Regulation of the Sulfur Environment in Clusters to Construct a Mn-Sn 2 S 6 Framework for Mercury Bonding.

The remarkable chemical activity of metal-sulfur clusters lies in their unique spatial configuration associated with the abundant unsaturated-coordination nature of sulfur sites. Yet, the manipulation of sulfur sites normally requires direct contact with other metal atoms, which inevitably changes the state of the coordinated sulfur. Herein, we facilely construct a Mn-Sn 2 S 6 framework by regulating the sulfur environment of the [Sn 2 S 6 ] 4- cluster with metal ions. Mn-Sn 2 S 6 showed superior removal performance to gaseous elemental mercury (Hg 0 ) at low temperatures (20-60 °C) and exhibited high resistance against SO 2 . Moreover, Mn-Sn 2 S 6 can completely remove liquid Hg 2+ ions with low or high concentrations from acid wastewater. In addition, the adsorption capacities of Mn-Sn 2 S 6 toward Hg 0 and Hg 2+ reached 21.05 and 413.3 mg/g, respectively. The results of physico-chemical characterizations revealed that compared with Cu 2+ , Co 2+ , and Fe 2+ , the moderate regulation of Mn 2+ led to the special porous spherical structure of Mn-Sn 2 S 6 with uniform element distribution, due to the difference of electrode potentials [ E θ (Mn 2+ /Mn) < E θ (S/S 2- ) < E θ (Sn 4+ /Sn 2+ )]. The porous structure was beneficial to Hg 0 and Hg 2+ adsorption, and the presence of Mn 4+ /Mn 3+ and S 1- promoted the oxidation of Hg 0 , resulting in stable HgS species. The constructed Mn-Sn 2 S 6 , thus, is a promising sorbent for both Hg 0 ang Hg 2+ removal and provides guidelines for cluster-based materials design and tuning.