Transition metal-coordinated metastable [MoS4]2- cluster for SO2-facilitated gaseous mercury adsorption from wet flue gas.

The removal of gaseous elemental mercury (Hg0) from SO2-containing wet flue gas via adsorption is hindered by surface sulfation and pore clogging on adsorbents. This study addresses these challenges by leveraging the metastable [MoS4]2- cluster, which converts to MoSx induced by SO2 under wet conditions. By coordinating transition metal ions (M = Cu, Zn, Mn, Ni) with [MoS4]2-, we simultaneously achieved the regulation of active sulfur sites and the enhancement of SO2 on Hg0 adsorption. Cu-MoS4 exhibited a porous heterostructure of MoSₓ and CuS, achieving a superior Hg0 adsorption capacity of 337.4 mg/g. Notably, Cu-MoS4 demonstrated significantly higher Hg0 removal efficiency in the presence of both SO2 and H2O compared to their individual effects. Mechanistic studies revealed that Cu2+ coordination increased unsaturated coordinated Sn2- and high-valent Mo6+ proportions. The SO32- wet interface formed on Cu-MoS4 by SO2 and H2O underwent reverse disproportionation with S2-, replenishing 42.6 % of Sn2- sites, thereby enhancing its performance. This work introduces a novel approach combining ex-situ and in-situ regulation of sulfur coordination environments, offering material and methodological advancements for Hg0 removal from industrial flue gas.