Nanostructured Lateral Boryl Substitution Conjugated Donor–Acceptor Oligomers for Visible‐Light‐Driven Hydrogen Production

Abstract Poor charge separation is the main factor that limits the photocatalytic hydrogen generation efficiency of organic conjugated polymers. In this work, a series of linear donor–acceptor (D–A) type oligomers are synthesized by a palladium‐catalyzed Sonogashira–Hagihara coupling of electron‐deficient diborane unit and different dihalide substitution sulfur functionalized monomers. Such diborane‐based A unit exerts great impact on the resulting oligomers, including distinct semiconductor characters with isolated lowest unoccupied molecular orbital (LUMO) orbits locating in diborane‐containing fragment, and elevated LUMO level higher than water reduction potential. Relative to A‐A type counterpart, the enhanced dipole polarization effect in D–A oligomers facilitates separation of photogenerated charge carriers, as evidenced by notably prolonged electron lifetime. Owing to π–π stacking of rigid backbone, the oligomers can aggregate into an interesting 2D semicrystalline nanosheet (≈2.74 nm), which is rarely reported in linear polymeric photocatalysts prepared by similar carbon–carbon coupling reaction. Despite low surface area (30.3 m 2 g −1 ), such ultrathin nanosheet D–A oligomer offers outstanding visible light (λ > 420 nm) hydrogen evolution rate of 833 µmol g −1 h −1 , 14 times greater than its A‐A analogue (61 µmol g −1 h −1 ). The study highlights the great potential of using boron element to construct D–A type oligomers for efficient photocatalytic hydrogen generation.