Stepwise Condensation to Diversify Cyano-Substituted Vinylene-Linked COFs for Boosting H2O2 Photosynthesis

Driven by growing demand for structural diversification and practical application of vinylene-linked covalent organic frameworks (COFs), it is critical to develop sustainable routes to monomers with highly tunable connectivity and functionality. Herein, we report an efficient route to a new class of aromatic DCP derivatives (DCP = 2,6-dimethyl-3,5-dicyanopyridine) via Hantzsch-type condensation from low-cost commodity chemicals. Using arene-bridged DCP dimers (arene = phenyl, biphenyl, naphthalenyl) as tetratopic monomers, we constructed three new vinylene-linked COFs via Knoevenagel condensation with 4,4'-biphenyldicarbaldehyde. Thorough characterization reveals their long-range ordered structures and high porosity. Their semiconducting properties are finely tuned by varying the monomer arene bridges. In pure water, these COFs deliver excellent photocatalytic H2O2 production up to 7020 μmol g-1 h-1, outperforming the cyano-free counterpart. This phenomenon can be directly attributed to the abundant cyano substituents with strong dipolar and π-extended character in the as-prepared COFs. These cyano moieties enhance light harvesting and photogenerated charge utilization, and provide strong hydrogen-bonding interactions to stabilize the key *OOH intermediate, thereby facilitating oxygen reduction, as supported by theoretical investigations. This work provides an economical strategy to tailor vinylene-linked COF structures and functions for broader practical applications.