. This study demonstrates the efficacy of CO₂ as a metal-free catalyst for the chemical recycling of common waste polyester and polycarbonate plastics via alcoholysis to yield valuable organic chemicals. CO₂ was proposed to act as a Lewis acid–base pair, activating both alcohol and ester (carbonate) functional groups during the catalytic process. The depolymerization mechanism was thoroughly investigated by monitoring conversion rates and changes in M_n values. Pre-treatment of the polymer materials in THF was found to accelerate the depolymerization rate. End-of-life waste materials were completely degraded into valuable organic molecules, irrespective of their physical and chemical properties. Unlike conventional solid and liquid catalysts, CO₂ leaves no residue in the final products. Moreover, this work unveils the catalytic role for CO₂, expanding its traditional function as a C1 building block in synthetic chemistry.