Naphthalenediimide-based donor–acceptor COFs with low exciton binding energy toward sunlight-driven synthesis of multisubstituted olefins and sulfoxides

Abstract

Incorporating both electron donor and acceptor chromophores as co-monomers within a COF for light harvesting and photocatalysis remains a major synthesis challenge. Concurrently, achieving high-efficiency and selective synthesis of sulfoxides and multisubstituted olefins under mild conditions is critically important for scientific and industrial progress. Hence, two imine-linked two-dimensional donor–acceptor COFs, SF-COF-1 and SF-COF-2, with different linker lengths, have been successfully constructed from benzo[1,2-b:3,4-b′:5,6-b″]trithiophene-2,5,8-tricarbaldehyde (BTT) and naphthalenediimide (NDI) derivatives. The obtained COFs have well-defined crystallinity and exhibit linker length-dependent photocatalytic performance for sulfide oxidation and for the synthesis of multisubstituted olefins. Combined experimental and theoretical studies demonstrated that SF-COF-1 exhibits a lower exciton binding energy than SF-COF-2, resulting in enhanced charge separation and more efficient in-plane electron transfer. Consequently, SF-COF-1 demonstrated higher photocatalytic activity in sulfide oxidation, although the activity of the catalysts was comparable in the synthesis of multisubstituted olefins. Moreover, SF-COF-1 functions effectively as a photocatalyst under natural sunlight and ambient air without requiring additional energy input, underscoring its strong industrial viability.