Phytic acid-bridged MXene/Fe-MOF nanohybrids: A dual synergy for enhanced flame retardancy, smoke suppression and mechanical properties in poly (l-lactic acid)

Poly(lactic acid), a biodegradable polymer, suffers from flammability and low strength. A hierarchical layered flame retardant (MXene@P–Fe) was constructed via a pH-regulated self-assembly strategy, in which phytic acid (PA) served as a bridging ligand to intercalate Fe-based MOFs into MXene nanosheets. When incorporated into PLA at a loading of 12  wt %, the composite exhibited significantly enhanced flame retardancy, as evidenced by an increased LOI of 30%. In addition, the peak heat release rate and total heat release were reduced by 40.3% and 43.1%, respectively, evidencing effective suppression of heat and toxicity. Mechanistic investigations revealed that synergistic interactions among MXene, PA, and Fe-MOFs promoted cyclic compound formation, yielding a graphitized Ti/C-based barrier that inhibited heat and mass transfer. Furthermore, the tensile strength of PLA/4MXene@P–Fe reached 79.3 MPa, representing a 32.6% improvement over pristine PLA. This work provides a novel and practical pathway for constructing high-performance, fire-safe polymeric materials based on sustainable PLA.