Fused Ring Engineering Induced Topology Control in Covalent Organic Frameworks: Unlocking Promoted Photocatalytic H 2 O 2 Production and Selective Methane Oxidation

ABSTRACT Efficient solar‐to‐chemical energy conversion and the selective activation of methane remain grand challenges in artificial photosynthesis. Here, we report the rational design of two covalent organic frameworks (COFs), Phen‐TTA and O‐TTA, in which framework topology and π‐conjugation are regulated by pairing a triazine‐based acceptor with either a rigid 1,10‐phenanthroline or a twisted 2,2′‐bipyridine donor. The results show that the Phen‐TTA, bearing a rigid kgd‐v topology, features a narrowed bandgap, reduced exciton binding energy, and accelerated charge‐carrier kinetics relative to O‐TTA with an hcb topology. Consequently, Phen‐TTA delivers a high photocatalytic H 2 O 2 production behavior (21.5 mmol h −1 g −1 and an apparent quantum yield of 5.45% at 450 nm), placing it among the most active COF‐based photocatalysts ever reported. Notably, Phen‐TTA further enables selective photocatalytic methane oxidation to ethanol (30.1 µmol h −1 g −1 , 365 nm irradiation) in the absence of noble‐metal cocatalysts. Mechanistic investigations indicate that the enhanced framework rigidity promotes sequential one‐electron oxygen reduction to H 2 O 2 , while the sustained H 2 O 2 supply undergoes photolysis to yield • OH that drive C─H activation. This work establishes topology engineering as an effective strategy to overcome excitonic and charge‐transport limitations in polymeric photocatalysts and demonstrates a rare single‐component organic framework for tandem solar‐driven methane valorization.