Water-soluble conjugated polyelectrolytes for efficient photoreduction of atmospheric CO₂ pairing with H₂O₂ generation in pure water

Photocatalytic reduction of CO₂ into energy-enriched carbon fuels paired with H₂O₂ production represents a key strategy for alleviating the concern of global warming and concurrently providing valuable chemicals. For this purpose, we develop a series of fluorene-based conjugated polyelectrolytes (CPEs) consisting of dibenzothiophene or dibenzothiophene-S,S-dioxane with different linking patterns for photocatalytic coproduction of CO and H₂O₂ from air and pure water. The effect of comonomers and their linkage sites on the photocatalytic performances of CPEs have been studied. Compared to the counterparts with 3,7-linking pattern (V-S and V-SO), the CPEs with 2,8-linking pattern (L-S and L-SO) exhibited greatly boosted photoactivity because the 2,8-linking pattern of CPEs could extend the length of conjugated chain and improve the coplanarity of the polymer. Moreover, the comonomers varying from dibenzothiophene to dibenzothiophene-S,S-dioxane in the main chain of CPEs can collaboratively enhance the charge separation and light absorption to increase the photocatalytic efficiency. As a result, L-SO with 2,8-linking pattern delivers excellent CO and H₂O₂ yields of 871.6 and 1133.4 μmol h⁻¹ g⁻¹ under the illumination of simulated solar light. Our work highlights the rational design of water-soluble CPEs as dual functional photocatalysts for direct CO₂ reduction and clean H₂O₂ production from air and water.