Eco-Friendly, Multifunctional Antibacterial Chitosan/Covalent Organic Framework Composite Films via Molecular Weaving...

Chitosan-based eco-friendly packaging materials present a promising route to alleviate mitigating greenhouse gas emissions and global climate change by replacing traditional petroleum-based packaging materials used for food preservation. Nevertheless, the practical application of chitosan-based films is hindered by insufficient antimicrobial activity and susceptible to breakage. In this study, a covalent organic framework (TpPa-SO₃H) was synthesized at room temperature and exhibited inhibitory efficacies of 90.92% and 92.53% against Escherichia coli and Staphylococcus aureus. Chitosan/TpPa-SO₃H film was formed through a molecular weaving strategy, and its elongation at break and tensile strength were remarkably enhanced to 148% and 403%, respectively, influenced by the concentration of TpPa-SO₃H and the molecular weight of chitosan. The composite film achieves exceptional oxygen and carbon dioxide barrier properties. The water vapor control ability of the film depends on the hydrophilicity of TpPa-SO₃H, while the UV blocking ability is mainly attributed to UV light harvesting and photocatalysis activity of TpPa-SO₃H. The shelf life of grapes, strawberries, and blueberries has doubled thanks to the preservation of the Chitosan/TpPa-SO₃H film, while maintaining the postharvest quality and antioxidant activity of the fruits. Furthermore, the Chitosan/TpPa-SO₃H film for 45 days underwent considerable degradation. All the contributors make chitosan film an eco-friendly packaging material for fruit preservation.