Synthesis of Water Stable γ-Cyclodextrin Metal-Organic Frameworks as a Carbon Dioxide-Selective Layer for...

Modified atmosphere packaging (MAP) is widely used in the preservation of fruit, but CO₂ concentration in most MAP continues to increase because of the respiration of fruit, which causes CO₂ injury to fruit. Herein, a three-layer composite film is prepared by using a layer-by-layer stacking method, with diphenyl carbonate crosslinked cyclodextrin metal-organic framework (DPC-CL-CD-MOF) as the inner layer, polycaprolactone nanofiber film as the middle layer, and chitosan casting film as the outer layer. Among three layers, the DPC-CL-CD-MOF layer can increase the CO₂ permeability and CO₂/O₂ selectivity of the composite film because of its CO₂ adsorption capacity. The film exhibits moderate thermal stability but lacks mechanical strength. Gas permeability tests show that with increasing DPC-CL-CD-MOF loading content from 5% to 15%, the CO₂ permeability coefficient decreases of the film from 2002.16 to 582.69 barrer. The CO₂/O₂ selectivity peaks at 19.12 with 10% DPC-CL-CD-MOF. When applied in preserving fresh-cut pears under active MAP conditions (5% O₂, 10% CO₂), the three-layer composite film with 10% DPC-CL-CD-MOF effectively prevents fresh-cut pears from CO₂ injury, inhibiting browning and softening of pears, reducing polyphenol oxidase activity, malondialdehyde content, and hydrogen peroxide content of fresh-cut pears.