Integrated Cyano Groups into the Skeleton of Conjugated Polymers to Activate Molecular Oxygen for Boosting Photocatalytic H2O2 Efficiency

Conjugated polymers (CPs) have shown promising potential in the field of hydrogen peroxide (H₂O₂) photosynthesis. However, a deeper understanding of the interactions between building units and specific functional groups within the molecular skeleton is necessary to elucidate the mechanisms driving H₂O₂ generation. Herein, a series of typical donor-acceptor (D-A) conjugated polymers (B-B, B-CN, B-DCN) were synthesized by introducing different amounts of cyano groups (-CN) into the molecular skeleton. The strong electron withdrawing properties of cyano can greatly promote the effective separation and transfer of photogenerated charges between building units, resulting in an impressive efficiency of H₂O₂ generation (2128.5 μmol g^-1 h^-1) for B-DCN, representing a 96-fold enhancement compared to B-B. More importantly, experimental results and theoretical calculations further revealed that the introduction of -CN can markedly reduce the adsorption energy (E_ad) of O₂, while serving as an active site to induce the conversion of crucial intermediate superoxide anions (⋅O₂ ^-) into singlet oxygen (¹O₂), achieving dual-channel H₂O₂ generation (O₂→⋅O₂ ^-→H₂O₂, O₂→⋅O₂ ^-→¹O₂→H₂O₂). This work provides valuable insights into the design of efficient H₂O₂ photosynthesis materials.