Magnetic double-layer MOF nanocomposites Fe3O4@ZIF-8@ZIF-67 for efficient adsorptive removal of organic dye and antibiotic

Abstract

A magnetic double-layer metal-organic framework composite (Fe₃O₄@ZIF-8@ZIF-67) was successfully synthesized through a facile layer-by-layer self-assembly method at room temperature and thoroughly characterized using various techniques. The composite Fe₃O₄@ZIF-8@ZIF-67 was explored as an adsorbent for the removal of two harmful organic pollutants, Congo red (CR) and tetracycline hydrochloride (TC). Some essential parameters, including initial concentration, adsorbent dose, contact time, pH, and temperature, were systematically optimized. Under optimal conditions, Fe₃O₄@ZIF-8@ZIF-67 demonstrated the maximum adsorption capacities of 276.77 mg/g for CR and and 356.12 mg/g for TC, respectively. The double-layer structure endowed Fe₃O₄@ZIF-8@ZIF-67 high adsorption efficiency for CR (99.44%) than the pristine Fe₃O₄@ZIF-8 (73.26%). Adsorption kinetics and isotherms studies revealed that the adsorption process followed pseudo-second-order kinetics and Langmuir model, indicating a monolayer chemisorption-dominated mechanism. Furthermore, the spent Fe₃O₄@ZIF-8@ZIF-67 was regenerated through a Fenton-like oxidative degradation reaction, maintaining a removal efficiency above 70% after three consecutive cycles. With its facile synthesis, cost-effectiveness, mild operating conditions, and high selectivity for anionic dyes, Fe₃O₄@ZIF-8@ZIF-67 emerges as a highly promising material for advanced wastewater treatment applications.