Glycine photosynthesis via C-N coupling of waste plastic and nitrate over diatomic Pd-B catalyst

Photocatalytic C-N coupling offers a promising approach for the sustainable production of amino acids, but the uncontrolled coupling pathway of reaction intermediates limits yield and selectivity. This paper describes a Pd-B diatomic catalyst that can selectively catalyze the photosynthesis of glycine via C-N coupling reaction between waste poly(ethylene terephthalate)-derived ethylene glycol and nitrate, achieving a glycine yield of 2.9 mmol g_cat^-1 h^-1 with a selectivity of 92%. Mechanistic investigations reveal that ethylene glycol is photo-oxidized to glycolaldehyde at the hole-rich B site, while nitrate is photo-reduced to NH₄⁺/NH₃ at the electron-rich Pd site. Subsequently, glycolaldehyde undergoes C-N coupling with NH₄⁺/NH₃, and further photo-oxidized to form glycine. The Pd-B diatomic site more effectively stabilizes the glycolaldehyde intermediate, resulting in a more favorable C-N coupling pathway than metal oxide and enhancing glycine selectivity. Thus, we show a catalytic system for selective glycine photosynthesis by precisely regulating the reaction pathways of key intermediates.