Core–shell hybrid zeolitic imidazolate framework-derived hierarchical carbon for capacitive deionization

Abstract

We introduce a viable strategy for the fabrication of core–shell ZIF-8@PVP–PDA/Zn by in situ 2-methylimidazole-assisted dopamine self-polymerization. The role of polyvinyl pyrrolidone (PVP) and 2-methylimidazole (2-MI) towards ZIF-8@PVP–PDA/Zn formation is systematically demonstrated. In particular, 2-MI not only is employed as the organic ligand for ZIF-8 but also provides an alkaline environment for the polymerization of dopamine. Moreover, it also protects the ZIF-8 structure from etching. After pyrolysis, the ZIF-8@PVP–PDA/Zn is converted into ant-nest-like hierarchical carbon (ANHC), which has a wide pore distribution, high pore volume (2.35 cm³ g⁻¹) and high nitrogen (7.12%) content. Superior capacitive deionization (CDI) performance (25.4 mg g⁻¹) and stable electrosorption cycles of ANHC are achieved, which demonstrates its potential for CDI applications.