No abstract

Cyclohexanone is an important intermediate in the manufacture of polyamides in chemical industry, but direct selective hydrogenation of phenol to cyclohexanone under mild conditions is a challenge. We report here a catalyst made of Pd nanoparticles supported on a mesoporous graphitic carbon nitride, Pd@mpg-C(3)N(4), which was shown to be highly active and promoted the selective formation of cyclohexanone under atmospheric pressure of hydrogen in aqueous media without additives. Conversion of 99% and a selectivity higher than 99% were achieved within 2 h at 65 °C. The reaction can be accelerated at higher temperature, but even at room temperature, 99% conversion and 96% selectivity could still be obtained. The generality of the Pd@mpg-C(3)N(4) catalyst for this reaction was demonstrated by selective hydrogenation of other hydroxylated aromatic compounds with similar performance.

We report a catalyst made of Pd nanoparticles (NPs) supported on mesoporous N-doped carbon, Pd@CN(0132), which was shown to be highly active in promoting biomass refining. The use of a task-specific ionic liquid (3-methyl-1-butylpyridine dicyanamide) as a precursor and silica NPs as a hard template afforded a high-nitrogen-content (12 wt %) mesoporous carbon material that showed high activity in stabilizing Pd NPs. The resulting Pd@CN(0.132) catalyst showed very high catalytic activity in hydrodeoxygenation of vanillin (a typical model compound of lignin) at low H(2) pressure under mild conditions in aqueous media. Excellent catalytic results (100% conversion of vanillin and 100% selectivity for 2-methoxy-4-methylphenol) were achieved, and no loss of catalytic activity was observed after six recycles.

The emission of carbon dioxide (CO 2 ) from fossil fuels has received worldwide attention because it has been implicated in climate change, which threatens economies and environments. Accordingly, new materials that can capture CO 2 from the burning of fossil fuels efficiently, economically, and with potential energy savings must be developed. The traditional technology for the capture of CO 2 in industry is chemical adsorption by an aqueous solution of amine, which has some advantages, such as low cost, good reactivity, and high capacity.[1] However, this process for the capture of CO 2 is highly energy intensive owing to the thermodynamic properties of water and high enthalpy of absorption.[2] It is estimated that the output of energy would drop by about 30 % when this capture technology was applied at coal-fired power plants, which significantly increases the cost of energy.[3] Currently, the goal is to design industrial attractive sorbent materials with high capacity and energy-saving for CO 2 capture.Ionic liquids (ILs) offer a new opportunity for addressing this challenge to develop novel CO 2 capture systems because of their unique properties, including negligible vapor pressures, high thermal stabilities, and tunable properties.[4] A great deal of effort has focused on the experimental and theoretical studies on the physical absorption of CO 2 in ILs.[5]The enthalpy of CO 2 physical absorption by ILs is about 20 kJ mol À1 , indicating that only a quarter energy is required to release the physical absorbed CO 2 from ILs in the regeneration step relative to amine solution method.[6] However, the absorption capacity of CO 2 by these ILs is up to about 3 mol % under atmospheric pressure. Another strategy is based on the chemisorption for CO 2 capture by task-specific ILs. Davis and co-workers [7] reported the first example of CO 2 chemisorption that employs an amino-functionalized IL; in their work, 0.5 mol CO 2 was captured per mole of IL under ambient pressure. Subsequently, some other amino-functionalized ILs, including sulfone anions with ammonium cations and amino acid anions with imidazolium or phosphonium cations, were reported for the capture of CO 2 .[8] Recently, a novel method for the capture of CO 2 in a 1:1 manner by superbase-derived protic ILs and substituted aprotic ILs using the reactivity of anion was reported.[9] Normally, the chemisorption has high absorption capacity for CO 2 along with high energy requirement for regeneration.[10] One commonly used parameter to access the regeneration energy requirement is the enthalpy of CO 2 absorption. We need reduce the enthalpy of absorption to design the energy-saving ILs for CO 2 capture. Then, how can we design suitable chemical structures of ILs to reduce the enthalpy of CO 2 chemisorption? Can we prepare highly stable ILs for energy-saving and equimolar CO 2 capture?Herein, we present a strategy to tune the enthalpy of CO 2 absorption by tunable basic ionic liquids, which were prepared by neutralizing weak proton donors with different pK a valu...

A novel strategy for SO(2) capture through multiple-site absorption in the anion of several azole-based ionic liquids is reported. An extremely high capacity of SO(2) (>3.5 mol/mol) and excellent reversibility (28 recycles) were achieved by tuning the interaction between the basic anion and acidic SO(2). Spectroscopic investigations and quantum-mechanical calculations showed that such high SO(2) capacity originates from the multiple sites of interaction between the anion and SO(2). These tunable azole-based ionic liquids with multiple sites offer significant improvements over commonly used absorbents, indicating the promise for industrial applications in acid gas separation.