Synthesis of new crosslinked porous ammonium‐based poly(ionic liquid) and application in CO2 adsorption

A new poly(ionic liquid) of N,N‐methylenebisacrylamide (MBA)‐crosslinked‐poly(4‐vinylbenzyltriethylammonium hexafluorophosphate)(MBA‐crosslinked‐P[VBTEA][PF₆]) is prepared through the ion exchange of KPF₆ with the precursor of MBA‐crosslinked‐P[VBTEA][Cl]; the precursor is synthesized by 4‐vinylbenzyltriethylammonium chloride and MBA via inverse suspension polymerization. MBA‐crosslinked‐P[VBTEA][PF₆] is a thermally stable (decomposes at nearly 300°C) and porous (apparent porosity of 64.3% and specific surface of 39.12 m²/g) polymer particle with high purity, as indicated by Fourier transformed infrared, energy dispersive spectroscopy, thermogravimetric, scanning electron microscopy, and porous analyses. It is observed that MBA‐crosslinked‐P[VBTEA][PF₆] has good CO₂ adsorption capability of 14.04 mg/g at 0.2 MPa and 25°C, and can be recovered by desorption at vacuum and 80°C, and reused with 99% CO₂ adsorption after four cycles. POLYM. ENG. SCI., 54:59–63, 2014. © 2013 Society of Plastics Engineers     

Ionic liquid effects on the reaction of β-enaminones and tert-butylhydrazine and applications for the synthesis of pyrazoles

In order to evaluate the effect of a series of 10 different ionic liquids ([BMIM][BF₄], [BMIM][Br], [OMIM][BF₄], [BMIM][PF₆], [DBMIM][Br], [DBMIM][BF₄], [BMIM][OH], [BMIM][SCN], [HMIM][HSO₄] and [HMIM][CF₃CO₂]) the cyclocondensation reaction between 4-dimethylamino-1-phenyl-3-alken-2-ones (RC(O)CHCHNMe₂, where R = Ph, 4-Me-Ph, 4-F-Ph, 4-Cl-Ph, 4-Br-Ph, 4-NO₂-Ph, thien-2-yl, fur-2-yl, pyrrol-2-yl, pyrid-2-yl, hexyl, dimethoxymethyl) and tert-butylhydrazine was performed. The effects of each ionic liquid are discussed and the best yields for the cyclocondensation reaction studied were obtained using [BMIM][BF₄].     

Porous Cd-carboxylate frameworks tuned by the bulk of linker: Interpenetrated nets,selective CO2 uptakes and high water vapor adsorption

Reported herein are two porous interpenetrated anionic Cd-carboxylate frameworks tuned by the length of organic linker. Shorter BDC linker and [Cd(COO)₄] building blocks in 1 generate a rare 4-connected 2-fold interpenetrating qtz network. But longer NDC linker in 2 produces a self-penetrated 8-connected bcu framework with [Cd₃(COO)₈] SBUs. 1 and 2 both show selective CO₂ adsorption and significantly, 2 exhibits the highest water vapor uptake performance (281 cm³·g^− 1 at 298 K and P/P₀ = 0.95) among all the interpenetrated MOFs.     

Polymeric ionic liquid modified silica for CO2 adsorption and diffusivity

Two types of polymeric ionic liquids (PILs) modified porous silica for CO₂ sorption were synthesized by the polymerization of dialkylphosphate di‐butyl phosphate [VYIM][Bu₂PO₄] and 1‐allyl‐3‐methylimidazolium tetrafluoroborate [AMIM][BF₄] with alkoxyl‐modified silica. The PILs‐modified silica (SiO₂‐P[VYIM][Bu₂PO₄] and SiO₂‐P[AMIM][BF₄]) were evaluated by CO₂ adsorption isotherms at 273 K for investigating the porous structures. The adsorption and desorption behaviors of CO₂ (at 298, 313, and 333 K) and N₂ (at 313 K) up to 0.2 MPa were also investigated using a gravimetric method. In comparison with bare silica, the grafting of PILs on the support surface leads to a loss of microporosity, resulting in a slight decrease in CO₂ sorption capacity. The difference of CO₂ sorption capacity between SiO₂‐P[VYIM][Bu₂PO₄] and SiO₂‐P[AMIM][BF₄] is little, especially under 0.1 MPa. CO₂/N₂ selectivity is however notably improved, and especially [AMIM][BF₄] modified silica shows the best performance. The homogeneous surface diffusion model (HSDM) was used to estimate the diffusivities and good agreement between experimental values and fitting curves was obtained. The diffusion coefficients of CO₂ in the PILs‐modified silica are level with that of bare silica at level of 10⁻⁷−10⁻⁸ m²/s, about two to three orders of magnitude faster than that of reported [BMIM][BF₄]. POLYM. COMPOS., 38:759–766, 2017. © 2015 Society of Plastics Engineers     

Extraction of lanthanide ions from aqueous solution by bis(2-ethylhexyl)phosphoric acid with room-temperature ionic liquids

Extractions of five kinds of lanthanide metal ions by bis(2-ethylhexyl)phosphoric acid (DEHPA) with [1-Cn-3-methylimidazolium][PF₆](Cn = C₂, C₄) or [1-butyl-4-methylpyridinium][PF₆] were carried out under various DEHPA and HNO₃ concentrations from 0 to 1 M and under different temperature conditions from 298 to 333 K. These results were compared with those using the conventional organic solvent, hexane, in terms of their distribution coefficient values. Under all of the conditions in this study, the ionic liquid system shows more than three times greater extractability for lanthanide compared to when hexane was used. The distribution coefficient of lanthanide ions decreased as the length of the alkyl chain increased from the ethyl to the butyl. In addition, the imidazolium cation generally shows a higher distribution coefficient compared to the pyridinium cation in an ionic liquid. The concentration ratio of lanthanides and DEHPA resulted in an extraction affinity transition for lanthanides. Also evaluated in this study were issues related to the selectivity associated with the lanthanide mixture and the dependency of the ionic radius during lanthanide extraction.     

Superior carbon-based CO2 adsorbents prepared from poplar anthers

A series of renewable nitrogen-containing granular porous carbons with developed porosities and controlled surface chemical properties were prepared from poplar anthers. The preparation conditions such as pre-carbonization and activation temperatures and KOH amount significantly influence the structures and chemical compositions of the porous carbons, the CO₂ adsorption capacities of which are highly dependent on their pore structures, surface areas, nitrogen contents and adsorption conditions. The sample with developed microporosity, especially with the pores between 0.43 and 1 nm and high nitrogen content shows high CO₂ adsorption capacity at 1 bar and 25 °C. In contrast, when the adsorption pressure is higher than 5 bar, its CO₂ adsorption capacity is dominated by its surface area, and more accurately by its pore volume. Irrespective of this, if the pressure was decreased to 0.1 bar, its CO₂ capture ability is closely correlated to its nitrogen content but not to its porosity. By optimizing the preparation conditions, a porous carbon with a surface area of 3322 m² g⁻¹ and a CO₂ adsorption capacity as high as 51.3 mmol g⁻¹ at 50 bar and 25 °C was prepared.     

Tetrachloroferrate containing ionic liquids: Magnetic- and aggregation behavior

The magnetic behavior of a binary salt of tricaprylylmethylammonium tetrachloroferrate and tricaprylylmethylammonium chloride, [A336][FeCl₄]_0.73[Cl]_0.27, was evaluated. With a magnetic susceptibility of 0.011 emu mol^? 1 this binary salt exhibited a remarkable response to an external magnetic field. Dynamic light scattering (DLS) measurements allowed to study the aggregation behavior of [A336][FeCl₄]_0.73[Cl]_0.27 as well as of further magnetic ionic liquids [PR_6,6,6,14][FeCl₄] and (BMIM)[FeCl₄] in ethylacetate and ethanol.     

PEG-modified magnetic hypercrosslinked poly(styrene-co-divinylbenzene) microspheres to minimize sorption of serum proteins

Monodisperse poly(styrene-co-divinylbenzene) [P(St-DVB)] microspheres were prepared by the precipitation polymerization of styrene (St) and divinylbenzene (DVB) in acetonitrile (ACN). Effect of St/DVB ratio and monomer concentration on morphology and particle size was investigated. Monodisperse 4.1 μm P(St-DVB) microspheres were chloromethylated with chloromethyl methyl ether (CMME) and hypercrosslinked using anhydrous FeCl₃ as a catalyst to form a very fine porous structure and to introduce reactive chloromethyl groups in the resulting product denoted as HC-P(St-DVB) particles. The hypercrosslinked microspheres were then functionalized with amino groups to yield HC-P(St-DVB)-NH₂ particles and iron oxide was precipitated within their pores. The obtained microparticles were highly magnetic with iron content ～38 wt% Fe. The surface of the magnetic microspheres was newly hydrophilized with methoxy-poly(ethylene glycol) (methoxy-PEG) which was confirmed by ATR FT-IR spectroscopy. The poly(ethylene glycol) (PEG)-modified magnetic microspheres were investigated in terms of sorption of serum proteins under different conditions and compared with the sorption on neat magnetic HC-P(St-DVB)-NH₂ particles. The surface modification of magnetic microspheres significantly minimized the adsorption of the serum proteins.     

Synthesis,structure, and electrochemical behavior of a new dinuclear Rh(III) complex bridged by a bpp− ligand (bpp− = 3,5-bis(2-pyridyl)pyrazolate)

The new dinuclear rhodium complex [(Cp*RhCl)₂(bpp)](PF₆) ([1](PF₆), Cp* = pentamethylcyclopentadienyl, bpp = 3,5-bis(2-pyridyl)pyrazolate) was synthesized by the reaction of [Cp*RhCl₂]₂ with 3,5-bis(2-pyridyl)pyrazole (bppH). [1](PF₆) was characterized by ¹H- and ¹³C{¹H}-NMR spectroscopy and X-ray diffraction. The distance between the two Rh atoms in [1](PF₆) is 4.746(3) Å. A cyclic voltammogram of [1](PF₆) in acetonitrile shows three-step reduction peaks at E_pc = − 1.44, − 1.68 and − 1.88 V (vs. Fc⁺/Fc), which are assigned to the reduction of the two Rh(III) centers and the bpp⁻ ligand, respectively. [1](PF₆) catalyzes the reduction reaction of NAD⁺ (nicotinamide adenine dinucleotide) using HCO₂⁻ as a reductant.     

Hexachloroplatinate(IV) anion-induced cucurbit[5]uril and cucurbit[8]uril supramolecular assemblies with linear channels

Two Q[n]-based porous compounds, Q[5]·[PtCl₆]^2 −·2H₃O·12H₂O and 2Q[8]·[PtCl₆]^2 −·2H₃O·74H₂O in cooperating the hexachloroplatinate(IV) anion ([PtCl₆]^2 −) as an inorganic structure directing agent are demonstrated. The driving forces for the formation of such novel Q[n]-based porous compounds are considered to be the outer surface interactions of Q[n]s, including dipole interactions between Q[n]s and ion-dipole interactions between [PtCl₆]^2 − anions and Q[n]s. Moreover, the Q[5]-based porous compound displays absorption distinctness for tetrachloromethane, whereas the Q[8]-based porous compound displays absorption distinctness for methanol.     

Utilization of Crofton weed for preparation of activated carbon by microwave induced CO2 activation

Crofton weed was converted into a high-quality activated carbon (CWAC) via microwave-induced CO₂ physical activation. The operational variables including activation temperature, activation duration and CO₂ flow rate on the adsorption capability and activated carbon yield were identified. Additionally the surface characteristics of CWAC were characterized by nitrogen adsorption isotherms, FTIR and SEM. The operating variables were optimized utilizing the response surface methodology and were identified to be an activation temperature of 980 °C, an activation duration of 90 min and a CO₂ flow rate of 300 ml/min with a iodine adsorption capacity of 972 mg/g and yield of 18.03%. The key parameters that characterize quality of the porous carbon such as the BET surface area, total pore volume and average pore diameter were estimated to be 1036 m²/g, 0.71 ml/g and 2.75 nm, respectively. The findings strongly support the feasibility of microwave heating for preparation of high surface area porous carbon from Crofton weed via CO₂ activation.     

High selectivity of TiC-CDC for CO2/N2 separation

A series of carbide-derived carbons (CDC) have been prepared starting from TiC and using different chlorine treatment temperatures (500–1200 °C). Contrary to N₂ adsorption measurements at −196 °C, CO₂ adsorption measurements at room temperature and high pressure (up to 1 MPa) together with immersion calorimetry measurements into dichloromethane suggest that the synthesized CDC exhibit a similar porous structure, in terms of narrow pore volume, independently of the temperature of the reactive extraction treatment used (samples synthesized below 1000 °C). Apparently, these carbide-derived carbons exhibit narrow constrictions were CO₂ adsorption under standard conditions (0 °C and atmospheric pressure) is kinetically restricted. The same accounts for a slightly larger molecule as N₂ at a lower adsorption temperature (−196 °C), i.e. textural parameters obtained from N₂ adsorption measurements on CDC must be underestimated. Furthermore, here we show experimentally that nitrogen exhibits an unusual behavior, poor affinity, on these carbide-derived carbons. CH₄ with a slightly larger diameter (0.39 nm) is able to partially access the inner porous structure whereas N₂, with a slightly smaller diameter (0.36 nm), does not. Consequently, these CDC can be envisaged as excellent sorbent for selective CO₂ capture in flue-gas streams.     

Enhanced CO2/N2 selectivity in amidoxime-modified porous carbon

In this work, we examine the use of the amidoxime functional group grafted onto a hierarchical porous carbon framework for the selective capture and removal of carbon dioxide from combustion streams. Measured CO₂/N₂ ideal selectivity values for the amidoxime-grafted carbon were significantly higher than the pristine porous carbon with improvements of 65%. Though the overall CO₂ capacity decreased slightly for the activated carbon from 4.97 mmol g⁻¹ to 4.24 mmol g⁻¹ after surface modification due to a reduction in the total surface area, the isosteric heats of adsorption increased after amidoxime incorporation indicating an increased interaction of CO₂ with the sorbent. Total capacity was reproducible and stable after multiple adsorption/desorption cycles with no loss of capacity suggesting that modification with the amidoxime group is a potential method to enhance carbon capture.     

Preparation and carbon dioxide uptake capacity of N-doped porous carbon materials derived from direct carbonization of zeolitic imidazolate framework

The preparation, characterization and CO₂ uptake performance of N-doped porous carbon materials and composites derived from direct carbonization of ZIF-8 under various conditions are presented for the first time. It is found that the carbonization temperature has remarkable effect on the compositions, the textural properties and consequently the CO₂ adsorption capacities of the ZIF-derived porous materials. Changing the carbonization temperature from 600 to 1000 °C, the composites and the resulting porous carbon materials possess a tuneable nitrogen content in the range of 7.1–24.8 wt%, a surface area of 362–1466 m² g⁻¹ and a pore volume of 0.27–0.87 cm³ g⁻¹, where a significant proportion of the porosity is contributed by micropores. These N-doped porous composites and carbons exhibit excellent CO₂ uptake capacities up to 3.8 mmol g⁻¹ at 25 °C and 1 bar with a CO₂ adsorption energy up to 26 kJ mol⁻¹ at higher CO₂ coverages. The average adsorption energy for CO₂ is one of the highest ever reported for any porous carbon materials. Moreover, the influence of textural properties on CO₂ capture performance of the resulting porous adsorbents has been discussed, which may pave the way to further develop higher efficient CO₂ adsorbent materials.     

Enhancement of CO2 adsorption on phenolic resin-based mesoporous carbons by KOH activation

Carbons with high surface area and large volume of ultramicropores were synthesized for CO₂ adsorption. First, mesoporous carbons were produced by soft-templating method using triblock copolymer Pluronic F127 as a structure directing agent and formaldehyde and either phloroglucinol or resorcinol as carbon precursors. The resulting carbons were mainly mesoporous with well-developed surface area, large total pore volume, and only moderate CO₂ uptake. To improve CO₂ adsorption, these carbons were subjected to KOH activation to enhance their microporosity. Activated carbons showed 2–3-fold increase in the specific surface area, resulting from substantial development of microporosity (3–5-fold increase in the micropore volume). KOH activation resulted in enhanced CO₂ adsorption at 760 mmHg pressure: 4.4 mmol g⁻¹ at 25 °C, and 7 mmol g⁻¹ at 0 °C. This substantial increase in the CO₂ uptake was achieved due to the development of ultramicroporosity, which was shown to be beneficial for CO₂ physisorption at low pressures. The resulting materials were investigated using low-temperature nitrogen physisorption, CO₂ sorption, and small-angle powder X-ray diffraction. High CO₂ uptake and good cyclability (without noticeable loss in CO₂ uptake after five runs) render ultramicroporous carbons as efficient CO₂ adsorbents at ambient conditions.     

Solute recovery from ionic liquids: A conceptual design study for recovery of styrene monomer from [4-mebupy][BF4]

Extractive distillation using ionic liquids (ILs) is a promising technology to separate the close-boiling mixture ethylbenzene/styrene. A proper solvent regeneration is crucial to obtain a technical and economic feasible process. In this work, several regeneration technologies were studied to recover styrene from the IL [4-mebupy][BF₄] using Aspen Plus. Stripping with a hot gas (N₂ or ethylbenzene), supercritical CO₂ extraction, distillation by adding a co-solvent, and evaporation were investigated. It was found that the IL that was fed as solvent to the extractive distillation column should have a purity of at least 99.6 wt% to maintain the purities of the top and bottom products from the extractive distillation column. This purity could not be obtained with an evaporator using mild conditions (T = 130 °C, T_condenser ≥ 20 °C). From the process models and the economic evaluation for a typical production capacity of 500,000 mta, the conclusion can be drawn that evaporation using very low pressures (P < 10 mbar) and stripping with ethylbenzene are the most promising technologies to recover styrene monomer from the IL [4-mebupy][BF₄].     

An intriguing NO2⋯π and CN⋯π interactions in [1-(4′-nitrobenzyl)pyrazinium][Ni(mnt)2]: Crystal structure,magnetic property and DFT calculation

A charge-transfer compound, [NO₂BzPz][Ni(mnt)₂] (NO₂BzPz⁺ = 1-(4′-nitrobenzyl)pyrazinium and mnt^2? = maleonitriledithiolate), has been structurally characterized, which shows rare noncovalently intermolecular interactions between lone-pair electron and electron-deficient pyrazine rings (NO₂?π and CN?π), theoretical analysis reveals that such intermolecular interactions can be attributed to Coulomb interaction. The paramagnetic [Ni(mnt)₂]^? anions in [NO₂BzPz][Ni(mnt)₂] form a dimerized stack and strong antiferromagnetic coupling interaction is observed in such a spin dimer which lead to weak paramagnetic feature in this compound.     

High pressure phase behavior of poly[isopropyl acrylate] and poly[isopropyl methacrylate] in supercritical fluid (SCF) solvent and SCF solvent + cosolvent mixtures

Cloud-point data are reported for poly(isopropyl acrylate) [P(IPA)] in CO₂, propane, propylene, butane, 1-butene, and dimethyl ether (DME) and for poly(isopropyl methacrylate) [P(IPMA)] in CO₂. P(IPA) + alkene cloud-point curves are ∼100 °C lower than the P(IPA) + alkane curves, which are close to the P(IPA) + CO₂ curve located at temperatures greater than 130 °C and pressures of 2500 bar. P(IPA) dissolves in pure DME at conditions as mild as 50 °C and 200 bar. Since IPA and IPMA monomers are used as cosolvents with CO₂, binary IPA + CO₂ and IPMA + CO₂ data are reported to complement the ternary cloud-point data. Both monomer + CO₂ mixtures exhibit type-I behavior and both are adequately modeled with the Peng–Robinson equation of state. IPMA is a more effective cosolvent than IPA. The polymer + CO₂ + monomer phase behavior suggests that it is viable to polymerize IPA or IPMA in CO₂ at moderate operating conditions.     

Synthesis and characterization of trans-[Ru(NO)Cl(L)4](PF6)2 (L = isonicotinamide; 4-acetylpyridine) and related species

The trans-[RuCl₂(L)₄], trans-[Ru(NO)Cl (L)₄](PF₆)₂ (L = isonicotinamide and 4-acetylpyridine) and trans-[Ru(NO)(OH)(py)₄]Cl₂ (py = pyridine) complexes have been prepared and characterized by elemental analysis, UV–visible, infrared, and ¹H NMR spectroscopies, and cyclic voltammetry. The MLCT band energies of trans-[RuCl₂(L)₄] increase in the order 4-acpy < isn < py. The reduction potentials of trans-[RuCl₂(L)₄] and trans-[Ru(NO)Cl(L)₄]²⁺ increase in the order py < isn < 4-acpy. The stretching band frequency, ν_NO, of the nitrosyl complexes ranges from 1913 to 1852 cm^?1 indicating a nitrosonium character for the NO ligand. Due to the large π-acceptor ability of the equatorial ligands, the coordinated water is much more acidic in the water soluble trans-[Ru(NO)(H₂O)(py)₄]³⁺ than in trans-[Ru(NO)(H₂O)(NH₃)₄]³⁺.     

Adsorption characteristics of a fully exchanged potassium chabazite zeolite prepared from decomposition of zeolite Y

In this work a comprehensive study was undertaken to characterize the porous nature of a fully exchanged potassium chabazite zeolite (KCHA) and evaluate its adsorption properties under different conditions. A synthetic chabazite was prepared from the decomposition of zeolite Y and ion-exchanged to produce a fully exchanged potassium chabazite with Si/Al ratio of 2.4. In addition, sodium chabazite (NaCHA) and lithium chabazite (LiCHA) were synthesized for comparison purposes. Equilibrium isotherms for N₂ and CO₂ were measured at 273 K for further characterization. Our results show that the porous structure characterization by N₂ at 77 K and Ar at 87 K following the standard methods of BET for surface area, t-plot, DR and DFT for pore size distribution and volume reveal pore blockage phenomenon with substantially diminished adsorption capacities. However, CO₂ adsorption capacity on KCHA at 273 K reveals magnitudes of 70.1% and 78.7% of those on LiCHA and NaCHA, and a DFT pore volume of 0.214 cm³ g^?1. The surface area of KCHA calculated from the CO₂ isotherm using the Tóth model in its revised form demonstrates a surface area of 584.4 m² g^?1. This is in contrast to 17.82 and 13.48 m² g^?1 obtained from the BET model using N₂ and Ar at 77 and 87 K, respectively. It was concluded that the reliability of standard methods (viz. BET using N₂ at 77 K) for characterizing these particular porous solids is questionable under certain circumstances leading to misevaluation of adsorbent properties.