Qingqing Mei

Zinc(II)-catalyzed reactions of carbon dioxide and propargylic alcohols to carbonates at room temperature

Carbon dioxide (CO2) is an abundant and renewable feedstock for the production of value-added chemicals. Herein, we carried out the first work to use ZnI2/NEt3 as the catalyst for the reactions of CO2 and propargylic alcohols to form α-alkylidene cyclic carbonates. It was discovered that the catalyst system could efficiently promote the reaction at room temperature under solvent-free conditions, and the yields of the target products could reach 99%. The zinc(II) and NEt3 play excellent synergistic roles in activating both CO2 and propargylic alcohols.

The physicochemical properties of some imidazolium-based ionic liquids and their binary mixtures

The density, viscosity and conductivity of ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), 1-octyl-3-methylimidazolium chloride ([omim][Cl]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim] BF4]), 1-hexyl-3-methylimidazolium chloride ([hmim][Cl]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]), and the [omim][BF4] + [omim][Cl], [hmim][BF4] + [hmim][Cl], and [hmim][PF6] + [hmim][Cl] binary mixtures were studied at different temperatures. It was demonstrated that the densities of both the neat ILs and their mixtures varied linearly with temperature. The density sensitivity of a binary mixture is between those of the two components. The excess molar volumes (VE) of [hmim][BF4] + [hmim][Cl] and [hmim][PF6] + [hmim][Cl] mixtures are positive in the whole composition range. For [omim][BF4] + [omim][Cl], the VE is also positive in the [omim][Cl]-rich region, but is negative in the [omim][BF4]-rich region. The viscosity or conductivity of a mixture is in the intermediate of those of the two neat ILs. For all the neat ILs and the binary mixtures studied, the order of conductivity is opposite to that of the viscosity. The Vogel-Tammann-Fulcher (VTF) equations can be used to fit the viscosity and conductivity of all the neat ILs and the binary mixtures. The neat ILs and their mixtures obey the Fractional Walden Rule very well, and the values of the Walden slopes are all smaller than unit, indicating obvious ion associations in the neat ILs and the binary mixtures.

Copper-catalyzed N-formylation of amines with CO2 under ambient conditions

We carried out work on N-formylation of amines with CO2 and PhSiH3 to produce formamides catalyzed by a copper complex. It was found that the Cu(OAc)2–bis(diphenylphosphino)ethane (dppe) catalytic system was very efficient for these kind of reactions at room temperature and 1 atm CO2 with only 0.1 mol% catalyst loading.

Synthesis of formamides containing unsaturated groups by N-formylation of amines using CO2 with H2

Formamides have wide applications in the industry and have been synthesized using CO2 as a carbon source and H2 as a reducing agent. However, previous systems required a noble catalyst and high temperature to achieve high efficiency, and the substrate scope was mostly limited to saturated amines. The selective N-formylation of amines containing unsaturated groups using CO2 and H2 is challenging because the efficient catalysts for the N-formylation are usually very active for hydrogenation of the unsaturated groups. Herein, we achieved for the first time a selective and efficient N-formylation of amines containing unsaturated groups using CO2 and H2 with a Cu(OAc)2–4-dimethylaminopyridine (DMAP) catalytic system. The substrates were converted to the desired formamides, while the unsaturated groups, such as the carbonyl group, the CC bond, CN bond and the ester group remained. The main reason for the excellent selectivity of the Cu(OAc)2–DMAP catalytic system was that it was very active for the N-formylation reaction, but was not active for the hydrogenation of the unsaturated groups.

Atmospheric CO2 promoted synthesis of N-containing heterocycles over B(C6F5)3 catalyst

B(C6F5)3 combined with atmospheric CO2 was found to be highly effective for the cyclization of ortho-substituted aniline derivatives with N,N-dimethylformamide (DMF), and a series of N-containing heterocycles including benzothiazoles, benzimidazoles, quinazolinone and benzoxazole were obtained in good to excellent yields.

Solvent effects on geometrical structures and electronic properties of metal Au, Ag, and Cu nanoparticles of different sizes

Study of the geometrical structures and electronic properties of metal nanoparticles is a very interesting topic. In this work we studied the effects of cyclohexane, benzene, ethanol, and water on bond lengths, Mulliken charge distributions, binding energy (BE), energy gap between highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) (Δ(HL)), ionization potential (IP) and electron affinity (EA) of Au20, Ag20, Cu20, Au38, Ag38, and Cu38 nanoparticles by using density functional theory (DFT). The results indicated that the properties of the solvents influence the geometrical structures and electronic properties of the metallic nanoparticles considerably, and the solvent effect depends on the properties of the solvents, the size of the metal particles, and the category of the metals. Generally, the properties of smaller particles are more sensitive to the change of the solvents, and the polar solvents have larger effect on the properties.

Heterogeneous Cobalt-Catalyzed Direct N-Formylation of Isoquinolines with CO2 and H2

Isoquinolines (IQs) are an abundant feedstock, and N‐formyl‐1,2,3,4‐tetrahydroisoquinolines (FTHIQs) are valuable fine chemicals and key intermediates. Herein, we report for the first time the Co0/ZnCl2‐catalyzed direct N‐formylation of IQs by using CO2 with H2 to produce FTHIQs. It was discovered that the Co catalyst and ZnCl2 worked synergistically in catalyzing the N‐formylation reactions, and moderate to high yields of the desired products could be obtained, depending on the nature of the substrates. The Co0 catalyst could be reused at least five times without a notable decrease in activity. A possible reaction mechanism is proposed on the basis of control experiments.

N-vinyl pyrrolidone promoted aqueous-phase dehydrogenation of formic acid over PVP-stabilized Ru nanoclusters

In this work, we fabricated the poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium(0) nanoclusters by reduction of RuCl3 using different reducing agents, and studied their catalytic activity in hydrogen generation from the decomposition of formic acid. It was demonstrated that N-vinyl-2-pyrrolidone (NVP), which is a monomer of PVP, could promote the reaction by coordination with Ru nanoparticles. The Ru nanoparticles catalyst reduced by sodium borohydride (NaBH4) exhibited highest catalytic activity for the decomposition of formic acid into H2 and CO2. The turnover of numenber (TOF) value could reach 26113 h–1 at 80 °C. We believe that the effective catalysts have potential of application in hydrogen storage by formic acid.

Selective Utilization of the Methoxy Group in Lignin to Produce Acetic Acid

Selective transformation of lignin into a valuable chemical is of great importance and challenge owing to its complex structure. Herein, we propose a strategy for the transformation of methoxy group (-OCH3 ) which is abundant in lignin into pure highly valuable chemicals. As an example to apply this strategy, a route to produce acetic acid with high selectivity by conversion of methoxy group of lignin was developed. It was demonstrated that the methoxy group in lignin could react with CO and water to generate acetic acid over RhCl3 in the presence of a promoter. The conversions of methoxy group in the kraft lignin and organosolv lignin reached 87.5 % and 80.4 %, respectively, and no by-product was generated. This work opens the way to produce pure chemicals using lignin as the feedstock.

Ultrathin and Porous Carbon Nanosheet Supporting Bimetallic Nanoparticles for High Performance Electrocatalysis

Developing hybrid carbon materials with unique micro/nanostructured and multicomponent features is of great importance in catalysis, energy storage, and energy conversion. Herein, we demonstrate the formation of a novel kind of hybrid carbon material, that is, bimetallic nanoparticles supported by ultrathin (≈5.5 nm) and porous carbon nanosheets, by the pyrolysis of preformed bimetallic metal–organic framework nanosheets. This hybrid carbon nanostructure combines the advantages of highly exposed nanoparticles that are readily accessible to the reactant, multiple active sites such as metal–metal and metal–nitrogen sites and ultrathin carbon layers, and highly efficient electron transport. Owing to these unique features, the bimetallic carbon nanosheets exhibit excellent electrocatalytic performance for the oxygen reduction reaction.