Nanotubular Metal Research Articles

Imogolite prepared from cement kiln dust removes arsenite from water

Imogolite belongs to the family of nanotubular metal oxides which are useful for the construction of new materials in nanotechnology. This study aims to develop a simple waste valorization method to obtain imogolite from cement kiln dust (CKD) via solubilization of CKD and subsequent precipitation of imogolite (Imo-CKD) in a hydrothermal process. The newly synthesized Imo-CKD and a conventional imogolite (Imo) showed similar diameter (Ø) and length (L) of nanotubes [Ø≅ 1.9 nm and L ≅ 200 nm] and crystallinity grade but different values of isoelectric point (IEP) [IEPImo−CKD=8.86 and IEPImo=9 .92]. The shift in the IEP value of Imo-CKD to a lower value was attributed to the presence of allophane as a subproduct during Imo-CKD synthesis. Arsenite [As(III)] removal from water by both the imogolites was a rapid (t ≤ 20 min) and spontaneous process. The kinetic As(III) removal data obeyed the pseudo-second order model, while surface diffusion also controlled the As(III) adsorption process. The activation energy (Ea > 40 kJ mol−1) suggested a chemical adsorption of As(III) in both materials. The Imo-CKD (0.377 mmol g−1) removed As(III) from water more efficiently than Imo (0.334 mmol g−1), despite the formation of allophane byproduct in the synthesis process. Results of this study can promote the reuse of inexpensive CKD as a viable alternative to replace costly tetraethyl orthosilicate for imogolite synthesis and use of imogolite for water pollutant removal.

Multicomponent Anti-Kasha’s Rule Emission from Nanotubular Metal–Organic Frameworks for Selective Detection of Small Molecules

The peak photoluminescence (PL) of conventional fluorophores is independent of the excitation wavelength (called Kasha's rule), while the search of metal-organic framework materials with the so-called anti-Kasha's rule emission remains very limited. Herein, we report the observation of anti-Kasha's rule emission in a multicomponent PL three-dimensional nanotubular metal-organic framework (abbr. MOF-NT), [Zn(μ-L)(μ-bix)]n·0.33nH2O [H2L = biphenyl-3,5-dicarboxylic acid; bix = 1,4-bis(imidazole-1-ylmethyl)benzene]. The MOF-NT crystalline sample represents a notable example of strong excitation-dependent fluorescence from the ultraviolet to the visible spectral region. Moreover, by virtue of electronic flexibility and high PL efficiency, MOF-NT shows a discriminative PL response between isomeric nitroaromatic compounds. The work demonstrated the intrinsic anti-Kasha's rule emission in the crystalline-state MOF materials, providing new visions for the development of advanced solid-state emissive materials.

A stable nanotubular metal–organic framework as heterogeneous catalyst for efficient chemical fixation of CO2

The incorporation of high-density and easily accessible Lewis acid sites is of great significance to obtain high catalytic activity in the CO2cycloaddition reaction of epoxides.

A Nanotubular Metal-Organic Framework with a Narrow Bandgap from Extended Conjugation*.

A one‐dimensional nanotubular metal–organic framework (MOF) [Ni(Cu‐H4TPPA)]⋅2 (CH3)2NH2 + (H8TPPA=5,10,15,20‐tetrakis[p‐phenylphosphonic acid] porphyrin) constructed by using the arylphosphonic acid H8TPPA is reported. The structure of this MOF, known as GTUB‐4, was solved by using single‐crystal X‐ray diffraction and its geometric accessible surface area was calculated to be 1102 m2 g−1, making it the phosphonate MOF with the highest reported surface area. Due to the extended conjugation of its porphyrin core, GTUB‐4 possesses narrow indirect and direct bandgaps (1.9 eV and 2.16 eV, respectively) in the semiconductor regime. Thermogravimetric analysis suggests that GTUB‐4 is thermally stable up to 400 °C. Owing to its high surface area, low bandgap, and high thermal stability, GTUB‐4 could find applications as electrodes in supercapacitors.

An Anionic Nanotubular Metal-Organic Framework for High-Capacity Dye Adsorption and Dye Degradation in Darkness.

A metal-organic framework (MOF), named SCNU-Z2, based on a new heterotopic tripodal nitrogen-containing ligand, has been constructed. Due to the replacement of one imidazole group in the reported ligand with one tetrazole group, the charge of the framework is changed from cationic to anionic but retains the same framework structure. The framework consists of tubular channels with a diameter of 1.5 nm and exhibits satisfactory stability in water with a pH range of 3-11. The anionic nature of the framework allows the effective adsorption of the cationic dyes MLB, CV, and RhB with capacities of 455.6, 847.4, and 751.8 mg/g, respectively. Among them, the adsorption capacities for SCNU-Z2 on CV and RhB rank as the highest when compared with other reported MOFs. In contrast, SCNU-Z2 exhibits an extremely low capacity for anionic dyes MO and AO, making it useful for the separation of anionic and cationic dyes based on a charge-dependent mode. Interestingly, SCNU-Z2 can be used to degrade an anionic dye, MB, within 30 min under darkness at room temperature. The apparent activation energy of the dye degradation reaction is calculated to be approximately 18.96 kJ·mol-1, implying that the catalytic reaction of MB can be considered as a low-temperature thermocatalytic reaction in the dark/SCNU-Z2 system.

Homochiral iron(ii)-based metal-organic nanotubes: metamagnetism and selective nitric oxide adsorption in a confined channel.

Homochiral iron(ii)-based nanotubular metal phosphonates (R)- and (S)-[Fe(pemp)(H2O)2] [pemp2- = (R)- or (S)-(1-phenylethylamino)methylphosphonate] are reported showing metamagnetism at low temperature. The dehydrated product features coordinatively unsaturated and redox-active metal ion sites that enable it to strongly bind nitric oxide at room temperature.

All-solid-state formation of titania nanotube arrays and their application in photoelectrochemical water splitting

The present work demonstrates for the first time the facile fabrication of TiO2 nanotube arrays (TNTAs) by a fluoride-free solid-state anodization process using LiClO4 containing solid polymeric electrolyte. The resulting nanotubes were tested for photoelectrochemical water splitting. The elimination of liquid electrolytes in electrochemical anodization constitutes a paradigm shift for the formation of nanoporous and nanotubular metal oxides. Our results open a new area of research that uses the distinctive properties of solid polymer electrolytes to achieve targeted doping and nano-morphologies. Characterization of the grown TNTAs indicated solid state anodized TNTAs to consist purely of the anatase phase of titania. The solid-state anodization process provides several advantages over conventional liquid electrolytes such as easy handling and processing, better charge transport, environmentally benign chemicals and methodology. Photoelectrochemical water splitting experiments were performed which confirmed the viability of TNTAs grown by the new solid-state process for photocatalytic applications.

Size-exclusive and coordination-induced selective dye adsorption in a nanotubular metal–organic framework

A nanotubular MOF, BUT-51, performs coordination-induced selective dye adsorption, which changes its stability and porosity to give a robust partner.

Design and development of an integrated device consisting of an independent solar cell with electrical storage capacity

A thin film-integrated device was constructed consisting of photovoltaic layers combined with additional layers to store charge in real time within the same device. In our design, a dye-sensitized solar cell and capacitor layers are integrated by a double-anodized titanium plate, which consists of TiO2 nanotubes grown on either side by electrochemical anodization. The combination device can act either as an independent solar cell, a capacitor, or as a solar cell/capacitor device. The results presented here illustrate the capacitive behavior of high surface area nanotubular metal oxide films, with an achieved capacitance of 140 μF cm−2. Copyright © 2012 John Wiley & Sons, Ltd.

A novel 1D independent metal–organic nanotube based on cyclotriveratrylene ligand

A novel nanotubular metal–organic framework [Cu3L2(EtOH)(Py)2(H2O)2]·9DEF·8H2O (CTV-Cu) was prepared by assembly of the rigid, trigonal pyramidal ligand tri-(4-carboxy-phenyl)-trimethoxycyclobenzylene (H33L) and Cu(NO3)2·3H2O viasolvothermal reaction. The Cu(II) ions in the crystal serve as square and linear molecular building blocks, thus forming a framework with ternary topology. One single open-ended nanotube contains two identical orthogonally interpenetrated two-nodal nets. This framework exhibits permanent microporosity and relatively high surface area.

Anodic formation of nanoporous and nanotubular metal oxides

A localized dielectric breakdown model with good universality is introduced to explain the pore initiation, separation and growth processes of nanoporous and nanotubular anodic metal oxides. It is suggested that the degree of localized dielectric breakdown, which is mainly determined by the dielectric strength and energy band gap of the anodic oxide, electrolyte used, anodizing field and also temperature during anodization, has a significant effect on the pore formation. Continuous nanoporous films tend to grow under low degree of localized dielectric breakdown of the anodic oxides, and the growth in number and size of voids induced by high degree of localized dielectric breakdown at the inter-pore areas leads to the separation of neighbouring pores and, therefore, formation of nanotubular structures. Specially, anodic TiO2 nanotubes are believed to grow by continuous localized dielectric breakdown and self-healing processes at the base of main pores. Alternating dielectric breakdown and oxidation processes at the inter-pores areas lead to the formation of commonly observed O-ring like ridges.

Nanotubular Metal−Organic Frameworks with High Porosity Based on T-Shaped Pyridyl Dicarboxylate Ligands

Two nanotubular metal-organic frameworks (MOFs), {Cu(L1)·2H(2)O·1.5DMF}(∞) (1) and {Cu(2)(L2)(2)(H(2)O)(2)·7H(2)O·3DMF}(∞) (2), with novel topologies have been constructed based on Cu(2+), 5-(pyridin-4-yl)isophthalic acid (L1) and 5-(pyridin-3-yl)isophthalic acid (L2), respectively. Two MOFs were characterized by IR spectroscopy, thermogravimetry, single-crystal, and powder X-ray diffraction methods. Network analysis reveals a two-nodal (3,6)-connected (4·6(2))(2)(4(2)·6(10)·8(3)) net and a three-nodal (3,4)-connected (4·8(2))(4)(4(2)·8(2)·10(2))(2)(8(4)·12(2)) net. Interpenetration is inherently prevented by both of the topologies of the frameworks. The porosity of MOF 1 was confirmed by N(2) and CO(2) gas adsorption investigations. MOF 1 exhibits remarkable hydrogen sorption hysteresis at low pressure and a H(2) uptake capacity of 1.05 wt% at 77 K and 1 atm.

The self-assembly of single-walled metal–organic nanotubes constructed from CuCl2 chains and ditetrazoles

A very unusual two-dimensional metal–organic nanotubular structure, [CuCl2(DTB)2] (DTB = 1,3-di(1H-tetrazol-1-yl)benzene) constructed from CuCl2 chains and ditetrazoles is reported, which represents the first example of nanotubular metal–organic frameworks based on Cu–X (X = halogen) chains.

A nanotubular metal–organic framework with permanent porosity: structure analysis and gas sorption studies

A nanotubular metal-organic framework, PCN-19, was constructed based on a micro3-oxo-trinickel basic carboxylate secondary building unit (SBU) and the 9,10-anthracenedicarboxylate ligand; its permanent porosity was confirmed by N2 adsorption isotherms, and its H2 storage performances were evaluated under both low and high pressures at 77 K.