Kuan Huang

Multi-Molar Absorption of CO2 by the Activation of Carboxylate Groups in Amino Acid Ionic Liquids

A new strategy for multi-molar absorption of CO2 is reported based on activating a carboxylate group in amino acid ionic liquids. It was illustrated that introducing an electron-withdrawing site to amino acid anions could reduce the negative inductive effect of the amino group while simultaneously activating the carboxylate group to interact with CO2 very efficiently. An extremely high absorption capacity of CO2 (up to 1.69 mol mol(-1) ) in aminopolycarboxylate-based amino acid ionic liquids was thus achieved. The evidence of spectroscopic investigations and quantum-chemical calculations confirmed the interactions between two kinds of sites in the anion and CO2 that resulted in superior CO2 capacities.

Dicarboxylic acid salts as task-specific ionic liquids for reversible absorption of SO2 with a low enthalpy change

Six acid salt ionic liquids (ASILs), triethylbutylammonium dicarboxylates, have been synthesized to act as green materials for SO2 capture. The experimental results reveal that the ASILs can trap SO2 reversibly and chemically with a large capacity of 0.112 up to 0.232 (mass ratio) at 15.5 kPa and of 0.374 to 0.456 (mass ratio) at 100 kPa and 40 °C. Two of these ASILs are interestingly found to have a low viscosity that enables the fast mass transfer of SO2. A reaction mechanism is proposed to explain the chemical absorption based on FTIR spectra and structural calculations using the density functional theory. Thermodynamic analysis indicates the enthalpy of the reaction of SO2 with the ASILs is low (−29.9 and −42.2 kJ mol−1 for [N2224][dimaleate] and [N2224][dimalonate], respectively). Additionally, the ASILs have a high thermal stability, which favors their potential application in flue gas desulfurization.

Solvent‐Free Self‐Assembly to the Synthesis of Nitrogen‐Doped Ordered Mesoporous Polymers for Highly Selective Capture and Conversion of CO2

A solvent-free induced self-assembly technology for the synthesis of nitrogen-doped ordered mesoporous polymers (N-OMPs) is developed, which is realized by mixing polymer precursors with block copolymer templates, curing at 140-180 °C, and calcination to remove the templates. This synthetic strategy represents a significant advancement in the preparation of functional porous polymers through a fast and scalable yet environmentally friendly route, since no solvents or catalysts are used. The synthesized N-OMPs and their derived catalysts are found to exhibit competitive CO2 capacities (0.67-0.91 mmol g-1 at 25 °C and 0.15 bar), extraordinary CO2 /N2 selectivities (98-205 at 25 °C), and excellent activities for catalyzing conversion of CO2 into cyclic carbonate (conversion >95% at 100 °C and 1.2 MPa for 1.5 h). The solvent-free technology developed in this work can also be extended to the synthesis of N-OMP/SiO2 nanocomposites, mesoporous SiO2 , crystalline mesoporous TiO2 , and TiPO, demonstrating its wide applicability in porous material synthesis.

Solvothermal synthesis of hierarchically nanoporous organic polymers with tunable nitrogen functionality for highly selective capture of CO2

A series of porous organic polymers (POPs) with tunable nitrogen functionality and hierarchical porosity were successfully synthesized from the one-step copolymerization of divinylbenzene with 4-vinylpyridine or 1-vinylimidazolate under solvothermal conditions. The FTIR results, XPS spectra, and elemental analysis validated the incorporation of different kinds and contents of nitrogen species into the framework-synthesized POPs. The N2 adsorption isotherms at −196 °C and SEM and TEM images revealed that the synthesized POPs have large surface areas and abundant meso–macropores. The CO2 and N2 adsorption experiments demonstrated that the synthesized POPs have competitive capacity for CO2 at a relatively low pressure of 0.15 bar (0.64–1.47 mmol g−1 at 0 °C and 0.49–0.87 mmol g−1 at 25 °C) and exceptionally high IAST selectivity for CO2/N2 (0.15/0.85) at 1 bar (74.9–154.8 at 0 °C and 91.8–224.5 at 25 °C). The CO2/N2 selectivity is superior to that of most other reported physical adsorbents. This work provides a facile approach to the targeted synthesis of nitrogen-functionalized POPs with potential applications in the selective capture of CO2 from flue gas.

Impact of α-D-glucose pentaacetate on the selective separation of CO2 and SO2 in supported ionic liquid membranes

A biocompatible, nontoxic, and nonvolatile compound, α-D-glucose pentaacetate (GPA), was impregnated in supported ionic liquid membranes (SILMs) and used for the selective separation of CO2 and SO2. It was found that GPA could cooperate with [Bmim][BF4] to influence the permeability of CO2 and enhance the CO2/N2 selectivity. Further permeation experiments demonstrated that the addition of GPA could reduce the permeability of N2 in the SILMs and thereby improve the CO2/N2 and SO2/N2 selectivities. The highest CO2/N2 selectivity obtained in the paper is 79 ± 0.9 for dry gas and 86 ± 1.6 for humidified gas, and the highest SO2/N2 selectivity is 686 ± 19.8 for dry gas. This environmentally benign separation process with high gas permeability and good selectivity may be expected to have a potential application for the separation of CO2 and SO2 from a flue gas stream.

The ionic liquid-mediated Claus reaction: a highly efficient capture and conversion of hydrogen sulfide

Ionic liquids (ILs) were demonstrated to be highly efficient media for the liquid-phase Claus reaction. The reaction of H2S with SO2 in ILs proceeds very fast and almost completely to result in solid sulfur (S8) under mild conditions without the addition of any catalysts. Various ILs with different cations and anions were investigated and a simple IL 1-hexyl-3-methylimidazolium chloride ([hmim][Cl]) was found to be the most effective for the capture and conversion of H2S. It enables the transformation of H2S to S8 with a conversion ratio as high as >96% within 3 min. This finding opens up a promising method for the capture and conversion of H2S from gas streams.

One-step synthesis of nitrogen-doped graphene-like meso-macroporous carbons as highly efficient and selective adsorbents for CO2 capture

Graphene-like meso-macroporous carbons (GMCs) with high nitrogen contents and controllable nitrogen sites were synthesized by one-step carbonization of dicyandiamide or melamine with glucose. The unique layered structure and the presence of abundant meso-macropores in GMCs largely enhance the degree of exposure and accessibility of anchored nitrogen sites to CO2, which provides the GMCs with excellent performance for the selective capture of CO2.

Ordered Mesoporous Polymers for Biomass Conversions and Cross‐Coupling Reactions

Amino group-functionalized, ordered mesoporous polymers (OMP-NH2 ) were prepared using a solvent-free synthesis by grinding mixtures of solid raw precursors (aminophenol, terephthaldehyde), using block copolymer templates, and curing at 140-180 °C. OMP-NH2 was functionalized with acidic sites and incorporated with palladium, giving multifunctional solid catalysts with large Brunauer-Emmett-Teller (BET) surface areas, abundant and ordered mesopores, good thermal stabilities, controllable concentrations, and good dispersion of active centers. The resultant solid catalysts showed excellent catalytic activities and good reusability in biomass conversions and cross-coupling reactions-much superior to those of various reported solid catalysts such as Amberlyst 15, SBA-15-SO3 H, and Pd/C and comparable to those of homogeneous catalysts such as heteropoly acid, HCl, and palladium acetate. A facile green approach was developed for the synthesis of ordered mesoporous polymeric solid catalysts with excellent activities for conversion of low-cost feedstocks into useful chemicals and clean biofuels.

Aminopolymer functionalization of boron nitride nanosheets for highly efficient capture of carbon dioxide

Boron nitrides (BNs) are a class of materials with unique properties that exhibit promise for applications in CO2 capture. However, the surface electron-deficiency of BNs makes their interaction with Lewis acidic CO2 very weak. By utilizing the strong interaction between electron-deficient boron atoms and electron-donating amine groups, BN nanosheets were functionalized with polyethyleneimine (PEI) which is rich in amine density, through simple impregnation to improve their performance for CO2 capture. The important roles of the boron–amine interaction in the incorporation, distribution and stabilization of PEI, as well as the facilitation of CO2 adsorption and desorption were both experimentally and theoretically investigated. It is demonstrated that after functionalization with PEI, the capacity of pure CO2 on BN nanosheets was significantly improved (3.12 mmol g−1 for BN functionalized with 54.9 wt% of PEI vs. 0.29 mmol g−1 for pristine BN at 75 °C). Furthermore, the adsorbed CO2 can be facilely released through N2 purge at 75 °C, and the PEI-functionalized BN nanosheets exhibit high stability throughout consecutive cycles.

Remarkably efficient hydrolysis of cinnamaldehyde to natural benzaldehyde in amino acid ionic liquids

The hydrolysis of cinnamaldehyde to natural benzaldehyde was investigated systematically using tetramethylammonium- based amino acid ionic liquids as homogeneous catalysts. The results indicated that tetramethylammonium prolinate ([N1111][Pro]) can be a powerful catalyst for the highly efficient hydrolysis of cinnamaldehyde, in which natural benzaldehyde was obtained with almost 94% yield and over 99% selectivity in 1 h. Moreover, kinetic study showed that compared with other catalysts, the catalytic system of [N1111][Pro] has a lower activation energy of 38.30 kJ·mol−1 in the hydrolysis reaction, indicating superior catalytic performance of [N1111][Pro]. Quantum-mechanical calculations further manifested that such high performance originates from the cooperative catalysis of the secondary amino and carboxyl group in the anion [Pro].