A Generic Platform for Upcycling Polystyrene to Aryl Ketones and Organosulfur Compounds.

Polystyrene (PS) is one of the least recycled large-volume commodity plastics due to bulkiness of foam products and associated contaminants. PS recycling is also severely hampered by the lack of financial incentive, limited versatility, and poor selectivity of existing methods. To this end, herein we report a thermochemical recycling strategy of "degradation-upcycling" to synthesize a library of high-value aromatic chemicals from PS wastes with high versatility and selectivity. Two cascade reactions are selected to first degrade PS to benzene under mild temperatures, followed by the derivatization thereof utilizing a variety of acyl/alkyl and sulfinyl chloride additives. To demonstrate the versatility, nine ketones and sulfides of cosmetic and pharmaceutical relevance were prepared, including propiophenone, benzophenone, and diphenyl sulfide. The approach is also amenable to sophisticated upcycling reaction designs and can produce desired products stepwise. The facile and versatile approach will provide a scalable and profitable methodology for upcycling PS waste into value-added chemicals.