Controllable Preparation\nof a N‑Doped Hierarchical\nPorous Carbon Framework Derived from ZIF‑8 for Highly Efficient\nCapacitive Deionization

Abstract

Capacitive deionization (CDI) is a promising desalination\ntechnology,\nand metal–organic framework (MOF)-derived carbon as an electrode\nmaterial has received more and more attention due to its designable\nstructure. However, MOF-derived carbon materials with single-pore\nstructures have been difficult to meet the technical needs of related\nfields. In this work, the ordered hierarchical porous carbon framework\n(OMCF) was prepared by the template method using zeolitic imidazolate\nframeworks-8 (ZIF-8) as a precursor. The pore structures, surface\nproperties, electrochemical properties, and CDI performances of the\nOMCF were investigated and compared with the microporous carbon framework\n(MCF), also derived from ZIF-8. The results show that the hierarchical\nporous carbon OMCF possessed a higher specific surface area, better\nhydrophilic surface (with a contact angle of 13.45°), and higher\nspecific capacitance and ion diffusion rate than those of the MCF,\nwhich made the OMCF exhibit excellent CDI performances. The adsorption\ncapacity and salt adsorption rate of the OMCF in a 500 mg·L^–1 NaCl solution at 1.2 V and a 20 mL·min^–1 flow rate were 12.17 mg·g^–1 and 3.34 mg·g^–1·min^–1, respectively, higher\nthan those of the MCF. The deionization processes of the OMCF and\nMCF closely follow the pseudo-first-order kinetics, indicating the\ndouble-layer capacitance control. This work serves as a valuable reference\nfor the CDI application of N-doped hierarchical porous carbon derived\nfrom MOFs.