Upcycling Waste Polyoxymethylene to Value-added Chemicals Using Reusable Polymeric Acid Catalysts at ppm Levels

Waste polyoxymethylene (POM) plastic was upcycled using m-phenolsuflonic acid-formaldehyde resin, a polymeric heterogeneous catalyst, to afford multiple value-added chemicals, including solvents, insecticides, and pillar[5]arenes using biomass-derived alcohols or water as reactants. The acid catalyst exhibited stable and reliable performance at a 260 mol ppm loading and remained active after five reuse cycles without any loss of catalytic efficiency. The upcycling process was effective even at a 166 mmol (5-gram) scale. Under acid-catalyzed conditions, the POM moiety in carbon-fiber-reinforced polymers (CFRPs; 360 mg-5 g scale) was selectively depolymerized, yielding carbon fibers free of POM residues, as confirmed by solid-state NMR. This process also mitigates environmental concerns by converting microplastics into value-added chemicals. Additionally, microwave irradiation proved more effective (99% upcycling) than conventional heating methods (73%). This upcycling process offers a sustainable approach to plastic waste management, enabling the synthesis of valuable chemicals and materials while reducing environmental pollution.