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Separation of propyne/propylene (C3H4/C3H6) is more difficult and challenging than that of acetylene/ethylene (C2H2/C2H4) because of their closer molecular sizes. A comprehensive screening of a series of metal–organic frameworks with broad types of structures, pore sizes, and functionalities was carried out. UTSA‐200 was identified as the best separating material for the removal of trace C3H4 from C3H4/C3H6 mixtures. Gas sorption isotherms reveal that UTSA‐200 exhibits by far the highest C3H4 adsorption capacity (95 cm3 cm−3 at 0.01 bar and 298 K) and record C3H4/C3H6 selectivity, which was mainly attributed to the suitable dynamic pore size to efficiently block the larger C3H6 molecule whilst the strong binding sites and pore flexibility capture smaller C3H4. This material thus provides record purification capacity for the removal of C3H4 from a 1:99 (or 0.1:99.9, v/v) C3H4/C3H6 mixture to produce 99.9999 % pure C3H6 with a productivity of 62.0 (or 142.8) mmol g−1. Record removal: A series of metal–organic frameworks with broad types of structures, pore sizes, and functionalities were used to identify UTSA‐200 as the best separating agent for removal of trace C3H4 from C3H4/C3H6 mixtures. The efficiency is mainly attributed to the optimally dynamic pore size to efficiently block the larger C3H6 whilst retaining strong binding sites to selectively take up C3H4, thus producing high‐purity C3H6 (99.9999 %). [ABSTRACT FROM AUTHOR]

Adsorptive separation of acetylene from ethylene/acetylene mixtures is a technologically very important and highly challenging task. In this work, we describe two flexible metal-organic frameworks (MOFs), ELM-11 and ELM-13, that display adsorbate discriminatory gate effects. The two MOFs exhibit gate-opening-type adsorption properties for C2H2 but not for C2H4, leading to a highly selective adsorption of acetylene over ethylene at 273-298 K. The potential of the flexible MOFs for the separation is established by combining measurements of adsorption isotherms, ideal adsorbed solution theory (IAST) calculations of the adsorption equilibrium of the mixture, and transient breakthrough experiments. The results suggest the potential of both flexible MOFs for the industrial removal of acetylene from ethylene/acetylene mixtures through the energy-efficient adsorption separation process. [ABSTRACT FROM AUTHOR]

Although having shown great promise for efficient gas separation, relevant study of Ti‐MOF membranes remains very scarce, owing to limited Ti source types and uncertain factors which dominate the separation properties. In this work, we pioneered the use of the Ti8(μ2‐O)8(OOCC6H5)16 cluster as the Ti source of MIL‐125 membranes, which led to lower reaction temperature and higher missing‐linker number within the framework and therefore, enhanced CO2/N2 adsorption selectivity. The MIL‐125 membrane prepared by combining single‐mode microwave heating with tertiary growth displayed an ideal CO2/N2 selectivity of 38.7, which ranked the highest among all pristine pure MOF membranes measured under comparable conditions. In addition, the ideal H2/N2 and H2/CH4 selectivity was as high as 64.9 and 40.7, thus showing great promise for versatile utility in gas separation. [ABSTRACT FROM AUTHOR]

Although having shown great promise for efficient gas separation, relevant study of Ti‐MOF membranes remains very scarce, owing to limited Ti source types and uncertain factors which dominate the separation properties. In this work, we pioneered the use of the Ti8(μ2‐O)8(OOCC6H5)16 cluster as the Ti source of MIL‐125 membranes, which led to lower reaction temperature and higher missing‐linker number within the framework and therefore, enhanced CO2/N2 adsorption selectivity. The MIL‐125 membrane prepared by combining single‐mode microwave heating with tertiary growth displayed an ideal CO2/N2 selectivity of 38.7, which ranked the highest among all pristine pure MOF membranes measured under comparable conditions. In addition, the ideal H2/N2 and H2/CH4 selectivity was as high as 64.9 and 40.7, thus showing great promise for versatile utility in gas separation. [ABSTRACT FROM AUTHOR]

For the separation of ethane from ethylene, it remains challenging to target both high C2H6 adsorption and selectivity in a C2H6‐selective material. Herein, we report a reversible solid‐state transformation in a labile hydrogen‐bonded organic framework to generate a new rod‐packing desolvated framework (ZJU‐HOF‐1) with suitable cavity spaces and functional surfaces to optimally interact with C2H6. ZJU‐HOF‐1 thus exhibits simultaneously high C2H6 uptake (88 cm3 g−1 at 0.5 bar and 298 K) and C2H6/C2H4 selectivity (2.25), which are significantly higher than those of most top‐performing materials. Theoretical calculations revealed that the cage‐like cavities and functional sites synergistically "match" better with C2H6 to provide stronger multipoint interactions with C2H6 than C2H4. In combination with its high stability and ultralow water uptake, this material can efficiently capture C2H6 from 50/50 C2H6/C2H4 mixtures in ambient conditions under 60 % RH, providing a record polymer‐grade C2H4 productivity of 0.98 mmol g−1. [ABSTRACT FROM AUTHOR]

For the separation of ethane from ethylene, it remains challenging to target both high C2H6 adsorption and selectivity in a C2H6‐selective material. Herein, we report a reversible solid‐state transformation in a labile hydrogen‐bonded organic framework to generate a new rod‐packing desolvated framework (ZJU‐HOF‐1) with suitable cavity spaces and functional surfaces to optimally interact with C2H6. ZJU‐HOF‐1 thus exhibits simultaneously high C2H6 uptake (88 cm3 g−1 at 0.5 bar and 298 K) and C2H6/C2H4 selectivity (2.25), which are significantly higher than those of most top‐performing materials. Theoretical calculations revealed that the cage‐like cavities and functional sites synergistically "match" better with C2H6 to provide stronger multipoint interactions with C2H6 than C2H4. In combination with its high stability and ultralow water uptake, this material can efficiently capture C2H6 from 50/50 C2H6/C2H4 mixtures in ambient conditions under 60 % RH, providing a record polymer‐grade C2H4 productivity of 0.98 mmol g−1. [ABSTRACT FROM AUTHOR]

Polycrystalline metal–organic framework (MOF) layers hold great promise as molecular sieve membranes for efficient gas separation. Nevertheless, the high crystallinity tends to cause inter‐crystalline defects/cracks in the nearby crystals, which makes crystalline porous materials face a great challenge in the fabrication of defect‐free membranes. Herein, for the first time, we demonstrate the balance between crystallinity and film formation of MOF membrane through a facile in situ modulation strategy. Monocarboxylic acid was introduced as a modulator to regulate the crystallinity via competitive complexation and thus concomitantly control the film‐forming state during membrane growth. Through adjusting the ratio of modulator acid/linker acid, an appropriate balance between this structural "trade‐off" was achieved. The resulting MOF membrane with moderate crystallinity and coherent morphology exhibits molecular sieving for H2/CO2 separation with selectivity up to 82.5. [ABSTRACT FROM AUTHOR]

Developing hydrogen‐bonded organic frameworks (HOFs) that combine functional sites, size control, and storage capability for targeting gas molecule capture is a novel and challenging venture. However, there is a lack of effective strategies to tune the hydrogen‐bonded network to achieve high‐performance HOFs. Here, a series of HOFs termed as HOF‐ZSTU‐M (M=1, 2, and 3) with different pore structures are obtained by introducing structure‐directing agents (SDAs) into the hydrogen‐bonding network of tetrakis (4‐carboxyphenyl) porphyrin (TCPP). These HOFs have distinct space configurations with pore channels ranging from discrete to continuous multi‐dimensional. Single‐crystal X‐ray diffraction (SCXRD) analysis reveals a rare diversity of hydrogen‐bonding models dominated by SDAs. HOF‐ZSTU‐2, which forms a strong layered hydrogen‐bonding network with ammonium (NH4+) through multiple carboxyl groups, has a suitable 1D "pearl‐chain" channel for the selective capture of propylene (C3H6). At 298 K and 1 bar, the C3H6 storage density of HOF‐ZSTU‐2 reaches 0.6 kg L−1, representing one of the best C3H6 storage materials, while offering a propylene/propane (C3H6/C3H8) selectivity of 12.2. Theoretical calculations and in situ SCXRD provide a detailed analysis of the binding strength of C3H6 at different locations in the pearl‐chain channel. Dynamic breakthrough tests confirm that HOF‐ZSTU‐2 can effectively separate C3H6 from multi‐mixtures. [ABSTRACT FROM AUTHOR]

Polycrystalline metal–organic framework (MOF) layers hold great promise as molecular sieve membranes for efficient gas separation. Nevertheless, the high crystallinity tends to cause inter‐crystalline defects/cracks in the nearby crystals, which makes crystalline porous materials face a great challenge in the fabrication of defect‐free membranes. Herein, for the first time, we demonstrate the balance between crystallinity and film formation of MOF membrane through a facile in situ modulation strategy. Monocarboxylic acid was introduced as a modulator to regulate the crystallinity via competitive complexation and thus concomitantly control the film‐forming state during membrane growth. Through adjusting the ratio of modulator acid/linker acid, an appropriate balance between this structural "trade‐off" was achieved. The resulting MOF membrane with moderate crystallinity and coherent morphology exhibits molecular sieving for H2/CO2 separation with selectivity up to 82.5. [ABSTRACT FROM AUTHOR]

Developing hydrogen‐bonded organic frameworks (HOFs) that combine functional sites, size control, and storage capability for targeting gas molecule capture is a novel and challenging venture. However, there is a lack of effective strategies to tune the hydrogen‐bonded network to achieve high‐performance HOFs. Here, a series of HOFs termed as HOF‐ZSTU‐M (M=1, 2, and 3) with different pore structures are obtained by introducing structure‐directing agents (SDAs) into the hydrogen‐bonding network of tetrakis (4‐carboxyphenyl) porphyrin (TCPP). These HOFs have distinct space configurations with pore channels ranging from discrete to continuous multi‐dimensional. Single‐crystal X‐ray diffraction (SCXRD) analysis reveals a rare diversity of hydrogen‐bonding models dominated by SDAs. HOF‐ZSTU‐2, which forms a strong layered hydrogen‐bonding network with ammonium (NH4+) through multiple carboxyl groups, has a suitable 1D "pearl‐chain" channel for the selective capture of propylene (C3H6). At 298 K and 1 bar, the C3H6 storage density of HOF‐ZSTU‐2 reaches 0.6 kg L−1, representing one of the best C3H6 storage materials, while offering a propylene/propane (C3H6/C3H8) selectivity of 12.2. Theoretical calculations and in situ SCXRD provide a detailed analysis of the binding strength of C3H6 at different locations in the pearl‐chain channel. Dynamic breakthrough tests confirm that HOF‐ZSTU‐2 can effectively separate C3H6 from multi‐mixtures. [ABSTRACT FROM AUTHOR]

• Simulate He/CH 4 passing MXene nanopores with NEMD, Non-Equilibrium Molecular Dynamics. • MXene nanopores exhibit excellent P He (permeance) & S He/CH4 , even for He/CH 4 mixture. • Gas passes through nanopores with various mechanisms, depending on the pore diameter. • Applied transition state theory to predict S He/CH4 (selectivity) for small nanopores. • Relate density profiles of Equilibrium Molecular Dynamics simulations to P from NEMD. Natural gas is currently the main industrial source of helium, thus He/CH 4 separation has become increasing important. Nanopores based on two-dimensional materials have been considered as very promising for He/CH 4 separation, but the transport mechanism through them is yet unclear. Here, both non-equilibrium molecular dynamics (NEMD) and equilibrium MD (EMD) were employed to study the transport of He/CH 4 through nanopores of different MXenes with various pore diameters (d), pore density and functional groups, which showed two main transport mechanisms, molecular sieving and Knudsen diffusion. Small d was found to be crucial for the molecular sieving and consequently, high He/CH 4 selectivity (S He/CH4). The density profiles of gas molecules in EMD simulations were used to predict S He/CH4 and the permeance for gas passing through different nanopores, yielding results well agreeing with NEMD simulations. This work provides theoretical insights for gas transport through MXene nanopore and may help designing nanopores in the future. [ABSTRACT FROM AUTHOR]

Adsorptive separation of propylene/propane (C3H6/C3H8) mixture is desired for its potential energy saving on replacing currently deployed and energy‐intensive cryogenic distillation. Realizing efficient C3H6/C3H8 separation in the emerging hydrogen‐bonded organic frameworks (HOFs) is very challenging owing to the lack of functional sites for preferential gas binding. By virtue of crystal engineering, we herein report a functionalized HOF (HOF‐16) with free ‐COOH sites for the efficient separation of C3H6/C3H8 mixtures. Under ambient conditions, HOF‐16 shows a significant C3H6/C3H8 uptake difference (by 76 %) and selectivity (5.4) in contrast to other carboxylic acid‐based HOFs. Modeling studies indicate that free ‐COOH groups together with the suitable pore confinement facilitate the recognition and high‐density packing of gas molecules. The separation performance of HOF‐16 was validated by breakthrough experiments. HOF‐16 is stable towards strong acidity and water. [ABSTRACT FROM AUTHOR]

Adsorptive separation of propylene/propane (C3H6/C3H8) mixture is desired for its potential energy saving on replacing currently deployed and energy‐intensive cryogenic distillation. Realizing efficient C3H6/C3H8 separation in the emerging hydrogen‐bonded organic frameworks (HOFs) is very challenging owing to the lack of functional sites for preferential gas binding. By virtue of crystal engineering, we herein report a functionalized HOF (HOF‐16) with free ‐COOH sites for the efficient separation of C3H6/C3H8 mixtures. Under ambient conditions, HOF‐16 shows a significant C3H6/C3H8 uptake difference (by 76 %) and selectivity (5.4) in contrast to other carboxylic acid‐based HOFs. Modeling studies indicate that free ‐COOH groups together with the suitable pore confinement facilitate the recognition and high‐density packing of gas molecules. The separation performance of HOF‐16 was validated by breakthrough experiments. HOF‐16 is stable towards strong acidity and water. [ABSTRACT FROM AUTHOR]

Separation of acetylene from carbon dioxide remains a daunting challenge because of their very similar molecular sizes and physical properties. We herein report the first example of using copper(I)‐alkynyl chemistry within an ultra‐microporous MOF (CuI@UiO‐66‐(COOH)2) to achieve ultrahigh C2H2/CO2 separation selectivity. The anchored CuI ions on the pore surfaces can specifically and strongly interact with C2H2 molecule through copper(I)‐alkynyl π‐complexation and thus rapidly adsorb large amount of C2H2 at low‐pressure region, while effectively reduce CO2 uptake due to the small pore sizes. This material thus exhibits the record high C2H2/CO2 selectivity of 185 at ambient conditions, significantly higher than the previous benchmark ZJU‐74a (36.5) and ATC‐Cu (53.6). Theoretical calculations reveal that the unique π‐complexation between CuI and C2H2 mainly contributes to the ultra‐strong C2H2 binding affinity and record selectivity. The exceptional separation performance was evidenced by breakthrough experiments for C2H2/CO2 gas mixtures. This work suggests a new perspective to functionalizing MOFs with copper(I)‐alkynyl chemistry for highly selective separation of C2H2 over CO2. [ABSTRACT FROM AUTHOR]

Separation of acetylene from carbon dioxide remains a daunting challenge because of their very similar molecular sizes and physical properties. We herein report the first example of using copper(I)‐alkynyl chemistry within an ultra‐microporous MOF (CuI@UiO‐66‐(COOH)2) to achieve ultrahigh C2H2/CO2 separation selectivity. The anchored CuI ions on the pore surfaces can specifically and strongly interact with C2H2 molecule through copper(I)‐alkynyl π‐complexation and thus rapidly adsorb large amount of C2H2 at low‐pressure region, while effectively reduce CO2 uptake due to the small pore sizes. This material thus exhibits the record high C2H2/CO2 selectivity of 185 at ambient conditions, significantly higher than the previous benchmark ZJU‐74a (36.5) and ATC‐Cu (53.6). Theoretical calculations reveal that the unique π‐complexation between CuI and C2H2 mainly contributes to the ultra‐strong C2H2 binding affinity and record selectivity. The exceptional separation performance was evidenced by breakthrough experiments for C2H2/CO2 gas mixtures. This work suggests a new perspective to functionalizing MOFs with copper(I)‐alkynyl chemistry for highly selective separation of C2H2 over CO2. [ABSTRACT FROM AUTHOR]

Simultaneous removal of trace amounts of propyne and propadiene from propylene is an important but challenging industrial process. We report herein a class of microporous metal–organic frameworks (NKMOF‐1‐M) with exceptional water stability and remarkably high uptakes for both propyne and propadiene at low pressures. NKMOF‐1‐M separated a ternary propyne/propadiene/propylene (0.5 : 0.5 : 99.0) mixture with the highest reported selectivity for the production of polymer‐grade propylene (99.996 %) at ambient temperature, as attributed to its strong binding affinity for propyne and propadiene over propylene. Moreover, we were able to visualize propyne and propadiene molecules in the single‐crystal structure of NKMOF‐1‐M through a convenient approach under ambient conditions, which helped to precisely understand the binding sites and affinity for propyne and propadiene. These results provide important guidance on using ultramicroporous MOFs as physisorbent materials. [ABSTRACT FROM AUTHOR]

Methane (CH 4) purification using energy-efficient separation technology is important for the economic and safety of natural gas refining. Meanwhile, the common impurity acetylene (C 2 H 2) was also served as raw material to produce various organic products, therefore the highly efficient purification of CH 4 and C 2 H 2 are very important and challenging. Herein, we demonstrate the separation ability of HOF-16 for C 2 H 2 /CH 4 and CO 2 /CH 4 mixtures in detail. HOF-16 has a potential affinity for C 2 H 2 capture, resulting from the exposed free –COOH sites in the suitable pore channel. Gas sorption isotherms reveal that HOF-16a creates a high C 2 H 2 /CH 4 uptake ratio of 7.9 at 298 K and 1 bar, resulting in a C 2 H 2 /CH 4 separation selectivity of 107 (50/50, v/v) under ambient conditions, which is a record value among HOFs and even exceeds many MOFs. Theoretical calculations confirm that the free –COOH sites in the HOF-16a channel provide additional interactions for the C 2 H 2 molecules. Dynamic breakthrough experiments indicate that C 2 H 2 could be highly selective removed from C 2 H 2 /CH 4 (1/99, v/v) mixture. Combined with the low isosteric heat of adsorption (Q st), HOF-16a can efficiently extract C 2 H 2 from the adsorption bed and purify CH 4 into high purity (>99.9%) with low energy consumption. HOF-16 for separating C 2 H 2 /CH 4 gas mixture into high purity gas. [Display omitted] • HOF-16 was synthesized and has free –COOH after activation. • Activated phase HOF-16a has a suitable pore size and a polar pore environment. • HOF-16a exhibits C 2 H 2 /CH 4 selectivity of 107 and C 2 H 2 /CH 4 uptake ratio of 6.9. • HOF-16a can efficiently separate C 2 H 2 /CH 4 mixture in one sorption-desorption cycle. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu(BDC)(DMF) using BDC as a cheap ligand was prepared using a simple and easy-to-scale up method. • Cu(BDC) simultaneously meets the requirements of high C 2 H 6 uptake and excellent ethane/ethylene separation selectivity. • Cu(BDC) exhibits excellent thermal stability and could be stored at room temperature for>1 year. • Cu(BDC) shows excellent separation ability with superior regeneration capability. Separating ethane (C 2 H 6) from ethylene (C 2 H 4) using ethane-selective adsorbents to replace energy-intensive cryogenic distillation technology is an important energy-saving method in the petrochemical industry to obtain high purity C 2 H 4. Limited to the low separation efficiency in current commercial materials, it is very urgent and promising to fabricate such alkane selective adsorbents using cheap ligands and simple synthesis methods, which have characteristics such as stable structure, high C 2 H 6 uptake, and adsorption selectivity. In this work, we have used one of the cheapest ligands (terephthalic acid, H 2 BDC) to prepare Cu(BDC)(DMF) via a simple and easy-to-scale up solvothermal method. The activated Cu(BDC) exposed diamond-shaped one-dimensional pores form a stronger affinity with C 2 H 6 than C 2 H 4 through the double function of C-H∙∙∙π interactions and C-H∙∙∙O hydrogen bonds. Benefiting from the difference in these interactions, Cu(BDC) exhibited a higher adsorption capacity of C 2 H 6 (51.5 cm3/g) compared to C 2 H 4 (45.1 cm3/g) at 1 bar and 298 K, which resulted in high adsorption selectivity (2.0) for the C 2 H 6 /C 2 H 4 mixture (50/50, v/v). Breakthrough experiments indicated that Cu(BDC) successfully achieved the removal of C 2 H 6 from C 2 H 6 /C 2 H 4 (50/50 and 10/90, v/v) mixtures to obtain high purity C 2 H 4 (> 99.99%) using a one-step separation process. When compared with the benchmark materials, Fe 2 (O 2)(dobdc) and NIIC-20, Cu(BDC) had the advantages of much lower preparation cost and enhanced structural stability. These comprehensive properties indicated that Cu(BDC) with a commercially viable price and synthesis process, could be potentially used for the C 2 H 6 removal step during the production of high purity C 2 H 4. [ABSTRACT FROM AUTHOR]

[Display omitted] • UiO-66 functionalized with trifluoromethyl groups exhibits high structural stability. • Optimized pore environment and functionalization enhance C 2 H 2 recognition. • UiO-66-(CF 3) 2 displays improved C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 IAST selectivities. • UiO-66-(CF 3) 2 shows remarkable separation performance with good cycling capability. The potential of metal–organic frameworks (MOFs) for application in gas separation processes has been widely recognized. Nonetheless, due to their structural instability and high cost, few MOFs have been utilized in the industry. Among them, UiO-66 is one of the most promising materials which displays good structural stability and its preparation is considered economical. Notably, it also provides a valuable platform for the construction of other robust MOFs for various applications. Herein, trifluoromethyl ligands were introduced into the UiO-66 framework to optimize pore environment also to improve its C 2 H 2 recognition ability. Single component adsorption and the corresponding IAST calculation confirmed that compared to UiO-66, UiO-66-(CF 3) 2 exhibited 2 ~ 3 times higher selectivity for C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 separation. Enhanced selectivity resulted in a significantly improved C 2 H 4 separation productivity (56 compared to 36 cm3/cm3) and a reduction in the co-adsorption time. Importantly, the modified UiO-66 framework could be prepared using a simple method and inherited a highly stable structure and good cycling performance of the original material. [ABSTRACT FROM AUTHOR]

• Gate-opening pressure difference is used to separate twin-like gases CO 2 and N 2 O. • The performance of flexible MOFs ELM-11, ELM-12 and MIL-53Al for N 2 O-CO 2 separation is researched systematically. • Efficient separation of CO 2 -N 2 O (50%/50%) in the mixture breakthrough at high pressure is carried. • MIL-53Al has great potential to separate N 2 O and CO 2 at 8 bar. N 2 O and CO 2 are two linear molecules, which have almost the same molecular size and similar physical properties (polarizability and quadrupole moment). Therefore, the separation of CO 2 and N 2 O is extremely challenging. Flexible metal organic frameworks exhibit a gate-opening phenomenon for one type of gas molecule, but not for another, thus enabling excellent selectivity for twin-like molecules. In this study, the separation of CO 2 /N 2 O by flexible metal organic frameworks with different structures was studied systematically using a combination of adsorption and breakthrough tests. The results show that the gate-opening pressure of CO 2 is lower than that of N 2 O on Cu(bpy) 2 (BF 4) 2 (ELM-11) and Cu(bpy) 2 (OTf) 2 (ELM-12), which are two-dimensional layered flexible MOFs, whereas N 2 O has a lower gate-opening pressure than CO 2 on MIL-53Al, a three-dimensional breathing structure with an adsorption capacity of up to 8 mmol/g was observed at 298 K and ~5 bar, indicating its good separation properties for N 2 O from CO 2 under high pressure. Breakthrough experiments for N 2 O/CO 2 mixtures confirmed that MIL-53Al is capable of separating N 2 O and CO 2 under the optimized conditions (8 bar), making it a promising material for industrial application. [ABSTRACT FROM AUTHOR]