High-performance and selective adsorption of ZIF-8/MIL-100 hybrids towards organic pollutants

Abstract

Environmental contamination by organic pollutants has become a pressing concern. In this study, metal–organic framework composites with a core–shell structure of MIL-100 wrapped around ZIF-8 (ZIF-MIL hybrids) were synthesized and characterized for their effectiveness to remove organic pollutants. First, a sequence of routine characterizations will examine the ZIF-MIL series samples' physicochemical properties and morphological characteristics. Then, the adsorption capacities of ZIF-MIL towards organic pollutants, including cationic dyes (methylene blue (MB), and rhodamine B (RHB)), anionic dyes (methyl orange (MO)), neutral pollutants (Sudan III (SD-III), tetracycline (TC) and amoxicillin (AMX)), were investigated. Among the ZIF-MIL series, ZIF-MIL-4 has an excellent specific surface area with high uptake of TC (1288 mg g⁻¹) and RHB (1181 mg g⁻¹). Based on the adsorption data from kinetic and dynamic studies, the adsorption process was closest to the pseudo-second-order kinetic model and Freundlich isotherm. In terms of thermodynamic parameter values, the adsorption of TC is an endothermic and spontaneous process, while the adsorption of RHB is an exothermic and spontaneous process. Furthermore, the reusability and selectivity studies of ZIF-MIL-4 towards TC and RHB exhibited significant regeneration ability and high selectivity. The effects of ionic strength and pH on pollutant removal efficiency were also tested. The experimental results showed that the main interactions between ZIF-MIL-4 and RHB or TC were weak coordination, electrostatic, hydrogen bonding, and π–π stacking interactions. Thus, the proposed MOF hybrid, by forming mixtures with other MOFs, can be a potential purifier with improved adsorption capacity and selectivity for organic pollutants as well as self-reusability.