Indanone-based conjugated polymers enabling ultrafast electron transfer for visible light-driven hydrogen evolution from water

Photocatalytic hydrogen production (PHP) from water is a promising solution for environmental pollution due to its high energy density and the abundant availability of water and solar energy on Earth. 1,1-dicyanomethylene-3-indanone (IC) has been widely used as an end group in organic photovoltaics owing to its strong electron-withdrawing ability and planarity. However, research on the application of IC structures in PHP is limited due to synthesis challenges. In this study, we designed a series of novel IC-based monomers incorporating a dibenzothiophene-S,S-dioxide unit through Suzuki coupling. These monomers were used to synthesize polymers with varying degrees of malononitrile substitution, referred to as ICFTDB, ICTDB, and IDMTDB. We investigated the correlation between the optical, electrochemical, and hydrogen evolution performances of these polymers. Through transient absorption spectroscopy, we demonstrated that ICTDB exhibited enhanced capabilities for ultrafast electron transfer and reduced recombination effects. As a result, ICTDB, photocatalysts with IC-containing structures achieved a hydrogen evolution rate of 30.0 mmol g⁻¹ h⁻¹, which was 11.5 times higher than that of ICFTDB, the polymer with no malononitrile substitution. This study provides valuable insights into the potential of IC-based conjugated polymers for photocatalytic hydrogen evolution.