Magnetic mesoporous Co/Ni ZIF-derived core–shell hollow nanocomposites for efficient removal of methylene blue and tetracycline chloride

In view of the urgent need for efficient and low-cost treatment of organic pollutants in printing and dyeing wastewater, magnetic porous adsorbents have attracted significant attention owing to their high efficiency and reusability. Herein, magnetic bimetallic zeolitic imidazolate framework (mZIFs) nanoparticles with Fe₃O₄ cores were synthesized as the initial precursor. Subsequently, the novel hollow mZIFs core–shell nanocomposites (defined as mNCs) were prepared through a mild tannic acid etching method, designed for efficient removal of organic pollutants from wastewater. The mNCs displayed remarkable adsorption potential, reaching up to 879.49 mg/g for methylene blue (MB) and 262.50 mg/g for tetracycline hydrochloride (TC) at 303 K, with adsorption following the pseudo-second-order kinetic model and fitting well to the Langmuir isotherm. Thermodynamic analysis revealed that the adsorption of MB and TC by mNCs proceeds spontaneously through an endothermic process, and the mNCs retained over 80% of their MB removal efficiency even after five adsorption–desorption cycles. These results highlight the potential of mNCs as an efficient and reusable adsorbent for eliminating organic contaminants in wastewater treatment.