One-pot synthesis of O-doped BN nanosheets as a capacitive deionization electrode for efficient removal of heavy metal ions from water

O-Doped BN nanosheets with a thickness of 1.033 nm were prepared via the direct reaction of CuB23 with NOCl at room temperature in ionic liquids. It had a large high specific surface area of 858 m2 g−1, and showed a high electrical conductivity of 34.3 S m−1 and a good specific capacity of 187 F g−1. Meanwhile, the obtained sample demonstrated excellent performance as the electrode material for capacitive deionization (CDI) to remove Cd2+ from water in a wide range of concentrations from 0.05 to 600 ppm with a maximum adsorption capacity of 2281 mg g−1. It is attributed to its unique structural characteristics and the ability of its NO– groups to coordinate Cd2+ which promotes the electrosorption. More importantly, it exhibited outstanding capability for the total, rapid, and simultaneous removal of multiple metal ions (Zn2+, Cd2+, Pb2+, Ni2+, Co2+, Cu2+, Mg2+, Ca2+, Fe2+, Fe3+ and Na+) by CDI within 20 min. These results suggest promising applications of our BNO nanosheets for water purification and water-softening devices based on CDI.