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.