Regulating Built‐in Electric Fields in Methylquinoline‐Derived Vinylene‐Linked Covalent Organic Frameworks for Enhanced Photocatalytic H ₂ O ₂ Production

The integration of functional moieties through robust covalent linkages is crucial for enhancing the stability, structural diversity, and photocatalytic utility of covalent organic frameworks (COFs). Herein, we report the synthesis of a series of vinylene-linked quinoline-based COFs (MQ-PT, MQ-PB, and MQ-BT) via Knoevenagel condensation of a newly designed C₃-symmetric quinoline monomer. The methyl groups adjacent to the quinoline nitrogen atoms serve as reactive sites for coupling with aldehydes under mild, acid-catalyzed conditions. The resulting vinylene-linked quinoline-based COFs exhibit high crystallinity, tunable light-harvesting properties, and excellent physicochemical stability. Notably, MQ-BT, featuring a benzo[1,2-b:3,4-b':5,6-b″]trithiophene donor moiety, demonstrates improved charge separation facilitated by an intensified built-in electric field, affording exceptional photocatalytic H₂O₂ production rates of 7095 µmol g^-1 h^-1 in pure water and 16892 µmol g^-1 h^-1 with benzyl alcohol as a sacrificial agent under visible-light irradiation, outperforming most reported COF-based photocatalysts. Remarkably, under continuous-flow conditions, MQ-BT exhibits both elevated H₂O₂ generation and pronounced photocatalytic degradation efficiency toward environmental pollutants, reflecting its significant prospects for large-scale industrial deployment. This work enriches synthetic strategies for fully conjugated functional COFs and provides design principles for efficient photocatalysts in solar-to-chemical energy conversion.