π-Bridge strategy in conjugated organic polymers activates charge- and energy-involved dual pathways for photocatalytic H₂O₂ production

Conjugated organic polymers (COPs) are promising organic semiconductors for photocatalysis; however, their performance is typically limited by high exciton binding energy (E b ) and poor charge carrier separation. Herein, we report that the π-bridge in porphyrin-based COPs is an effective strategy to tune the E b , charge separation and surface reactions in photocatalytic hydrogen peroxide (H₂O₂) production via the two-electron oxygen reduction reaction (2e − ORR). Initially three COPs with progressively extended π-conjugation were synthesized using distinct linkages between porphyrin units: (i) TBPP-COP featuring an aryl–aryl C(sp 2 )–C(sp 2 ) σ bond, (ii) TEPP-TBPP-COP incorporating an acetylene (–C ≡ C–) bridge, and (iii) TEPP-COP containing a diacetylene (–C ≡ C–C ≡ C–) bridge. Compared with the σ-linked TBPP-COP, the two π-bridged COPs exhibit reduced E b , enhanced charge separation efficiency, and a more negative conduction band position, collectively enabling superior H₂O₂ production. In a visible-light-driven biphasic benzyl alcohol–water system, TEPP-COP achieves an H₂O₂ formation rate of 3845 ± 247 μmol g cat −1 h −1 and an apparent quantum yield of 23.8% at 420 nm, together with good recyclability. Radical-quenching experiments and electron paramagnetic resonance (EPR) spectroscopy, supported by density functional theory calculations, reveal that the enhanced 2e − ORR performance of TEPP-COP originates from a dual-intermediate pathway involving •O₂ − and 1 O₂, and strengthened O₂ adsorption at β-C sites within the diacetylene-linked framework. Overall, this work establishes π-bridge engineering as an effective strategy for optimizing COP-based photocatalysts toward efficient solar-driven H₂O₂ production.