Linkage-Engineered Fabrication of a Robust 1,6-Anthrazoline-Linked Covalent Organic Framework with Significantly Promoted Exciton Dissociation for Superior Photocatalysis

Covalent organic frameworks (COFs) are promising polymeric photocatalysts for solar-driven hydrogen evolution, yet their performance is often hampered by tightly bound excitons that suppress efficient charge separation. Herein, we present a linkage engineering strategy that directly attenuates excitonic effects through a facile two-step postsynthetic protocol combining imine bond locking with site-specific protonation. This approach affords a new class of readily functionalizable 1,6-anthrazoline-linked COFs (TP-PACOFs) featuring cationic, fully conjugated backbones with high planarity, tunable donor–acceptor character, and well-preserved crystallinity. Such a structurally synergistic design enables the cyano-containing derivative, TP-PACOF-CN, to overcome the “trade-off” barrier among synthetic accessibility, light-harvesting capability, exciton binding strength, surface wettability, and chemical stability. Strikingly, TP-PACOF-CN achieves a benchmark sacrificial photocatalytic hydrogen evolution rate of 307.8 mmol g–1 h–1 under visible-light irradiation, which is 1.9 times higher than that of its biquinoline-linked analogue and surpasses nearly all reported COF-based photocatalysts. Moreover, it delivers an apparent quantum yield (AQY) of 31.6% at 420 nm, retains activity up to 700 nm (AQY = 1.9%) and exhibits excellent recyclability. Comprehensive spectroscopic investigations and theoretical simulations demonstrate that the ingenious architectural motif of TP-PACOF-CN significantly promotes exciton dissociation and facilitates charge-carrier dynamics. This work provides valuable insights into exciton management in organic semiconductors and underscores the potential of structurally engineered COFs for high-efficiency solar fuel production.