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Lignin is a phenolic polymer accumulating in the cell walls of specific plant cell types to confer unique properties such as hydrophobicity, mechanical strengthening, and resistance to degradation....

Zeolites with appropriately narrow pore apertures can kinetically enhance the selective adsorption of CO2 over N-2. Here, we showed that the exchangeable cations (e.g., Na' or K) on zeolite ZK-4 play, an important role in the CO2 selectivity. Zeolites NaK ZK-4 with Si/Al = 1.8-2.8 had very high CO2 selectivity when an intermediate number of the exchangeable cations were K+ (the rest being Na+) Zeolites NaK ZK-4 with Si/Al = 1.8 had high CO, uptake capacity and very high CO2-over-N-2 selectivity (1190). Zeolite NaK ZK-4 with Si/A1 = 2.3 and 2.8 also had enhanced CO2 selectivity with an intermediate number of K cations. The high CO, selectivity was related to the I(' cation in the 8 -rings of the alpha-cage, together with Na+ cations in the 6 -ring, obstructing the diffusion of N2 throughout the zeolite. The positions of the K+ cation in the 8 -ring moved slightly (max 0.2 angstrom) toward the center of the a-cage upon the adsorption of CO2, as revealed by in situ X-ray diffraction. The CO2-over-N-2 selectivity was somewhat reduced when the number of K+ cations approached 100%. This was possibly due to the shift in the IC' cation positions in the 8 -ring when the number of Na+ was going toward 0%, glowing N, diffusion through the 8 -ring. According to 'm situ infrared spectroscopy, the amount of chemisorbed CO2 was reduced on zeolite ZK-4s with increasing Si/Al ratio. In the context of potential applications, a kinetically enhanced selection of CO2 could be relevant for applications in carbon capture and bio- and natural gas upgrading.

Understanding the molecular-level mechanisms of phase transformation in solids is of fundamental interest for functional materials such as zeolites. Two-dimensional (2D) zeolites, when used as shape-selective catalysts, can offer improved access to the catalytically active sites and a shortened diffusion length in comparison with their 3D analogues. However, few materials are known to maintain both their intralayer microporosity and structure during calcination for organic structure-directing agent (SDA) removal. Herein we report that PST-9, a new 2D zeolite which has been synthesized via the multiple inorganic cation approach and fulfills the requirements for true layered zeolites, can be transformed into the small-pore zeolite EU-12 under its crystallization conditions through the single-layer folding process, but not through the traditional dissolution/recrystallization route. We also show that zeolite crystal growth pathway can differ according to the type of organic SDAs employed.

Hierarchically porous carbon foams with specific surface areas exceeding 600 m2 g−1 can be derived from polystyrene foams that are synthesized via water-in-oil emulsion templating. However, most st ...

Amine-modified sorbents are relevant to the capturing of dilute carbon dioxide from gas mixtures, and micro-/mesoporous polymers are promising substrates due to their rich chemistry. Here, we prepared an aldehyde-rich polyimine with micro- and mesopores by a Schiff-base condensation of 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarboxaldehyde using an excess of aldehyde. The micropores were crucial to the physisorption of CO2, while the mesopores provided space for the post-modification with tris(2-aminoethyl)amine (tren) that induced the chemisorption of CO2. The amine modified polymer showed a high uptake of CO2 at low pressures (1.13 mmol g−1 at 0.05 bar and 273 K) and a high estimated CO2-over-N2 selectivity (1.04 × 103 at 273 K for 5 v%/95 v% CO2/N2 mixture). CO2 both physisorbed and chemisorbed on the amine-modified polyimine, which we confirmed by studying the CO2-amine chemistry using in situ FTIR spectroscopy and solid state 13C NMR spectroscopy. Carbamic acid formed during the chemisorption of CO2, as the CO2 reacted with the amine groups. Due to the formation of carbamic acid, the isosteric heat of adsorption was high, with values up to 80 kJ mol−1 at a low coverage of CO2. It appears that amine-modified porous polymers could be relevant to the removal of CO2 from gas streams with low concentrations.

A range of titanium silicates (ETS-4 and CTS-1) with interesting gas separation properties were studied as CO2 adsorbents. Some of these adsorbents, in particular NaMg-CTS-1, showed the ability to ...

A modular design for a novel heterogeneous synergistic catalytic system, which simultaneously activates the electrophile and nucleophile by the combined activation modes of a separate metal and non ...

A new porous vanadoborate was synthesized by employing the scale chemistry theory with the vanadoborate cluster V10B28. The twofold interpenetrated lvt network was assembled with zinc-containing elliptical vanadoborate clusters and Zn polyhedra. The single lvt framework contains a three-dimensional 38×38×20 ring channel system with the pore size (24.7×12.7 Å) reaching the mesoscale, thus indicating the possibility of constructing 3D ordered mesopores with vanadoborate clusters. The porosity of the SUT-7 structure was confirmed by CO2 adsorption of the as-synthesized materials.

Detailed molecular aspects of carbon dioxide sorption on porous silica with different amounts of tethered and cross-linked n-propylamine groups were investigated. Infrared spectroscopy was applied ...

We report on a new series of isoreticular frameworks based on zinc and 2-substituted imidazolate-4-amide-5-imidate (IFP-1-4, IFP = imidazolate framework Potsdam) that form one-dimensional, microporous hexagonal channels. Varying R in the 2-substitued linker (R = Me (IFP-1), Cl (IFP-2), Br (IFP-3), Et (IFP-4)) allowed the channel diameter (4.0-1.7 Å), the polarisability and functionality of the channel walls to be tuned. Frameworks IFP-2, IFP-3 and IFP-4 are isostructural to previously reported IFP-1. The structures of IFP-2 and IFP-3 were solved by X-ray crystallographic analyses. The structure of IFP-4 was determined by a combination of PXRD and structure modelling and was confirmed by IR spectroscopy and (1)H MAS and (13)C CP-MAS NMR spectroscopy. All IFPs showed high thermal stability (345-400 °C); IFP-1 and IFP-4 were stable in boiling water for 7 d. A detailed porosity analysis was performed on the basis of adsorption measurements by using various gases. The potential of the materials to undergo specific interactions with CO(2) was investigated by measuring the isosteric heats of adsorption. The capacity to adsorb CH(4) (at 298 K), CO(2) (at 298 K) and H(2) (at 77 K) at high pressure were also investigated. In situ IR spectroscopy showed that CO(2) is physisorbed on IFP-1-4 under dry conditions and that both CO(2) and H(2)O are physisorbed on IFP-1 under moist conditions.

Silicoaluminophosphates (SAPO-17, SAPO-35, SAPO-56 and SAPO-RHO) synthesised via hydrothermal means are tested for their abilities to adsorb carbon dioxide. These 8-ring microporous phosphates show ...

The fine structural details of mesoporous materials possessing Pmn symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystall ...

Two phenyl rings of triphenylphosphane have been modified by electron-withdrawing trifluoromethyl groups. A methoxy group has been introduced at the para-position of the third ring. Due to the activating effect of the methoxy group, the phosphane can be monosulfonated under mild conditions and with complete selectivity. The novel ligand, sodium 5-[bis-(4-trifluoromethylphenyl)-phosphanyl]-2-methoxybenzenesulfonate, has been obtained in quantitative yield, and it has an outstanding π-acceptor capacity among the known sulfonated triarylphosphanes. It is not soluble in water but soluble in light alcohols and ionic liquids. Its solubility properties allow facile catalyst separation without water.

Amorphous order: Amorphous calcium carbonates (ACC) have an intrinsic structure relating to the crystalline polymorphs of calcite and vaterite. The proto-crystalline structures of calcite and vater ...

Narrow channels with polar walls are the structural and functional features responsible for the high capacity of a zinc-organic framework based on an imidazolate-amide-imidate ligand for the uptake of H2 and CO2 (see structure: orange Zn, blue N, red O, dark gray C, light gray H). The rigid and stable chelating ligand was synthesized in situ by partial hydrolysis of a dicyanoimidazole compound.

Porosity and chirality are two of the most important properties for materials in the chemical and pharmaceutical industry. Inorganic microporous materials such as zeolites have been widely used in ion-exchange, selective sorption/separation and catalytic processes. The pore size and shape in zeolites play important roles for specific applications(1-3). Chiral inorganic microporous materials are particularly desirable with respect to their possible use in enantioselective sorption, separation and catalysis(4). At present, among the 179 zeolite framework types reported, only three exhibit chiral frameworks(5-7). Synthesizing enantiopure, porous tetrahedral framework structures represents a great challenge for chemists. Here, we report the silicogermanates SU-32 (polymorph A), SU-15 (polymorph B) (SU, Stockholm University) and a hypothetical polymorph C, all built by different stacking of a novel building layer. Whereas polymorphs B and C are achiral, each crystal of polymorph A exhibits only one hand and has an intrinsically chiral zeolite structure. SU-15 and SU-32 are thermally stable on calcination.

The uptake of carbon dioxide and nitrogen gas by zeolite NaKA was studied. A very high ideal CO(2)-over-N(2) selectivity and a high CO(2) capacity were observed at an optimal K(+) content of 17 at.%. NaKA is a very promising adsorbent for CO(2) separation from water-free flue gases.