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

Abstract

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 (111), (200), and (220) 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.