Single-Crystalline Organic–Inorganic Layered Cobalt Hydroxide Nanofibers: Facile Synthesis, Characterization, and Reversible Water-Induced Structural Conversion

Abstract

New pink organic-inorganic layered cobalt hydroxide nanofibers intercalated with benzoate ions [Co(OH)(C6H5COO)·H2O] have been synthesized by using cobalt nitrate and sodium benzoate as reactants in water with no addition of organic solvent or surfactant. The high-purity nanofibers are single-crystalline in nature and very uniform in size with a diameter of about 100 nm and variable lengths over a wide range from 200 μm down to 2 μm by simply adjusting reactant concentrations. The as-synthesized products are well-characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), fast Fourier transforms (FFT), X-ray diffraction (XRD), energy dispersive X-ray spectra (EDX), X-ray photoelectron spectra (XPS), elemental analysis (EA), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and UV-vis diffuse reflectance spectra (UV-vis). Our results demonstrate that the structure consists of octahedral cobalt layers and the benzoate anions, which are arranged in a bilayer due to the π-π stacking of small aromatics. The carboxylate groups of benzoate anions are coordinated to Co(II) ions in a strong bridging mode, which is the driving force for the anisotropic growth of nanofibers. When NaOH is added during the synthesis, green irregular shaped platelets are obtained, in which the carboxylate groups of benzoate anions are coordinated to the Co(II) ions in a unidentate fashion. Interestingly, the nanofibers exhibit a reversible transformation of the coordination geometry of the Co(II) ions between octahedral and pseudotetrahedral with a concomitant color change between pink and blue, which involves the loss and reuptake of unusual weakly coordinated water molecules without destroying the structure. This work offers a facile, cost-effective, and green strategy to rationally design and synthesize functional nanomaterials for future applications in catalysis, magnetism, gas storage or separation, and sensing technology.

Facile synthesis of novel metal-organic nickel hydroxide nanorods for high performance supercapacitor

“…The nyquist plots consist of a depressed semicircle diameter in high-to-medium frequency regions and a straight line in low-frequency region. As proved in our previous work [21], the depressed semicircle diameter represents the charge transfer resistance, which can reflect the speed and capability of faradic reaction. Compared with the reported layered Co-based MOF film [12] and Ni-based MOFs sheet electrode [15], the as-prepared Ni-based MOF nanorod electrode has shorter semicircle diameter, indicating lower charge transfer resistance and better electrochemical performances.…”

“…In comparison with the XRD spectrum of organic linker HOC 6 H 4 COONa (curve b), new diffraction peaks appeared at 6.05°, 11.88°, 13.79° and 21.82° for the Ni-based MOFs, corresponding to benzoate intercalated nickel hydroxide [15,[20][21][22].…”

Electrodeposited Stable Binder‐Free Organic Ni(OH)2 Flexible Nanohybrid Electrodes for High‐Performance Supercapacitors

“…In peptide molecules, the polar moieties such as carboxylate anions could facilitate the interaction with Ni 2+ ions . The aromatic rings in the peptide molecules could form attractive intermolecular interactions such as π–π stacking interactions providing structural stability to the hybrid nanoscale architecture of the thin films . The amide functional groups over the peptide backbone induce the formation of peptide self‐assembly through intermolecular hydrogen bonding interactions.…”

Benzoate Anion‐Intercalated Layered Cobalt Hydroxide Nanoarray: An Efficient Electrocatalyst for the Oxygen Evolution Reaction

“…42-1835), accordingt oapreviousr eport. [21] Twoi ntense peaks at 44.528 and 51.888 are assigned to the NF substrate. Based on the (001) interplanar d-spacing (14.72 )a nd the thickness of ab rucite-like octahedral sheet (ca.…”

“…7 ), [15] [a] R. Ge suggesting that benzoatea nions stack into ab ilayer-like structure. [21] For comparison, carbonate anion with al ength of about 2.8 was employed as ac ounterion to preparec arbonate-Co(OH) 2 , [23] which has al ower interlayer spacing of 8.81 and al ower gallery heighto fa pproximately 4.01 (see Figures S1 and S2 for detailed characterization), compared to benzoate-Co(OH) 2 .T he FTIR spectrumo fb enzoate-Co(OH) 2 (Figure 1b)s hows as harp band at 3602 cm À1 ,w hich is ascribed to the OÀHs tretching vibration of free OH groupsi nbrucite-like sheets. [24] Ab road band centered around 3434 cm À1 arises from interlayer water molecules and H-bound OH groups.…”