Magnetic amino-functionalized-MOF(M = Fe, Ti, Zr)@COFs with superior biocompatibility: Performance and mechanism on adsorption of azo dyes in soft drinks

Azo dyes in soft drinks present a serious risk to human health and are strictly limited in many countries. Herein, we demonstrate that covalent-organic framework (COF) can be facilely grown on magnetic metal–organic framework (MOF) to form three kinds of porous Fe3O4@MOF(M = Fe, Ti, Zr)@COFs composites for efficient azo dyes adsorption. Adsorption performances of Fe3O4@MOF(M = Fe, Ti, Zr)@COFs toward azo dyes were systemically investigated by adsorption kinetics, adsorption isotherms and adsorption thermodynamics. Under optimized conditions, the maximum adsorption capacities of both Fe3O4@MOF(Fe)@COF and Fe3O4@MOF(Zr)@COF for Congo red (CR) are 1250.02 and 625.13 mg g−1, and the Fe3O4@MOF(Ti)@COF for Chrysoidine (CYD) is 294.12 mg g−1, all which are higher than those of mostly previous reports. Furthermore, possible mechanisms of adsorption were revealed through Fourier-transform infrared spectra and X-ray photoelectron spectroscopy analysis. These Fe3O4@MOF(M = Fe, Ti, Zr)@COFs composites also present good biocompatibility, and exhibit high adsorption capacities for CR or CYD in soft drinks, which can be suggested as effective adsorbents for the azo dyes removal from soft drinks.