Immobilizing 2-methylimidazole and Zn2+ using metal-organic framework structures for synergistic mildew resistance and enhanced anti-leaching properties

Traditional inorganic anti-mildew materials exhibit limited anti-mildew efficacy when applied to bamboo, while organic anti-mildew reagents face issues of low loading and easy leaching. To address these challenges, this study explored the use of a two-dimensional leaf-shaped zeolitic imidazolate framework (ZIF-L), formed by the coordination of 2-methylimidazole with Zn 2+ , as an anti-fungi additive in polyurethane (PU) coatings. The objective was to enhance the anti-mildew properties of bamboo and its products in outdoor environments. Analysis of the mechanical properties reveals that the dynamic mechanical performance of the modified PU coating is significantly improved compared to that of pure PU coatings. The anti-mildew tests further demonstrate that, compared to inorganic zinc oxide (ZnO) nanoparticles and small-molecule 2-methylimidazole, the ZIF-L structure exhibits a synergistic anti-mildew effect of Zn 2+ and the 2-methylimidazole ligand, resulting in superior mildew resistance. No fungal growth was observed over 28 days. Furthermore, the ZIF-L modified PU coating demonstrated excellent resistance to leaching in a simulated rainfall exposure experiment, with an extremely low leaching rate of anti-mildew agent in the PU coating. The anti-mildew test after the simulated rainfall exposure confirmed its anti-mildew effect remained durable and stable, with significantly lower area of mold infection. These results reveal that the metal–organic framework (MOF) structure effectively immobilizes 2-methylimidazole and Zn 2+ , providing synergistic mildew resistance. The interaction between ZIF-L and PU enhances the anti-leaching properties of the coating.