Cyclohexane Solution Research Articles

Kaolinite surface charges developed in cyclohexane suspension with dissolved Span 80 or bitumen: Electrodeposition and adsorption/desorption studies

In this study, we investigated the surface charges of kaolinite particles suspended in cyclohexane with or without the addition of Span 80 or bitumen. Kaolinite particles did not carry a net charge when dispersed in cyclohexane. They were found to acquire positive charges after adding Span 80 and negative charges after adding bitumen. Furthermore, when Span 80 was removed from the cyclohexane solution, the kaolinite surface charges disappeared, but when bitumen was removed, the kaolinite particles remained negatively charged. Our investigations showed that the bitumen adsorbed on the kaolinite surface caused the negative surface charges of kaolinite in cyclohexane. This was different from the widely accepted conventional charging mechanism which states that solid particles in a nonpolar organic liquid acquire charges due to the formation of reverse micelles from added surfactants, such as Span 80, and the reverse micelles house and stabilize free opposite charges to maintain the net particle surface charge. On the other hand, bitumen-coated kaolinite could carry net charges in cyclohexane due to the selective dissolution of charge-carrying species induced by an external electric field. Our electrochemical quartz crystal microbalance with dissipation (EQCM-D) measurements showed that about 3.7 wt% of the adsorbed bitumen was desorbed from kaolinite surface under a 5 V external electric field. Elemental analysis showed that the carbon content on the surface of bitumen-coated kaolinite particles decreased from 4.43 wt% for suspended kaolinite particles to 4.21 wt% for kaolinite particles deposited on the electrodes. Both measurements revealed shedding of bitumen from the bitumen coating layer on kaolinite surface.

Preparation, in vitro and in vivo evaluation of solid-in-oil dispersion-based formulation the anti-glaucoma drug, timolol maleate

Lowering Intraocular pressure (IOP) is a main therapeutic objective in glaucoma patients because IOP is an important risk factor for glaucoma progression. The objective of this work was to formulate and evaluate, in vitro and in vivo, a stable and effective Solid in Oil (S/O) topical formulation of the antiglaucoma drug, timolol maleate (TM). S/O dispersions were prepared by emulsification of aqueous TM solutions in cyclohexane using different amount of the span 85 then lyophilizing the emulsion to produce TM – Span 85 complexes. The complexes were then dispersed in castor oil using tip sonicator to produce S/O nanodispersions. S/O nanodispersions were evaluated in terms of particle size, polydispersity index, encapsulation efficiency, morphology, physical stability, as well as transcorneal permeation and accumulation of TM. In addition, the in vivo tolerability and efficacy of the prepared formulation in lowering intraocular pressure were evaluated in rabbits.
 Spherical nanoparticles of TM with a particle size of about 134-155 nm were successfully prepared and found to be physically stable. The encapsulation efficiency was high and was found to be dependent on the level of Span 85 used.
 In comparison to TM solution, S/O nanodispersion enhanced TM permeation and decreased accumulation in transcorneal diffusion studies. In addition, application TM S/O nanodispersion onto rabbit eyes resulted in a significant reduction in IOP in comparison to TM aqueous solution.

Construction of a novel ursolic acid-based supramolecular gel for efficient removal of iodine from solution

Pentacyclic triterpenes is a natural amphipathic product which possess a rigid backbone and several polar functional groups such as hydroxyl, carbonyl and carboxyl groups. The amphipathic character makes it easy to realize self-assemble into complex nano structure and therefore attract extensive attention due to the simple synthetic processes and renewable raw materials. Hence, a novel Ursolic acid-based hydrogel was prepared successfully via a simple self-assembly of triterpenoid derivative in methanol by capture water molecule in air. The resulting hydrogel show a porous morphology and good elasticity including strong heat resistance. Based on the characteristic above, the hydrogel showed a good iodine adsorption capacity and can removal 75.0% of the iodine from cyclohexane solution and 66.3% from aqueous solution within 36 h. Data analysis indicate that all the iodine adsorption process are dominated by chemisorption and belongs to the multi-site adsorption on heterogenous surfaces. In addition, the obtained hydrogel also possesses a good recyclability which can maintain more than 82% of its capacity after 5 cycles. The simple preparation method and easily available raw materials endow it a great potential in future pollutant treatment.

Fabrication of polyamide hollow fiber nanofiltration membrane with intensified positive surface charge density via a secondary interfacial polymerization

In this work, a positively charged hollow fiber nanofiltration (NF) membrane based on twice interfacial polymerization (IP) reactions was developed for water soften and heavy metal ions removal. The first IP reaction was conducted on the polyethersulfone (PES) hollow fiber substrate using a mixture of branched polyethyleneimine (PEI) and piperazine (PIP) as the aqueous phase monomers in the aqueous phase reacting with trimesoyl chloride (TMC) in the cyclohexane solution. Then, a secondary IP reaction was performed between tris(2-aminoethyl) amine (TAEA) solution and the residual acyl chloride groups on the membrane to increase the positive charge density on the membrane surface. Consequently, a NF membrane with intensified positive surface charge density was successfully fabricated. The optimized membranes achieved a high rejection of MgCl2 of 97.6% while maintaining a pure water permeability (PWP) of 16.0 L m−2 h−1 bar−1. Meanwhile, the membranes exhibit high rejection values of 99.8% to Cu2+ and 99.7% to Zn2+, respectively. In conclusion, this work provides a facile way to prepare a positively charged membrane for efficient water softening and metal ions removal.

Adsorption and Detection of Iodine Species by a Thorium-Based Metal–Organic Framework

Actinide-bearing metal-organic frameworks (MOFs) encompass intriguing structures and properties, but the radioactivity of actinide cripples their applications. Herein, we have constructed a new thorium-based MOF (Th-BDAT) as a bifunctional platform for the adsorption and detection of radioiodine, a more radioactive fission product that can readily spread through the atmosphere in its molecular form or via solution as anionic species. The iodine capture within the framework of Th-BDAT from both the vapor phase and the cyclohexane solution has been verified, showing that Th-BDAT features maximum I2 adsorption capacities (Qmax) of 959 and 1046 mg/g, respectively. Notably, the Qmax of Th-BDAT toward I2 from cyclohexane solution ranks among the highest value for Th-MOFs reported to date. Furthermore, incorporating highly extended and π-electron-rich BDAT4- ligands renders Th-BDAT as a luminescent chemosensor whose emission can be selectively quenched by iodate with a detection limit of 1.367 μM. Our findings thus foreshadow promising directions that might unlock the full potential of actinide-based MOFs from the point of view of practical application.

Zn, O Co-adsorption based on MOF-5 for efficient capture of radioactive iodine

The harmful effects of iodine in nuclear waste gas on humans and the environment, as well as the high kinetic energy of iodine molecules caused by the high-temperature environment, make it very important to develop and produce adsorbents with many active sites. The performance and mechanism of iodine capture by MOF-5 were investigated by experiments and molecular simulations for environmental protection. It was found that the synthesized MOF-5 can remove iodine from the gas phase and cyclohexane solution, with a high iodine capture capacity (0.63 g g-1) at 75 ℃. The cycling test illustrated the better recoverability and stability of MOF-5. The iodine capture capacity of MOF-5 in the liquid phase was 155 mg g-1, which is not the same as that of iodine in the gas phase. The multi-scale mechanistic analysis revealed that the adsorption process of MOF-5 on iodine was dominated by chemisorption, and the efficient capture of iodine was achieved by the co-adsorption of the central metal Zn atom and the tetrahedral apex O atom of MOF-5. This study provides insight into the iodine trapping process and adsorption mechanism, which is instructive for environmental protection engineering.

MIL-101-NH2-TFR and MIL-101-NH2-TFR/Cu2+ as novel hybrid materials for efficient adsorption of iodine and reduction of Cr(VI)

Today, due to the earnest jeopardies of environmental contaminants from various sources and their deteriorating effects on the ecosystem, the adsorption and reduction of these highly toxic pollutants with an efficient and cost-effective protocol can be considered a desirable phenomenon. Herein, a chromium-based metal-organic framework (MIL-101-NH2) was modified with thiourea and formaldehyde to form a polymeric layer on the surface (MIL-101-NH2-TFR). The resulting nanohybrid, as an adsorbent, was applied for efficient capture of iodine (I2) molecules from cyclohexane solution. MIL-101-NH2-TFR nanohybrid signified a superior adsorption performance for the capture of I2, compared to the pristine MIL-101-NH2, with a theoretical maximum uptake value of 625 mg/g and adsorption efficiency of 96.9 % through thionyl (CS), amino, and phenyl groups. The pseudo-second-order rate equation and the Langmuir model were best fitted for the I2 adsorption over MIL-101-NH2-TFR adsorbent. Quantum chemical calculations were conducted to reveal the mechanism of I2 adsorption onto the surface of MIL-101-NH2-TFR. Moreover, MIL-101-NH2-TFR was used to anchor Cu2+ to generate a catalytic system (MIL-101-NH2-TFR/Cu2+) for detoxification of Cr(VI) in the presence of formic acid as an eco-friendly reducing reagent in an aqueous medium. MIL-101-NH2-TFR and MIL-101-NH2-TFR/Cu2+ were reused several times for the adsorption/desorption process and the catalytic reduction, respectively.

Carbazole‐Dendronized Luminescent Radicals

AbstractA series of carbazole‐dendronized tris(2,4,6‐trichlorophenyl)methyl (TTM) radicals have been synthesized. The photophysical properties of dendronized radicals up to the fourth generation were compared systematically to understand how structure–property relationships evolve with generation. The photoluminescence quantum yield (PLQY) was found to increase with the increasing generation, and the fourth generation (G4TTM) in cyclohexane solution showed a PLQY as high as 63 % at a wavelength of 627 nm (in the deep‐red region) from the doublet state. The dendron modification strategy also showed a blue‐shift of the emission on increasing the generation number, and the photostability was also increased compared to the bare TTM radical.

Carbazole-Dendronized Luminescent Radicals.

A series of carbazole dendronized tri(2,4,6-trichlorophenyl)methyl (TTM) radicals were synthesized. The photophysical properties of up to 4th generations of radical dendrimers were compared systematically to understand how structure-property relationships evolve with generation. Photoluminescence quantum yield (PLQY) was found to increase with the increasing generation, and the fourth generation (G4TTM) in cyclohexane solution showed PLQY as high as 60% at a wavelength of 627 nm in the deep red region from the doublet state. The dendron modification strategy also showed a blue-shift of the emission when increasing the generation, and the photostability has also increased compared to the bare TTM radical.

A Novel Azo-Linked Polymer Bearing Trifluoromethyl Groups for I2 Capture.

In this work, a novel three nitro-group-bearing monomer 3,6-dinitro-9-(2-trifluoromethyl-4-nitrophenyl)-carbazole (Car-3NO2 -CF3 ) via a CN coupling reaction between 3,6-dinitro-9H-carbazole (Car-2NO2 ) and 2-chloro-5-nitrobenzotrifluoride is synthesized, and obtained single crystal and single crystal analysis data for this compound. The crystal system of Car-3NO2 -CF3 is monoclinic and it has a P 21/c space group. This new monomer (Car-3NO2 -CF3 ) is also utilized to synthesize a novel azo-linked polymer (Azo-Car-CF3 ). The trifluoromethyl group has polar CF bonds, and thus it is an effective functional group for the capture of iodine. Azo-Car-CF3 has great thermal stability with a mass loss of only 10% at 414°C, as well as good chemical stability as is demonstrated by its low solubility in common organic solvents such as tetrahydrofuran (THF), acetone, methanol, ethanol, and N,N-dimethylformamide (DMF). The specific surface area of Azo-Car-CF3 can reach as high as 335m2 g-1 . Azo-Car-CF3 exhibits an excellent capacity for iodine adsorption and can reach up to 1198mgg-1 in cyclohexane solution, and its adsorption capacity for iodine vapor can get to 2100mgg-1 . In addition, ethanol can be used to trigger the release of the captured iodine to be easily released from Azo-Car-CF3 .

Two New 1D Supramolecular Compounds Based on PbI2 for Efficient Iodine Capture

Two new inorganic-organic hybrid crystals based on PbI2 were assembled through the solvent evaporation method, namely, {[L1]·[Pb2I6]}n (1) and {[L2]2·[Pb3I10]}n (2). L1-L2 are a series of multivalent nitrogen-containing cationic ligands. Compounds 1-2 were characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR, powder X-ray diffraction, and thermogravimetric microanalysis. The results showed that the adsorption rate of 80 mg compound 1 to iodine reached 96.59%, indicating a high iodine capture performance in cyclohexane solution. In the meantime, the adsorption kinetics is most suitable for a pseudo-second-order model, and the adsorption process is mainly chemisorption. Adsorption thermodynamics is most suitable for the Langmuir model, indicating that adsorption occurs on the surface of the monolayer. According to the adsorption mechanism, it can be inferred that the structure of compound 1 contains amino, benzene, N heterocyclic, and other active groups, that is, indirectly increases the adsorption site with iodine, and the chemical reaction with iodine improves the removal rate of iodine in cyclohexane solution. In addition, compound 1 was found to have good iodine adsorption and recyclability by cyclic experiments. Therefore, the synthesized compound 1 can be used as a potential and excellent iodide capture adsorbent, which may have a good application prospects in the future.

A robust sp2 carbon-conjugated COF for efficient iodine uptake

Synthesis of fully sp2-carbon conjugated covalent organic frameworks (COFs) is generally considered extremely challenging due to the low reversibility of the CC bond. Herein, a novel sp2-carbon conjugated COF material, named sp2c-TFPA-pXD, was prepared by Knoevenagel reaction employing tris(4-formylphenyl)amine with triangular geometry as the knot and p-xylylene dicyanide with symmetric structure as the linker unit. The CC linkages topologically connect the two precursors to a fully sp2-carbon conjugated 2D lattice and develop an eclipsed layer framework, giving sp2c-TFPA-pXD outstanding stability. The prepared sp2c-TFPA-pXD does not decompose in nitrogen atmosphere up to 323 °C, and can be stably present in boiling water, acids, bases and common organic solvents. The excellent chemical and thermal stability of sp2c-TFPA-pXD makes it suitable for the harsh environment of radioiodine treatment. In fact, sp2c-TFPA-pXD shows moderate iodine capture capacity in iodine vapor (1.22 g/g), and also shows acceptable iodine capture performance under real industrial conditions of high temperatures and low iodine concentrations. The iodide capture properties of sp2c-TFPA-pXD can be attributed to its regular channels and sp2-carbon conjugate structure. In addition, sp2c-TFPA-pXD can be reused by simple ethanol soaking treatment, and can almost maintain its original iodine capture performance after five cycles. In addition, sp2c-TFPA-pXD also displays noteworthy capability as adsorbent for iodine in cyclohexane solution. Our study confirms that sp2c-TFPA-pXD is an excellent candidate material for capturing iodine from air and solutions in harsh environments. We hope that the report of sp2c-TFPA-pXD for iodine capture could open up new avenues for sp2-carbon conjugated COFs applications and encourage more research to explore the radioiodine capture potential of other stable COFs.

Nonaqueous Interfacial Polymerization-Derived Polyphosphazene Films for Sieving or Blocking Hydrogen Gas.

A series of cyclomatrix polyphosphazene films have been prepared by nonaqueous interfacial polymerization (IP) of small aromatic hydroxyl compounds in a potassium hydroxide dimethylsulfoxide solution and hexachlorocyclotriphosphazene in cyclohexane on top of ceramic supports. Via the amount of dissolved potassium hydroxide, the extent of deprotonation of the aromatic hydroxyl compounds can be changed, in turn affecting the molecular structure and permselective properties of the thin polymer networks ranging from hydrogen/oxygen barriers to membranes with persisting hydrogen permselectivities at high temperatures. Barrier films are obtained with a high potassium hydroxide concentration, revealing permeabilities as low as 9.4 × 10-17 cm3 cm cm-2 s-1 Pa-1 for hydrogen and 1.1 × 10-16 cm3 cm cm-2 s-1 Pa-1 for oxygen. For films obtained with a lower concentration of potassium hydroxide, single gas permeation experiments reveal a molecular sieving behavior, with a hydrogen permeance of around 10-8 mol m-2 s-1 Pa-1 and permselectivities of H2/N2 (52.8), H2/CH4 (100), and H2/CO2 (10.1) at 200 °C.

Formation of Droplets of Shear-Thinning Non-Newtonian Fluids in Asymmetrical Parallelized Microchannels.

Fluids containing polymers are frequently utilized in the chemical industry and exhibit shear-thinning characteristics. The flow distribution of non-Newtonian fluids in parallelized microchannels is a key issue to be solved during numbering-up. Numbering-up means increasing the number of parallelized microchannels. In this study, a high-speed camera is used to explore the distribution of fluid flow as well as the uniformity and stability of droplets in conceptual asymmetrical parallelized microchannels. Cyclohexane and carboxymethylcellulose sodium (CMC) aqueous solutions are used as the continuous phase and dispersed phase, respectively. The effects of fluctuation of pressure difference around the T-junction, the hydrodynamic resistance in microchannels, and the shear-thinning property of fluids on flow distribution and droplet formation are revealed. The uniformity and stability of droplets in microdevices with various cavity settings are compared, and an optimal configuration is proposed. Finally, prediction models for the flow distribution of shear-thinning fluids in asymmetrical parallelized microchannels are established.

Passive Enhancement of Retinol Skin Penetration by Jojoba Oil Measured Using the Skin Parallel Artificial Membrane Permeation Assay (Skin-PAMPA): A Pilot Study.

Retinol is known to have positive benefits on the skin including enhancements in barrier function, increased epidermal thickness, reductions in fine lines and wrinkles and reductions in hyperpigmentation. Improved methods to enhance the penetration of retinol are desirable. A study was conducted to examine if addition of natural jojoba (Simmondsia chinensis) oil might help passively enhance the penetration of retinol through the skin's lipid barrier. The model used to examine the passive penetration of the retinol is the skin parallel artificial membrane permeation assay (Skin-PAMPA). In this study, three formulations were examined. The formulations included two control blends: a moisturizing emulsion without retinol and the same product containing 1.0% retinol without jojoba oil. The remaining formulation contained similar concentrations of retinol with 10% jojoba oil. The studies were conducted by applying the products to the Skin-PAMPA models at 37°C/5% CO2 for 16 hours and then extraction of the acceptor reservoir with cyclohexane (ratio 1:5 acceptor fluid to cyclohexane). The resulting acceptor reservoir cyclohexane solutions were analyzed for retinol by High Performance Liquid Chromatography (HPLC). The formulations without retinol showed no indications of retinol penetration by HPLC. The control formulation with 1.0% retinol demonstrated that retinol had permeated the membrane in the 16-hour timeframe with a measured Area Under the Curve (AUC) of 7 units. Analysis of the formulation containing 1.0% retinol and 10% jojoba oil indicated retinol had permeated with a AUC of 285 units, a nearly 40-fold increase in active retinol permeation. The ability for jojoba oil to directly act to help skin permeation of a key skin care active like retinol has not been previously demonstrated. This potential for jojoba oil to enhance passive skin penetration of critical skin actives, like retinol, can help to improve the performance of skin care products employing active topical ingredients.

Fabrication of bimetallic-doped materials derived from a Cu-based complex for enhanced dye adsorption and iodine capture.

In this work, we used Cu(II) ions, a bis-pyridyl-bis-amide ligand [N,N'-bis(4-pyridinecarboxamide)-1,2-cyclohexane (4-bpah)], and an aromatic dicarboxylic acid [1,4-cyclohexanedicarboxylic acid (H2CHDA)] to construct a 1D binuclear Cu-based complex, namely {[Cu3(4-bpah)(CHDA)3(H2O)]·2H2O}n (1). Moreover, we also developed a facile method to synthesize two monometallic/bimetallic-doped materials which were derived from the Cu complex (C-N-1 and C-V-1, which were doped with nitrogen and vanadium, respectively). The as-synthesized derived materials were fully characterized and the iodine sorption/release capabilities were investigated in detail. We performed iodine adsorption experiments on the two monometallic/bimetallic-doped materials and found that C-N-1 and C-V-1 possess highly efficient adsorption activities for the adsorption of iodine from solution. The C-N-1 and C-V-1 complexes exhibited remarkable adsorption capacities of 1141.60 and 1170.70 mg g-1, respectively, for iodine from a cyclohexane solution. Moreover, the dye adsorption properties of C-N-1 and C-V-1 were also investigated in detail. The obtained C-N-1 and C-V-1 exhibit effective dye uptake performances in water solution. The adsorption of Congo red (CR) on a single metal carbon material C-N-1 doped with heteroatoms reached equilibrium within 240 min and reached an adsorption capacity of 1357.00 mg g-1 and the adsorption capacities of C-V-1 for methylene blue (MB), gentian violet (GV), rhodamine B (RhB), and CR at room temperature were found to be 187.60, 190.60 and 108.10 and 1501.00 mg g-1 in 180 min, respectively. By comparison, we found that doping vanadium could play an important role in the adsorption processes. The adsorption capacity of C-V-1 (containing the vanadium in its structure) was relatively higher than that of C-N-1, which indicated that the introduction of non-noble metals may effectively tune the adsorption kinetics activity and the introduction of noble metals can change the surface electronegativity of porous carbon materials, thus leading to significantly improved adsorption capabilities.

Construction of a triazine polycarboxylate Co-MOF with flexible and rigid coordination arms as well as excellent catalytic reduction and adsorption properties.

A new compound [Co2(H2BATD)(DMF)2]·2.5DMF·0.5H2O (1) was synthesized from the triazine ligand H6BATD (H6BATD = 5,5'-(6-biscarboxymethylamino-1,3,5-triazine-2,4-diyl) bis (azadiyl), DMF = N,N-dimethylformamide) and Co(NO3)2·6H2O. Compound 1 was characterized using infrared spectroscopy, UV-vis spectroscopy, PXRD, and thermogravimetry. The three-dimensional network of compound 1 was further constructed using [Co2(COO)6] building blocks from the flexible coordination arms and the rigid coordination arms from the ligand. In terms of functional properties, compound 1 can be used for the catalytic reduction of p-nitrophenol (PNP) to p-aminophenol (PAP), and compound 1 with a dose of 1 mg showed good catalytic reduction properties, as well as a conversion rate of over 90%. Based on the unique π-electron wall and carboxyl groups in the H6BATD ligand that provide abundant adsorption sites, compound 1 can be used to adsorb iodine in cyclohexane solution.

A general method for endowing hydrophobic nanoparticles with water dispersion abilities.

Inorganic nanoparticles with long-chain ligands are usually hydrophobic. However, simple and practical methods for converting hydrophobic nanoparticles to hydrophilic nanoparticles are still lacking. Herein, we developed a general method involving using dimercaptosuccinic acid (DMSA) for endowing hydrophobic nanoparticles with water dispersion abilities. By mixing a tetrahydrofuran solution of DMSA with a cyclohexane solution of hydrophobic nanoparticles, the long-chain ligands were replaced with DMSA, with the replacement due to the strong and broad-spectrum coordination abilities of sulphydryls and carboxyls. Four representative kinds of hydrophobic nanoparticles, namely Ag, NaGdF4, TiO2, and ZnS nanoparticles, were selected for verifying the performance of this DMSA-based modification method. Meanwhile, this method can also widen the applications of hydrophobic nanoparticles and facilitate their being subjected to further graft modifications. We hope that our research will increase the chances for applications of nanomaterials to be made.

Anomalous diffusion, gigahertz, and terahertz spectroscopy of aliphatic ketones.

The experimental results of the complex dielectric permittivity of aliphatic ketones in dilute solutions of inert solvent cyclohexane in the gigahertz (GHz) and terahertz (THz) frequencies of the electromagnetic spectrum are examined in terms of the theory of inertial anomalous diffusion of polar molecules, considered as an assembly of molecules with interacting dipolar groups, in polar liquids. The theory is based on the generalization of the Debye rotational diffusion model of dielectric relaxation of polar molecules. The model comprises two interacting dipolar groups-one lighter and the other heavier; each has a finite moment of inertia and each experiences a finite friction with an extensive range of damping or drag coefficient and the dipole moment ratio of the two groups. The lighter group refers to the reference molecule, whereas the heavier group simulates the neighboring molecules, and the two groups interact with each other via the dipole-dipole interaction potential. The resulting approximate expression contains terms in both the Rocard form and the Сole-Сole form. The experimental data on aliphatic ketones are shown to fit extremely well with the theory, and parameters of the fit offer physical significance. An agreement of the plot of the experimental data on dielectric loss versus frequency to the formulas derived from the model offers a mathematical basis of the semiempirical equations used in the literature to fit the experimental data. Experimental results of the dielectric loss of neat polar liquid acetone in GHz and THz, as an example, are shown to fit the theory; however, the interaction potential parameter compared to its dilute solution counterpart is significantly increased, reflecting the increase in the dipole-dipole interaction energy.

A cationic nanotubular metal-organic framework for the removal of Cr2O72− and iodine

In this work, two new metal-organic frameworks (MOFs) based on a pyrazole-imidazole heterotopic ligand, namely, SCNU-Z8(Co) and SCNU-Z8(Ni), are constructed. They are isostructural, and the crystal structure of SCNU-Z8(Co) is further analyzed by single-crystal X-ray diffraction. They are 3D cationic frameworks with 1D tubular channels and possess a highly (3,9)-connected binodal gfy network topology. SCNU-Z8(Ni) can be synthesized in high yield with high phase purity; thus, it is selected to be further explored. A stability study shows that its framework is stable in water at different pH values and in many organic solvents. It can be applied to capture Cr2O72− anions in water with a moderate adsorption capacity of 130 ​mg/g via anion-exchanged process. Iodine molecules in vapour phase and cyclohexane solution can also be captured by SCNU-Z8(Ni). In the case of iodine vapours and iodine cyclohexane solution, the adsorption capacity reaches up to 4.1 ​g/g and 640 ​mg/g, respectively, which are among the best in MOFs. Most of the absorbed iodine molecules are stably captured in the framework and hard to release, which may be conducive to allow the permanent storage of radioactive iodine.