Construction of Zn ₂ ( <scp>bIm</scp> ) ₄ ‐Based Core‐Shell Flame Retardant System for Enhancing the Fire Safety, Mechanical Properties, and Ultraviolet Resistance of Polylactic Acid

ABSTRACT Polylactic acid (PLA) is a biodegradable material with broad application prospects. However, its inherent flammability significantly hinders its practical applications, thereby necessitating advanced flame‐retardant strategies. In this study, a novel core‐shell structured flame retardant (APP/Zn 2 (bIm) 4 /GO) was designed, comprising ammonium polyphosphate (APP) as the core and shell formed by a metal–organic framework (Zn 2 (bIm) 4 ) and graphene oxide (GO). The results showed that with only 4 wt% APP/Zn 2 (bIm) 4 /GO loading, the PLA composites achieved a limiting oxygen index (LOI) of 31.5% and UL‐94 V‐0 level. Furthermore, compared to neat PLA, the peak heat release rate (pHRR) and peak smoke production rate (pSPR) of PLA/4APP/Zn 2 (bIm) 4 /GO were reduced by 25% and 84%, respectively, indicating a remarkable improvement in fire safety. Moreover, PLA/4APP/Zn 2 (bIm) 4 /GO also showed enhanced mechanical properties and ultraviolet (UV)‐resistant properties. This work develops a new approach to preparing core‐shell structured flame retardants, which simultaneously endow fire safety, mechanical properties, and UV resistance for PLA, offering a promising route for expanding its application scope.