Benzothiadiazole-based linear conjugated polymers bearing Re(I) complexes for CO2 photoreduction

Linear conjugated polymers represent an underexplored architecture for CO 2 photoreduction compared with cross-linked polymers and covalent organic frameworks. Here, two polymers incorporating benzothiadiazole and bipyridine units have been synthesized and coordinated with Re(CO) 3 Cl. Structural characterization has confirmed successful polymer formation and Re chelation. The resulting polymers exhibit favorable optical and electrochemical properties and achieve turnover numbers for CO (TON CO ) of 60.7 and 52.1 within 6 h, significantly outperforming the molecular reference chlorotricarbonyl(2,2′-bipyridine)rhenium(I) (TON CO = 14.4). Control experiments and 13 CO 2 isotope labeling have verified that the produced CO originates from CO 2 . Repetitive catalytic runs have further revealed enhanced stability of the polymer catalysts relative to the molecular complex. Transient absorption spectroscopy shows that longer excited-state absorption lifetimes correlate with higher photocatalytic activity, while time-dependent DFT calculations provide insight into the underlying electronic transitions. These results demonstrate that linear conjugated polymers coordinated with Re complexes are efficient and stable photocatalysts, highlighting the critical role of conjugated moiety selection and molecular design in optimizing CO 2 photoreduction performance.