Inspired by the catalytic properties of biological enzymes: Design of bifunctional catalytic flame retardants for enhanced polyurethane flame retardancy

The flammability of polymers limits their use, and traditional flame-retardant approaches no longer meet modern performance needs. To address issues with metal-based flame retardants—such as poor char-forming efficiency and mismatched decomposition—we designed a metal–ligand coordination system that mimics enzymatic catalysis to regulate polyurethane degradation. Under heat, the metal centers selectively cleave weak bonds, suppressing flammable small-molecule formation and promoting the generation of high-molecular-weight, carbon-rich intermediates. These intermediates rapidly crosslink and carbonize, forming a dense char layer that shifts degradation from gasification to carbonization. As a result, (Co-ATMP)₁-co-PU reduces HRR by 69.9%, SPR by 33%, and CO₂ release by 73.4%, while increasing char yield. This catalytic strategy significantly enhances flame retardancy and improves char stability at high temperature, offering a promising route to intrinsically flame-retardant polymers.