Recyclable Zinc Cyanamide Dual-Site Catalyst Enables Efficient PET Glycolysis

Metal cyanamides represent a category of inorganic functional materials with superior activity and stability. However, their potential application in plastic recycling remains unexplored. This study mainly focused on the utilization of zinc cyanamide (ZnNCN) as a poly(ethylene terephthalate) (PET) glycolysis catalyst. The PET glycolysis process is demonstrated to be promoted by a synergistic catalysis effect. Under optimal conditions, 100% PET conversion and 92.3% bis(2-hydroxyethyl) terephthalate (BHET) yield were achieved. Furthermore, successful depolymerization toward various real commercial PET wastes and excellent recycling performance proved promising application prospects. DFT study and NMR characterization have revealed that the remarkable catalytic activity stems from the synergistic effect of the Lewis acid site and hydrogen bonds between ethylene glycol (EG) and the catalyst. This work provides valuable insight into the application of metal cyanamides, paving the way for the development of effective catalysts for PET recycling.