Phenolic/carboxylic functionalized hypercrosslinked polymers for aromatic diamine recovery from polyurethane hydrolysate

Abstract Upcycling waste polyurethane (PU) via (bio)chemical depolymerization is a promising strategy for advancing a circular plastic economy, yet efficient recovery of toxic but valuable aromatic diamines remains a critical bottleneck. Herein, a phenolic‐ and carboxylic acid–functionalized hyper‐cross‐linked polymer (HCP–PCA) was designed for the selective recovery of 2,4‐toluene diamine (TDA) and 4,4′‐methylene dianiline (MDA) from PU biohydrolysates. HCP–PCA features a high surface area (610 m 2 /g), abundant acidic sites, and low material cost (~$0.102/g). Batch adsorption experiments demonstrated high capacities of 1.46 mmol/g for TDA and 2.65 mmol/g for MDA, along with rapid kinetics and strong selectivity. Spectroscopic analyses revealed that adsorption is driven by synergistic acid–base interactions, hydrogen bonding, π–π stacking, and hydrophobic effects. Dynamic column tests further confirmed efficient adsorption–desorption behavior and practical applicability. This work provides a scalable and sustainable strategy for aromatic diamine recovery, facilitating downstream PU bio‐upcycling and plastic waste valorization.