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 (Sx2-, X = 3, 4, 6) on the surface of a metal organic framework (MOF; type benzene-1,3,5-tricarboxylic/Cu(II). They are referred to as Sx-MOFs and were used for highly selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions. The structure of the Sx-MOFs was characterized by Raman spectroscopy, FT-IR, X-ray diffraction, and scanning electron microscopy. The Raman spectra of Sx-MOF is similar to the bare MOF and shows the MOFs structure to be well retained after Sx functionalization. The selective interaction of Sx with soft metal ions and the high surface area of MOFs resulted in excellent affinity and selectivity for ions such as Hg(II). The Sx-MOFs of type S4-MOF had the highest distribution coefficient Kd value (~107) and best extraction recovery (~100%) for Hg(II). The S4-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 0.13 μg L-1. The S4-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 S4-MOF is an excellent adsorbent for sorption of heavy metal ions even in the presence of the relatively high concentration of other ions. Graphical abstract A composite was synthesized via direct assembly of polysulfides (Sx2-, X = 3, 4, 6) on surface of the metal organic framework (Sx-MOF) and was used for selective and efficient extraction of ultra-trace amounts of heavy metal ions from aqueous solutions.