Catalysts developed from waste plastics: a versatile system for biomass conversion

Abstract The end-of-life treatment for post-consumer plastic waste constitutes one of modern society’s greatest problems, whereby highly unsustainable landfilling and incineration are the two main disposal routes. At present, the chemical upcycling of plastic waste is largely limited to its pyrolytic conversion into hydrocarbon fuels or nanomaterials. Herein, we demonstrate the upcycling of high-volume plastic waste by turning them into catalysts for biomass valorization. Many existing studies synthesize organocatalysts from a bottom-up approach using specialized monomers. Yet, transforming widely available waste polymers into functionalized materials for catalysis remains relatively unexplored. In this study, homogeneous and cross-linked heterogeneous catalysts derived from waste polystyrene food containers are shown to convert readily available saccharide precursors from biomass into 5-hydroxymethylfurfural (5-HMF), a key biorefinery platform chemical, under short reaction times and mild conditions. In addition, the heterogeneous catalyst can be reused multiple times with little loss of yield between repeated runs. Other than 5-HMF, doping the reaction with water or halide salts also allowed the formation of valuable products such as formic acid and diformylfuran. Our work expands on existing upcycling options for post-consumer plastic waste by giving them a new lease of life as value-added catalysts.