Magnetic Fe–Cu bimetallic metal organic frameworks and its application for removal of VOCs in wastewater

Metal organic frameworks (MOFs) are widely employed as separable and highly efficient adsorbents in VOCs (volatile organic compounds) pollution in the air. However, due to poor stability and easy hydrolysis in water, traditional MOFs cannot yet be used for the removal of VOCs in wastewater. Here, a novel series of magnetic Fe–Cu bimetallic MOFs possessing dual hydrophilic and hydrophobic functionality was prepared for VOCs removal in wastewater. The materials were characterized using scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicate that both of the morphological and adsorption performance of magnetic Fe–Cu bimetallic MOFs are highly dependent on the molar ratio of ethylenediamine to 4,4-bipyridine used during synthesis. When the molar ratios of ethylenediamine to 4,4-bipyridine are 5:1, 1:1, and 1:5, the morphologies of prepared magnetic Fe–Cu bimetallic MOFs are gravel-like, cobble-like and calcite-like, respectively. They are named as magnetic gravel-like Fe–Cu metal organic frameworks (Mag-Gra-Fe-Cu MOFs), magnetic cobble-like Fe–Cu metal organic frameworks (Mag-CoL-Fe-Cu MOFs) and calcite-like Fe–Cu metal organic frameworks (Mag-CaL-Fe-Cu MOFs). Moreover, the maximum adsorption capacity of Mag-Gra-Fe-Cu MOFs, Mag-CoL-Fe-Cu MOFs and Mag-CaL-Fe-Cu MOFs could reach up to 487.80–621.12 mg/g, 549.45–666.67 mg/g and 598.80–724.64 mg/g, respectively. Under optimal conditions, the adsorption of VOCs onto the magnetic Fe–Cu bimetallic MOFs followed the pseudo-second-order kinetic model (R² = 1) and the Langmuir isotherm model (R² > 0.999). Consequently, the magnetic Fe–Cu bimetallic MOFs developed in this work represent a viable and efficient option for removing VOCs from wastewater. Download: Download high-res image (251KB) Download: Download full-size image