Rational Design of Conjugated Acetylenic Polymers Enables a Two‐Electron Water Oxidation Pathway for Enhanced Photosynthetic Hydrogen Peroxide Generation

Abstract Herein, the design of conjugated acetylenic polymers (CAPs) featuring diverse spatial arrangements and intramolecular spacers of diacetylene moieties (─C≡C─C≡C─) for photocatalytic hydrogen peroxide (H₂O₂) production from water and O₂, without the need for sacrificial agents, is presented. It is shown that the linear configuration of diacetylene moieties within conjugated acetylenic polymers (CAPs) induces a pronounced polarization of electron distribution, which imparts enhanced charge‐carrier mobility when compared to CAPs’ networks featuring cross‐linked arrangements. Moreover, optimizing the intramolecular spacer between diacetylene moieties within the linear structure leads to the exceptional modulation of the band structures, specifically resulting in a downshifted valence band (VB) and rendering the two‐electron water oxidation pathway thermodynamically feasible for H₂O₂ production. Consequently, the optimized CAPs with a linear configuration (LCAP‐2), featuring spatially separated reduction centers (benzene rings) and oxidation centers (diacetylene moieties), exhibit a remarkable H₂O₂ yield rate of 920.1 µmol g⁻¹ h⁻¹, superior than that of the linear LCAP‐1 (593.2 µmol g⁻¹ h⁻¹) and the cross‐linked CCAP (433.4 µmol g⁻¹ h⁻¹). The apparent quantum efficiency (AQE) and solar‐to‐chemical energy conversion (SCC) efficiency of LCAP‐2 are calculated to be 9.1% (λ = 420 nm) and 0.59%, respectively, surpassing the performance of most previously reported conjugated polymers.