Magnetic metal-organic frameworks as adsorbents for the detection of azo pigments in food matrices

Azo pigments with azo functional groups (-NN-) are commonly used in foods. Through rational design, here we report synthesis of a novel magnetic metal-organic framework (MOF-545) and the use of Fe₃O₄@MOF-545 for the selective separation of azo pigments from beverages. We find that Fe₃O₄@MOF-545 exhibits excellent adsorption/removal capacities for new coccine (NC, 459 mg g^-1) and lemon yellow (LY, 476 mg g^-1) individually. The results indicated that the adsorption capacities of Fe₃O₄@MOF-545 were 5 times higher than reported previously. The large surface area (120.4 m²/g) and the suitable pore size (1.6 nm) of Fe₃O₄@MOF-545 provided multiple accessible channels for azo pigment adsorption. The adsorption kinetics, stability, recovery, and reusability of Fe₃O₄@MOF-545 were all reported. The recoveries ranged from 92.9 to 104.5%, reflecting the capacity of MOF-545 to efficiently separate NC and LY. Fe₃O₄@MOF-545 is suitable for azo pigment determination and separation in food matrices.