Chemoenzymatic Cascade Recycling and Upcycling of Polyurethane Elastomers

Abstract The complex structure of polyurethanes (PURs) presents a major barrier to their efficient recycling. Here, we report a chemoenzymatic cascade that enables the simultaneous recycling and upcycling of PUR through rapid alkaline pretreatment followed by urethanase-catalyzed depolymerization. Using in-house-synthesized model polyether- and polyester-based PUR elastomers, we establish that soft-segment chemistry dictates the composition, morphology, and accessibility of the pretreated residues, thereby governing the efficiency of the subsequent enzymatic hydrolysis. This insight enabled translation of the cascade to a commercial PUR elastomer, achieving >93% chemical conversion and recovery of up to 1 mM 4,4′-methylenedianiline (MDA) (97.2% purity), corresponding to a 40-fold increase over the nonenzymatic control, together with polyols obtained in 95% isolated yield that were directly reused for PUR synthesis. Mechanistic studies further show that alkaline pretreatment enhances substrate accessibility for the enzyme, and structural analysis of urethanase SP2 reveals a carbamate-specific hydrogen-bonding interaction that promotes urethane hydrolysis while minimizing esterase activity. The cascade was additionally applied to highly crosslinked commercial PUR foams and adhesives, demonstrating its versatility toward industrially relevant waste streams. Overall, this work establishes a mechanistically informed chemoenzymatic platform for PUR depolymerization and provides a strategy for converting chemically recalcitrant PUR waste into reusable molecular building blocks.