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[Display omitted] • Co/Fe co-doped ZIF-8 derived porous carbon for CDI removal of Cu2+ ions. • A stable carbon cage encapsulated a porous carbon structure. • CoFe-NC has better selectivity for Cu2+ ions. • CoFe-NC shows higher electrosorption capacity in application of CDI. Due to a threat to human life from heavy metal ions pollution, unprecedented interest has been gained in the development of water purification technologies. Here, we explore another new approach to exploit a prospective carbon material for removing copper ions from aqueous solution based on rapid and easy capacitive deionization (CDI). Reasonable carbon materials modification with ideal composition and improved morphological structure is essential to additionally optimize the capabilities of CDI. We prepared a nitrogen-rich hierarchically porous carbon composites (CoFe-NC) with uniform cobalt (Co) and iron (Fe) doped metal in carbon skeleton by a simple impregnation and pyrolysis method, derived from zeolitic imidazolate framework-8, to use as highly effective CDI electrode for copper ions removal. The addition of Fe can facilitate the uniform dispersion of metals, and enable the formation of a stable carbon cage after pyrolysis. It can sufficiently expose active sites of the electrode materials and promote interfacial charge transfer, thus improving CDI electrosorption efficiency. CoFe-NC composites electrode can achieve outstanding deionization capacity (91.31 mg g−1) in 25 mg L−1 CuSO 4 solution. The carbon cage structure of CoFe-NC not only prevents aggregation of metals and avoids destruction of rich multistage pore system by pyrolysis, but also induces a faster ions transport rate. In addition, density functional theory calculations demonstrated that the co-doping of Co and Fe can remarkably increase the adsorption energies of Cu2+ ions, leading to excellent selectivity, which indicates that CoFe-NC composites can be a desired CDI electrode material. [ABSTRACT FROM AUTHOR]

• Synergistic electrosorption of HBC bilayers and MoS 2 for Cu2+ complexation. • HBC shows excellent structural stability before and after MoS 2 loading. • High selective ion removal effect is still achieved in the presence of complex ions. • Used as an electrode in capacitive deionization technology. Capacitive deionization has been considered as a promising wastewater treatment technology because of its low-cost and highly efficient. Herein, we prepared hollow bowl-type carbon materials loaded with molybdenum sulfide (HBC-MoS 2) composites and fabricated it as an innovative electrode material to remove Cu2+ in a multi-ion coexistence system. With the synergistic effect of electric double layer (EDL) and complexation between MoS 2 and Cu2+, the HBC-MoS 2 -0.02 electrode achieved effective removal of copper ions from low concentration wastewater (25 mg/L) and high electrosorption capacity of 28.97 mg g−1 at 1.0 V. Even in the presence of competing ions (Na+/Zn2+/Cu2+), the HBC-MoS 2 -0.02 electrode still can effectively remove Cu2+ with a final adsorption capacity of 28 mg g−1, showing its superiority. The mechanism of Cu2+ removal by HBC-MoS 2 is mainly due to the synergistic effect of EDL and complexation. [ABSTRACT FROM AUTHOR]