Rational Design of Pyridine‐Pyrazine‐Pyridine‐Based Covalent‐Organic Framework for Efficient Photocatalytic H 2 O 2 Production

ABSTRACT Improvement of the hydrogen peroxide (H 2 O 2 ) production efficiency in pure water remains a challenge for COF‐based photocatalysts via photocatalytic technology due to the high exciton binding energy and the low exciton dissociation efficiency. For the first time, this study reports a pyridine‐pyrazine‐pyridine‐based covalent‐organic framework (COF) named PyPPz‐COF, whose nitrogen‐rich (N‐rich) electron acceptor integrates two pyridine‐pyrazine units (four‐N structures). Introducing the four‐N structures is expected to engineer the band structure and provide abundant catalytic sites for photocatalytic H 2 O 2 production. Under O 2 ‐saturated conditions, PyPPz‐COF exhibits a remarkable H 2 O 2 production rate of 6888.2 µmol g −1 h −1 , which is 2.17‐ and 7.42‐fold higher than those of PyPz‐COF and PyDa‐COF (lacking four‐N structures), respectively. This rate surpasses those of the state‐of‐the‐art COF‐based photocatalysts containing either single‐N or dual‐N catalytic sites. It is attributed to the abundant pyridine‐pyrazine units in PyPPz‐COF, which optimize the band structure (a narrow band gap of 2.02 eV for visible‐light absorption) and enhance O 2 adsorption. This facilitates efficient O 2 utilization and promotes the one‐step 2‐electron oxygen reduction reaction (2 e − ORR) pathway, thereby enhancing PyPPz‐COF's photocatalytic H 2 O 2 production activity. This work demonstrates that four‐N atom‐engineering in COFs can synergistically accelerate photocatalytic H 2 O 2 production by modulating both band structure and reaction dynamics.