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 Mn 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.