Citral Encapsulated into a Zeolite Imidazolate Framework-67 (ZIF-67) Cage via Biomimetic Mineralization as an Efficient Preservative for Long-Term Antimildew Efficacy of Bamboo

Natural mildew preventives, like citral, have great potential to protect bamboo from mildew, while their long-lasting antimildew performance is yet to be challenged owing to their oxidability and volatility. Inspired by biomimetic mineralization, in this work, citral@ZIF-67 particles were synthesized by encapsulating citral into a zeolite imidazolate framework-67 (ZIF-67) cage and introduced into a bamboo structure. Benefiting from the unique cage structure and large surface area of ZIF-67, it can encapsulate sufficient citral molecules. The encapsulation reduced the particle size of ZIF-67 due to the nucleation of citral. Furthermore, the surface area, pore size, and volume of citral@ZIF-67 particles gradually decreased with the increase in loading amounts of citral. ZIF-67 exhibited a certain antibacterial ability against E. coli and S. aureus. The encapsulation of citral can further enhance the antibacterial activity of ZIF-67. In addition, the citral@ZIF-67 showed slow-release performance that followed the Fickian diffusion mechanism. After the citral@ZIF-67 treatment, bamboo showed no mold spots on the surface with an infection grade of 0, which was retained, even though bamboo was conditioned at 50 °C and 85% relative humidity for 10 days. This proposed method can effectively improve the stability of natural mildew preventives and endow bamboo with long-term antimildew properties with low cost and minimized environmental impacts.