Photocatalytically active ladder polymers

Vogel, Anastasia and Forster, Mark and Wilbraham, Liam and Smith, Charlotte L. and Cowan, Alexander J. and Zwijnenburg, Martijn A. and Sprick, Reiner Sebastian and Cooper, Andrew I. (2019) Photocatalytically active ladder polymers. Faraday Discussions, 215. pp. 84-97. ISSN 1359-6640 (https://doi.org/10.1039/c8fd00197a)

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Abstract

Conjugated ladder polymers (cLaPs) are introduced as organic semiconductors for photocatalytic hydrogen evolution from water under sacrificial conditions. Starting from a linear conjugated polymer (cLiP1), two ladder polymers are synthesized via post-polymerization annulation and oxidation techniques to generate rigidified, planarized materials bearing dibenzo[b,d]thiophene (cLaP1) and dibenzo[b,d]thiophene sulfone subunits (cLaP2). The high photocatalytic activity of cLaP1 (1307 μmol h-1 g-1) in comparison to that of cLaP2 (18 μmol h-1 g-1) under broadband illumination (λ > 295 nm) in the presence of a hole-scavenger is attributed to a higher yield of long-lived charges (μs to ms timescale), as evidenced by transient absorption spectroscopy. Additionally, cLaP1 has a larger overpotential for proton reduction and thus an increased driving force for the evolution of hydrogen under sacrificial conditions.

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