Photosynthesis of H₂O₂ using Phenothiazine-Based Covalent-Organic Frameworks Mimicking Coenzyme Q

Mimicking natural enzymes through artificial enzyme engineering represents a powerful strategy to fine-tune the performance of photocatalysts, while the manipulation of electron transfer systems through atomic precision control is challenging. Herein, we reported a series of covalent organic frameworks (COFs) based on progressively oxidized phenothiazine (PTH) core as the platform for emulating Coenzyme Q, achieved through meticulous stepwise adjustments of their redox states. Compared to the original PTH-S-COF, the COFs with incrementally oxidized sulfur sites exhibited enhanced charge transfer efficiencies, facilitating efficient electron donation to O₂ and thereby providing a favorable pathway for H₂O₂ synthesis. Notably, the PTH-SO₂-COF achieved a remarkable synthesis rate of 7755 μmol g⁻¹ h⁻¹, marking a 720 % improvement over the PTH-S-COF baseline. Furthermore, upon adjusting the sacrificial agent ratio, this rate soared to an impressive 13565 μmol g⁻¹ h⁻¹, surpassing the most reported photo-active COFs. In situ characterizations and simulations verified that three H₂O₂ evolution pathways (2e⁻ ORR, 4e⁻ OER, and 4e⁻ ORR) all involved in the H₂O₂ production process. As a result, our findings introduce a novel pathway for the development of high-performance COF-based photocatalysts through the innovative application of artificial enzyme-mimicking techniques.