Tunable Conjugated Organoborane Oligomers for Visible-Light-Driven Hydrogen Evolution

A series of linear conjugated organoborane oligomers are synthesized here by introducing electron-deficient borole units to the well-explored thiophene unit of variable length. It is found that the photophysical properties, particularly the band structures of products, alter regularly with the extension of thiophene. Interestingly, such oligomers exhibit high activity for photocatalytic hydrogen evolution under visible light (λ > 420 nm), outperforming most of the reported linear polymers. The enhanced performance is possibly attributed to the strong electron-accepting nature of the borole group, as well as the good electron donor and light-harvesting properties of the thiophene group. The combination of these two units facilitates charge separation of oligomers, thus allowing the participation of as many photogenerated charge carriers as possible in the desired water reduction reaction. The results indicate the success of our strategy and the importance of rational molecular design for developing conjugated (oligo)­polymers for efficient photocatalytic hydrogen evolution.