Photocatalytic Upcycling of Plastic Waste for Selective Acetamide Synthesis by Intercepting Carbon Intermediates

Powered by solar energy, the photocatalytic upcycling of plastic waste into value-added products by forming C–X bonds presents an innovative method to reintegrate waste plastics into the utilization cycle. In this work, we introduced a cocatalyst-free CdS photocatalytic system to effectively upcycle polyethylene terephthalate (PET) plastic waste into acetamide. This selective upcycling of plastic waste to acetamide not only provides a promising route for acetamide synthesis but also promotes a circular plastic economy. In the absence of a nitrogen resource, the PET monomer, ethylene glycol (EG), can be selectively oxidized to C 2 -based acetic acid via an acetaldehyde intermediate. When ammonia (NH 3 ) is present, the acetaldehyde intermediate is captured by the NH 3 nucleophile, resulting in the formation of acetamide (up to 3.68 mmol g –1 ) as the C–N coupling product. A series of control experiments demonstrate that neutral conditions are essential for facilitating C–N coupling between the EG monomer and NH 3 . In addition, potential reaction pathways are investigated by using density functional theory (DFT) calculations, which reveal that the dehydrogenation of *CHOHCH 2 to *CHOCH 2 is the rate-determining step. This strategy is also applicable to real-world PET waste, achieving efficient acetamide synthesis (up to 4.33 mmol g –1 ) when using a PET bottle as the substrate. By optimizing the volume ratio of PET-derived EG to NH 3 ·H 2 O, the C 2 product ratio─acetamide to acetic acid─can reach as high as ∼32, highlighting the superior selectivity of this photocatalytic system. This photocatalytic transformation of plastic waste, coupled with the formation of C–N bonds for the production of targeted organonitrogen compounds, paves the way for innovative methods to harness carbon resources from plastic waste.