Carbon Vacancies in a Melon Polymeric Matrix Promote Photocatalytic Carbon Dioxide Conversion

Photosynthetic conversion of CO₂ into fuel and chemicals is a promising but challenging technology. The bottleneck of this reaction lies in the activation of CO₂, owing to the chemical inertness of linear CO₂. Herein, we present a defect‐engineering methodology to construct CO₂ activation sites by implanting carbon vacancies (CVs) in the melon polymer (MP) matrix. Positron annihilation spectroscopy confirmed the location and density of the CVs in the MP skeleton. In situ diffuse reflectance infrared Fourier transform spectroscopy and a DFT study revealed that the CVs can function as active sites for CO₂ activation while stabilizing COOH* intermediates, thereby boosting the reaction kinetics. As a result, the modified MP‐TAP‐CVs displayed a 45‐fold improvement in CO₂‐to‐CO activity over the pristine MP. The apparent quantum efficiency of the MP‐TAP‐CVs was 4.8 % at 420 nm. This study sheds new light on the design of high‐efficiency polymer semiconductors for CO₂ conversion.