Microporous Metal–Organic Framework Based on a Bifunctional Linker for Selective Sorption of CO2 over N2 and CH4

Metal-organic frameworks with a sulfur-rich heterocycle: synthesis, gas adsorption properties, and metal exchange

Three new three-dimensional (3D) metal-organic frameworks [M2(ttdc)2(dabco)] (M = Zn(II), 1-Zn; Cu(II), 1-Cu; and Zn/Cu, 1-ZnCu) based on thieno[3,2-b]thiophene-2,5-dicarboxylate (ttdc2-) were synthesized and characterized by a combination of physicochemical methods (single crystal X-ray diffraction, powder X-ray diffraction, chemical and thermogravimetric analyses and IR spectroscopy). 1-Cu demonstrated permanent porosity (Vpore = 0.790 cm3 g-1 and SBET = 1725 m2 g-1) and significant CO2, CH4, C2H2, C2H4 and C2H6 gas uptakes under ambient conditions. The adsorption selectivities for gas mixtures, calculated by IAST, were 10.8 (10.7), 14.6 (9.4), 1.7 (1.6) and 1.5 (1.6) for the equimolar gas mixture compositions CO2/N2, C2H6/CH4, C2H6/C2H4 and C2H6/C2H2 at 1 bar and 273 K (298 K), respectively. The mixed-metal compound 1-ZnCu was prepared by a crystal-to-crystal ion exchange metathesis reaction from 1-Zn with a 52% degree of ion substitution, confirmed by energy-dispersive X-ray spectroscopy, optical microscopy and single crystal X-ray diffraction analysis.

Enhanced Adsorption Selectivity of Carbon Dioxide and Ethane on Porous Metal-Organic Framework Functionalized by a Sulfur-Rich Heterocycle

Porous metal-organic framework [Zn₂(ttdc)₂(bpy)] (1) based on thieno [3,2-b]thiophenedicarboxylate (ttdc) was synthesized and characterized. The structure contains intersected zig-zag channels with an average aperture of 4 × 6 Å and a 49% (v/v) guest-accessible pore volume. Gas adsorption studies confirmed the microporous nature of 1 with a specific surface area (BET model) of 952 m²·g^-1 and a pore volume of 0.37 cm³·g^-1. Extensive CO₂, N₂, O₂, CO, CH₄, C₂H₂, C₂H₄ and C₂H₆ gas adsorption experiments at 273 K and 298 K were carried out, which revealed the great adsorption selectivity of C₂H₆ over CH₄ (IAST selectivity factor 14.8 at 298 K). The sulfur-rich ligands and double framework interpenetration in 1 result in a dense decoration of the inner surface by thiophene heterocyclic moieties, which are known to be effective secondary adsorption sites for carbon dioxide. As a result, remarkable CO₂ adsorption selectivities were obtained for CO₂/CH₄ (11.7) and CO₂/N₂ (27.2 for CO₂:N₂ = 1:1, 56.4 for CO₂:N₂ = 15:85 gas mixtures). The computational DFT calculations revealed the decisive role of the sulfur-containing heterocycle moieties in the adsorption of CO₂ and C₂H₆. High CO₂ adsorption selectivity values and a relatively low isosteric heat of CO₂ adsorption (31.4 kJ·mol^-1) make the porous material 1 a promising candidate for practical separation of biogas as well as for CO₂ sequestration from flue gas or natural gas.

Crystal structure of dichlorido-bis[2-(2-(3-(pyridin-2-yl)-1H-1,2,4-triazol-5-yl)phenoxy)benzoic acidmanganese(II) monohydrate, C40H30N8O7MnCl2

C40H30N8O7MnCl2, monoclinic, C2/c (no. 15), a = 13.0864(7) Å, b = 25.6216(9) Å, c = 12.2253(7) Å, β = 112.027(6)°, V = 3799.9(3) Å3, Z = 4, R gt(F) = 0.0413, wR ref(F 2) = 0.1001, T = 293(2) K.

Acid-Base-Resistant Metal-Organic Framework for Size-Selective Carbon Dioxide Capture

The development of practical porous materials for the selective capture of CO₂ from flue gas and crude biogas is highly critical for both environment protection and energy safety. Here, a novel metal-organic framework (FJI-H29) has been prepared, which not only has excellent acid-base resistance but also possesses polar micropores (3.4-4.3 Å) that can match CO₂ molecules well. FJI-H29 can selectively capture CO₂ from N₂ and CH₄ with excellent separation efficiency and suitable adsorption enthalpy under ambient conditions. Breakthrough experiments further confirm its practicability for both CO₂/N₂ and CO₂/CH₄ separation. All of these confirm FJI-H29 is a practical CO₂ adsorbent. Modeling calculations reveal that the confinement effect of micropores and the polar environment synergistically promotes the selective adsorption of CO₂, which will provide a potential strategy for the synthesis of a practical metal-organic framework for CO₂ capture.

Structural Tuning and Pore Modulation of Three Cu(II)-Organic Frameworks: Enhancement of Stability and Functionality

Through use of an irregular pentacarboxylate ligand, 2,2'-(pyridine-2,6-diyl)diterephthalic acid (H₄L), two Cu(II)-based metal-organic frameworks, {[(Me₂NH₂)_0.5][Cu_0.75(L)_0.5(DMA)_0.375]·H₂O}_n (1) and {[Cu₄(L)₂(H₂O)₄]·4DMF·8H₂O}_n (2), have been synthesized. A structural analysis demonstrates that 1 is a 2D layer and 2 shows a 3D framework, which exhibit hopeful possibilities for the selective separations of C₂H₂/CH₄ and CO₂/CH₄. To enhance the adsorption properties, 5-amino-1H-tetrazole (HAT) has been introduced in the synthesis system, and a new framework, {[Cu₄(L)₂(ATZ)₂(H₂O)]·5DMF·5H₂O}_n (3), has been obtained. 3 is a 3D framework. Especially, 3 is constructed from multiple SBUs and displays an unusual (3,4,6)-connected topology. Furthermore, especially 3 performs better than 1 and 2 in terms of uptake capacity as well as adsorption selectivity, which might be ascribed to the more proper pore space of 3.

Near-infrared luminescence and magnetic properties of dinuclear rare earth complexes modulated by β-diketone co-ligands

The magnetic properties of complexes based on a Schiff base ligand H₂L can be modulated by subtle changes in the coordination environment resulting from changes in the co-ligand substituents.

Hexanuclear Cu3O-3Cu triazole-based units as novel core motifs for high nuclearity copper(ii) frameworks

The asymmetric 3,5-disubstituted 1,2,4-triazole ligand H₂V (5-amino-3-picolinamido-1,2,4-triazole) by reaction with an excess of Cu(ii) perchlorate (Cu : H₂V being 12 : 1) has produced a novel hexanuclear {Cu₆(μ₃-O/H)(HV/V)₃} fragment, with one triangular Cu₃(μ₃-O/H) group connected to three peripheral single Cu(ii) ions through a cis-cis-trans bridging mode of the ligand, which is the building block of the three structures described here: one hexanuclear, [Cu₆(μ₃-O)(HV)₃(ClO₄)₇(H₂O)₉]·8H₂O (1), one dodecanuclear, [Cu₁₂(μ₃-O)₂(V)₆(ClO₄)₅(H₂O)₁₈](ClO₄)₃·6H₂O (2), and one tetradecanuclear 1D-polymer, {[Cu₁₄(μ₃-OH)₂(V)₆(HV)(ClO₄)₁₁(H₂O)₂₀](ClO₄)₂·14H₂O} _n (3), the last two containing hexanuclear subunits linked by perchlorato bridges. The Cu-Cu av. intra-triangle distance is 3.352(2) Å and the Cu(central)-Cu(bridged external) av. distance is 5.338(3) Å. The magnetic properties of the hexanuclear "Cu₃O-3Cu" cluster have been studied, resulting as best fit parameters: g = 2.18(1), J(intra-triangle) = -247.0(1) cm^-1 and j(central Cu^II - external Cu^II) = -5.15(2) cm^-1.

Two ultramicroporous metal-organic frameworks assembled from binuclear secondary building units for highly selective CO2/N2 separation

Two novel metal-organic frameworks [Ni₂(μ₂-Cl)(BTBA)₂·DMF]·Cl·3DMF (JLU-MOF56, BTBA = 3,5-bis(triazol-1-yl)benzoic acid) and [Co₂(μ₂-Cl)(BTBA)₂·DMF]·Cl·3DMF (JLU-MOF57) have been successfully synthesized under solvothermal conditions. Crystallographic analysis indicates that the two compounds with different metal ions are isoreticular and both are constructed from binuclear [M₂(μ₂-Cl)(COO)₂N₄] (M = Co, Ni) and a 3-connected hetero-N,O donor ligand. The overall framework possesses a (3,6)-connected dag topology. Furthermore, both of them feature ultramicroporous channels of 3.5 Å× 3.4 Å, which are suitable for adsorbing smaller carbon dioxide (CO₂) gas molecules but not larger nitrogen (N₂) gas molecules. Therefore, JLU-MOF56 and JLU-MOF57 exhibit good performance for CO₂/N₂ separation, and are promising materials for gas adsorption and purification.

Near-Perfect CO2/CH4 Selectivity Achieved through Reversible Guest Templating in the Flexible Metal-Organic Framework Co(bdp)

Metal-organic frameworks are among the most promising materials for industrial gas separations, including the removal of carbon dioxide from natural gas, although substantial improvements in adsorption selectivity are still sought. Herein, we use equilibrium adsorption experiments to demonstrate that the flexible metal-organic framework Co(bdp) (bdp^2- = 1,4-benzenedipyrazolate) exhibits a large CO₂ adsorption capacity and approaches complete exclusion of CH₄ under 50:50 mixtures of the two gases, leading to outstanding CO₂/CH₄ selectivity under these conditions. In situ powder X-ray diffraction data indicate that this selectivity arises from reversible guest templating, in which the framework expands to form a CO₂ clathrate and then collapses to the nontemplated phase upon desorption. Under an atmosphere dominated by CH₄, Co(bdp) adsorbs minor amounts of CH₄ along with CO₂, highlighting the importance of studying all relevant pressure and composition ranges via multicomponent measurements when examining mixed-gas selectivity in structurally flexible materials. Altogether, these results show that Co(bdp) may be a promising CO₂/CH₄ separation material and provide insights for the further study of flexible adsorbents for gas separations.

A flexible doubly interpenetrated metal–organic framework with gate opening effect for highly selective C2H2/C2H4 separation at room temperature

A flexible doubly interpenetrated MOF is realized at room temperature, whose pore spaces could accommodate a significant amount of C₂H₂ at room temperature via the gate-opening effect but exclude C₂H₄ and C₂H₆ outside.

Humidity-induced CO2 capture enhancement in Mg-CUK-1

Mg-CUK-1 showed a 1.8-fold increase in CO₂ capture (from 4.6 wt% to 8.5 wt%) in the presence of 18% RH.

Regulating the luminescent and magnetic properties of rare-earth complexes with β-diketonate coligands

By introducing different β-diketonate coligands, Dy₂ complexes exhibit different SMM behaviors.

Three new super water-stable lanthanide–organic frameworks for luminescence sensing and magnetic properties

Three new lanthanide compounds, [Ln(HL)(H₂O)₃]_n (1-Ln) (Ln = Eu, Tb and Dy), with isostructural structures have been constructed by a semi-rigid ligand 1-(3,5-dicarboxylatobenzyl)-3,5-pyrazole dicarboxylic acid (H₄L) and Ln(NO₃)₃·6H₂O using the solvothermal method.

Polycatenation tuned microporosity of two metal–tris(4′-carboxybiphenyl)amine frameworks with multilayer structures

By employing a nanosized tris(4′-carboxybiphenyl)amine ligand to assemble with Zn²⁺ ions, a novel trilayer network (FIR-37) and an unprecedented 2D → 3D microporous polycatenation framework (FIR-38) based on unusual tetralayers have been synthesized and structurally characterized.

Crystal structure of dimethanolo-bis[μ-(2-(2-(5-(pyridin-2-yl)-1H-1,2,4-triazol-3-yl)phenoxy)benzoato)-κ5 O,O′,N:N′,N′′]dicopper(II) — methanol (1/2), C46H48Cu2N8O12

C46H32Cu2N8O12, monoclinic, P21/c, a = 9.5638(9)Å, b = 20.2142(19) Å, c = 12.0825(11) Å, β = 94.696(1)°, V = 2328.0(4) Å3, Z = 2, R gt(F) = 0.0273, wR ref(F 2) = 0.0711, T = 100 K.

Synthesis of Highly Porous Coordination Polymers with Open Metal Sites for Enhanced Gas Uptake and Separation

Metal-containing amorphous microporous polymers are an emerging class of functional porous materials in which the surface properties and functions of polymers are dictated by the nature of the metal ions incorporated into the framework. In an effort to introduce coordinatively unsaturated metal sites into the porous polymers, we demonstrate herein an aqueous-phase synthesis of porous coordination polymers (PCPs) incorporating bis(o-diiminobenzosemiquinonato)-Cu(II) or -Ni(II) bridges by simply reacting hexaminotriptycene with CuSO₄·5H₂O [Cu(II)-PCP] or NiCl₂·6H₂O [Ni(II)-PCP] in H₂O. The resulting polymers showed surface areas of up to 489 m² g^-1 along with a narrow pore size distribution. The presence of open metal sites significantly improved the gas affinity of these frameworks, leading to an exceptional isosteric heat of adsorption of 10.3 kJ·mol^-1 for H₂ at zero coverage. The high affinities of Cu(II)- and Ni(II)-PCPs toward CO₂ prompted us to investigate the removal of CO₂ from natural and landfill gas conditions. We found that the higher affinity of Cu(II)-PCP compared to that of Ni(II)-PCP not only allowed for the tuning of the affinity of CO₂ molecules toward the sorbent, but also led to an exceptional CO₂/CH₄ selectivity of 35.1 for landfill gas and 20.7 for natural gas at 298 K. These high selectivities were further verified by breakthrough measurements under the simulated natural and landfill gas conditions, in which both Cu(II)- and Ni(II)-PCPs showed complete removal of CO₂. These results clearly demonstrate the promising attributes of metal-containing porous polymers for gas storage and separation applications.

Moisture-Stable Zn(II) Metal-Organic Framework as a Multifunctional Platform for Highly Efficient CO2 Capture and Nitro Pollutant Vapor Detection

A moisture-stable three-dimensional (3D) metal-organic framework (MOF), {(Me2NH2)[Zn2(bpydb)2(ATZ)](DMA)(NMF)2}n (1, where bpydb = 4,4'-(4,4'-bipyridine-2,6-diyl)dibenzoate, ATZ = deprotonated 5-aminotetrazole, DMA = N,N-dimethylacetamide, and NMF = N-methylformamide), with uncoordinated N-donor sites and charged framework skeleton was fabricated. This MOF exhibits interesting structural dynamic upon CO2 sorption at 195 K and high CO2/N2 (127) and CO2/CH4 (131) sorption selectivity at 298 K and 1 bar. Particularly, its CO2/CH4 selectivity is among the highest MOFs for selective CO2 separation. The results of Grand Canonical Monte Carlo (GCMC) simulation indicate that the polar framework contributes to the strong framework-CO2 binding at zero loading, and the tetrazole pillar contributes to the high CO2 uptake capacity at high loading. Furthermore, the solvent-responsive luminescent properties of 1 indicate that it could be utilized as a fluorescent sensor to detect trace amounts of nitrobenzene in both solvent and vapor systems.

Selective separation of CO2–CH4 mixed gases via magnesium aminoethylphosphonate nanoparticles

Magnesium 2-aminoethylphosphonate (Mg₂O(2AEP) × 4H₂O) nanoparticles (particle diameter: 20–30 nm; specific surface area: 360 m² g⁻¹) are presented for selective separation of CO₂ and CH₄.

Can a highly flexible copper(i) cluster-containing 1D and 2D coordination polymers exhibit MOF-like properties?

The p-TolS(CH₂)₈STol-p and p-tBuC₆H₄S(CH₂)₈SC₆H₄-tBu-p ligands react with CuI respectively in MeCN and EtCN and in EtCN form the 2D and 1D polymers [Cu₈I₈(p-TolS(CH₂)₈STol-p)₃(solvent)₂]_n (solvent = MeCN, EtCN) and [Cu₄I₄(p-tBuC₆H₄S(CH₂)₈SC₆H₄-tBu-p)₂(EtCN)]_n susceptible to exchange solvent molecules.

A chiral metal–organic framework with polar channels: unique interweaving six-fold helices and high CO2/CH4 separation

A chiral Cu(ii) metal–organic framework, possesses interesting polar channels based on interweaving heterochiral [4 + 2] helices, exhibiting multiple CO₂ binding sites and highly selective capture for CO₂ over CH₄.

Experimental and theoretical investigation of a stable zinc-based metal–organic framework for CO2 removal from syngas

The experimental and theoretical investigation of a new water-stable Zn-based metal–organic framework for CO₂ removal from syngas (a binary gas mixture of CO and H₂) is presented.