A designable magnetic MOF composite and facile coordination-based post-synthetic strategy for the enhanced removal of Hg2+ from water

Abstract

A magnetic MOF composite was successfully prepared by a novel and green strategy through reasonable design. The nano Fe₃O₄@SiO₂ core was first coated by a shell of Cu(OH)₂ as the self-template, followed by a conversion of Cu(OH)₂ into HKUST-1 at room temperature in a water–ethanol mixture solvent, and Fe₃O₄@SiO₂@HKUST-1 core–shell nanostructures were obtained successfully. Based on this, a Bi-I-functionalized-magnetic HKUST-1 composite was prepared through a flexible coordination-based post-synthetic strategy. Powder X-ray diffraction spectrometry, N₂ sorption–desorption isotherms and Fourier transform infrared spectroscopy were used for the characterization of the magnetic MOF composites. The core–shell morphology was confirmed by transmission electron microscope images and the result of thermogravimetric analysis showed that the magnetic composites had excellent thermal stability. Besides, the adsorption of Hg²⁺ on Fe₃O₄@SiO₂, Fe₃O₄@SiO₂@HKUST-1 and Bi-I-functionalized magnetic MOF composites was investigated, and a good adsorption selectivity of Bi-I-functionalized magnetic MOF composites towards Hg²⁺ was demonstrated, with high adsorption capacity (264 mg g⁻¹) and fast adsorption dynamics. The Bi-I-functionalized magnetic HKUST-1 composite was then successfully employed for the selective removal of Hg²⁺ from water, demonstrating great potential application of the prepared magnetic MOF composite as a fascinating adsorbent in environmental monitoring.