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

Azo pigments with azo functional groups (-N--N-) 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) individ-ually. 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 reus-ability 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.