Pyridine Nitrogen-modified Covalent Organic Frameworks for Photocatalytic One-step 2e⁻ H₂O₂ Production

Abstract

The precise regulation of photocatalytic oxygen reduction reaction (ORR) pathways, particularly the more energy-efficient one-step 2e⁻ route, is of fundamental importance for optimizing H₂O₂ production efficiency in rationally designed covalent organic frameworks (COFs). Here, a strengthened donor-acceptor (D-A) structured TPCN-COF [COF synthesized from 2,4,6-hydroxy-1,3,5-benzotricarboxaldehyde and 1,3,5-tris (4-aminophenyl) benzene] photocatalyst was developed through the strategic incorporation of pyridine nitrogen moieties into the COF skeleton. The strengthened D-A structure facilitates effective separation of photogenerated charge carriers while promoting rapid electron transfer kinetics. Concurrently, the introduced pyridine nitrogen units increase the surface polarity, thereby improving hydrophilicity and enabling more efficient proton delivery to active sites. Remarkably, the synergistic combination of enhanced charge separation and optimized proton transport in TPCN-COF effectively shifts the ORR mechanism from two-step 1e⁻ pathway to one-step 2e⁻ process. As a result, TPCN-COF achieves an exceptional H₂O₂ production rate of 1320.9 μmol·g⁻¹·h⁻¹ under visible light irradiation (λ⩾420 nm) in an air-equilibrated aqueous system, representing a nearly 3-fold enhancement compared to the unmodified TPCC-COF [COF synthesized from 2,4,6-hydroxy-1,3,5-benzotricarboxaldehyde and 5,5′,5″- (benzene-1,3,5-triyl) tris (pyridin-2-ylamino)]. This work establishes an effective design strategy for constructing COFs photocatalysts with strong D-A structures, and elucidates the synergistic regulatory mechanism, by which both electronic structure and surface properties govern ORR pathway selectivity in COF-based systems.

Keywords

Photocatalysis / Covalent organic framework (COF) / H₂O₂ preparation / D-A structure / Reaction pathway

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RIGHTS & PERMISSIONS

Jilin University, The Editorial Department of Chemical Research in Chinese Universities and Springer-Verlag GmbH