Fully Conjugated Ladder Polymers as Metal‐Free Photocatalysts for Visible‐Light‐Driven Water Oxidation

Main observation and conclusion Green plants and algae utilize complicated yet delicate structures to oxidize water into molecular oxygen while releasing electrons for dark reactions. The photocatalytic water oxidation reaction in photosystem II is challenging as it involves in transferring multiple electrons and protons and requires a large overpotential. Herein, for the first time, we report that conjugated ladder polymers with suitable band structures are potential metal‐free photocatalysts for efficient and stable water oxidation. Two structurally similar conjugated ladder polymers are synthesized via the condensation reaction between amine‐ and ketone‐containing monomers. Photocatalytic tests reveal that different polymer structures exhibit different photocatalytic performances which are determined by their inherent optoelectronics properties. Meanwhile, our first‐principles calculations confirm that photocatalytic water oxidation is thermodynamically feasible for both conjugated ladder polymers under visible light irradiation. Our study unveils a novel class of polymer materials for the water oxidation reaction and further indicates that metal‐free photocatalysts hold great potential for future solar‐to‐chemical conversion.