Regulating nitrogen distribution in covalent organic frameworks for dual-pathway photocatalytic H2O2 production

The regulation of nitrogen distribution in COFs led to a marked improvement in photocatalytic activity. • PDE-PT achieved a high H 2 O 2 evolution rate of 5015 μmol·g −1 ·h −1 under air without any sacrificial agent. • Concentrated N sites in PDE-PT drove D-A separation and charge migration, improving photorespone. • Concentrated nitrogen distribution induced a charge-transfer state, promoting dual-pathway ORR/WOR for H 2 O 2 production. Covalent organic frameworks (COFs) are promising photocatalysts for H 2 O 2 production, yet the charge separation and transport remain a major bottleneck restricting their photocatalytic efficiency. Herein, we proposed a strategy for regulating nitrogen sites to construct a delocalized electronic structure across the COF framework, which facilitates intramolecular charge transfer and suppresses charge recombination. Three COF materials with distinct nitrogen sites were designed and synthesized, namely PDE-PB (nitrogen-free), PDE-PA (pyridine nitrogen), and PDE-PT (triazine nitrogen). Concentrated triazine nitrogen sites in PDE-PT induced donor-acceptor (D-A) separation and charge migration, enhancing optical absorption and photocurrent response. Consequently, PDE-PT delivered a H 2 O 2 production of 5015 µmol·g −1 ·h −1 under pure water and air conditions, markedly surpassing PDE-PA and PDE-PB. Notably, PDE-PT maintained a high H 2 O 2 yield of over 3600 µmol·g −1 ·h −1 in real water matrices, highlighting robust adaptability. Additionally, EPR/scavenger experiments confirmed that PDE-PT utilized both ORR and WOR pathways, with the ORR pathway being the dominant contributor (> 97%) and the WOR pathway contributing approximately 2.6%. Density functional theory (DFT) calculations further revealed that the outstanding performance of PDE-PT stemmed from both the intrinsic electronic structure of triazine and its concentrated configuration, which induced a typical charge-transfer (CT) state. This work provides insights into the influence of nitrogen sites on H 2 O 2 photosynthesis and offers perspectives for catalyst design. Download: Download high-res image (199KB) Download: Download full-size image