Stable and Super-Acidic Nafion for Visible Light-Driven Oxidative Upcycling of Polystyrene

Photocatalytic oxidative cleavage of polystyrene waste is considered as a promising strategy for the production of valuable molecules (upcycling strategy). Recently, many kinds of photocatalysts were reported. However, they display different drawbacks, such as only UV responsiveness, un-recyclability, and un-stability. Inspired by the photo-activation of aromatic rings under acidic conditions, an easy-to-use heterogeneous proton source (Nafion, a sulfonic resin) was tested for visible light-driven upcycling of PS under O₂ atmosphere. Such approach resulted in an efficient deconstruction of commercial PS waste under visible light (yield of benzoic acid up to 70%), meanwhile, Nafion could be used in five consecutive runs. Furthermore, the mechanism was systematically investigated. Apart from Nafion, generated oxidized polystyrene intermediates were shown to play an important role on the photocatalytic degradation. This work proposes an interesting pathway to upgrade PS plastics through heterogeneous catalysis, although progress still needs to be made in terms of quantum yield.