Mercury, as a highly poisonous pollutant, poses a severe threat to the global population. However, the removal of Hg0 can only be carried out at below 100 °C due to the weak binding of the adsorbent. Herein, a series of carbon-based materials with different coordination environments and atomic dispersion of single-site manganese were prepared, and their elemental mercury removal performance was systematically investigated. It was demonstrated that the coordination environment around manganese determines its electronic structure and size, thus affecting its affinity with mercury. The obtained best adsorbents atomically dispersed Mn with atom size near 0.2 nm, achieves high Hg0 removal efficiency and over 13 mg/g Hg0 adsorption capacity at 200 °C. And the SO2 resistance performance of single atoms (∼0.2 nm) is much better than clusters (∼1-2 nm) because of its high selectivity, that the effect of SO2 is only 3%. Density functional theory (DFT) reveals that Mn with four-nitrogen atoms (Mn-N4-C═O) is more active than other number nitrogen coordination materials. Moreover, the presence of carboxyl groups around manganese also promotes affinity for Hg0. This work might shed new light on the enhancement of Hg0 affinity in carbon-based materials and the rational design of the coordination structure of the tunable Hg0 activities.
Keywords: SO2 resistance; coordination environment; elemental mercury; high-temperature adsorption; single atoms.