Chemical Recycling\nof Poly(cyclohexene carbonate)s\nvia Synergistic Catalysis

Chemical recycling of polymers to the corresponding monomers\noffers\na valuable solution to address the current plastics crisis for creating\nan ideal and circular polymer economy. Here, we present a bimetallic\nsynergistic depolymerization of the widely studied CO<sub>2</sub>-based\npolycarbonates, poly(cyclohexene carbonate)s, to epoxide monomers\nefficiently. The bimetallic Cr<sup>III</sup>-complex-mediated highly\nselective depolymerization and repolymerization was achieved via the\nregulation of reaction temperature, thus closing the circular loop\nof poly(cyclohexene carbonate)s <i>in situ</i>. Mechanistic\ninvestigation has revealed that the formation of epoxides undergoes\na direct chain-end unzipping process. A bimetallic catalysis involving\na nucleophilic attack of the metal-alkoxide species toward the methine\ncarbon atom bound with an adjacent carbonyl that is activated by the\nother metal center features a lower energy barrier in DFT calculations,\nwhich promotes the epoxide extrusion.