A metal organic framework prepared from benzene-1,3,5-tricarboxylic acid and copper(II), and functionalized with various polysulfides as a sorbent for selective sorption of trace amounts of heavy metal ions

Novel composites were obtained via direct assembly of polysulfides (S-x(2-), X=3, 4, 6) on the surface of a metal organic framework (MOF; typebenzene-1,3,5-tricarboxylic/Cu(II). Theyare referred to asS(x)-MOFs and were used for highly selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions. The structure of theS(x)-MOFs was characterized by Raman spectroscopy, FT-IR, X-ray diffraction, and scanning electron microscopy. The Raman spectra of S-x-MOF is similar to the bare MOF and shows the MOFs structure to be well retained after S-x functionalization. The selective interaction of S-x with soft metal ions and the high surface area of MOFs resulted inexcellent affinity and selectivity for ions such as Hg(II). The S-x-MOFs of type S-4-MOF had the highest distribution coefficient K-d value (10(7)) and best extraction recovery (100%) for Hg(II). The S-4-MOF also has high selectivity in the following order: Hg(II) >>Pb(II)>Zn(II)>Ni(II)>Co(II). The binding process of the metals occurs via M-S bonding. The ions were quantified by inductively coupled plasma optical emission spectrometry (ICP-OES). The detection limit for Hg(II) is 0.13gL(-1). The S-4-MOF was applied to the extraction of trace metal ions from natural and contaminated waters and data were compared with other sorbets. The results revealed that S-4-MOF is an excellent adsorbent for sorption of heavy metal ions even in the presence of the relatively high concentration of other ions.