Thioether-based recyclable metal-organic frameworks for selective and efficient removal of Hg2+ from water.

Hg2+ is highly toxic and hazardous and widely found in polluted water. To remove mercury ions from wastewater, there is an urgent need to investigate and develop new adsorbents. Herein, we synthesized three novel thioether-based metal-organic frameworks (MOFs) through a facile diffusion method or a solvothermal strategy, i.e. [(ZnCl2)3(L1)2·χ(solvent)]n (1), [(Cu2I3O2)4(CH4N0.5)4(L1)4(DMA)4·3(H2O)·χ(solvent)]n (2) and [(CuBr2)2(L2)2 CH3CN·χ(solvent)]n (3), where L1 = 1,3,5-tris((pyridin-4-ylthio)methyl)benzene and L2 = 2,4,6-trimethoxy-1,3,5-tris((pyridin-4-ylthio)methyl)benzene. The obtained thioether-based MOFs were characterized by single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis and thermogravimetric analysis. Further studies revealed that they could remove Hg2+ from water. They have high adsorptivity (up to 362 mg g-1) and are highly efficient in removing Hg2+ (up to 95%). Besides, these MOFs can be recycled and can selectively remove Hg2+ from water in the presence of other metal ions. Consequently, these MOFs are highly promising candidates for the selective absorption and removal of mercury ions from water.