Device‐Integrated Covalent Organic Framework Photocatalysts for Hydrogen Peroxide Production: From Molecular Design to Scalable Reactors

ABSTRACT

Hydrogen peroxide (H ₂ O ₂ ) is an important green oxidant and a promising liquid energy carrier, yet it is still produced mainly via the energy‐intensive anthraquinone process. Photocatalytic synthesis from water and oxygen offers a mild route to H ₂ O ₂ generation and holds promise for on‐site production driven by sunlight. Covalent organic frameworks (COFs)‐based photocatalysts are particularly attractive because their porosity and optoelectronic structures can be tailored at the molecular level. However, progress is increasingly limited not by the intrinsic activity measured in small‐batch experiments, but by device‐ and reactor‐related limitations, including oxygen transport, light utilization, catalyst immobilization and recovery, and suppression of H ₂ O ₂ decomposition during H ₂ O ₂ production. These factors complicate scale‐up and hinder meaningful comparisons across studies. This review summarizes COF‐based photocatalytic H ₂ O ₂ synthesis from catalyst design to reactor implementation. We first discuss the main reaction pathways for oxygen reduction and the coupled oxidation reactions and highlight material design strategies in four levels, including framework‐level design, active‐site engineering, post‐synthesis modification and multicomponent COF, and interface engineering of heterostructures that promote charge separation and selective O ₂ activation. We further review reactor and device designs that make COF powders into scalable systems. By analyzing reported examples, we classify three representative reactor formats, such as membrane‐assisted photoreactors, panel‐type photoreactors, and continuous‐flow photoreactors. We clearly discuss how each addresses transport and stability bottlenecks to improve H ₂ O ₂ concentration, productivity, and operational stability. We further summarize in situ utilization of photogenerated H ₂ O ₂ in one‐pot oxidation and water‐treatment processes, linking H ₂ O ₂ generation to practical chemical transformations. Finally, we outline key next steps, including standardized testing and reporting, scalable fabrication of COF‐based devices with controlled interfaces, and mechanism‐guided modeling under realistic operating conditions, so that COF‐enabled solar H ₂ O ₂ production can be evaluated and scaled in practical reactor settings.