Photocracking of Polystyrene into Aromatic Products in CH₂Cl₂

Photocatalytic cracking of polystyrene (PS) into valuable aromatic chemicals presents a key route to plastic waste upcycling under mild conditions, in which CH₂Cl₂ is often used as an inert solvent. Represented herein is to report an unexpected cracking of PS to C6-C8 aromatic products in CH₂Cl₂ without any additional photocatalysts under an O₂ atmosphere and 365-415 nm irradiation. Remarkably, this photocatalyst-free system achieves a maximum generation rate of 15.9 µmol/h for C6-C8 aromatic products, competitive with state-of-the-art systems that rely on external photocatalysts. Radical scavenging experiments and EPR spectra reveal that chlorine (Cl•) radicals generated from CH₂Cl₂ under irradiation contribute to the cleavage of C─H/C─C bonds in PS, leading to the formation of C6-C8 aromatic products. Under aerobic conditions, these Cl• radicals also promote the transformation of PS into carbonylated intermediates as the light-absorbing species with an absorption range of 300-500 nm, thereby accelerating the activation of PS and derivatives. Importantly, this work identifies, for the first time, CH₂Cl₂ as a vital photochemical reagent in PS conversion to value-added aromatics even under visible light irradiation.