Photochemical C-N coupling via adsorption modulation: Selective synthesis of glycine from waste...

Photocatalytic C-N coupling from polyols and nitrogen-containing small molecules for glycine synthesis provides an attractive strategy for upgrading of plastic/biomass waste. However, the uncontrolled intermediates coupling challenges the efficient glycine production regarding yield or selectivity. Here we report an In₂O₃ photocatalyst that can achieve a glycine formation rate of 1.167 mmol g^-1 h^-1 with 89% selectivity from waste poly(ethylene terephthalate) (PET) plastic-derived ethylene glycol (EG) and nitrate. Mechanism research reveals that EG is photo-oxidized into glycolaldehyde as a key intermediate over In₂O₃ catalyst, which subsequently undergoes C-N coupling with NH₄⁺ obtained from nitrate reduction to form glycine. Compared to TiO₂ catalyst, In₂O₃ can significantly inhibit the over-oxidation process of key intermediates, thereby suppressing the formation of by-product formic acid. This process is also successfully extended to transform real-word PET plastic and biomass-derived polyols into high-value glycine or amide. Techno-economic analysis (TEA) and life cycle assessment (LCA) further confirm the economic viability and environmental benefits of this C-N coupling system. This work provides a sustainable catalytic system for selective glycine photosynthesis by precisely regulating the C-N coupling routes of key intermediates, which achieves synergistic value-added conversion of dual waste streams, effectively alleviating environmental pressures.