Metal-free upcycling of plastic waste: photo-induced oxidative degradation of polystyrene in air

Abstract

Chemical recycling of plastics, as a promising strategy to reduce waste pollution and yield value-added chemicals, is showing great potential in the circular economy. In this work, a photooxidation method was reported to facilitate the degradation of polystyrene (PS) in air using porphyrin-based porous organic polymers (PPOPs) as the photocatalysts, associated with the recovery of benzoic acid in high yield (72%) and with excellent selectivity (97%). From the method aspect, the degradation could happen under very mild conditions using EtOAc as the green solvent and air as the oxidant. From the application perspective, such a method could efficiently facilitate the degradation of numerous PS derivatives and PS-based plastic wastes, with the recovery of benzoic acid. The optimized PPOP structure was screened with the desired degradation efficiency and benzoic acid recovery yield. Detailed mechanisms have been investigated to demonstrate that reactive oxygen species generated by light-triggered PPOPs play crucial roles in plastic waste upcycling.