Engineering Superparamagnetic Fe₃O₄@Mg-MOF-74 for Advanced CO₂ Capture Application

This research discusses a novel approach to reduce the demanding regeneration phase in the carbon dioxide adsorption process. Through the employment of the magnetic induction swing adsorption technology, in situ heating adsorbents were developed, which were responsive to the induced magnetic field. The novel material, superparamagnetic Fe₃O₄@Mg-MOF-74, was synthesized via a layer-by-layer approach that integrates iron-(III) oxide (Fe₃O₄) as its magnetic core and Mg-MOF-74 as its highly porous shell in a defined core-shell structure. Ultrasonication and solvothermal methods were adopted to enhance nucleation efficiency and achieve control over particle morphology and phase composition. Morphology analysis using X-ray diffraction and FTIR confirmed the homogeneous formation, while transmission electron microscopy imaging revealed a shell morphology. The composite exhibited thermal stability up to 350 °C, along with favorable surface area (261.24 m²/g) and pore volume (0.23 cm³/g), while displaying mesoporous and multilayer N₂ adsorption. It is a promising CO₂ adsorbent as evaluated in isothermal measurements at 25.00 °C up to 1.20 bar. The Type 1 isotherm plot was revealed, indicative of microporous physisorption. The composite achieved a maximum uptake of 0.60 mmol/g, which was attributed to the porous Mg-MOF-74. Lastly, magnetic analysis using vibrating sample magnetometer demonstrated superparamagnetic behavior from the sigmoidal hysteresis curve. Its high magnetic saturation and minute remanence, at 67.95 A·m²/kg and 1.34 A·m²/kg, respectively, with coercivity at 10.98 G, highlight its excellence responsiveness to magnetic fluctuations, crucial for magnetic hyperthermia and efficient phase transition. The combined properties in Fe₃O₄@Mg-MOF-74 make it a multifunctional adsorbent with strong potential for carbon capture and magnetically assisted regeneration applications.