Upcycling of non-biodegradable plastics by base metal photocatalysis

Summary

Plastics have become indispensable in our daily lives, but plastic waste has proliferated in landfills and oceans since most plastics are non-biodegradable and cannot be mechanically recycled. Existing chemical recycling processes such as pyrolysis and hydrogenolysis typically use high temperatures, generate unnecessary greenhouse gas emissions, often require expensive noble metals, and show limited generality. In addition, the latest efforts in the photochemical upcycling of plastics near ambient temperatures are mainly restricted to polystyrene. Here, we report a base metal photo-driven upcycling of most conventional plastics such as polystyrene, polypropylene, polyethylene, polyvinyl chloride, and polyvinyl acetate by a tandem carbon–hydrogen bond oxidation/carbon–carbon bond cleavage reaction, with carbon recoveries up to 77% and selective formation of valuable, isolable products including formic, acetic, and benzoic acids. We successfully applied the optimized ambient conditions on copolymers, multilayered packaging, and actual plastic waste. Gram-scale reactions were demonstrated using a flow photoreactor with recirculation.