Hexagonal boron nitride (h-BN), as a novel carbon-free layered material, has received extensive attention owing to its high mechanical strength and excellent chemical and thermal stability. Herein, an h-BN nanosheet is employed to capture elemental mercury (Hg-0) from simulated flue gas in a fixed-bed reactor at low temperatures. The h-BN displays mercury adsorption capability with the Hg-0 removal efficiency of 26.4-43.6% within 50-200 degrees C. CuS decoration can remarkably enhance the mercury capture performance of h-BN. The 10CuS/h-BN with a CuS loading value of 10 wt % performs the best. Complete mercury capture can be achieved over 10CuS/h-BN at 50-100 degrees C. The presence of NO inhibits Hg-0 removal to some extent, while the presence of SO2 hardly shows any impact on Hg-0 capture. The copper and polysulfide sites as well as the nanoscale lamellar structure of h-BN account for the good Hg-0 capture performance of CuS-loaded h-BN.