Selective Co-Upcycling of Waste PET Plastic and Nitrate to Glycine via C–N Coupling on a WO ₃ Photocatalyst

Photocatalytic conversion of polyols and nitrogen-containing small molecules into value-added chemicals via C–N coupling reaction represents a promising route for dual waste treatment of waste plastics and wastewater. However, precisely controlling the coupling pathway of key intermediates to achieve high product selectivity remains a significant challenge. Here, we report a WO 3 photocatalyst that enables the highly selective synthesis of glycine from waste poly(ethylene terephthalate) (PET)-derived ethylene glycol (EG) and nitrate, achieving a remarkable glycine yield of 1.87 mmol g cat –1 h –1 with 89% selectivity, which significantly outperforms conventional TiO 2 -based systems. Mechanistic studies indicate that the high selectivity stems from the distinct reaction pathway on WO 3, where glycolaldehyde is stabilized as the key intermediate to efficient C–N coupling with NH 4 + derived from NO 3 – reduction. This contrasts with the TiO 2 -catalyzed pathway that proceeds via the more oxidized glyoxal, which readily undergoes overoxidation to the byproduct formic acid. By using different plastic/biomass-derived feedstocks (methanol, ethylene glycol, and glycerol), this process can be expanded to the scale synthesis of various C–N compounds. Preliminary techno-economic analysis and life-cycle assessments suggest the potential economic viability and environmental benefits of this process. This work establishes a sustainable photocatalytic strategy for the valorization of waste plastic and wastewater by regulating key intermediates to enable a selective C–N coupling pathway.