Simultaneously Enhancing Flame Retardant, Smoke-Suppressing Antibacterial and Mechanical Performance of Corn Stalk/Polypropylene Composites via Engineering Arginine/ZIF-67 Dual-Modified Ammonium Polyphosphate

The expanding application of corn stalk/polypropylene composites (CPCs) is accompanied by increasingly stringent performance requirements. Consequently, endowing flame retardancy, smoke suppression, and multifunctionality to CPCs while maintaining their mechanical properties is significant. Herein, a biobased flame retardant, arginine/ZIF-67 dual-modified ammonium polyphosphate (APP-Arg-MOF; MOF, metal–organic framework), for CPCs was engineered. APP was first functionalized with Arg via ion exchange to enhance its compatibility and flame retardancy. Subsequently, ZIF-67 was uniformly grown on APP-Arg through coordination-driven assembly using cobalt ions and 2-methylimidazole. The experimental results explained the exceptional multifunctional enhancement. The CPC/APP-Arg-MOF composite achieved a limiting oxygen index of 29.2% and passed the UL-94 V-0 rating. Cone calorimetry revealed significant reductions in the peak heat release rate (63.1%), total heat release (21.9%), and total smoke production (34.7%). Remarkably, the bending and tensile strengths increased by 10.0% and 26.9%, respectively, relative to CPC/APP, attributed to improved interfacial compatibility via Arg and ZIF-67 nanostructures. Furthermore, the CPC/APP-Arg-MOF composite exhibited potent antimicrobial activity, with inhibition rates of 97% against E. coli and 99% against S. aureus, leveraging synergistic effects of Arg and Co 2+ release from ZIF-67. Meanwhile, the composite also maintained flame-retardant and antibacterial properties after 200 h of UV aging. Therefore, this work presents a sustainable APP surface modification strategy by utilizing Arg and ZIF-67 to simultaneously enhance fire safety, smoke suppression, and mechanical, antimicrobial, and anti-UV aging performances of CPC, offering significant potential for CPC applications.