Sulfonate-Functionalized Two-Dimensional Metal–Organic Framework as a “Dispersant” for Polyaniline to Boost Its Electrochemical Capacitive Performance

Abstract

Polyaniline (PANI) is a conducting polymer with remarkable electrochemical performance for supercapacitors. On the other hand, materials with sulfonate groups, such as polystyrenesulfonate and Nafion, are commonly used as the dispersants to spatially separate the polymeric chains of PANI by means of the electrostatic interaction between the aniline unit and the negatively charged sulfonate. Herein, a two-dimensional (2D) zirconium-based metal−organic framework (MOF) with enriched sulfonate-based ligands postsynthetically coordinated onto its nodes, ZrBTB−SO 3 (BTB = 1,3,5-tri(4-carboxyphenyl)benzene), is utilized as the dispersant during the in situ polymerization of aniline; composites with various ratios between PANI and ZrBTB−SO 3 are thus synthesized. For comparison, the pristine 2D MOF without sulfonate groups is also subjected to the in situ polymerization to synthesize the PANI@ZrBTB composite. Crystallinity, porosity, morphology, elemental composition, and electrical conductivity of each composite are examined. These PANI-based materials are thereafter cast on the electrodes as thin films to investigate their electrochemical capacitive performances in acidic aqueous electrolytes. With the help of the negatively charged sulfonatefunctionalized 2D MOF sheets as the dispersant, the resulting PANI in the composite can achieve a specific capacitance of 515 F/g at a charge−discharge current of 0.5 mA/cm 2 , which is much higher than those achieved by the pristine PANI (230 F/g), PANI@ ZrBTB (137 F/g), and the physical mixture of PANI and ZrBTB−SO 3 (130 F/g). Findings here open numerous opportunities for utilizing such water-stable and sulfonate-functionalized 2D MOFs to spatially disperse various conducting polymers and boost their performances in a range of applications.

Immobilization of europium and terbium ions with tunable ratios on a dispersible two-dimensional metal–organic framework for ratiometric photoluminescence detection of D2O

“…2D sheets, respectively. 50,61 This characteristic in the isotherm and the BET surface area are in general consistent with the reported features of ZrBTB. 50,[61][62][63] After the installation of various compositions of lanthanide ions, all obtained materials possess BET surface areas ranging between 180 and 260 m 2 g −1 with similar characteristics in the low-pressure region in their isotherms, which suggests that the major microporosity of ZrBTB can be preserved after the installation of both europium and terbium.…”

Dual modifications of sensitizers and lanthanide ions on a two-dimensional zirconium-based metal–organic framework for photoluminescent detection

“…One noticeable peak located at 1705 cm −1 belongs to the characteristic FTIR signal of the CO bond present in the uncoordinated carboxylic group. 54,63,65 This peak with a weak intensity can be observed in the FTIR spectrum of ZrBTB, implying the presence of BTB linkers that are not fully coordinated, either on the edge of MOF sheets or at the defective sites. 63 This peak is still obvious in the FTIR spectrum of ZrBTB-bzpdc, but completely disappears in the spectrum of ZrBTB-bzpdc-Tb-120.…”

“…54,63,65 This peak with a weak intensity can be observed in the FTIR spectrum of ZrBTB, implying the presence of BTB linkers that are not fully coordinated, either on the edge of MOF sheets or at the defective sites. 63 This peak is still obvious in the FTIR spectrum of ZrBTB-bzpdc, but completely disappears in the spectrum of ZrBTB-bzpdc-Tb-120. This finding clearly indicates that during the second PSM, terbium ions were coordinated onto the uncoordinated carboxylic groups of both the installed bzpdc ligand and the edged BTB linker.…”

“…5. Characteristic peaks located at 1606, 1590, 1451 and 1416 cm −1 , which are associated with the coordinated carboxylate group and aromatic CC bond of ZrBTB, 46,63 can be observed in the spectra of all the MOF-based materials. The peak at 1654 cm −1 corresponds to the CO bond in the ketone group of bzpdc, 64 which can be seen in all FTIR spectra.…”

“…† ZrBTB possesses a low-pressure uptake and a hysteresis loop within the high-pressure region in its isotherm with a BET surface area of 316 m 2 g −1 , agreeing well with the reported characteristics of ZrBTB. 62,63 All other materials after the installation of bzpdc and terbium have similar BET surface areas ranging from 233 to 338 m 2 g −1 , indicating that the major porosity of ZrBTB is not significantly altered by these PSM processes. Density functional theory (DFT) pore size distributions were thereafter extracted from the isotherms by employing the original DFT model for carbon-slit pores filled with N 2 at 77 K. As shown in Fig.…”