Enhanced hydrogen peroxide photosynthesis via charge-complementary π-electron sites.

Abstract

Organic photocatalysts with porphyrin conjugated chromophore core are promising for artificial hydrogen peroxide (H₂O₂) photosynthesis, but the lack of bottom-up paradigm for oxygen (O₂) adsorption sites hinders their activity. Here, we introduce imidazole groups as π-electron sites with charge-complementarity to the O₂ molecules, enhancing O₂ binding via sub-atomically mirrored electrostatic cooperative π-π dispersion forces. In situ spectroscopy and theory reveal that the ~2 Å linear δ⁺-δ^--δ⁺ domain of the imidazole substituent exhibits 2.8-folds stronger O₂ adsorption than neutral π-electron substituents, accompanied by the generation of energetically peroxide intermediates. Consequently, imidazole-substituted porphyrin photocatalysts achieve a solar-to-chemical conversion efficiency of 1.85% using only H₂O and O₂. In scalable membranes with photocatalysts, enabling daily photosynthetic production of 80 L m^-2 of Fenton-applicable H₂O₂ solution. This work offers a strategy to modulate the electrostatic distribution of oxygen photoreduction sites, providing insights into overcoming gas activation rate-limiting steps in photocatalytic processes.