Photocatalytic Solar Hydrogen Peroxide Production on Donor+Acceptor Linear Polymer Semiconductor Powders Reconfigurable by H‐Bonding and π‐Stacking Interactions

Developing an artificial photosynthesis technology that converts earth‐abundant resources into fuels using metal‐free photocatalysts with water as an electron donor is challenging. A few active organic semiconductors require harsh synthesis conditions and expensive reagents. Here, we report that a 1,4‐conjugated linear polymer, poly(2,3‐dihydroxynaphthalene) [poly23DHN], synthesized by the polymerization of inexpensive 23DHN at room temperature, behaves as a heterogeneous catalyst for artificial photosynthesis of hydrogen peroxide (H 2 O 2 ) in water with O 2 . The polymer is soluble in polar organic solvents but insoluble in water. The insolubilization of the polymer leads to self‐assembly of a hydroquinone–quinone donor+acceptor semiconducting architecture via H‐bonding and π‐stacking interactions. The formed powders catalyze water oxidation and O 2 reduction under visible light up to ∼700 nm. Photocatalyst sheets easily prepared by dropping a polymer‐dissolved solution onto a substrate stably generate H 2 O 2 . This polymer design that creates semiconducting structure through spontaneous H‐bonding and π‐stacking offers a scalable, easy‐to‐handle, cost‐effective approach for solar fuel generation.