Potassium benzoate-cyclodextrin metal-organic frameworks with multi-dimensional cavities: An adsorbent for removing aldehyde fishy odorants in aquatic products.

Fishy odorants substantially impair the flavor and quality of aquatic products, creating an urgent need for safe and effective deodorization methods. Herein, potassium benzoate-cyclodextrin metal-organic frameworks (PB-CD-MOFs) with multi-dimensional cavities was formulated to remove fishy odorants (2,4-decadienal, 4-heptenal, and nonanal). And the underlying adsorption mechanism of PB-CD-MOFs for fishy odorants was clarified by adsorption kinetics, isotherms, thermodynamics, and density functional theory (DFT) calculations. Based on the Single-crystal X-ray diffraction (SCXRD) analysis, PB-CD-MOFs possessed a multi-dimensional cavity structure featuring two distinct pore channels. The larger pores (9.5 Å) were from the cavities of γ-CD, while the smaller pores (7.8 Å) were formed through the self-assembly of PB and γ-CD. Compared with γ-CD, PB-CD-MOFs showed fourfold adsorption capacity, probably due to its multi-dimensional pores. Meanwhile, PB-CD-MOFs exhibited excellent adsorption capacities for 2,4-decadienal, 4-heptenal, and nonanal (238.55, 196.91, and 213.88 mg/g), which can be attributed to aldehydes entering the multi-dimensional pore channels and binding to active sites on the pore walls, as evidenced by DFT calculations. The adsorption process followed the pseudo-first-order kinetic model, indicating physisorption. According to the adsorption isotherms of Langmuir, Freundlich, and Redlich-Peterson, PB-CD-MOFs underwent multi-layered heterogeneous adsorption. Thermodynamic and DFT analysis illustrated that the adsorption was a spontaneously exothermic reaction and also revealed that hydrogen bonding and van der Waals forces were the principal driving forces for aldehyde adsorption by PB-CD-MOFs. The research offers a new approach to remove fishy odorants, elucidates the related mechanism, and facilitates broader application of CD-MOFs in the food industry.