Solvent-assisted ligand exchange as a post-synthetic surface modification approach of Zn-based (ZIF-7, ZIF-8) and Co-based (ZIF-9, ZIF-67) zeolitic frameworks for energy storage application

In this research, we tried to change in overall ZIF structure by adding another linker via post-synthetic solvent-assisted ligand exchange (SALE) and investigated the energy storage properties as a supercapac-itor. To identify materials, these analyzes were performed, such as PXRD to confirm the structure of four hybrids (ZIF-7@ZIF-8, ZIF-8@ZIF-7, ZIF-9@ZIF-67, and ZIF-67@ZIF-9). The functional groups of each ligand were identified using FT-IR and C-13 NMR. SEM images confirm the material morphology and the EDX spectrum for the distribution of elements in the structures as well as for supercapacitor application. These studies used KOH 6 M as the electrolyte and included cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). As the best compound, ZIF-67@ZIF-9, at a current density of 3 A/g, had a high specific capacitance of 300 F/g. The following section covers how to construct an asymmetric supercapacitor using activated carbon as a negative electrode and a ZIF-67@ZIF-9 as a positive electrode. In current densities of 1 and 20 A/g, this device can supply specific energy up to 8.1 Wh/kg and specific power of 16 kW/kg and retains 89 % of its capacitance after 3000 cycles. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this research, the overall ZIF structure was modified by introducing another linker using post-synthetic solvent-assisted ligand exchange (SALE), and its energy storage properties as a supercapacitor were investigated. Various analyses were conducted to identify the materials, and the functional groups of each ligand were determined. The performance of the materials was evaluated through electrochemical tests using different electrolytes. The study identified the best compound and discussed the construction of an asymmetric supercapacitor. The asymmetric supercapacitor exhibited high specific capacitance, specific energy, and retained its capacitance after multiple cycles.