Preparation and characterization of H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript>/ZrO<Subscript>2</Subscript> catalyst for carbonation of methanol into dimethyl carbonate

A H₃PW₁₂O₄₀/ZrO₂ catalyst for effective dimethyl carbonate (DMC) formation via methanol carbonation was prepared using the sol–gel method. X-ray photoelectron spectra showed that reactive and dominant (63%) W(VI) species, in WO₃ or H₂WO₄, enhanced the catalytic performances of the supported ZrO₂. The mesoporous structure of H₃PW₁₂O₄₀/ZrO₂ was identified by nitrogen adsorption–desorption isotherms. In particular, partial sintering of catalyst particles in the duration of methanol carbonation caused a decrease in the Brunauer–Emmett–Teller surface area of the catalyst from 39 to 19 m²/g. The strong acidity of H₃PW₁₂O₄₀/ZrO₂ was confirmed by the desorption peak observed at 415 °C in NH₃ temperature-programmed desorption curve. At various reaction temperatures (T?=?110, 170, and 220 °C) and CO₂/N₂ volumetric flow rate ratios (CO₂/N₂?=?1/4, 1/7, and 1/9), the calculated catalytic performances showed that the optimal methanol conversion, DMC selectivity, and DMC yield were 4.45, 89.93, and 4.00%, respectively, when T?=?170 °C and CO₂/N₂?=?1/7. Furthermore, linear regression of the pseudo-first-order model and Arrhenius equation deduced the optimal rate constant (4.24?×?10^?3 min^?1) and activation energy (E_a?=?15.54 kJ/mol) at 170 °C with CO₂/N₂?=?1/7 which were favorable for DMC formation.     

Organometallic coordination polymers based on silver carboxylates: [AgCF<Subscript>3</Subscript>CO<Subscript>2</Subscript>(2,3-Et<Subscript>2</Subscript>Pyz)] and [AgCF<Subscript>3</Subscript>CO<Subscript>2</Subscript>(Bpeta)]

Coordination polymers [AgCF₃CO₂(2,3-Et₂Pyz)](I)(2,3-Et₂Pyz-C₈H₁₂N₂) and [AgCF₃CO₂(Bpeta)] (II) (Bpeta is 4′4-bipyridylethane, C₁₂H₁₂N₂) are synthesized. Their structures are determined. The crystals of compound I are monoclinic, space group P2(1)/n, a = 7.185(1), b = 14.754(1), c = 12.317(1)Å, β = 97.09(1)°, V = 1295.7(2) ų, ρ_calcd = 1.831 g/cm³, Z = 4. Structure I consists of infinite chains of doubled polymeric chains joined by silver carboxylate dimers [[Ag₂(CF₃CO₂)₂(Et₂Pyz)₂]_∞. The coordination polyhedron of Ag⁺ is a distorted tetrahedron. The crystals of compound II are orthorhombic, space group Pbca, a = 13.555(3), b = 13.991(3), c = 16.449(3) Å, V = 3119.5(11) ų, ρ_calcd = 1.725 g/cm³, Z = 8. Doubled polymeric chains with the Ag…Ag bond (3.16 Å) are also formed in structure II. Supramolecular layers are formed in the structure due to the weak π-π-stacking interaction between the aromatic groups of chains. The CF₃CO ₂ ^? anion is weakly bound to Ag⁺ (Ag-O_avg 2.790 Å).     

Preparation and characterization of (Pebax 1657 + silica nanoparticle)/PVC mixed matrix composite membrane for CO<Subscript>2</Subscript>/N<Subscript>2</Subscript> separation

In this work, the films of poly(ether-block-amide) (Pebax 1657) and hydrophilic/hydrophobic silica nanoparticles (0–10 wt%) were coated on a poly(vinyl chloride) (PVC) ultrafiltration membrane to form new mixed matrix composite membranes (MMCMs) for CO₂/N₂ separation. The membranes were characterized by SEM, FTIR, DSC and XRD. Successful formation of a non-porous defect-free dense top layer with ~4 μm of thickness and also uniform dispersion of silica nanoparticles up to 8 wt% loading in Pebax matrix were confirmed by SEM images. The gas permeation results showed an increase in the permeance of all gases and an increase in ideal CO₂/N₂ selectivity with the increase in silica nanoparticle contents. Comparison between the incorporation of hydrophilic and hydrophobic silica nanoparticle into Pebax matrix revealed that the great enhancement of CO₂ solubility is the key factor for the performance improvement of Pebax + silica nanoparticle membranes. The best separation performance of the hydrophilic silica nanoparticle-incorporated Pebax/PVC membrane for pure gases (at 1 bar and 25 °C) was obtained with a CO₂ permeability of 124 barrer and an ideal CO₂/N₂ selectivity of 76, i.e., 63 and 35% higher than those of neat Pebax membrane, respectively. The corresponding values for hydrophobic silica nanoparticle-incorporated Pebax/PVC membrane were 107 barrer for CO₂ permeability and 61 for ideal CO₂/N₂ selectivity. Also the performances of MMCMs improved upon pressure increase (1–10 bar) owing to the shift in plasticizing effect of CO₂ towards the higher pressures. In addition, an increase in permeabilities with a decrease in ideal selectivity was observed upon temperature increase (25–50 °C) due to the intensification of chain mobility.     

Highly efficient mesoporous WO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/KIT-6 catalysts for oxidative desulfurization of dibenzothiophene with hydrogen peroxide

Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m²/g), and three-dimensional pore network (WO _x /KIT-6). The prepared WO _x /KIT-6 catalysts (5–20 wt% WO _x ) were characterized by X-ray diffraction analysis, N₂ sorption measurements, electron microscopy, H₂-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WO _x /KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WO _x /KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity.     

Triamine-grafted pore-expanded mesoporous silica for CO<Subscript>2</Subscript> capture: Effect of moisture and adsorbent regeneration strategies

Adsorption of carbon dioxide (CO₂) was investigated on triamine-grafted, pore-expanded MCM-41 mesoporous silica (TRI-PE-MCM-41). Measurements of adsorption capacity using mass spectrometry showed an enhanced CO₂ adsorption capacity in humid streams compared to dry CO₂. This was corroborated with breakthrough experiments, which also showed that TRI-PE-MCM-41 offered a practically infinite selectivity towards CO₂ over nitrogen. Cyclic measurements of pure CO₂ and CO₂:N₂ = 10:90 mixture using different regeneration modes showed that amine-grafted PE-MCM-41 is particularly suitable for CO₂ removal using temperature swing adsorption (TSA) at adsorption temperatures higher than ambient, while temperature-vacuum swing adsorption (TVSA) may be attractive at ambient temperature.     

CO<Subscript>2</Subscript> Biofixation of <Emphasis Type="Italic">Actinobacillus succinogenes</Emphasis> Through Novel Amine-Functionalized Polystyrene Microsphere Materials

CO₂-derived succinate production was enhanced by Actinobacillus succinogenes through polystyrene (PSt) microsphere materials for CO₂ adsorption in bioreactor, and the adhesion forces between A. succinogenes bacteria and PSt materials were characterized. Synthesized uniformly sized and highly cross-linked PSt microspheres had high specific surface areas. After modification with amine functional groups, the novel amine-functionalized PSt microspheres exhibited a high adsorption capacity of 25.3 mg CO₂/g materials. After addition with the functionalized microspheres into the culture broth, CO₂ supply to the cells increased. Succinate production by A. succinogenes can be enhanced from 29.6 to 48.1 g L^?1. Moreover, the characterization of interaction forces between A. succinogenes cells and the microspheres indicated that the maximal adhesive force was about 250 pN. The amine-functionalized PSt microspheres can adsorb a large amount of CO₂ and be employed for A. succinogenes anaerobic cultivation in bioreactor for high-efficiency production of CO₂-derived succinate.     

Effect of amine double-functionalization on CO<Subscript>2</Subscript> adsorption behaviors of silica gel-supported adsorbents

Amine double-functionalized adsorbents were fabricated using silica gel as supports and their capabilities for CO₂ capture were examined. Aminopropyltrimethoxysilane (1N-APS), and N¹-(3-trimethoxysilylpropyl)diethylenetriamine (3N-APS) were used as grafted amine compounds, and tetraethylenepentamine and polyethyleneimine were used as impregnated species. The influence of double-functionalization method on the CO₂ adsorption performance and textural properties of adsorbents was investigated. The adsorption capacity, the amine efficiency, and the thermal stability of double-functionalized sorbents depend strongly upon molecular variables associated with two different functional states (i.e., chemically grafted and physically impregnated amines). The temperature dependence of adsorption isotherms reveals that the CO₂ adsorption behavior in the double-functionalized adsorbents follow the diffusion limitation model proposed by Xu et al. (Energy Fuels 16:1463–1469, 2002) where the CO₂ adsorption is helped by the diffusion of impregnated amines. It is also found that the adsorption isotherm in the double-functionalized sorbent system with a proper choice for grafted and impregnated amines is nearly independent of temperature, which may offer a novel means to fabricate practically useful sorbents that can be used in a wide range of temperature without loss of CO₂ adsorption capacity.     

Facile Synthesis of Polyethylenimine and Nano-TiO<Subscript>2</Subscript> Particles Functionalized PolyHIPE Beads for CO<Subscript>2</Subscript> Capture

Polyethylenimine (PEI) and titanium dioxide nanoparticles (nano-TiO₂) functionalized poly- HIPE beads were synthesized by suspension polymerization of styrene/divinylbenzene high internal phase emulsion (HIPE) containing PEI and nano-TiO₂ particles in inner phase. The products are uniform and spherical beads with average diameter of 1 mm. Characterization results showed good thermal stability and desired mechanical strength. CO₂ adsorption tests were performed with CO₂/H₂O/N₂ (1 : 1 : 8) gas mixture. Nano-TiO₂ particles distinctly improved the CO₂ adsorption performance of the polyHIPE beads, resulting in enhanced CO₂ adsorption capacity and fast adsorption/desorption kinetics. Besides, the functionalized polyHIPE beads exhibited remarkable cycle stability.     

CO<Subscript>2</Subscript>-responsive Polymeric Fluorescent Sensor with Ultrafast Response

Abstract Response speed is one of the most important evaluation criteria for CO₂ sensors. In this work, we report an ultrafast CO₂ fluorescent sensor based on poly[oligo(ethylene glycol) methyl ether methacrylate]-b-poly[N,N-diethylaminoethyl methacrylate-r-4-(2-methylacryloyloxyethylamino)-7-nitro-2,1,3-benzoxadiazole] [POEGMA-b-P(DEAEMA-r-NBDMA)], in which DEAEMA units act as the CO₂-responsive segment and 4-nitrobenzo-2-oxa-1,3-diazole (NBD) is the chromophore. The micelles composed of this copolymer could disassemble in 2 s upon CO₂ bubbling, accompanying with enhanced fluorescence emission with bathochromic shift. Furthermore, the quantum yield of the NBD chromophore increases with both the CO₂ aeration time and the NBD content. Thus we attribute the fluorescent enhancement to the inhibition of the photo-induced electron transfer between unprotonated tertiary amine groups and NBD fluorophores. The sensor is durable although it is based on “soft” materials. These micellar sensors could be facilely recycled by alternative CO₂/Ar purging for at least 5 times, indicating good reversibility.     

Investigation of environmental and concentration effects on fluorescence properties of AlQ<Subscript>3</Subscript> using mesoporous silica and polyacrylate

In this work, for the first time, control over the position of maximum emission peak for fluorophore, using embedded tris(8-hydroxyquinoline) aluminum (AlQ₃) complexes into different types of host materials, can be achieved. Moreover, the environmental and concentration effects on luminescent properties were studied. In this regard, different concentrations of AlQ₃ were embedded into the poly(methyl methacrylate-co-butyl acrylate) (PMMA-co-PBuA) nanoparticles as organic host materials by emulsion polymerization. It is established that the dilution of AlQ₃ in the polymer matrix leads to blue-shift of the luminescence maximum up to 0.32 eV compared to pure AlQ₃. Moreover, AlQ₃ was embedded in SBA-15 type mesoporous silica as an inorganic host material by physical adsorption. Finally, this functionalized mesoporous silica was incorporated into PMMA-co-PBuA transparent matrix by blending method to obtain Co-Poly-AlQ₃-SBA-15 as organic–inorganic composite material. It was found that there is no significant wavelength shift on the maximum emission peak of the organic–inorganic composite at various concentrations of AlQ₃-SBA-15. The prepared materials were characterized by powder X-ray diffraction (XRD), N₂ adsorption–desorption, NMR, Fourier transform infrared (FT-IR), dynamic light scattering (DLS), scanning electron microscopy (SEM) and fluorescence spectra.     

Double helix of the coordination polymer of silver with 1,3-bis(4-pyridyl)propane: Synthesis and crystal structure of [Ag(C<Subscript>13</Subscript>H<Subscript>14</Subscript>N<Subscript>2</Subscript>)](CF<Subscript>3</Subscript>CO<Subscript>2</Subscript>)

The [Ag(Bpp)](CF₃CO₂) complex (Bpp is 1,3-bis(4-pyridyl)propane, C₁₃H₁₄N₂) is synthesized, and its structure is determined. The crystals are monoclinic, space group C2/c, a = 26.169(5), b = 10.521(2), c = 12.906(3) Å, β = 117.99(3)°, V = 3137.7(11) ų, ρ_calcd = 1.775 g/cm³, Z = 8. The structure contains double helices of-Ag-Bpp-Ag-Bpp-cationic chains with a helix period of 21.042 Å. The Ag…Ag distance between a pair of silver atoms from different chains in the helix is 3.201 Å, and the distance between the adjacent helices is 3.279 Å. The silver atom is linked with two bridging nitrogen atoms of two Bpp ligands in an almost linear coordination: Ag-N_avg 2.142 Å; NagN, 171.3(4)°. The CF₃C ₂ ^? anion has a weak contact with the silver ion (Ag…O 2.62(2) Å).     

Structure of arsenic 8-mercaptoquinolinate: Synthesis and crystal structure of arsenic 4-methoxy-8-mercaptoquinolinate As[C<Subscript>9</Subscript>H<Subscript>5</Subscript>(OCH<Subscript>3</Subscript>)NS]<Subscript>3</Subscript>

Arsenic 4-methoxy-8-mercaptoquinolinate As[C₉H₅(4-OCH₃)NS]₃ (I) was synthesized and studied by X-ray diffraction. Crystals are trigonal: space group R3, a = b = 13.9867(4) Å, c = 12.4991(5) Å, γ = 120°, V = 2117.58(12) ų, ρ = 1.519 g/cm³, Z = 3. An arsenic atom in the crystal structure occupies a special position on axis 3. The structural unit of the crystal (neutral complex I) has symmetry C3. 4-Methoxy-8-mercaptoquinoline acts as a bidentate (N,S-) ligand. The coordination polyhedron of the arsenic atom is a symmetric octahedron (3S + 3N) or, with allowance for the lone electron pair, ψ-one-capped octahedron (3S + 3N + E). Bond lengths are as follows: As-S, 2.3179(7)Å; As…N 2.688(3) Å. The geometries of coordination polyhedra of arsenic atoms are compared in the crystal structures of As(C₉H₆NS)₃, As[C₉H₅(2-CH₃)NS]₃, and As[C₉H₅(4-CH₃)NS]₃.     

Crystal and molecular structure of [Au(C<Subscript>14</Subscript>H<Subscript>24</Subscript>N<Subscript>4</Subscript>)][H<Subscript>3</Subscript>O](ClO<Subscript>4</Subscript>)<Subscript>4</Subscript>

The crystal and molecular structure of doubly protonated tetraazamacrocyclic complex of gold(III) [Au(C₁₄H₂₄N₄)][H₃O](ClO₄)₄ has been determined. The crystals are monoclinic: a = 11.158(2) Å, b = 8.243(1) Å, c = 14.756(2) Å; β = 98.65(1)°, V = 1341.8(3) ų, Z = 2, ρ(calc) = 1.134 g/cm³, space group P2₁/n. The structure is built of almost flat centrosymmetrical Au(C₁₄H₂₄N₄)]³⁺ and [H₃O]⁺ cations and [ClO₄]^? anions. The gold atom is coordinated with four nitrogen atoms of the ligand forming a flat square. The coordinated ligand is protonated at its γ-carbon atoms of the two six-membered chelate rings. The Au-N bond lengths are almost identical (the mean value is 1.994 Å). The six-membered rings of the complex contain C=N diimine bonds. The [H₃O]⁺ oxonium ion has H-bonds with the oxygen atoms of perchlorate ions.     

FT-IR study on CO<Subscript>2</Subscript> adsorbed species of CO<Subscript>2</Subscript> sorbents

The stability of amine-functionalized silica sorbents prepared through the incipient wetness technique with primary, secondary, and tertiary amino organosilanes was investigated. The prepared sorbents were exposed to different gaseous streams including CO₂/N₂, dry CO₂/air with varying concentration, and humid CO₂/air mixtures to demonstrate the effect of the gas conditions on the CO₂ adsorption capacity and the stability of the different amine structures. The primary and secondary amine-functionalized adsorbents exhibited CO₂ sorption capacity, while tertiary amine adsorbent hardly adsorbed any CO₂. The secondary amine adsorbent showed better stability than the primary amine sorbent in all the gas conditions, especially dry conditions. Deactivation species were evaluated using FT-IR spectra, and the presence of urea was confirmed to be the main deactivation product of the primary amine adsorbent under dry condition. Furthermore, it was found that the CO₂ concentration can affect the CO₂ sorption capacity as well as the extent of degradation of sorbents.     

Study of the monocarbonate complex of pentavalent neptunium (NH<Subscript>4</Subscript>)[NpO<Subscript>2</Subscript>(CO<Subscript>3</Subscript>)]

The single crystals of the Np(V) complex (NH₄)[NpO₂(CO₃)] (I) were synthesized and studied by X-ray diffraction. At 100 K, the crystals are hexagonal, space group P6₃ μmc, a = 5.0734(1) Å, c = 10.9191(2) Å, V= 243.399(11) ų, Z = 2, ρ(calcd) = 4.735 g/cm³. The absorption spectra of a crystal of I in the visible and infrared ranges were measured.     

Molecular structure of NiO<Subscript>2</Subscript>N<Subscript>2</Subscript>C<Subscript>16</Subscript>H<Subscript>14</Subscript> from gas-phase electron diffraction and quantum chemical data

Gas-phase electron diffractometry was used to study the molecular structure of N,N′-ethylenebis(salicylaldiminato)nickel(II), NiO₂N₂C₁₆H₁₄, [hereinafter Ni(salen)] at 583(5) K. The molecule has C ₂ symmetry with a practically planar structure of the NiN₂O₂ coordination unit and with internuclear distances r _α (Ni-O) = 1.882(21) Å and r _α (Ni-N) = 1.889(22) Å. The results of B3LYP/CEP-31G molecular structure calculations are in good agreement with experimental data, whereas the RHF/CEP-31G method significantly overestimates the Ni-N internuclear distance and gives worse results for other structural parameters. According to 3LYP/CEP-31G calculations, the ¹ A low-spin state is 28 kJ/mole lower in energy than the ³ B high-spin state.     

Equilibrium isotherms and isosteric heat for CO<Subscript>2</Subscript> adsorption on nanoporous carbons from polymers

Four nanoporous carbons obtained from different polymers: polypyrrole, polyvinylidene fluoride, sulfonated styrene–divinylbenzene resin, and phenol–formaldehyde resin, were investigated as potential adsorbents for carbon dioxide. CO₂ adsorption isotherms measured at eight temperatures between 0 and 60 °C were used to study adsorption properties of these polymer-derived carbons, especially CO₂ uptakes at ambient pressure and different temperatures, working capacity, and isosteric heat of adsorption. The specific surface areas and the volumes of micropores and ultramicropores estimated for these materials by using the density functional theory-based software for pore size analysis ranged from 840 to 1990 m² g^?1, from 0.22 to 1.47 cm³ g^?1, and from 0.18 to 0.64 cm³ g^?1, respectively. The observed differences in the nanoporosity of these carbons had a pronounced effect on the CO₂ adsorption properties. The highest CO₂ uptakes, 6.92 mmol g^?1 (0 °C, 1 atm) and 1.89 mmol g^?1 (60 °C, 1 atm), were obtained for the polypyrrole-derived activated carbon prepared through a single carbonization-KOH activation step. The working capacity for this adsorbent was estimated to be 3.70 mmol g^?1. Depending on the adsorbent, the CO₂ isosteric heats of adsorption varied from 32.9 to 16.3 kJ mol^?1 in 0–2.5 mmol g^?1 range. Overall, the carbons studied showed well-developed microporosity and exceptional CO₂ adsorption, which make them viable candidates for CO₂ capture, and for other adsorption and environmental-related applications.     

Synthesis,characterization, and KOH activation of nanoporous carbon for increasing CO2 adsorption capacity

Ordered nanoporous carbons (ONCs) were prepared using a soft-templating method. To improve the CO₂ adsorption efficiency, ONCs were chemically activated to obtain high specific surface area and micro-/mesopore volume with different KOH amounts (i.e., 0, 1, 2, 3, and 4) as an activating agent. The prepared nanoporous carbons (NCs) materials were analyzed by low-angle X-ray diffraction for confirmation of synthesized ONCs structures. The structural properties of the NCs materials were analyzed by high-angle X-ray diffraction. The textural properties of the NCs materials were examined using the N₂/77 K adsorption isotherms according to the Brunauer–Emmett–Teller equation. The CO₂ adsorption capacity was measured by CO₂ isothermal adsorption at 298 K/1 bar. From the results, the NCs activated with KOH showed that the increasing specific surface areas and total pore volumes resulted in the enhancement of CO₂ adsorption capacity.     

Crystal structure of DienH<Subscript>3</Subscript>[PtCl<Subscript>6</Subscript>]Cl

The DienH₃[PtCl₆]Cl complex was synthesized, and its crystal structure was determined. Crystal data for C₄H₁₆Cl₇N₃Pt: a = 6.8831(3) Å, b = 23.2767(12) Å, c = 9.6058(4) Å, = 90.593(2)°, V = 1538.92(12) ų, space group P2(1)/n, Z = 4, ρ_calc = 2.371 g/cm³.     

Synthesis and structure of coordination polymer compounds of AgReO<Subscript>4</Subscript> and AgPF<Subscript>6</Subscript> with piperazine

Coordination polymers [Ag(C₄H₁₀N₂)]ReO₄ (I) and [Ag(C₄H₁₀N₂)]PF₆ (II) (C₄H₁₀N₂ is piperazine, Ppz) were synthesized and their structures were determined. Crystals of compound I are monoclinic, space group P2₁/c, a = 6.207(1) Å, b = 12.533(1) Å, c = 11.386(1) Å, β = 93.41(1)°, V = 884.2(2) ų, ρ_calc = 3.337 g/cm³, Z = 4. Crystals of II are monoclinic, space group C2/m, a = 8.723(1) Å, b = 9.083(1) Å, c = 5.797(1) Å, β = 95.07(1)°, V = 457.5(1) ų, ρ_calc = 2.548 g/cm³, Z = 2. Structure I contains polymer chains [Ag(Ppz)] _∞ ⁺ . The silver atom is linked with two nitrogen atoms of the adjacent Ppz ligands to form a nearly linear fragment; the Ag-N_av distance is 2.173 Å, and the NAgN angle is 169.4(3)°. The chains are linked with each other by weak interactions Ag…O(ReO₄) (2.643(8) Å) and N-H…O hydrogen bonds. The structure of compound II also contains cationic polymer chains [Ag(Ppz)] _∞ ⁺ . The Ag⁺ ion is located in the inversion center and has a linear coordination (Ag-N distance is 2.171(9) Å). The central P atom of the octahedral fluorophos-phate ion is also located in the inversion center; the anion is slightly distorted and has no contacts with silver ions at a distance <3.4 Å.