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

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.