Suitable Pore Space Research Articles

Aromatic pore engineering in microporous metal–organic frameworks for high-production one-step methane purification from ternary alkanes mixtures

The exploitation of competent isolation and purification technology of methane (CH4) is an imperative and challenging task for full utilization of clean natural gas in petrochemical industry. Compared to traditional energy-intensive low-temperature distillation, adsorptive separation using porous metal–organic framework (MOF) materials provides an alternative technique with low energy consumption and high efficiency. In this situation, an aromatic pore engineering strategy in a series of pillar-layered Zn-based MOFs by introducing organic linkers with different degrees of aromatic units was investigated to tune pore size and pore environment for simultaneously removing propane (C3H8) and ethane (C2H6) from C3H8/C2H6/CH4 mixtures. Compared to the other two analogues, i.e. Zn(BDC)(TED)0.5 and Zn(ADC)(TED)0.5, obtained Zn(NDC)(TED)0.5 showed high adsorption capacity for C3H8 (5.18 mmol/g) and C2H6 (5.04 mmol/g) and selectivity for C3H8/CH4 and C2H6/CH4 at 298 K and 1.0 bar. Breakthrough tests proved the three MOFs can effectively separate ternary C3H8/C2H6/CH4 mixtures, and Zn(NDC)(TED)0.5 especially exhibited excellent high-purity CH4 yield of 10.07 mmol/g. Computational simulations showed that suitable pore space and surface aromatic environment in Zn(NDC)(TED)0.5 created beneficial interactions with C3H8 and C2H6 molecules, which ultimately contributed to its favourable adsorption and separation property. This system work provides insights for the development of pore control method in MOF materials for natural gas purification.

A novel hydrophobic carborane-hybrid microporous material for reversed C2H6 adsorption and efficient C2H4/C2H6 separation under humid conditions.

Since ethylene (C2H4) is important feedstock in the chemical industry, developing economical and energy-efficient adsorption separation techniques based on ethane (C2H6)-selective adsorbents to replace the energy-intensive cryogenic distillation is highly demanded, which however remains a daunting challenge. While previous anionic boron cluster hybrid microporous materials display C2H4-selective features, we herein reported that the incorporation of a neutral para-carborane backbone and aliphatic 1,4-diazabicyclo[2.2.2]octane (DABCO) enables the reversed adsorption of C2H6 over C2H4. The generated carborane-hybrid microporous material ZNU-10 (ZNU = Zhejiang Normal University) is highly stable in humid air and maintains good C2H6/C2H4 separation performance under high humidity. Gas loaded single crystal structure and density-functional theory (DFT) calculations revealed that the weakly polarized carborane and DABCO within ZNU-10 induce more specific C-Hδ+⋯Hδ--B dihydrogen bonds and other van der Waals interactions with C2H6, while the suitable pore space allows the high C2H6 uptake. Approximately 14.5 L kg-1 of polymer grade C2H4 can be produced from simulated C2H6/C2H4 (v/v 10/90) mixtures under ambient conditions in a single step, comparable to those of many popular materials.

Cucurbituril-Shaped Cd18(triazolate)12 Unit-Based Metal-Organic Framework Exhibiting an C2H2/CO2 Separation Ability.

Herein, a metal-organic framework (MOF), {[(Me2NH2)4][Cd(H2O)6][Cd18(TrZ)12(TPD)15(DMF)6]}n (denoted as JXNU-18, TrZ = triazolate), constructed from the unique cucurbituril-shaped Cd18(TrZ)12 secondary building units bridged by 2,5-thiophenedicarboxylic (TPD2-) ligands, is presented. The formation of the cucurbituril-shaped Cd18(TrZ)12 unit is unprecedented, demonstrating the geometric compatibility of the organic linkers and the coordination configurations of the cadmium atoms. Each Cd18(TrZ)12 unit is connected to eight neighboring Cd18(TrZ)12 units through 30 TPD2- linkers, affording the three-dimensional structure of JXNU-18. More interesting is that JXNU-18 displays an efficient C2H2/CO2 separation ability, as revealed by the gas adsorption experiments and dynamic gas breakthrough experiments, which afford insights into the potential applications of JXNU-18 in gas separation. The tubular pores composed of two Cd18(TrZ)12 units bridged by six 2,5-thiophenedicarboxylic linkers provide the suitable pore space for C2H2 trapping, as unveiled by computational simulations.

A Microporous Metal-Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2 H6 /C2 H4 Separation.

Developing adsorptive separation processes based on C2 H6 -selective sorbents to replace energy-intensive cryogenic distillation is a promising alternative for C2 H4 purification from C2 H4 /C2 H6 mixtures, which however remains challenging. During our studies on two isostructural metal-organic frameworks (Ni-MOF 1 and Ni-MOF 2), we found that Ni-MOF 2 exhibited significantly higher performance for C2 H6 /C2 H4 separation than Ni-MOF-1, as clearly established by gas sorption isotherms and breakthrough experiments. Density-Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni-MOF 2 induce more and stronger C-H⋅⋅⋅π with C2 H6 over C2 H4 while the suitable pore spaces enforce its high C2 H6 uptake capacity, featuring Ni-MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg-1 of polymer-grade C2 H4 product from equimolar C2 H6 /C2 H4 mixtures at ambient conditions.

A Microporous Metal‐Organic Framework with Unique Aromatic Pore Surfaces for High Performance C2H6/C2H4 Separation

AbstractDeveloping adsorptive separation processes based on C2H6‐selective sorbents to replace energy‐intensive cryogenic distillation is a promising alternative for C2H4 purification from C2H4/C2H6 mixtures, which however remains challenging. During our studies on two isostructural metal–organic frameworks (Ni‐MOF 1 and Ni‐MOF 2), we found that Ni‐MOF 2 exhibited significantly higher performance for C2H6/C2H4 separation than Ni‐MOF‐1, as clearly established by gas sorption isotherms and breakthrough experiments. Density‐Functional Theory (DFT) studies showed that the unblocked unique aromatic pore surfaces within Ni‐MOF 2 induce more and stronger C−H⋅⋅⋅π with C2H6 over C2H4 while the suitable pore spaces enforce its high C2H6 uptake capacity, featuring Ni‐MOF 2 as one of the best porous materials for this very important gas separation. It generates 12 L kg−1 of polymer‐grade C2H4 product from equimolar C2H6/C2H4 mixtures at ambient conditions.

Dicopper(II) paddle-wheel metal-organic frameworks for high propyne storage under ambient conditions.

Fluorinated dicopper(II) metal-organic framework JXNU-16F with 1,3,5-tri(3,5-bifluoro-4-carboxyphenyl)benzene ligands and nonfluorinated JXNU-16 exhibit high propyne uptakes of 443 and 496 cm3 g-1 under ambient conditions, respectively. Their remarkable propyne uptakes result from suitable pore spaces and strong propyne⋯propyne interactions amongst the adsorbed propyne molecules, as revealed by computational simulations.

Reversing adsorption and separation of 1-phenylethanol and acetophenone in organic phase via β-ketoenamine-linked covalent organic frameworks

Adsorption is considered as a promising method to purify the mixed acetophenone (AP) and 1-phenylethanol (1-PE) that are generally difficult to separate. Many efforts have been made to improve the preferential uptake of AP over 1-PE in aqueous phase, but there exists a practical bottleneck associated with their limited aqueous solubility. Herein, we demonstrate unprecedented reversal of selectivity in the organic medium enabled by β-ketoenamine-linked covalent organic frameworks (COFs), which were fabricated successfully by polycondensation between 1,3,5-triformylphloroglucinol (Tp) and diamines. The dependence of selective adsorption ability toward 1-PE on pore size was firstly investigated experimentally, indicating that TpBZ-COF with moderate pore size outperformed other analogues. The adsorption behaviors of 1-PE and AP onto TpBZ-COF were examined systematically. The evaluation results revealed a strong affinity toward 1-PE versus AP as well as excellent stability in recycling experiments. Further, the dynamic breakthrough experiments confirmed the practical application potential and remarkable recyclability. To probe the mechanism and structure–activity relationship, an imine-linked COF possessing similar porous structure was used as a reference for comparison of separation performance both experimentally and theoretically. The occurrence of hydrogen bonding between the hydroxyl of 1-PE and β-ketoenamine-linkage as H-bond acceptor in suitable pore spaces endows TpBZ-COF a fantastic candidate for purifying 1-PE and AP from petrochemical by-products.

Cage-Like Porous Materials with Simultaneous High C2 H2 Storage and Excellent C2 H2 /CO2 Separation Performance.

Adsorption-based separation is an important technology for C2 H2 purification due to the environmentally friendly and energy-efficient advantage. In addition to the high selectivity of C2 H2 /CO2 , the high uptake of C2 H2 also plays an important role in the separation progress. However, the trade-off between adsorption capacity and separation performance is still in a dilemma. Herein, we report a series of cage-like porous materials named FJI-H8-R (R=Me, Et, n Pr and i Pr) which all have high C2 H2 uptakes at 1 bar and 298 K. Dynamic breakthrough studies show that they all exhibit excellent C2 H2 /CO2 separation performance. Particularly, FJI-H8-Me possesses a long breakthrough time up to 90 min g-1 . Additionally, Grand Canonical Monte Carlo (GCMC) simulation reveals that the suitable pore space and geometry contribute much to the excellent separation performance.

Cage‐Like Porous Materials with Simultaneous High C2H2Storage and Excellent C2H2/CO2Separation Performance

AbstractAdsorption‐based separation is an important technology for C2H2purification due to the environmentally friendly and energy‐efficient advantage. In addition to the high selectivity of C2H2/CO2, the high uptake of C2H2also plays an important role in the separation progress. However, the trade‐off between adsorption capacity and separation performance is still in a dilemma. Herein, we report a series of cage‐like porous materials named FJI‐H8‐R (R=Me, Et,nPr andiPr) which all have high C2H2uptakes at 1 bar and 298 K. Dynamic breakthrough studies show that they all exhibit excellent C2H2/CO2separation performance. Particularly, FJI‐H8‐Me possesses a long breakthrough time up to 90 min g−1. Additionally, Grand Canonical Monte Carlo (GCMC) simulation reveals that the suitable pore space and geometry contribute much to the excellent separation performance.

A Stable Interpenetrated Zn-MOF with Efficient Light Hydrocarbon Adsorption/Separation Performance

The design of MOFs with functionalized groups as well as suitable pore space plays a momentous part in gas adsorption and separation. Herein, a new Zn-MOF (Zn4(BTB-NH2)3·xsolvent, UPC-98, H3BTB-NH2...

A microporous metal–organic framework with soc topology for adsorption and separation selectivity of C2H2/CO2

The microporous metal–organic framework [Co3O(H2O)3](ABTC)1.5·(solv)x, (H4ABTC = 3,3′,5,5′-azobenzenetetracarboxylic acid) Co-ABTC, with suitable pore space was synthesized by solvothermal reaction. Co-ABTC shows the spherical pores with a radius of 5.2 × 5.2 A2, taking into account the van der Waals’ force. The specific surface area (BET) is 585.9 m2/g through N2 adsorption at 77 K. The activated Co-ABTCa shows the moderately high separation selectivity for C2H2/CO2 of 4.28 (298 K) at extremely low pressures by utilizing ideal adsorbed solution theory simulation. A new microporous metal–organic framework with optimizing pore space has been realized to exhibit highly selective C2H2/CO2 gas separation property.

A new metal-organic framework for separation of C2H2/CH4 and CO2/CH4 at room temperature

A 3D microporous metal-organic framework with open Cu2+ sites and suitable pore space, [Cu2(L)(H2O)2]·(H2O)4(DMF)8 (ZJU-15, H4L = 5,5′-(9H-carbazole-2,7-diyl)diisophthalic acid; DMF = N,N-dimethylformamide; ZJU = Zhejiang University), has been constructed and characterized. The activated ZJU-15a has three different types of cages and exhibits BET surface area of 1660m2g−1, and can separate gas mixture of C2H2/CH4 and CO2/CH4 at room temperature.

Three isoreticular ssa-type MOFs derived from bent diisophthalate ligands: exploring the substituent effect on structural stabilities and selective C2H2/CH4 and CO2/CH4 adsorption properties.

Evaluating the effect of the substituents on structural stabilities and gas adsorption properties of MOFs is fundamentally important for rational design and synthesis of new MOFs with better performance. For this purpose, three isoreticular copper-based MOFs (ZJNU-87, ZJNU-88 and ZJNU-89) with ssa-type topology were successfully constructed from bent diisophthalate ligands bearing different substituents. Permanent porosity studies reveal that the substituent has a significant effect on framework stabilities against desolvation. Utilizing nonpolar n-hexane as an activation solvent can give more optimized permanent porosity for nonpolar or less-polar substituent-modified ZJNU-88 and ZJNU-89. Furthermore, their gas adsorption properties with respect to C2H2, CO2 and CH4 were systematically investigated, revealing their promising potential for selective C2H2/CH4 and CO2/CH4 separations. In particular, methoxy-modified ZJNU-89 performs better than the methyl-modified ZJNU-88 in terms of uptake capacity and adsorption selectivity, which might be attributed to more suitable pore space of ZJNU-89.

A Porous Zn(II)-Metal–Organic Framework Constructed from Fluorinated Ligands for Gas Adsorption

A three-dimensional functional metal–organic framework (LIFM-38) has been successfully synthesized with a fluorinated bicarboxylate ligand. LIFM-38 exhibits good stability and a surface area of 803 m2 g–1. Owing to the synergistic effect of different functional groups, cocrystallized amine active sites, and suitable pore space, LIFM-38 shows good selective CO2 and C2+ hydrocarbons adsorption over CH4 and N2; in addition, LIFM-38 exhibits good selective C3 hydrocarbons adsorption over C2 hydrocarbons.

A novel NbO-type metal-organic framework for highly separation of methane from C2-hydrocarbon at room temperature

A novel 3D microporous metal-organic framework with suitable pore space and open copper sites, [Cu2(L)(H2O)2]·(DMF)5·(H2O)·(MeCN) (ZJU-11, ZJU=Zhejiang University; H4L=2′-methyl-[1,1′:4′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid; DMF=N,N-dimethylformamide; MeCN=acetonitrile), has been synthesized and structurally characterized. ZJU-11a exhibits high BET surface area of 2531m2g−1 and pore volume of 1.0087cm3g−1, and can separate CH4 from C2-hydrocarbon gas mixtures at room temperature.

Two Functional Porous Metal–Organic Frameworks Constructed from Expanded Tetracarboxylates for Gas Adsorption and Organosulfurs Removal

Two fof-type porous metal–organic frameworks (MOFs), [Cu2(bdfdpa)(H2O)2]·8DMF·2H2O (JLU-Liu29) and [Cu2(btadpa)(H2O)2]·7DMF·8H2O (JLU-Liu30) (H4bdfdpa = 5,5′-(benzo[1,2-b:4,5-b′]difuran-2,6-diyl)diisophthalic acid and H4btadpa = 5,5′-(benzo[c][1,2,5]thiadiazole-4,7-diylbis(ethyne-2,1-diyl))diisophthalic acid), have been successfully synthesized by using different expanded tetracarboxylate ligands. Both of them exhibit good permanent porosity and high surface areas of 2205 and 1791 m2 g–1, respectively. Due to open metal sites, different functional groups, and suitable pore spaces, the two porous MOFs exhibit high adsorption performance for small molecule gases (CO2, CH4, C2H6, and C3H8) and removal of refractory organosulfur compounds.

A porous metal-organic framework with ultrahigh acetylene uptake capacity under ambient conditions.

Acetylene, an important petrochemical raw material, is very difficult to store safely under compression because of its highly explosive nature. Here we present a porous metal-organic framework named FJI-H8, with both suitable pore space and rich open metal sites, for efficient storage of acetylene under ambient conditions. Compared with existing reports, FJI-H8 shows a record-high gravimetric acetylene uptake of 224 cm3 (STP) g−1 and the second-highest volumetric uptake of 196 cm3 (STP) cm−3 at 295 K and 1 atm. Increasing the storage temperature to 308 K has only a small effect on its acetylene storage capacity (∼200 cm3 (STP) g−1). Furthermore, FJI-H8 exhibits an excellent repeatability with only 3.8% loss of its acetylene storage capacity after five cycles of adsorption–desorption tests. Grand canonical Monte Carlo simulation reveals that not only open metal sites but also the suitable pore space and geometry play key roles in its remarkable acetylene uptake.

Microporous metal-organic frameworks with suitable pore spaces for acetylene storage and purification

Two isostructural metal-organic frameworks (MOFs) Cu2TPTC-Me and Cu2TPTC-OMe have been synthesized and characterized. The as-synthesized MOFs show good thermal stability and hydrothermal stability. With open metal sites, suitable pore spaces and functional groups to confine acetylene molecules in frameworks, both MOFs exhibit high gravimetric acetylene storage capacities: Cu2TPTC-Me has a gravimetric capacity of 203 cm3 g−1 at 298 K and 1 bar, and Cu2TPTC-OMe has the highest gravimetric acetylene storage capacity ever reported with the capacity of 204 cm3 g−1 under the same conditions. Furthermore, Cu2TPTC-Me possesses both high separation selectivities of C2H2/CH4 and C2H2/CO2 with the Henry law's selectivity of 60 and 12.7 at room temperature, respectively.

A NbO type microporous metal–organic framework constructed from a naphthalene derived ligand for CH4and C2H2storage at room temperature

A novel NbO type microporous metal–organic framework [Cu2(C26H12O8)(H2O)2]·(DMF)2·(MeCN)3·(H2O)4, (ZJU-7, ZJU = Zhejiang University; H4L = 5,5′-(naphthalene-1,4-diyl)diisophthalic acid; DMF = N,N-dimethylformamide; MeCN = acetonitrile) has been synthesized and structurally characterized. With open metal sites, suitable pore spaces and moderately high permanent porosity, the activated ZJU-7a exhibits moderately high CH4 storage of 160 cm3(STP) per cm3 at 35 bar and 298 K. Meanwhile, ZJU-7a also displays moderate C2H2 gravimetric storage of 180 cm3 g−1 at 1 atm and 298 K.

A new microporous metal–organic framework with potential for highly selective separation methane from acetylene, ethylene and ethane at room temperature

A new three-dimensional microporous metal–organic framework, Cu2(OFDI) (ZJU-61, H4OFDI=5,5′-(9-oxo-9H-fluorene-2,7-diyl)diisophthalic acid) was solvothermally synthesized. ZJU-61 features a three-dimensional structure with a rare sty-a type topology and has three different types of pore apertures. With open metal sites and suitable pore spaces, ZJU-61 can readily separate methane from gas mixture at room temperature with the highest C2H2/CH4 separation selectivity of 74.4.