Enhanced Photocatalytic H ₂ O ₂ Generation of Porous Organic Polymers through Molecular Polarization and Conjugation Engineering Strategy

Porous organic polymer (POP)-based photocatalysts can generate H 2 O 2 under light irradiation. However, their performance is suppressed by strong polarization and low π-conjugation, which limit the photogenerated electron separation and the selectivity of two-electron oxygen reduction reaction (2e – ORR). In this study, three kinds of POPs were designed and prepared from 1,3,5-tris( p -formylphenyl)benzene (TFPB) with different nitrogen-containing (N-containing) monomers, including melamine (MA), 2,4,6-triaminopyrimidine (TA), and 1,3,5-triaminobenzene (TAB), yielding POP-MA, POP-TA, and POP-TAB, respectively. Results demonstrated that variations in the monomer structure significantly regulated the π-conjugation degree and localized polarization of POPs, consequently influencing the charge-carrier migration and the 2e – ORR pathway. POP-TAB exhibited the most favorable conjugated structure and moderate polarization and delivered the highest photocatalytic activity of H 2 O 2 generation (1291.5 μmol g –1 h –1 ) as expected, significantly outperforming POP-TA (919.6 μmol g –1 h –1 ) and POP-MA (260.9 μmol g –1 h –1 ). Furthermore, the superoxide radical anion ( • O 2 – ) was confirmed as the key reactive intermediate, and H 2 O 2 was predominantly generated via the 2e – ORR pathway. This work elucidates the synergistic roles of electronic structure and polarization of N-containing monomers in regulating H 2 O 2 generation over metal-free POP photocatalysts. It provides a promising design strategy for achieving efficient solar-driven H 2 O 2 generation through the combined engineering of π-conjugation and localized polarization.