Porous carbon with uniformly distributed cobalt nanoparticles derived from ZIF-67 for efficient removal of vapor elemental mercury: A combined experimental and DFT study

A novel N-doped porous carbon (NC) adsorbent with uniformly distributed Cobalt nanoparticles (Co/NC) for vapor elemental mercury removal was synthesized by direct pyrolysis of zeolitic imidazolate framework 67 (ZIF-67). Doped N atoms and uniformly distributed cobalt nanoparticles in the carbon framework of Co/NC provided both physisorption and chemisorption sites for mercury removal. Specifically, Co/NC exhibited a strong affinity for Hg0 over a broad range of temperatures (30–240 °C) with the average Hg0 removal efficiency higher than 85%. DFT calculations revealed that mercury was mainly chemisorbed on crystal planes (1 1 1), (2 0 0), and (2 2 0) of cobalt nanoparticles, and physically adsorbed on doped nitrogen in the carbon framework. Moreover, exposed facets with nanoscale anisotropic morphologies significantly affected the mercury removal performance of Co/NC, indicating that Hg0 adsorption on Co/NC was morphology-dependent. These results contributed an in-depth understanding of structural and sorption properties of ZIF-67-derived carbon sorbents, and suggested that fixed-bed of such materials can be integrated into the mercury emission control technology for ultra-low emission power stations.