Chiral Organic Semiconductors – Lending a Hand in Photocatalysis

Society’s ever-growing energy demands and simultaneous rapid depletion of current greenhouse gas-emitting resources showcase the need to find clean, renewable alternatives. Generation of hydrogen through the combined action of sunlight, water and a photocatalyst, the water splitting reaction (WSR), offers a promising solution to this long-standing problem. However, the WSR suffers from uncontrolled spin alignment of OH radicals, producing hydrogen peroxide (H₂O₂) as a by-product, which greatly hinders the efficacy and scalability of this process.[1] As chiral molecules are sensitive to electron spin orientation, due to the Chiral Induced Spin Selectivity (CISS) effect, they could behave as spin filters in photocatalysis, thus providing a unique pathway to cleaner energy by impeding hydrogen peroxide formation.[1],[2]<br/><br/>Conjugated polymers are a class of material that have gained increasing attention due to their applications in many electronic devices such as transistors, organic light emitting diodes (OLEDs) and flexible organic photovoltaics (OPVs). This is owing to their tuneable optoelectronic properties, intrinsic flexibility, solution-processability, low cost and abundance. Application of these features to photocatalysis, in combination with the spin selectivity of chiral molecules, could result in efficient, scalable production of hydrogen for clean energy resources.[2],[3]<br/><br/>This work focuses on the synthesis and spectroscopic characterisation of a series of novel, chiral conjugated polymers to generate the desired CISS effect for the suppression of H₂O₂ in the WSR. Development of these systems relies on gaining a deeper understanding on how the nanoscale chirality impacts the overall chiral expression. We therefore investigate the effect of chiral centre positioning on the polymer microstructure. In addition to pursuing renewable, cleaner energy for society, this work could also have a profound impact on our understanding between the interplay of chiral centres and polymer microstructure.<br/><br/>References:<br/>[1] W. Mtangi et al., <b><i>J. Am. </i></b><b><i>Chem. Soc.</i></b><i>,</i> 2017, 139, 2794–2798.<br/>[2] R. Naaman et al., <b><i>J. Phys. Chem. </i></b><b><i>Lett.,</i></b> 2012, 3, 2178–2187.<br/>[3] J. Kosco et al., <b><i>Nat. Mater., </i></b>2020, 19, 559-565.