Novel conjugated organic polymers as candidates for visible-light-driven photocatalytic hydrogen production

Artificial photosynthesis aiming to capture and convert renewable solar energy into solar fuels (e.g., hydrogen, chemicals) provides a blueprint for sustainable and carbon-neutral world. In artificial photosynthesis, developing novel semiconductors for visible-light-driven photocatalytic water splitting is one of the most demanding challenges. Herein, we designed and explored two kinds of novel bipyridine-based covalent organic polymers, Bp-COP (2,2′-bipyridine-5,5′-diamine: Bp-NH 2 ) and BpZn-COP (2,2′-bipyridine-5,5′-diamine Zn complex: Bp-Zn), both of which exhibit excellent light-harvesting properties with absorption edges expanding to larger than 600 nm and have appropriate band structures for water splitting. Polymers Bp-COP and BpZn-COP are found to enable efficient photocatalytic hydrogen production under visible light irradiation with Pt as the proton reduction cocatalyst. Further assembling conjugated organic polymers with TiO 2 as charge transferring mediate can remarkably boost their photocatalytic activities to more than 8 times (1333 vs. 162 μmol g −1  h −1 ), giving an apparent quantum efficiency (AQE) of over 2.5% at the input wavelength of 420 nm. This work not only presents a methodology for designing and synthesizing novel organic-based polymers, but also provides promising candidates for potential applications in solar energy conversion.