Carbonization of MOF-5/Polyaniline Composites to N,O-Doped Carbon/ZnO/ZnS and N,O-Doped Carbon/ZnO Composites with High Specific Capacitance, Specific Surface Area and Electrical Conductivity

Abstract

Composites of carbons with metal oxides and metal sulfides have attracted a lot of interest as materials for energy conversion and storage applications. Herein, we report on novel N,O-doped carbon/ZnO/ZnS and N,O-doped carbon/ZnO composites (generally named C-(MOF-5/PANI)), synthesized by the carbonization of metal–organic framework MOF-5/polyaniline (PANI) composites. The produced C-(MOF-5/PANI)s are comprehensively characterized in terms of composition, molecular and crystalline structure, morphology, electrical conductivity, surface area, and electrochemical behavior. The composition and properties of C-(MOF-5/PANI) composites are dictated by the composition of MOF-5/PANI precursors and the form of PANI (conducting emeraldine salt (ES) or nonconducting emeraldine base). The ZnS phase is formed only with the PANI-ES form due to S-containing counter-ions. XRPD revealed that ZnO and ZnS existed as pure wurtzite crystalline phases. PANI and MOF-5 acted synergistically to produce C-(MOF-5/PANI)s with high SBET (up to 609 m2 g−1), electrical conductivity (up to 0.24 S cm−1), and specific capacitance, Cspec, (up to 238.2 F g−1 at 10 mV s−1). Values of Cspec commensurated with N content in C-(MOF-5/PANI) composites (1–10 wt.%) and overcame Cspec of carbonized individual components PANI and MOF-5. By acid etching treatment of C-(MOF-5/PANI), SBET and Cspec increased to 1148 m2 g−1 and 341 F g−1, respectively. The developed composites represent promising electrode materials for supercapacitors.

Environmental Potential of Carbonized MOF-5/PANI Composites for Pesticide, Dye, and Metal Cations—Can They Actually Retain Them All?

“…The cMOF.E and cMOF.EBc samples show mean particle sizes of 145 and 139 nm, respectively, whil similar value is obtained for the cMOF sample, 132 nm. These differences in the me particle size and particle size distribution of the tested materials may be associated w the more hydrophilic surface of cMOF.ESb, indicated by thermogravimetric measu ments [29], and its better dispersibility in water, in comparison to the cMOF.EB sample…”

“…Two forms of PANI, synthesized by the oxidative polymerization of aniline with ammonium peroxydisulfate (APS), were used for MOF-5/PANI composites prepa-ration: conducting emeraldine salt, ES, synthesized in the solution of HCl (0.2 M aniline hydrochloride, 0.25 M APS) and nonconducting emeraldine base, EB, synthesized in water without added acid (0.2 M aniline, 0.25 M APS) and dedoped by an excess of alkali, according to refs. [28,29]. The composite is denoted as MOF.ESb, with 77 wt.% MOF-5 content, was prepared by mechanical mixing of MOF-5 and ES components in the presence of chloroform [28].…”

“…Recently, a series of MOF-5/PANI composites showed interesting features, such as remarkable surface area, conductivity, and high microporosity [28]. Moreover, the carbonization of such structures enabled the formation of electroactive N,O-doped carbon/ZnO-type composite materials, C-(MOF-5/PANI), with preserved high surface area, where PANI was the source of N heteroatoms [29]. In this way, multifunctional carbons doped with two heteroatoms (N, O) were obtained, which enables them to be widely used in environmental studies [30] targeting both efficient pollutant removal and application in energy storage [29].…”

Optimization of a Conductive Polymer Layer on MOF-Derived Carbon Materials for High-Performance Supercapacitor Electrodes

“…In situ polymerization, however, requires the addition of several chemicals and is a time-consuming and complicated process. Savic et al 35 reported C-MOF-5/polyaniline composites by combining MOF-5 and polyaniline in the emeraldine salt state, followed by carbonization. Unfortunately, the carbonization of conductive polymers can lead to a loss of their electrochemical properties.…”

“…Recently, three-dimensional carbon electrodes have been fabricated owing to their porous networks that enhance electron transport, contributing to electrochemical stability. − Metal–organic frameworks (MOFs) have attracted particular attention owing to their high micropore volume and large surface area (>1000 m 2 g –1 ), which potentially generate electrochemically active sites. − Among them, the zeolitic imidazolate framework (ZIF)-8 has widespread applications because of its stable structure and robustness. , ZIF-8 carbonization enables the fabrication of three-dimensional carbon electrodes with improved electrical conductivity while preserving the nanoporous networks. − As ZIF-8 contains heteroatoms (such as N) in the ligand, the carbon resulting from the organic ligand is doped with heteroatoms, which facilitates rapid electron transport to the redox reaction by the pseudocapacitive effect. − Additionally, the evaporation of Zn leads to the formation of micropores, rendering porous carbon materials with excellent electrical conductivity and a high specific surface area. , The specific surface area of carbonized ZIF-8 (C-ZIF-8) can be adjusted according to the original particle size of ZIF-8 . For the aforementioned materials to be successfully applied in various energy storage system applications, C-ZIF-8 requires improved electrical conductivity and electrochemical and physical stability.…”