Strong charge concentration polarization induced by the cross-conjugated system of imide-linked porous organic polymers for efficient photocatalytic H2O2 production

Abstract

Suppressing ultrafast charge recombination remains a central challenge in semiconductor photocatalysis. Herein, we report a cross-conjugation-driven charge concentration polarization strategy for promoting charge separation in imide-linked porous organic polymers. Two polymers with distinct conjugation topologies, TAPB–PMDA and TAPB–HPMDA, were constructed as model systems to elucidate the relationship between conjugation structure and charge migration behavior. Compared with the TAPB–HPMDA, the cross-conjugated TAPB–PMDA induces asymmetric electron delocalization and establishes a spatial gradient of photogenerated electron density within the polymer framework, which enables efficient charge separation. The locally high electron concentration microenvironment, regulated by charge gradient polarization, activates the CO bonds, significantly optimizing O₂ adsorption and activation while stabilizing the ·OOH intermediate. Consequently, this material exhibits a highly selective two-electron oxygen reduction to H₂O₂ reaction, achieving a yield of 2440.74 μmol g⁻¹ h⁻¹ in pure water along with improved photocatalytic degradation of antibiotics, including rapid removal and significant mineralization of ciprofloxacin. After adding benzyl alcohol as a sacrificial agent, the yield was further increased to 16 350 μmol g⁻¹ h⁻¹. This work provides mechanistic insight into how molecular polarization in porous organic frameworks influences reactive oxygen species generation, offering a design strategy for developing efficient organic photocatalysts for sustainable water purification.