A π-Extended Polyimide-Linked COF with Built-In Proton Relays for Visible-Light Photocatalytic H ₂ O ₂ Synthesis and Halogen Removal

Photocatalytic hydrogen peroxide (H 2 O 2 ) production via the two-electron oxygen reduction reaction (2e – ORR) presents a promising green route, yet its efficiency is hampered by sluggish interfacial charge-transfer kinetics and mismatched proton-coupled electron transfer (PCET) processes. Herein, two polyimide-linked covalent organic frameworks (COFs), namely NDI-COF and PDI-COF, were constructed from melamine donors and naphthalene diimide (NDI) or perylene diimide (PDI) acceptors. Spectral and electrochemical analyses reveal that PDI-COF, featuring a larger π-conjugated architecture, exhibits broadened visible-light absorption (λ max = 600 nm), enhanced charge delocalization, and significantly accelerated intramolecular charge migration. Critically, the abundant imide carbonyl groups within the framework serve as built-in proton-relay sites, which concurrently stabilize the *OOH intermediate and synchronize proton delivery, thereby efficiently facilitating the PCET process. Under visible-light irradiation (λ > 420 nm) in an O 2 atmosphere and an aqueous/ethanol mixed solution, PDI-COF achieves a remarkable H 2 O 2 production rate of 16.2 mmol·g –1 ·h –1, which is 2.5-fold higher than that of NDI-COF and surpasses most reported nonmetallic COF photocatalysts. The material retains over 90.7% of its initial activity after five consecutive cycles while maintaining structural integrity, demonstrating excellent stability. Systematic electron paramagnetic resonance and linear sweep voltammetry experiments corroborate that H 2 O 2 generation proceeds predominantly via the 2e – ORR pathway, involving O 2 – and adsorbed *OOH as key intermediates. Furthermore, leveraging its potent photogenerated electron-reducing power, PDI-COF efficiently drives the photocatalytic dehalogenation of diverse aryl halides under mild conditions, achieving near-complete conversion and thus showcasing its broad potential as a versatile photocatalytic platform for redox transformations.