“Two-birds-one-stone” strategy: Phytic acid-chelated MOFs and NiMoO₄ nanorods integrated polyurea for multifunctional flame retardancy, mechanical, and UV protection

Metal-organic frameworks (MOFs) and molybdates have been established as effective functional additives in polyurea (PUA) composites. However, simple physical blending fails to fully realize their potential. In this study, an innovative biomass-based supramolecular flame retardant was rationally designed through a simple strategy involving ligand exchange between phytic acid and MOFs, as well as hydrogen bonding interactions with transition metal species, named PCu-M@NiMoO₄. Compared to pristine PUA and physically blended systems, the incorporation of PCu-M@NiMoO₄ into the PUA matrix significantly improved both mechanical properties and flame retardancy. Specifically, the addition of 4 wt% PCu-M@NiMoO₄ reduced the peak heat release rate, total smoke production, and peak carbon dioxide production rate by 39.95 %, 64.72 %, and 56.13 %, respectively, relative to pure PUA. In comparison to physical blends, the PUA/PCu-M@NiMoO₄ composite exhibited a 26.83 % increase in tensile strength, with tensile strength reaching 14.18 MPa and elongation at break reaching 396.97 %. Moreover, the general applicability of this strategy was confirmed by extending it to other common MOFs such as MIL-53 and ZIF-67, resulting in PFe-M@NiMoO₄ and PCo-M@NiMoO₄ with similarly enhanced performance. Furthermore, PFe-M@NiMoO₄ maintained over 90 % of its tensile strength after 200 h of UV aging. This work provides a straightforward and adaptable approach to the creation of high-performance PUA materials.