Two‐step coupled methanolysis and hydrogenation process for upcycling waste <scp>PET</scp> into high‐value <scp>1,4‐cyclohexanedicarboxylate</scp>

Abstract Waste polyethylene terephthalate (PET) methanolysis into dimethyl terephthalate (DMT) is a promising route for industrial application but still faces harsh methanolysis conditions and low economic effectiveness. Herein, we proposed a strategy for the upcycling waste PET into the high‐value dimethyl 1,4‐cyclohexanedicarboxylate (DMCD) via two‐step coupled PET methanolysis and DMT hydrogenation at mild reaction conditions. density functional theory‐based various quantum chemical descriptors of deep eutectic solvents and corresponding DMT yields were correlated using machine learning algorithms, and found that metal‐free 1,5‐diazabicyclo[4.3.0]non‐5‐ene/4‐methylimidazole possesses the best catalytic performance for PET methanolysis with DMT and ethylene glycol yields reaching 95% and 89%, respectively, under mild conditions, and exhibits good applicability to various real waste PET and other polyesters. The novel Ru/Al 2 O 3 catalyst for resultant DMT hydrogenation was developed to yield 99.1% DMCD at 160°C, 4 MPa H 2 with superb catalytic activity and stability. This work provides a two‐step integrated upcycling route for waste PET.