Bifunctional conjugated polymer photocatalysts for visible light water oxidation and CO2 reduction: function- and site-selective hybridisation of Ru(ii) complex catalysts

Abstract

Conjugated polymers have shown potential as photocatalyst materials owing to their molecular design flexibility in tuning their properties, including visible-light absorption. However, most reported conjugated polymers have only a single type of catalytic site and thus exhibit a single photocatalytic function, for example, H₂ evolution, CO₂ reduction, or water oxidation. To achieve artificial photosynthetic reactions, such as CO₂ reduction coupled with water oxidation, it is desirable to develop a strategy for introducing two different catalytic centres for selective oxidation and reduction; these catalysts should be positioned appropriately for photoinduced charge separation in the photocatalyst material. In this study, conjugated polymer photocatalysts were rationally designed for the functional- and site-selective introduction of two different Ru complex catalysts for water oxidation and CO₂ reduction. A pyrene moiety with condensed aromatic rings blended into a carbazole–bipyridine-based conjugated polymer anchors an isoquinoline ligand of a Ru complex, which facilitates water oxidation, whereas the bipyridine moiety selectively hosts another Ru complex for CO₂ reduction. Function- and site-selective hybridisation of the two specific Ru(II) complex catalysts enables the donor–acceptor polymer to act as a bifunctional photocatalyst for visible-light water oxidation and CO₂ reduction.