Conjugated Bicyclic Polybenzoxazine Microspheres as Photocatalysts for Hydrogen Peroxide (H ₂ O ₂ ) Production

Abstract Hydrogen peroxide (H 2 O 2 ) is a crucial chemical, but its industrial production via the anthraquinone method suffers from high energy consumption, environmental pollution, and carbon emissions. Photocatalytic H 2 O 2 synthesis using water and oxygen as feedstocks, driven by light without sacrificial agents, emerges as a promising alternative. In this study, we synthesized conjugated bicyclic benzoxazine (BZ) via the Mannich reaction, followed by thermal ring‐opening polymerization to obtain cross‐linked polybenzoxazine (PBZ), which was further ground into micron‐scale particles (denoted as Micro‐PBZ) via a quartz ball mill. As a photocatalyst, Micro‐PBZ exhibited efficient and stable photocatalytic H 2 O 2 production under visible light ( λ > 420 nm) in O 2 ‐saturated water, with a production rate of 86.39 µmol·h −1 and maintained a yield range of 380–410 µmol after 11 cycles. Mechanistic investigations via density functional theory (DFT) calculations revealed that the conjugated structure, tertiary amine groups, and π–π stacking interactions in Micro‐PBZ facilitate photogenerated charge separation, O 2 adsorption/activation, and stepwise protonation/electron transfer—ultimately promoting H 2 O 2 formation*. Additionally, Micro‐PBZ showed excellent hydrolysis resistance and long‐term durability, attributed to the absence of hydrolyzable functional groups, high cross‐linking density, and intermolecular hydrogen bonds. This work provides insights into the design of efficient organic photocatalysts for sustainable H 2 O 2 synthesis.