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.