Polyimide with enhanced O2 activation for hydrogen peroxide photosynthesis

Abstract

Visible-light-driven O₂ activation is an appealing and sustainable approach for H₂O₂ production. However, insufficient O₂ activation during H₂O₂ photosynthesis severely limits H₂O₂ production efficiency. Herein, a polymeric C₃N₅ oligomer is reacted with anhydride and polymerized into a semiconductor polyimide. The obtained poly(heptaazaacenaphthylene imide) (PHI) features a donor–acceptor structure and is capable of outstanding O₂ activation performance. The built-in electronic field induced by a donor–acceptor structure increases electron–hole pair separation and migration efficiencies. Benefiting from the boosted carrier kinetics and O₂ activation, PHI exhibits a visible-light-driven H₂O₂ production rate of 560 μmol g⁻¹ h⁻¹ (λ > 420 nm) and an apparent quantum yield (AQY) of 5.1% at 395 nm. Theoretical calculation results reveal that a low energy level is formed near the conduction band of PHI during the O₂ activation process, and the level can act as an acceptor level to decrease the Gibbs free energies of intermediates, thereby reducing the reaction barrier in H₂O₂ photosynthesis.