Different strengthening effects of amino and nitro groups on the bisphenol A adsorption of an aluminum metal-organic framework in aqueous solution

In recent years, metal-organic frameworks (MOFs) have been employed in numerous applications for adsorption. Researchers synthesize new MOFs by various methods, including the introduction of functional groups. In this study, three different aluminum-based MOFs (with non-functionalized, amino-functionalized, nitro-functionalized) were produced by hydrothermal synthesis and used for investigating typical endocrine disrupting chemicals (EDCs), namely for bisphenol A (BPA) adsorption. We used several methods to characterize the MOFs and conducted batch adsorption experiments to investigate their adsorption properties, and explore the influence of different functional groups on adsorption materials. The specific surface area of Al-MOF-NH2 is 6 times larger than that of Al-MOF according to the N2 adsorption and desorption isotherms of the material, that is, the BET of Al-MOF, Al-MOF-NH2, and Al-MOF-NO2 were 109.68, 644.03, and 146.60 m2/g. Note that although the same synthesis method is used, pore size is greatly changed because of the different functional groups. Al-MOF and Al-MOF-NO2 have more mesopores, and Al-MOF-NH2 is mainly microporous. The BPA adsorption capacities of Al-MOF, Al-MOF-NH2, and Al-MOF-NO2 were 46.43, 227.78, and 155.84 mg/L. The outcomes can also be explained by the improved adsorption performance from the addition of amino functional groups. In this research, the adsorption isotherms and adsorption kinetics of the three Al-MOFs for BPA were also investigated to explain the different adsorption properties of various functional groups. The results show that the amino-functionalized materials have remarkable characterization morphologies, uniform particle distributions, appropriate particle sizes, excellent specific surface areas, and superior adsorption effects.