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Water microdroplets possess unique interfacial properties that enable chemical reactions to occur spontaneously and increase the reaction rate by orders of magnitude. In this study, water containing styrene (SY) was cyclically sprayed into the air to form microdroplets with an average diameter of 6.7 μm. These microdroplets allowed SY to be oxidized into styrene oxide (SO) without catalysts. No oxidation products of SY were observed in the bulk solution under the same conditions, while in microdroplet reactions 4.2% conversion of SY with approximately 3.1 mM SO was detected. Compared with the traditional spraying microdroplet method, the oxidation product concentration was enhanced by 1000 times. Experiments proved that an aerobic environment boosts SY oxidation, leading to a proposed dual-path hydrogen peroxide (H2O2) oxidation mechanism at the droplet interface. This was confirmed by density functional theory calculations (DFT). Furthermore, in the presence of additional ultrasound, the SY oxidation process initiated by water droplets can be further enhanced, and 7.0% conversion of SY with approximately 5.2 mM SO was detected. The cyclic spraying method greatly enhanced the oxidation product concentration, showing the potential for large scale chemical production using microdroplets.

For the selective oxidation of toluene to benzaldehyde, the biggest challenge is to prevent the further oxidation of benzaldehyde as toluene conversion increases. Using benzyl benzoate as the solvent and adding benzoate to adjust the alkalinity of the system, the formation of the benzoyl radical can be well inhibited, but the oxidation of toluene is weakened. The decomposition of benzyl benzoate to benzaldehyde can activate the reaction at the initial stage, and the negative influence of alkalinity is avoided to some extent. Therefore, by using atmospheric air as an oxidant, a high selectivity and yield of benzaldehyde can be obtained in a benzyl benzoate catalytic system with alkali as an additive. The mechanism of alkaline regulation and selective oxidation of toluene was investigated by in situ infrared (IR) spectroscopy experiments. The benzaldehyde capacity is defined to characterize the tolerance of benzaldehyde in the system. Catalysts and alkaline regulators can be easily reused with high-boiling solvents, making it a convenient process for product separation and catalyst–alkaline solvent recycling.

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This work develops a novel way of H2S resource into mercaptan alcohol mediated by tertiary-amine functionalized protic ionic liquids.

Frustrated Lewis Pairs (FLPs) catalysts have been widely designed and synthesized in current chemistry, with the key being the selection of boron-based Lewis acids. Among novel boron-based Lewis acids, boron cations with higher Lewis acidity caused by cationic charge have been proven to have special reactivity. However, the current boron cations have only been used to construct homogeneous FLPs, which would be difficult to meet the industrial process demand for FLPs catalysts, possibly due to the lack of suitable stabilizers. In this paper, we propose a strategy to construct heterogeneous FLPs using covalent organic frameworks (COFs) stabilized boron cations as Lewis acid. Firstly, heterogeneous Lewis acid COFs@[B(C6F5)2]+[Al2Cl7]-was prepared by stabilizing boron cations with CN bonds in COFs, followed by introducing tBu3P to construct heterogeneous FLPs COFs@[B(C6F5)2]+[Al2Cl7]-/tBu3P. Meanwhile, these FLPs catalysts exhibited excellent catalytic and cyclic performance in the preparation of cyclic carbonates by CO2addition from epoxy compounds.

With the catalytic induction of ethylene glycol (EG), anhydrous N,N-dimethylethanolamine (DMEA) shows CO2absorption performance via chemical binding and physical storage under normal pressure. Among the absorbents, pure DMEA and EG can hardly absorb CO2directly, but when the zwitterionic alkylcarbonates are formed between CO2and DMEA-EG, which can be characterized by 13C NMR and FTIR spectroscopy, the absorption rate of CO2is improved. With the increase in the CO2loading as the mass fraction of EG in DMEA–EG, 80 wt % EG captures up to 0.72 mol/mol at 293 K and 101 kPa via chemical binding and physical storage. The amount that is chemically bound and physically stored is directly dependent on temperature; within the range of 293–323 K, an absorption–regeneration cycle can be formed in a closed vessel because the zwitterion DMEA–EG–CO2is unstable at higher temperatures. In other words, DMEA–EG–CO2can be easily regenerated upon appropriate depressurization or heating. The corresponding thermodynamic calculations prove that the regenerative energy of DMEA–EG–CO2is −27.33 kJ/mol, far less than that of other absorbent systems.

In this work, a series of novel proton-gradient-transfer acid complexes (PGTACs) were developed. Their physicochemical properties, including thermal stability, melting point, and Hammett acidity, were measured. The effects of catalyst loading, reaction temperature, and substrate expansion on the catalytic performance were systematically studied. It is found that the combination of bidentate N-heterocycle and H2SO4(1 : 2 M ratio) could form simultaneously N–H covalent bond and N⋯H hydrogen bond, which makes the PGTACs excellent catalysts integrate the advantages of strong acids (high catalytic activity) and ionic liquids (phase separation) in the esterification reaction. Moreover, these PGTACs can be reused by convenient phase separation without obvious diminution of catalytic activity. It is concluded that these PGTACs are potential alternative candidates for esterification reaction in the process of industrial catalysis.

An efficient cyclic(alkyl)(amino) carbene iridium complex (C-2) was developed for methanol carbonylation to methyl acetate (MA) directly. Compared with previous results, methanol carbonylation to MA catalyzed by C-2was performed quite well at a low temperature (120 °C). The reaction showed excellent selectivity toward MA (96%) even when the conversion was high (81%). The reaction processes were also investigated by stoichiometric experiments and theoretical calculations.

Removing H2S and CO2is of great significance for natural gas purification. With excellent gas affinity and tunable structure, ionic liquids (ILs) have been regarded as nontrivial candidates for fabricating polymer-based membranes. Herein, we firstly reported the incorporation of protic ILs (PILs) having ether-rich and carboxylate sites (ECPILs) into poly(ether-block-amide) (Pebax) matrix for efficient separation H2S and CO2from CH4. Notably, the optimal permeability of H2S reaches up to 4310 Barrer (40 ºC, 0.50 bar) in Pebax/ECPIL membranes, along with H2S/CH4and (H2S+CO2)/CH4selectivity of 97.7 and 112.3, respectively. These values are increased by 1125%, 160.8% and 145.9% compared to those in neat Pebax membrane. Additionally, the solubility and diffusion coefficients of the gases were measured, demonstrating that ECPIL can simultaneously strengthen the dissolution and diffusion of H2S and CO2, thus elevating the permeability and permselectivity. By using quantum chemical calculations and FT-IR spectroscopy, the highly reversible multi-site hydrogen bonding interaction between ECPILs and H2S was revealed, which is responsible for the fast permeation of H2S and good selectivity. Furthermore, H2S/CO2/CH4(3/3/94 mol%) ternary mixed gas can be efficiently and stably separated by Pebax/ECPIL membrane for at least 100 h. Overall, this work not only illustrates that PILs with ether-rich and carboxylate hydrogen bonding sites are outstanding materials for simultaneous removal of H2S and CO2, but may also provide a novel insight into the design of membrane materials for natural gas upgrading.

Deep eutectic solvents (DESs) are considered to be potential absorbents for CO2capture compared to traditional amine solutions, because they have many advantages such as lower volatility and better thermal stability. In this study, a series of novel γ− and ε− m−based amino acid salts (AASs) were prepared through one-step hydrolysis reaction of accessible and cheap lactams as hydrogen bond acceptor (HBA). The chemical structures of these AASs are characterized by ESI-MS and NMR. Dihydric alcohol was selected as hydrogen bond donor (HBD) to prepare AAS-based DESs because of its low specific heat capacity and high boiling point. The physical properties of AAS-based DESs, such as density at 313.2 to 353.2K, viscosity at 313.2 to 353.2K, the melting temperature from 173.2 to 273.2K, and thermal decomposition temperature from 300 to 750K, are also determined. The gas absorption experiments were carried out on a dual-chamber at temperatures from 313.2 to 333.2K and pressures up to 1.1bar. It is found that K[Gaba]-EG has the largest CO2uptake capacity with 0.12g·g−1at 1.0bar and 313.2K, better than almost all absorbent with AASs reported in literatures (0.02g·g−1~ 0.07g·g−1). The CO2absorption mechanisms were proved to be a combination of 2:1 and 1:1 stoichiometric reaction through thermomechanical analysis and NMR. This paper will present distinctive insights into the preparation of CO2absorbent for effective carbon capture.

Special proton-gradient-transfer acid complexes (PGTACs) in which the bonded protons are not equivalent and have gradients in transfer ability, acidity, and reactivity were reported. The acidity gradient of the protons gave the PGTACs excellent catalytic activity and selectivity in the esterification of terpenols. These PGTACs are “reaction-induced self-separation catalysts” and can be easily reused. The kinetics with PGTACs as catalyst in the esterification of geraniol were also studied for use in engineering design.

It has been of long concern that the separation and recovery of NH3from industrial processes, in addition to attracting huge economic interest, also reduce environmental pollution. So, it is very urgent to develop novel absorbents for highly efficient capture of NH3. In this study, several novel tetrazole (TetrZ)-based binary deep eutectic solvents (DESs) were formed by mixing TetrZ with 1,2,3-triazole (1,2,3-Tri), ethylene glycol (EG), 2-morpholinoethanol (2-Mor), or N-methyldiethanolemine (MDEA) to absorb NH3. TetrZ + 1,2,3-Tri (1:4, mole ratio) not only exhibits higher NH3absorption ability of 0.239 gNH3·gDES–1than that of most absorbents reported to date at 313.15 K and 101.3 kPa, but also shows elevated selectivities of 592.7 for NH3/CO2, 654.5 for NH3/N2, and 1033.7 for NH3/O2. Meanwhile, TetrZ + 1,2,3-Tri (1:4) can be reused 10 times with good absorption capacity retained. Additionally, the solubility data of NH3were correlated by the reaction equilibrium thermodynamic model. The NMR and FTIR spectroscopic characterizations were also used to study the absorption mechanism, and quantum chemistry calculation was utilized to further investigate the interactions between NH3and DESs from an atomic level perspective. The DESs developed in the present work have the potential to capture NH3sustainably, owing to their high solubility, superior selectivity, and desirable reversibility.

The deep-processing utility of pure hydrogen sulfide (H2S) is a significant direction in natural gas chemical industry. Herein, a brand-new strategy of H2S conversion by α,β-unsaturated carboxylate esters into thiols or thioethers using task-specific carboxylate ionic liquids (ILs) as catalyst has been developed, firstly accomplishing the phase separation of product and catalyst without introducing the third component. It can be considered as a cascade reaction in which the product selectivity can be controlled by adjusting the molar ratio of H2S to α,β-unsaturated carboxylate esters. Also, the effects of ILs with different anions and cations, intermittent feeding operations, as well as pressure−time kinetic behaviors on cascade reaction were investigated. Furthermore, the proposed interaction mechanism of H2S conversion using butyl acrylate catalyzed by [Emim][Ac] was revealed by DFT-based theoretical calculation. The approach enables the self−phase separation promotion of catalyst and product and achieves 99% quantitative conversion under mild conditions in the absence of solvent, making the entire process ecologically benign. High-efficiency reaction activity can still be maintained after ten cycles of the catalyst. Therefore, the good results, combined with its simplicity of operation and the high recyclability of the catalyst, make this green method environmentally friendly and cost−effective. It is anticipated that this self-separation method mediated by task-specific ILs will provide a feasible strategy for H2S utilization, which will guide its application on an industrial scale.

A new boron-centered polymer, which is named poly-BPh(C6F5)2(polymerized-bis(perfluorophenyl)-(phenyl)borane) was designed and synthesized, which is found to be an efficient catalyst for selective N-formylation and N-methylation of amines using CO2as C1 building block in the presence of hydrosilanes. Milder reaction conditions (even at room temperature and 1 bar of CO2), remarkable recyclability, tolerance against a variety of functional groups and excellent yields reveal the excellent stability and catalytic activity of poly-BPh(C6F5)2. The process herein represents a simple, ecologically friendly and efficient route for CO2chemical fixation into value-added chemicals.

The influence of ionic liquid (IL) modification on the reactivity of metalloporphyrins was carefully investigated to design a recoverable and highly effective metalloporphyrin catalyst. On the basis of the research, which included a total of 34 different catalysts, the following modification methods make metalloporphyrins more powerful: (1) increasing the spin density (SDO), charge (QO), or isotropic fermi contact couplings (IFCCO) of the O atom in the FeO part and (2) decreasing the spin density carried by the Fe atom (SDFe) or the HOMO–LUMO gap between a catalyst and reactant (LUMOC–HOMOR). The order of the correlation between the structure parameters and the reactivity is SDo> Qo> IFCCO≈ SDFe≈ LUMOC–HOMOR. Compared with changing the cation of metalloporphyrins, changing the anion is a more effective way to increase the reactivity. The order is AlBr4–> AlCl4–> BCl4–> PF6–> AsF6–> SbF6–> BF4–> Tf2N–> AlF4–> HSO4–> CF3SO3–> CF3CO2–> Cl–. However, the long distance between the IL part and the catalytic active center or electron-donating substituent on the N atom weaken the influence induced by the IL modification. These structure–reactivity relationships could be used in designing a catalyst.

The adsorption and activation of triplet O2on the surface of nitrogen-doped carbon nanotube (NCNT) with different diameter and length were investigated. It was found that, rather than the unfavorable adsorption on normal carbon nanotube (CNT), the adsorption of O2on NCNT was obviously exothermic and the electron transition of O2happened in the adsorption process. The oxygen adsorbed on NCNT showed an interesting electron configuration which was similar to the active oxygen anion. The spin density, charge, and bond length of O2changed with the size of NCNT. In combination with the recent results reported by Dai et al. (Science, 2009, 323, 760), it is reasonable to believe that these NCNTs should be a potential metal-free catalyst. The results presented here should be useful for designing and developing effective catalyst based on NCNT.

We present here results of a series of density functional theory studies on models of metalloporphyrins and address the influence of nitrogen-containing neutral axial ligands on the binding process of dioxygen (O2) to metalloporphyrins. There are two closely lying spin states for metalloporphyrins, namely, triplet and quintet. However, the ground state for oxy-metalloporphyrins is the open-shell singlet. DFT calculations indicate that back-donation to O2is more accessible because of the axial ligand, facilitating the binding of O2. Moreover, the axial ligands lengthen the O−O bond of oxy-metalloporphyrins and make the bound O2negatively charged with a spin population between that of 3O2and O2−. Therefore, the coordination of the axial ligand makes O2more active than free O2, triggering the catalytic oxidation processes. Finally, the larger the electronic density of the bound nitrogen atom (NL) of the axial ligand is, the more active the binding O2becomes.

Described herein presents a class of novel deep eutectic electrolytes (DEEs) with distinctive properties for sodium batteries. Instead of being limited by the presence of a hydrogen bond donor (HBD) or hydrogen bond acceptor (HBA), the concept of Na···N interactions was first brought in between sodium bis(fluorosulfonyl)imide (NaFSI) and 1,2-dimethylimidazole (DMIm). The deep eutectic phenomenon was caused by the strong ion–dipole interaction, which was conducive to the release of Na+from NaFSI and drove the DEE with a desirable ionic conductivity. Furthermore, the proposed mechanism of Na···N interactions was credibly confirmed by Raman, 23Na NMR, and theoretical calculations. The half-cell based on NaFSI/DMIm–1/4 can provide a reversible capacity of 316.7 mAh·g–1at 0.05 A·g–1, and Coulombic efficiency remains 91% after 500 charge–discharge cycles at 1.0 A·g–1in the application of sodium batteries. It is anticipated that this work will present distinct insights into the extension of electrolytes for sodium batteries.

In recent years, copper-based catalysts have been widely studied in hydrogenation of CO2to formic acid or formate. Although the advantages of low cost and low toxicity, the activity of copper-based catalysts is still not very satisfactory. In this work, CAAC cooper complex (CAAC-Cu) was supported on SBA-15 silica to give an efficient and recyclable catalyst SBA-15-CAAC-Cu for the hydrogenation of CO2to formate. The ordered mesoporous structure of SBA-15 and the structure of CAAC-Cu have been preserved after functionalization. Using SBA-15-CAAC-Cu as catalyst, up to 4660 TON can be obtained at 100 °C, which is much better than homogeneous CAAC-Cu catalysts. In addition, the SBA-15-CAAC-Cu catalyst can be easily recycled multiple times without obvious loss in activity.

We herein reported an effective and straightforward strategy for the synthesis of amino-functionalized ILs@SBA-15 catalysts viamechanochemical grafting. As-prepared catalysts showed impressive catalytic activity for the one-pot synthesis of cyclic carbonates from olefins and CO2under metal- and cocatalyst-free conditions. The catalyst was easily recovered without significant decrease in catalytic activity after multiple cycles. According to the results of the control experiment, a possible catalytic mechanism of oxidative carboxylation reaction of olefin was also proposed.

Polymerization brings a highly effective, stable, and recyclable cyclic (alkyl)(amino)carbenes Iridium (P-CAAC-Ir) for the CO2hydrogenation to formate.

Based on the recent advance of the aromaticity concept into all-metal species, we put forward a new kind of hydrogen bond: hydrogen bonding to all-metal aromatic species. The similarities and differences between the hydrogen bonds in all-metal aromatic systems and those in traditional organic aromatic systems are systematically explored: we investigated the interactions between all-metal aromatic complexes Al42−Al4M M Mg2, Ca2, 2Na and H–Y Y CH3, NH2, OH, F, Cl, Br as well as those between benzene and H–Y. Geometric configuration calculations, molecular orbital MO analysis, nuclear independent chemical shift NICS and frequency shift FS as well as binding energy calculations were employed for the investigation of the Al42−H–Y, Al4MH–Y and C6H6H–Y complexes. The calculated results revealed that there exist distinct differences between the hydrogen bonds in all-metal aromatic systems and those in traditional organic aromatic systems in many aspects such as binding energy and interaction distance as well as frequency shift of H–Y. Furthermore, because the aromaticity of all-metal aromatic systems can be changed by interaction with different metal ions, the intensity of hydrogen bonding can also be adjusted and controlled by changing the ions. The natures of hydrogen bonds in all-metal aromatic systems are summarized.

The capture and conversion of carbon dioxide (CO2) into useful and valuable chemicals are receiving more and more research interesting. Herein, we designed a new and efficient route to synthesize methyl phenyl carbonate (MPC) via the carbonylation of phenol (PhOH) with CO2and methanol (CH3OH). PhOH and CH3OH react with 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU) to form ionic liquids [DBUH][PhO] and [DBUH][CH3O]. The DBU-based ionic liquids exhibited outstanding performance in CO2capture and in situ conversion at room temperature. The reusability of the system had no obviously change after 6 cycles. This protocol provides a sustainable and environmentally friendly preferential technique for the production of MPC, and extends the chemical utilization of CO2.

Two strategies were reported to prevent the deactivation of Frustrated Lewis pairs (FLPs) in the hydrogenation of terminal alkynes: reducing the Lewis acidity and polymerizing the Lewis acid. A polymeric Lewis acid (P-BPh3) with high stability was designed and synthesized. Excellent conversion (up to 99%) and selectivity can be achieved in the hydrogenation of terminal alkynes catalyzed by P-BPh3. This catalytic system works quite well for different substrates. In addition, the P-BPh3can be easily recycled.

Though ammonia–borane (AB) is recognized as an excellent hydrogen storage material, efficient dehydrogenation of AB still remains a challenge. Herein, we report that cyclic (alkyl)(amino)carbene iridium complexes are highly efficient for both the thermal dehydrogenation and hydrolysis of AB under mild conditions. At 30 °C, the two processes are completed within 15 and 5 min, releasing 2.1 and 2.8 equiv of H2per AB, respectively. Moreover, 2.8 equiv of H2can be released within 10 min by thermal dehydrogenation at 60 °C. Kinetic studies revealed that the activation energies for thermal dehydrogenation and hydrolysis of AB are 10.7 and 8.5 kcal/mol, respectively. The catalyst can be recycled without significant loss of activity at least six times for both processes. The reaction mechanisms were further explored by theoretical calculations, stoichiometric reactions, and kinetic isotope effect experiments.

•Imidazolium hydrogen carbonate ionic liquids as an organic pre-catalysts for N-heterocyclic carbenes.•Imidazolium hydrogen carbonate ionic liquids balance to CnCmIm-CO2serving as the active species for conversion of CO2.•Good to excellent yields of cyclic carbonates and methylamines are obtained for varied substrates.•Air and water-stable C1C6ImHCO3was recyclable in up to five consecutive cycles.

The reactivity and selectivity of Fenton system (Fe2+/H2O2) were improved with N-hydroxyphthalimide (NHPI) as cocatalyst. The oxidation process of benzyl alcohol to benzaldehyde has been studied. The reaction catalyzed by this new Fe2+/H2O2/NHPI system can be well performed under room temperature without adding any organic solvent. Besides, this catalyst system is effective for the oxidation of different alcohols.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.