Hg0 removal performance at low temperature by mesoporous MOF-derived Cr2O3 nanoparticle with enriched metal sites and oxygen vacancy: Mechanism study on the role of oxygen species

The oxidation adsorption of Hg0 by metal oxide is an effective method to remove Hg0. A novel high-performance catalyst Cr2O3-MOF was prepared by direct calcination of MIL-101 (Cr) to improve the mercury adsorption capacity of MOFs at lower temperature ranges, overcome the weak resistance to different flue gas components and increase the recycling capacity. Cr2O3-MOF retains the skeleton structure of MOF with small particle sizes and scattered active sites. The oxygen vacancy (OV) formed after calcination can be filled by free oxygen to adjust the catalytic performance of the surface. Thus, Cr2O3-MOF has a mercury removal capacity to be reached at 100% in a wide temperature range (30–200 °C), especially has the ability of mercury adsorption at room temperature that many MOF adsorbents do not have. After continuous adsorption at 30 °C for 50 h, the mercury removal efficiency was maintained at 90.3%, and it could be recycled. Cr2O3-MOF also has excellent resistance to flue gas components such as SO2, NH3, NO, and H2O. Based on different characterization methods and density functional theory (DFT), the transition state theory explains that adsorbed oxygen (OAds) filled in OV has higher mercury capture activity than that of natural lattice oxygen (OLat) in the adsorbent. More importantly, compared with noble metal supported monatomic catalysts, Cr2O3-MOF has a lower cost with higher mercury removal efficiency, it has more industrial application prospects.