Ambient carbon dioxide capture by boron-rich boron nitride nanotube

Carbon dioxides (CO(2)) emitted from large-scale coal-fired power stations or industrial manufacturing plants have to be properly captured to minimize environmental side effects. From results of ab initio calculations using plane waves [PAW-PBE] and localized atomic orbitals [ONIOM(wB97X-D/6-31G*:AM1)], we report strong CO(2) adsorption on boron antisite (B(N)) in boron-rich boron nitride nanotube (BNNT). We have identified two adsorption states: (1) A linear CO(2) molecule is physically adsorbed on the B(N), showing electron donation from the CO(2) lone-pair states to the B(N) double-acceptor state, and (2) the physisorbed CO(2) undergoes a carboxylate-like structural distortion and C═O π-bond breaking due to electron back-donation from B(N) to CO(2). The CO(2) chemisorption energy on B(N) is almost independent of tube diameter and, more importantly, higher than the standard free energy of gaseous CO(2) at room temperature. This implies that boron-rich BNNT could capture CO(2) effectively at ambient conditions.     

Transition-metal-catalyzed reactions of propargylamine with carbon dioxide and carbon disulfide.

The reactions of propargylamine derivatives with carbon dioxide and carbon disulfide have been systematically examined in the presence of transition-metal catalysts. Pd(OAc)(2) is the best catalyst for the formation of the corresponding oxazolidinones. In addition, we found that, in the reaction of propargylamine with carbon dioxide catalyzed by palladium(0) metal catalyst in toluene, both oxazolidinone 1 and imidazolidinone 2 could be obtained under mild reaction conditions at the same time. The reaction of 1 with primary and secondary amines has been examined. A plausible reaction mechanism for the formation of 2 was proposed. In addition, in this paper, we first disclosed the ligand's effect on this reaction. Using PBu(t)(3) as a ligand with Pd(2)(dba)(3), 1 was exclusively formed in 90% yield.     

Theoretical analysis of pyrrole anions addition to carbon disulfide and carbon dioxide

Quantum chemical analysis (MP2/6‐31+G*) of the pyrrole anions addition to carbon disulfide and the substitution effects therein shows that pyrrole‐2 (5)‐carbodithioates are thermodynamically the most stable compounds, while 1‐isomer obtained from the unsubstituted pyrrole is likely a kinetic product. Steric hindrances destabilize N‐adducts when a methyl substituent appears in a 2(5) position and the 2,5‐dimethyl‐1‐pyrrolecarbodithioate anion turns out to be even less stable than the 2,5‐dimethyl‐3‐pyrrolecarbodithioate anion. By contrast, pyrrole‐1‐carboxylates are calculated to be the most stable adducts of CO₂ with pyrrole anions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Aqueous noncovalent functionalization and controlled near-surface carbon doping of multiwalled boron nitride nanotubes

Noncovalent functionalization of boron nitride nanotubes (BNNTs) in aqueous solution was achieved by means of pi-stacking of an anionic perylene derivative, through which carboxylate-functionalized BNNTs were prepared for the first time. Starting from the functionalized nanotubes, an innovative methodology was designed and demonstrated for the controlled near-surface carbon doping of BNNTs. As a result of such delicate doping, novel B-C-N/BN coaxial nanotubes have been fabricated, and their p-type semiconducting behaviors were elucidated through gate-dependent transport measurements.     

Highly efficient chemical fixations of carbon dioxide and carbon disulfide by cycloaddition to aziridine under atmospheric pressure

Cycloaddition of aziridine with carbon dioxide was successfully catalyzed by alkali metal halide or tetraalkylammonium halide to give the corresponding 5-membered cyclic urethane, 1,3-oxazolidin-2-one, selectively. The reaction can be performed at ambient temperature under atmospheric pressure. Analoguous reaction of aziridine with carbon disulfide also successfully gave the corresponding 5-membered cyclic dithiourethane, 1,3-thioxazolidine-2-thione.     

Chemical functionalization of silica and alumina particles for dispersion in carbon dioxide

The steric stabilization and flocculation of modified silica and alumina particle suspensions in condensed CO(2) were studied. Silica particles (average diameters of 7 and 12 nm) were functionalized using chlorosilanes of the form C(n)F(2n+1)CH(2)CH(2)Si(CH(3))(2)Cl (n = 8, 4, or 1) to give C(n)F(2n+1)-silica. Alumina particles (diameter of 8-14 nm) were grafted with C(8)F(17)CH(2)CH(2)Si(OEt)(3) and chemically modified with perfluorononanoic acid to yield C(8)F(17)-alumina and C(8)F(17)COOH-alumina, respectively. Elemental analysis and thermogravimetric analysis on the derivatized particles were carried out, and surface coverage was calculated. The stabilization of these modified particles in condensed CO(2) was quantified using turbidimetry. Particle stability was found to increase with increasing fluorinated tail length, temperature, and CO(2) density. Unmodified particles and those modified with only -CF(3) tails were unstable in condensed CO(2). Stabilization in supercritical CO(2) is continuous up to 24 h for the C(n)F(2n+1)-silica (n >/= 4) particles and 96 h for the C(8)F(17)-alumina particles. The C(8)F(17)COOH-alumina particles gave a significantly higher graft density than the C(8)F(17)-alumina particles but are not as stable in CO(2). The C(8)F(17)-alumina particles were stable at lower CO(2) densities than the modified silica particles. This stability difference may be attributed to the precursor organosilanes being monofunctional (modified silica) versus trifunctional (modified alumina), producing different structures on the surface.     

Reductive functionalization of carbon dioxide to methyl acrylate at zerovalent tungsten

Alkali metal reduction of tungsten tetrachloride in the presence of excess trimethylphosphite and ethylene affords moderate yields of trans-tetrakis(trimethylphosphite)tungsten bis(ethylene). This easily prepared species bearing inexpensive ancillary ligands promotes the oxidative coupling of carbon dioxide and ethylene at ambient temperature to produce two isomeric tetrakis(trimethylphosphite)tungsten acrylate hydride complexes. These isomers vary by the κ(2)-O,O and κ(3)-C,C,O coordination mode of the acrylate ligand, and swiftly interconvert in solution as detected by 2D NMR spectroscopy. The CO(2)-derived acrylate fragment may be released from the tungsten coordination sphere by treatment with methyl iodide to afford modest quantities of free methyl acrylate.     

Tailor-made functionalization of silicon nitride surfaces

This communication presents the first functionalization of a hydrogen-terminated silicon-rich silicon nitride (Si3Nx) surface with a well-defined, covalently attached organic monolayer. Properties of the resulting monolayers are monitored by measurement of the static water contact angle, X-ray photoelectron spectroscopy (XPS), and infrared reflection absorption spectroscopy (IRRAS). Further functionalization was performed by reaction of Si3Nx with a trifluoroethanol ester alkene (CH2=CH-(CH2)8CO2CH2CF3) followed by basic hydrolysis to afford the corresponding carboxylic acid-terminated monolayer with hydrophilic properties. These results show that Si3Nx can be functionalized with a tailor-made organic monolayer, has highly tunable wetting properties, and displays significant potential for further functionalization.     

Photoluminescent carbon nitride films grown by vapor transport of carbon nitride powders

The thermal vapor transport of nitrogen-rich carbon nitride powders produces carbon nitride films on substrates that retain significant nitrogen content, have conjugated bond character, and show blue photoluminescent emission near 450 nm.     

Functionalization of carbon dioxide and carbon disulfide using a stable uranium(III) alkyl complex

A rare uranium(III) alkyl complex, Tp*(2)U(CH(2)Ph) (2) (Tp* = hydrotris(3,5-dimethylpyrazolyl)borate), was synthesized by salt metathesis from Tp*(2)UI (1) and KCH(2)Ph and fully characterized using (1)H NMR, infrared, and electronic absorption spectroscopies as well as X-ray crystallography. This complex has a uranium-carbon distance of 2.57(2) ?, which is comparable to other uranium alkyls reported. Treating this compound with either carbon dioxide or carbon disulfide results in insertion into the uranium-carbon bond to generate Tp*(2)U(κ(2)-O(2)CCH(2)Ph) (3) and Tp*(2)U(SC(S)CH(2)Ph) (4), respectively. These species, characterized spectroscopically and by X-ray crystallography, feature new carboxylate and dithiocarboxylate ligands. Analysis by electronic absorption spectroscopy supports the trivalent oxidation state of the uranium center in both of these derivatives. Addition of trimethylsilylhalides (Me(3)SiX; X = Cl, I) to 3 results in the release of the free silyl ester, Me(3)SiOC(O)CH(2)Ph, forming the initial uranium monohalide species, Tp*(2)UX, which can then be used over multiple cycles for the functionalization of carbon dioxide.     

A computational study of adducts between atomic chlorine and carbon dioxide, carbonyl sulfide and carbon disulfide

The geometries and vibrational frequencies of the adducts ClCO₂, ClCOS and ClCS₂ were derived at the Hartree-Fock (HF) 3-21G (^*) level. The C_a, structure of ClCO₂ corresponds to one C-O bond and one C=O bond. Similarly, C_a, ClCS₂ has one C-S and one C=S bond, and ClCOS has one C-S and one C-O bond. Single-point spin-projected fourth-order Møller-Plesset (MP4) 3-21G (^*) calculations at these geometries were used in bond-separation reactions to derive ΔH^o₀ for adduct formation, which is calculated to be about 39 kJ mol⁻¹ exothermic for ClCOS and ClCS₂, but about 39 kJ mol⁻¹ endothermic for ClCO₂. The C_2v structures for ClCO₂ and ClCS₂ were also characterized. The geometry of ClCS₂ has not been determined experimentally; comparison with an available measured entropy for ClCS₂ suggests that the C_2v structure is the one formed by addition of Cl to CS₂, although the energy relative to the C_a form is not reliably calculated because of instability in the HF wavefunction.     

Organic functionalization of metal catalysts: Enhanced activity towards electroreduction of carbon dioxide

Electrochemical reduction of carbon dioxide has been attracting extensive interest due to its fundamental significance both in environmental protection and in energy storage. In this review, recent progress in the manipulation of the catalytic activity and selectivity of various transition metals towards CO₂ reduction reaction (CO₂RR) is summarized within the context of deliberate surface functionalization by select organic ligands. This is primarily manifested in three effects, interfacial charge transfer, suppression of hydrogen evolution, and stabilization of key reaction intermediates. The review is concluded with a perspective of the challenges and promises in the structural engineering of metal catalysts for enhanced CO₂RR performance.     

Vanadium disulfide: Metal substitution and lithium intercalation

The preparation and physical properties of the layered VS₂, M_yV_1?yS₂ (M = Fe or Cr), and their lithium intercalation adducts are described. These compounds were prepared by oxidative delithiation of LiM_yV_1?yS₂ with iodine. Crystallographic distortions present in Li_xVS₂ (0.25 ? x ? 0.6) are suppressed by Fe or Cr substitution for V. The electrochemical sluggishness of Li/Li⁺/VS₂ cells is reduced by the substitution.     

Multiple functionalization of single-walled carbon nanotubes by dip coating

Single walled carbon nanotubes were functionalized with different functionalities by simple dip coating. This fast and reproducible procedure was realized with nanotube coated electrodes for the construction of polyvalent biosensors. Three different pyrene derivatives were attached to the nanotube sidewalls by π-stacking interactions in a one-step reaction.     

Vanadium doped tin dioxide as a novel sulfur dioxide sensor

Considering the short-term exposure limit of SO2 to be 5 ppm, we first time report that semiconductor sensors based on vanadium doped SnO2 can be used for SO2 leak detection because of their good sensitivity towards SO2 at concentrations down to 5 ppm. Such sensors are quite selective in presence of other gases like carbon monoxide, methane and butane. The high sensitivity of vanadium doped tin dioxide towards SO2 may be understood by considering the oxidation of sulfur dioxide to sulfur trioxide on SnO2 surface through redox cycles of vanadium-sulfur-oxygen adsorbed species.     

Solvent-free functionalization of carbon nanotubes

A fundamentally new single-walled and multiwalled carbon nanotube sidewall functionalization technique has been developed in which solvent is not required and the reaction times are greatly shortened (1 h at 60 degrees C). Exploiting the long linear dimension of the nanotube ropes by macroscopic mechanical deformation, reactive sites are generated merely by mechanically deforming the tubes using a stir bar. This approach eliminates the need for large volumes of solvent ( approximately 2 L/g), which were formerly considered essential due to the insolubility of carbon nanotubes. Using a series of 4-substituted anilines and a nitrite, the aryl diazonium intermediates were generated in situ and permitted to react with the tubes. Raman, IR, and UV spectroscopies, coupled with thermogravimetric analyses and solubility studies, support the assignments.     

Organic functionalization of carbon nanotubes

A very general and versatile method for functionalizing different types of carbon nanotubes is described, using the 1,3-dipolar cycloaddition of azomethine ylides. Approximately one organic group per 100 carbon atoms of the nanotube is introduced, to yield remakably soluble bundles of nanotubes, as seen in transmission electron micrographs. The solubilization of the nanotubes generates a novel, interesting class of materials, which combines the properties of the nanotubes and the organic moiety, thus offering new opportunities for applications in materials science, including the preparation of nanocomposites.     

Cyclic amidine hydroiodide for the synthesis of cyclic carbonates and cyclic dithiocarbonates from carbon dioxide or carbon disulfide under mild conditions

Hydroiodides of amidines can catalyze the reaction of carbon dioxide and epoxides under mild conditions such as ordinary pressure and ambient temperature, and the corresponding five-membered cyclic carbonates were obtained in high yields. The reaction of epoxide with carbon disulfide was also examined under the same conditions. Detailed investigation showed that the catalytic activity was highly affected by the counter anions of the amidine salts; the iodides were effective catalysts for both of the reaction of epoxide with carbon dioxide and carbon disulfide, whereas the bromide, chloride and fluoride counterparts exhibited almost no catalysis.