Ni(II)-Based Metallosupramolecular Polymer with Carboxylic Acid Groups: A Stable Platform for Smooth Imidazole Loading and the Anhydrous Proton Channel Formation

Abstract

The Ni­(II)-based metallosupramolecular polymer with carboxylic acid groups (polyNi) was synthesized via a 1:1 complexation of Ni­(II) salt with (4,4′-(9,9-dihexyl-9H-fluorene-2,7-diyl)­bis­(pyridine-2,6-dicarboxylic acid) for the first time. The divalent state of Ni­(II) in the polymer was confirmed by the X-ray absorption fine structure analysis. Smooth loading of imidazole molecules into polyNi proceeded with the help of the carboxylic acid groups to form the imidazole-loaded polyNi (polyNi-Im). Thermogravimetric analysis of polyNi-Im revealed that approximately three imidazole molecules were incorporated per repeating unit of polyNi. The Fourier transform infrared spectrum of polyNi-Im showed a new peak at 3219 cm–1, which shows an ∼73 cm–1 enhancement to −N–H of pristine imidazole. The peak suggests the formation of an imidazolium cation in the polymer. Powder X-ray diffraction indicated no degradation of the polymer structure during the imidazole loading because the diffraction pattern of polyNi-Im was almost the same as that of polyNi except for the presence of peaks corresponding to the imidazole molecules. Interestingly, the scanning electron microscopy measurement showed a large morphological change to uniform spherical particles by loading imidazole to the polymer. PolyNi-Im exhibited good proton conductivity (1.05 × 10–2 mS/cm) at a high temperature (120 °C), which is around 7 orders of magnitude higher than that of pristine polyNi because of the proton conduction pathway formation along the polymer chains by the incorporated imidazole molecules.

One-Pot Synthesis of Three-Dimensionally Hyperbranched Eu/Fe-Based Heterometallo-Supramolecular Polymers as Thermally Tough Proton-Conducting Nanoparticles

“…Recently, the metallo-supramolecular polymer (MSP) has received significant interest because of its electrochemical, photochemical, catalytic and proton-conductive properties, and so forth for wide applications including photovoltaic devices, light-emitting diodes, sensors, self-healing materials, memory devices, electrochromic displays, fuel cells, and batteries. − MSPs are composed of metal ions and multitopic organic ligands. A one-dimensional (1D) structure of MSPs was synthesized by the 1:1 complexation of ditopic linear ligands with metal ions. ,, Two- and three-dimensional (3D) structures of MSPs (2D- and 3D-MSPs) were also prepared using tritopic ligands and so forth. − …”

Adsorption of Acid Orange and Reactive Red by DK110 Loaded Ionic Liquid

“…Infrared spectroscopy analysis was also used to determine the introduction of the ionic liquid to DK110, which is shown in Figure 3. In the spectrum of DK110, the characteristic peaks at 1550 cm −1 and 1400 cm −1 were due to the −COO − stretching vibration [45,46] . In Figure 3b, the the additional absorption at 1721 cm −1 was the characterized absorption ester carbonyl vibration [47,48] .…”

Role of Framework–Carrier Interactions in Proton-Conducting Crystalline Porous Materials

“…However, the low crystallinity of the MOF made it impossible to decipher the conducting pathway. Since then, various other crystalline polymers, especially covalent organic frameworks (COFs), have also been employed to study proton conduction. − However, the absence of long-term stability of the MOFs and COFs under harsh conditions remained a concern and there was a search for better materials with high thermal stability and consistent conductivity at high temperature as well as at low humidity. In addition to COFs and MOFs, porous organic polymers (POPs) and conjugated microporous polymers (CMPs) − have emerged as new proton-conducting materials owing to the presence of a conjugated structure and aromatic properties that induce high thermal and chemical stability.…”