Potassium benzoate-cyclodextrin metal-organic frameworks with multi-dimensional cavities: An adsorbent for removing...

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.