Electrocatalytic CO ₂ Upgrading to Biodegradable Plastic by Bromine‐Assisted C ₂ H ₄ Oxidation and Polymerization

The electrochemical upgrading of carbon dioxide (CO 2 ) to long‐chain value‐added products has remained challenging due to the complex reaction pathways with sluggish carbon‐carbon coupling kinetics. Although ethylene (C 2 H 4 ), a major CO 2 electroreduction product, may serve as a potential alternative for the coupling and carbon‐chain elongation, the efficient C 2 H 4 oxidation under ambient conditions and selective control of the oxidation level still represent two main bottlenecks for realizing long‐chain products. Herein, we demonstrate an efficient tandem electrochemical approach for synthesizing polyglycolic acid (PGA) from CO 2 via the bromine‐assisted C 2 H 4 oxidation, followed by polymerization under mild conditions. This process is enabled by the temperature‐mediated electro‐oxidation of C 2 H 4 to bromoacetate, which overcomes the diffusion limitation imposed by the electrical double layer at room temperature. The resulting bromoacetate with sp 2 ‐hybridized carbon preferentially undergoes intermolecular nucleophilic attack, thus driving polymerization to PGA. This work presents a potential approach for converting CO 2 to biodegradable polyesters.