Selective Co-Upcycling of Waste PET Plastic and Nitrate to Glycine via C-N Coupling on a WO3 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 WO3 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 gcat-1 h-1 with 89% selectivity, which significantly outperforms conventional TiO2-based systems. Mechanistic studies indicate that the high selectivity stems from the distinct reaction pathway on WO3, where glycolaldehyde is stabilized as the key intermediate to efficient C-N coupling with NH4+ derived from NO3- reduction. This contrasts with the TiO2-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.