High CO2 Adsorption Selectivity Research Articles

A porous metal–organic framework as active catalyst for multiple C–N/C–C bond formation reactions

A 3D porous metal–organic framework {[Cu(4-tba)2](solvent)}n (1⋅S) is assembled via 4-(1H-1,2,4-triazol-1-yl)benzoic acid (Htba) and Cu(II) nodes, which shows the [2+2] roto-translational interpenetrating network. Interestingly, 1 displays high CO2 adsorption selectivity over CH4/H2/O2/Ar/N2 gases, and acts an efficient catalyst precursor in some C–N/C–C bond formation reactions, including Chan–Lam coupling reaction of phenylboronic acid with imidazole, Suzuki–Miyoura coupling reaction of phenylboronic acids with aryl halides, and Heck coupling reaction of styrene with aryl halides.

A new self-penetrating amine-decorated microporous metal–organic framework: Crystal structure, adsorption selectivity, and luminescence properties

A new microporous metal–organic framework, [Cd(bpdc)0.5(atz)(DMF)]·0.5DMF (1) (H2bpdc=4,4′-biphenyldicarboxylic acid, Hatz=3-amino-1,2,4-triazole, DMF=N,N-dimethylformamide) has been solvothermally synthesized by employing the mixed H2bpdc and Hatz ligands. 1 is a 3D pillared-layer framework, consisting of Cd–triazolate layer and dicarboxylate pillar, which exhibits a 6-connected (46·68·8) self-penetrating net. Because of the pore system functionalized by amino groups and open metal sites, this material shows high CO2 adsorption selectivity over H2 and N2. In addition, 1 exhibits blue emission at ambient temperature.

A new anionic metal–organic framework showing tunable emission by lanthanide(III) doping and highly selective CO2 adsorption properties

A 3D porous anionic MOF (1), decorated with -NH2 and N sites, can serve as a host for the encapsulation of lanthanide(iii) cations for emission tuning. Besides, it also shows high adsorption selectivity for CO2 over CH4 and N2 at 273 K.

A novel acylamide MOF showing self-catenated hxg-d-4-Fddd nets with 3-fold interpenetration and highly selective adsorption of CO2 over N2, CH4, and CO

Reported here is a novel acylamide MOF, Zn(L) (tdca)·1.5 DMF(1), obtained by a mixed ligand approach, where N4,N4′-di(pyridin-4-yl)-[1,1′-biphenyl]-4,4′- dicarboxamide(L) and thiophene-2,5-dicarboxylic acid (tdca) are used. The 3D framework can be represented as a rare 4-connected self-catenated hxg-d-4-Fddd net with a 65.8 topological symbol. Notably, the MOF shows high CO2 adsorption selectivity over CH4, CO, and N2 gases.

Divergent kinetic and thermodynamic hydration of a porous Cu(II) coordination polymer with exclusive CO₂ sorption selectivity.

Selective adsorption and separation of CO2 are of great importance for different target applications. Metal-organic frameworks (MOFs) represent a promising class of porous materials for this purpose. Here we present a unique MOF material, [Cu(tba)2]n (tba = 4-(1H-1,2,4-triazol-1-yl)benzoate), which shows high CO2 adsorption selectivity over CH4/H2/O2/Ar/N2 gases (with IAST selectivity of 41-68 at 273 K and 33-51 at 293 K). By using a critical point dryer, the CO2 molecules can be well sealed in the 1D channels of [Cu(tba)2]n to allow a single-crystal X-ray analysis, which reveals the presence of not only C(δ+)-H···O(δ-) bonds between the host framework and CO2 but also quadrupole-quadrupole (CO2(δ-)···(δ+)CO2) interactions between the CO2 molecules. Furthermore, [Cu(tba)2]n will suffer divergent kinetic and thermodynamic hydration processes to form its isostructural hydrate {[Cu(tba)2](H2O)}n and a mononuclear complex [Cu(tba)2(H2O)4] via single-crystal to single-crystal transformations.

New CO2 separation membranes containing gas-selective Cu-MOFs

We examined the challenge of preparing CO2-selective bifunctional three-dimensional Cu-metal–organic frameworks (Cu-MOFs) for use in mixed-matrix membranes (MMMs) fabricated on an asymmetric polymer support. Two different gas-selective micro-sized frameworks, [{Cu2(Glu)2(µ-bpa)}·(CH3CN)]n (Cu-MOF1) and [{Cu2(Glu)2(µ-bpp)}·(C3H6O)]n (Cu-MOF2) (Glu=glutarate, bpa=1,2-bis(4-pyridyl)ethane, bpp=1,3-bis(4-pyridyl)propane), were synthesised and dispersed in polyoxazoline (POZ), as a matrix for the fabrication of the MMMs. SEM imaging indicated relatively good adhesion between the Cu-MOFs and POZ, without any surface treatment. The ideal selectivity of CO2/N2 was enhanced significantly in the Cu-MOF/POZ MMM, compared to that in a pristine POZ asymmetric membrane. Improvement in the CO2/N2 selectivity of the membranes was achieved via both high adsorption selectivity of CO2 over N2 by the Cu-MOFs, and the difference in pore sizes. The fabrication methods that use gas-selective MOFs may create new opportunities for gas-selective MOF/polymer combinations for MMMs with useful properties for large volume separations.

High performance gas adsorption and separation of natural gas in two microporous metal–organic frameworks with ternary building units

Two novel MMOFs, JLU-Liu5 and JLU-Liu6, are based on ternary building units and exhibit high adsorption selectivity for CO2, C2H6 and C3H8 over CH4, which is attributed to steric effects and host-guest interactions. These MMOFs are promising materials for gas adsorption and natural gas purification.

An improved CO2 adsorption efficiency for the zeolites impregnated with the amino group: A molecular simulation approach

The molecular dynamic and Grand Canonical Monte Carlo simulation study were conducted to investigate the adsorption and diffusion behaviors of mixture of CO2 and N2. Pure silicalite structures of zeolites TON, AFI, and LTL were selected as the host materials to be evaluated in this study. The effect of surface modification of TON, realized by impregnating the amino functional group on TON surface, on the adsorption and the diffusion were analyzed and compared with the normal TON structure. The results show that, in the adsorption behaviors, the modified TON adsorbs more CO2 than the normal TON structure, however, at high pressure regions, CO2 uptake is lower than the normal TON due to reductions of pore volume. As well as the adsorption isotherm, CO2/N2 adsorption selectivity was also calculated, and it suggested that although the modified TON has low adsorption capacity of CO2, it has a high adsorption selectivity of CO2 over N2 comparable with other sorbents. In the diffusion behaviors, the mixture in the modified TON has a lower diffusivity than the mixture in the normal TON due to additional attractive interaction between the amino group and mixture. In addition, because of the small pore size of the selected zeolite structures, the single file mobilities as well as the self-diffusion coefficients were employed to describe the observed diffusion behaviors. Afterward, parametric studies for effects of the different pore length and zeolite structures on the diffusion of the mixture were carried out.

Microporous metal organic framework [M2(hfipbb)2(ted)] (M=Zn, Co; H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine): Synthesis, structure analysis, pore characterization, small gas adsorption and CO2/N2 separation properties

Carbon dioxide is a greenhouse gas that is a major contributor to global warming. Developing methods that can effectively capture CO2 is the key to reduce its emission to the atmosphere. Recent research shows that microporous metal organic frameworks (MOFs) are emerging as a promising family of adsorbents that may be promising for use in adsorption based capture and separation of CO2 from power plant waste gases. In this work we report the synthesis, crystal structure analysis and pore characterization of two microporous MOF structures, [M2(hfipbb)2(ted)] (M=Zn (1), Co (2); H2hfipbb=4,4-(hexafluoroisopropylidene)-bis(benzoic acid); ted=triethylenediamine). The CO2 and N2 adsorption experiments and IAST calculations are carried out on [Zn2(hfipbb)2(ted)] under conditions that mimic post-combustion flue gas mixtures emitted from power plants. The results show that the framework interacts with CO2 strongly, giving rise to relatively high isosteric heats of adsorption (up to 28kJ/mol), and high adsorption selectivity for CO2 over N2, making it promising for capturing and separating CO2 from CO2/N2 mixtures.

Indium(iii)–dicarboxylic microporous frameworks with high adsorption selectivity for CO2 over N2

Two microporous metal-organic frameworks formulated as H2In3O(OH)3(1,3-bdc)3 (1) and HIn(1,4-bdc)2 (2) (bdc = benzenedicarboxylic) were designed and synthesized. Compound 2 shows a high adsorption selectivity for CO2 over N2 as well as a high stability.

Adsorption and molecular simulation of CO2 and CH4 in two-dimensional metal–organic frameworks with the same layered substrate

Cu(1,3-BDC) (1,3-BDC = 1,3-benzenedicarboxylic acid) was found in the interpenetrated metal–organic frameworks [Cu(1,3-BDC)(H2O)]·2H2O and Cu(1,3-BDC)(PY)2. We studied their CO2, CH4, and N2 adsorption isotherms at high pressure (10 bar) and used density functional theory methods to locate their most stable configurations. We show that [Cu(1,3-BDC)(H2O)]·2H2O has a high adsorption selectivity of CO2 over CH4 because of the total lack of CH4 adsorption. Although Cu(1,3-BDC)(PY)2 has the same layered substrate as [Cu(1,3-BDC)(H2O)]·2H2O, except for the insertion of pyridine rings between layers, it adsorbs significantly more CH4, leading to decreased CO2/CH4 adsorption selectivity and increased CH4/N2 adsorption selectivity. Our experimental and theoretical studies reveal that introducing suitable organic ligands provides more adsorption sites for CH4, while the ligands' occupancy of the spaces between the layers prevents the spread of CO2 molecules.

Building multiple adsorption sites in porous polymer networks for carbon capture applications

IAST calculations reveal that sulfonate ammonium salt grafting renders porous polymer networks (PPN-6-SO3NH4) with exceptionally high adsorption selectivity for CO2 over N2 and CO2 over CH4. Breakthrough experiments confirm the high CO2 adsorption capacity (1.7 mmol g−1, 75 mg g−1) by feeding 15% CO2 balanced with N2 at 295 K and 1 bar.

Selective adsorption of CO2 on amino-functionalized silica spheres with centrosymmetric radial mesopores and high amino loading

Amino-functionalized silica spheres with centrosymmetric radial mesopores and high amino loading were synthesized using the anionic surfactant N-lauroylsarcosine sodium (Sar-Na) as template and 3-aminopropyltrimethoxysilane (APTMS) as co-structure directing agent (CSDA) by an orthogonal experiment optimization. The synthesized amino-functionalized mesoporous silica (AFMS) was used as adsorbent to the selective adsorption of CO2. The effects of water vapor in the adsorptive stream on the adsorption properties of CO2 were investigated in detail. The results show that the synthesized adsorbent possesses a high adsorption selectivity for CO2 over CH4 and N2 due to the specific interactions between CO2 and amino groups. The presence of water vapor in the adsorptive stream can dramatically enhance the adsorbed amount of CO2 because of the partial formation of bicarbonate in the presence of moisture. Furthermore, the adsorbent shows a good stability, confirmed by adsorption-regeneration cycles. Based on these excellent properties, the application of the developed AFMS adsorbent in the selective adsorption of CO2 is anticipated.

Sulfonate-Grafted Porous Polymer Networks for Preferential CO2 Adsorption at Low Pressure

A porous polymer network (PPN) grafted with sulfonic acid (PPN-6-SO(3)H) and its lithium salt (PPN-6-SO(3)Li) exhibit significant increases in isosteric heats of CO(2) adsorption and CO(2)-uptake capacities. IAST calculations using single-component-isotherm data and a 15/85 CO(2)/N(2) ratio at 295 K and 1 bar revealed that the sulfonate-grafted PPN-6 networks show exceptionally high adsorption selectivity for CO(2) over N(2) (155 and 414 for PPN-6-SO(3)H and PPN-6-SO(3)Li, respectively). Since these PPNs also possess ultrahigh physicochemical stability, practical applications in postcombustion capture of CO(2) lie well within the realm of possibility.