Synergistic Bimetallic Catalysis for Closed-Loop Polyurethane Foam Upcycling via Proximity-Driven Depolymerization

The development of efficient catalytic systems for polyurethane foam (PUF) recycling under mild conditions remains a critical challenge in achieving sustainable plastic circularity. Here, we report a ternary catalyst (TMG/Cd/HMMI) featuring a bimetallic Cd(II) center coordinated with 1,1,3,3-tetramethylguanidine (TMG) and 1-methyl-2-hydroxymethylimidazole (HMMI), which synergistically enhances the depolymerization of PUF. Integrated with a multi-stage degradation strategy, the catalyst efficiently catalyzes the degradation of carbamate and urea bonds in PUF under mild conditions (180 – 200 °C, 4 h, 10 wt% degradation agent relative to PUF mass), enabling spontaneous phase separation into high-purity recycled polyols (RP) and isocyanate-derived hard segments (HS) without requiring purification. The RP exhibit near-identical properties to virgin polyols and can substitute up to 40 wt% in new foam synthesis without compromising mechanical performance. Meanwhile, the hard segment can be reused as a reinforcing additive of rigid foam. This approach ensures full resource recovery, aligning with circular economy principles.