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 Fe 3 O 4 @MOF-545 for the selective separation of azo pigments from beverages. We find that Fe 3 O 4 @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 Fe 3 O 4 @MOF-545 were 5 times higher than reported previously. The large surface area (120.4 m 2 /g) and the suitable pore size (1.6 nm) of Fe 3 O 4 @MOF-545 provided multiple accessible channels for azo pigment adsorption. The adsorption kinetics, stability, recovery, and reusability of Fe 3 O 4 @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. Fe 3 O 4 @MOF-545 is suitable for azo pigment determination and separation in food matrices.