Separation Of Light Hydrocarbons Research Articles

Isoreticular Metal-Organic Frameworks with Aromatic Pores and Dimethylammonium Cations Enable Separation of Light Hydrocarbons and Xenon/Krypton.

The separation of C2-C3 hydrocarbons from methane in natural gas and xenon/krypton purification are crucial yet challenging industrial processes. Herein, we report two isoreticular metal-organic frameworks, ZJU-89 and ZJU-90, featuring aromatic pore environments and dimethylammonium cations, that synergistically enhance the separation of these industrially relevant gas mixtures. ZJU-90 exhibits an exceptional separation performance, achieving C3H8/CH4 and C2H6/CH4 ideal adsorbed solution theory (IAST) selectivities of 1065 and 48, respectively, at ambient conditions, outperforming most reported adsorbent materials. Remarkably, ZJU-90 enables the recovery of >99.95% purity methane from a C3H8/C2H6/CH4 mixture in a single adsorption step. The material also demonstrates the efficient separation of xenon from krypton, even at low concentrations. The superior performance stems from the aromatic rings decorating the pore walls and the free dimethylammonium cations in the channels, which provide an ideal chemical environment for the selective binding of C2H6, C3H8, and Xe through multiple C-H···π interactions and van der Waals forces, as elucidated by theoretical calculations. This work highlights the power of reticular chemistry in designing materials with synergistic pore environments for efficient separations.

Solvent-vapor-triggered crystallization of a ZIF-90 membrane with versatile separation properties towards light hydrocarbons

Membrane separation has been well acknowledged as a forward-looking technology for hydrocarbon separation. Zeolitic imidazole framework-90 (ZIF-90) with effective pore size of 5.0 Å is a promising membrane material for hydrocarbon separation. Owing to the enormous challenges facing the fabrication process, the research on the ZIF-90 polycrystalline membrane is fairly underexplored. Herein we report a solvent-vapor-triggered crystallization strategy for the production of ZIF-90 membranes. The resultant ZIF-90 membrane had a typical polycrystalline membrane structure where the regular ZIF-90 grains propagated inside the whole porous support. Intriguingly, the membrane displayed two obvious sharp cut-off regions falling between the C3H6/C3H8 and n-C4H10/i-C4H10 gas pairs, respectively. The ZIF-90 membrane achieved ultrafast and selective permeation of C3H6 from the C3H6/C3H8 mixture. The C3H6 flux was about 3.4 kg·m−2·h−1 which was comparable to the commercial NaA zeolite membrane for organic solvent dehydration. Further, the distinctive gas transport kinetic nature enabled the ZIF-90 membranes to exclude i-C4H10 and thus harvest unprecedented n-/i-C4H10 separation ability in high-temperature regions. As the temperature elevated from 25 to 150 °C, the n-C4H10 permeance was enhanced from 3.0 × 10−9 to 12 × 10−9 mol·m−2·s−1·Pa−1 and the n-C4H10/i-C4H10 separation factors was improved from 63 to 95, respectively. The high permeance and permselectivity at industrially relevant high temperatures and pressures make ZIF-90 membrane attractive for industrial light hydrocarbon separation.

Spatially Confined π-Complexation within Pore-Space-Partitioned Metal-Organic Frameworks for Enhanced Light Hydrocarbon Separation and Purification.

Ultramicroporous metal-organic frameworks (MOFs) are demonstrated to be advantageous for the separation and purification of light hydrocarbons such as C2H2, C2H4, and CH4. The introduction of transition metal sites with strong π-complexation affinity into MOFs is more effective than other adsorption sites for the selective adsorption of π-electron-rich unsaturated hydrocarbon gases from their mixtures. However, lower coordination numbers make it challenging to produce robust MOFs directly utilizing metal ions with π-coordination activity, such as Cu+, Ag+, and Pd2+. Herein, a series of novel π-complexing MOFs (SNNU-33s) with a pore size of 4.6Å are precisely constructed by cleverly introducing symmetrically matched C3-type [Cu(pyz)3] (pyz = pyrazine) coordinated fragments into 1D hexagonal channels of MIL-88 prototype frameworks. Benifit from the spatial confinement combined with π-complex-active Cu+ of [Cu(pyz)3], pore-space-partitioned SNNU-33 MOFs all present excellent C2H2/CH4, C2H4/CH4, and CO2/CH4 separation ability. Notably, the optimized SNNU-33b adsorbent demonstrates top-level IAST selectivity values for C2H2/CH4 (597.4) and C2H4/CH4 (69.8), as well as excellent breakthrough performance. Theoretical calculations further reveal that such benchmark light hydrocarbon separation and purification ability is mainly ascribed to the extra-strong binding affinity between Cu+ and π-electron donor molecules via a spatially confined π-complexation process.

A Highly Stable Microporous Calcium-Based MOF for C2H2/CO2 Separation with Low Regenerative Energy.

Most of the porous materials used for acetylene/carbon dioxide separation have the problems of poor stability and high energy requirements for regeneration, which significantly hinder their practical application in industries. Here, we report a novel calcium-based metal-organic framework (NKM-123) with excellent chemical stability against water, acids, and bases. Additionally, it has exceptional thermal stability, retaining its structural integrity at temperatures up to 300 °C. This material exhibits promising potential for separating C2H2 and CO2 gases. Furthermore, it demonstrates an adsorption heat of 29.3 kJ mol-1 for C2H2, which is lower than that observed in the majority of MOFs used for C2H2/CO2 separations. The preferential adsorption of C2H2 over that of CO2 is confirmed by dispersion-corrected density functional theory (DFT-D) calculations. In addition, the potential of industrial feasibility of NKM-123 for C2H2/CO2 separation is confirmed by transient breakthrough tests. The robust cycle performance and structural stability of NKM-123 during multiple breakthrough tests show great potential in the industrial separation of light hydrocarbons.

A novel cage-based metal–organic framework for efficient separation of light hydrocarbons

A novel 3D MOF, SDU-CP-8, features an ellipsoid-shaped cage and a 3-nodal, (4,6,8)-connected network. It demonstrates excellent adsorption and separation capabilities for C3H8/C2H6/CH4 and C2H2/CO2 gas mixtures.

A stable paddle-wheel Co-MOF (FNU-2) for the efficient separation of light hydrocarbons

The separation of methane from higher hydrocarbons (C2–C3) in natural gas processing is a crucial and energy-intensive operation. This work presents a comprehensive study on the separation of propane and ethane from methane using cobalt-based metal-organic frameworks (FNU-2), which exhibit exceptional stability and selectivity and preferential adsorption towards C2–C3 hydrocarbons. The selectivity values of C2H6/CH4 and C3H8/CH4 calculated by IAST are 43.9 and 638.9, respectively. According to theoretical calculations, the Van der Waals interactions of guest molecules play crucial roles in influencing the separation performance. Moreover, dynamic breakthrough experiments have revealed the promising potential of this adsorbent in industrial separations. These experiments indicate that the adsorbent is highly suitable for effectively separating and purifying natural gas. This study overall presents a novel and efficient adsorbent that can be employed to separate and purify natural gas in various industrial applications.

A stable ultramicroporous Cd(II)-MOF with accessible oxygen sites for efficient separation of light hydrocarbons with high methane production

Metal-organic frameworks (MOFs) have garnered increasing attention for their effective separation of light hydrocarbons owing to their prominent separation selectivity and energy-efficient adsorption process. Here, we constructed a robust stable ultramicroporous Cd(II)-MOF ([Cd5(NTA)4(H2O)2] (Me2NH2+)2·10H2O (1)) with abundant accessible oxygen sites and investigated its adsorption performance for recovering high-purity methane (CH4) from natural gas (NG) including C1(CH4)/C2(C2H6)/C3(C3H8) mixtures. At ambient conditions, the theoretical equilibrium separation selectivity of 1 for C2H6/CH4 (v/v = 10/85) and C3H8/CH4 (v/v = 5/85) were found to be 34.3 and 223.8, respectively. The CH4/C2H6/C3H8 (v/v/v = 85/10/5) mixture breakthrough experiments for 1, conducted at 298 K, demonstrated effective separation performance with breakthrough times of up to 136 and 280 min·g−1 for C2H6 and C3H8. Particularly, the CH4 productivity (purity > 99.9 %) with 9.8 mmol·g−1 ranked the third in reported literatures, lower to the reported maximum value of 13.28 mmol·g−1 for Ni(TMBDC)(DABCO)0.5. Furthermore, Grand Canonical Monte Carlo (GCMC) simulations and first-principles density functional theory (DFT) calculations revealed that the high uptake and selectivity for C3H8 and C2H6 can be attributed to the abundant oxygen sites present in the pores. The dynamic breakthrough experiments comprehensively demonstrated that the proposed MOF can be an effective potential adsorbent for the practical separation of CH4/C2H6/C3H8 mixtures.

Energy integration of light hydrocarbon separation, LNG cold energy power generation, and BOG combustion: Thermo-economic optimization and analysis

To recover boil-off gas (BOG) and liquefied natural gas (LNG) cold energy, this paper proposes three systems integrating light hydrocarbon separation (LHS), BOG combustion, organic Rankine cycle (ORC) with different structures and natural gas (NG) direct expansion. Both single and multi-objective optimizations are implemented to find the best system performance. Meanwhile, two multi-objective decision methods are also used to refine this work. Single objective optimization depicts that the system with parallel ORC has the highest net electric power (NEP), exergy efficiency, and net present value (NPV) of 6.85 MW, 29.07%, and 31.08 × 107 $ respectively. Multi-objective optimization results indicate the NEP, exergy efficiency, and NPV of the system with parallel ORC still outperform the other two systems. From the energy analysis, it is found that the system with parallel ORC achieves 81.07% utilization of LNG cold energy, which is the highest among the three systems. The exergy analysis indicates that the combustion chamber and heat exchanger (HX) with the highest exergy destruction in any system. Moreover, economic analysis demonstrates that the three systems are more sensitive to fluctuations in interest rates than in electricity prices.

Highly efficient ethylene/ethane separation via molecular sieving using chitosan-derived ultramicroporous carbon

The selective separation of C2H4/C2H6 pair is of paramount importance in the petrochemical industry, which is yet challenged by their similar polarities, shapes, and kinetic diameters. The use of carbonaceous adsorbents with molecular sieving capability holds great promise in achieving the desired selectivity and economically feasibility. However, such progress has been hindered by the typically wide pore size distribution observed in traditional carbons. Herein, we report a series of chitosan-based ultramicroporous carbons with C2H4/C2H6 molecular sieving performance through an activating reagents-free method. The hydrothermal process of chitosan was initially employed to prepare condensed carbonaceous hydrochar rich in heteroatoms. The subsequent thermal etching led to the formation of sieving-based ultramicropores, stemming from the decomposition of heteroatoms and hot-shrinkage of pores at high temperature. The as-synthesized optimal CNC-700 sample achieved a high C2H4 uptake of 32.3 cm3 (STP) g−1 and negligible C2H6 adsorption at 298 K and 1.0 bar. The isosteric heat of C2H4 on CNC-700 reached 34.5 kJ mol−1, significantly lower than other thermodynamically driven carbonaceous adsorbents. The fixed-bed breakthrough experiments further validated the efficient separation of equimolar C2H4/C2H6 mixture under dynamic conditions. This work provides an important guideline to fabricate carbons with adjustable ultramicropore size derived from biomass for the highly effective separation of light hydrocarbons via molecular sieving.

An all-glass based micro gas chromatographic column for light hydrocarbon separation with HKUST-1 as stationary phase

BackgroundThe gas chromatography column is one of the key components of the gas chromatograph and typically be miniaturized using micro-electro-mechanical system (MEMS) technology. Due to the limited area of the Si wafer, the column length of micro gas chromatographic column (μGCC) is usually much smaller than that of commercial chromatographic columns. Therefore, it is always difficult to use μGCCs to separate small molecule gas components such as light hydrocarbons. More importantly, the heterogeneous microchannel surface formed by silicon glass bonding causes uneven stationary phase coating, further preventing the improvement of separation performance. ResultsIn this paper, a novel all-glass based μGCC with 2 m length for the separation of light hydrocarbons is proposed. The microchannels of the μGCC were directly prepared in the glass substrate by ultrafast laser assisted chemical etching (ULAE). The all-glass microchannels make the coating of the hydrophilic metal-organic frameworks (MOFs) stationary phase continuously because of the homogeneous material composition. Therefore, a widely used copper based hydrophilic MOFs HKUST-1 was used as stationary phase for coating and testing. The test results show that the μGCC which is an open tubular column can realize the baseline separation of light hydrocarbons at 100 °C. And the resolution of difficult separated compounds, methane and ethane, can reach 12.98, which is 201.86 % higher than the silica-based monolithic capillary column in the relevant research. The resolution of ethane and ethylene reaches 6.81 at 120 °C. SignificanceThe μGCC fabricated by ULAE method is composed of all-glass and has the uniform stationary phase coating because of the homogeneous microchannel surface which greatly improve the separation performance, resulting in a large resolution for methane and ethane. The all-glass μGCC has broad application prospects in light hydrocarbon separation.

Flexible-robust interlayer space in a 2D metal–organic framework for light hydrocarbons separation

The separation of light hydrocarbons is industrially important and scientifically challenging due to their high similarity in physicochemical properties. Two-dimensional metal–organic frameworks (2D MOFs) assembled by weak supramolecular interactions are more likely to induce structural flexibility and exhibit guest-dependent gate-opening behavior than 3D MOFs, opening new horizons for LHs storage and separation. Here, a 2D MOF (Cu-APC, APC = 2-aminopyrimidine-5-carboxylic acid) with flexible-robust interlayer space was effectively used as an adsorbent to realize C2 and C3 hydrocarbons separation. Evidenced by gas adsorption isotherms and the ideal adsorbed solution theory (IAST) calculations, Cu-APC exhibits moderate C2H2/CO2 selectivity (2.87), high C2H6/C2H4 selectivity (2.27) and unique multistep adsorption behavior toward C3H4/C3H6 at ambient conditions. Moreover, theoretical calculations revealed that C-H···N, C=O···H-C, and C-H···π interactions are formed with C2H2, CO2, C2H4, and C2H6 in the suitable pockets within Cu-APC. The separation performances of Cu-APC for C2H2/CO2, C2H6/C2H4, and C3H4/C3H6 mixtures were also confirmed by column breakthrough experiments.

Porous Metal-Organic Frameworks for Light Hydrocarbon Separation.

The separation of light hydrocarbon compounds is an important process in the chemical industry. Currently, its separation methods mainly include distillation, membrane separation, and physical adsorption. However, these traditional methods or materials have some drawbacks and disadvantages, such as expensive equipment costs and high energy consumption, poor selectivity, low separation ratios, and separation efficiencies. Therefore, it is important to develop novel separation materials for light hydrocarbon separation. As a new type of organic-inorganic hybrid crystalline material, metal-organic frameworks (MOFs) are promising materials for light hydrocarbon separation due to their designability of structure and easy modulation of function. This review provides an overview of recent advances in the design, synthesis, and application of MOFs for light hydrocarbon separation in recent years, with a focus on the separation of alkane, alkene, and alkyne. We discuss strategies for improving the adsorption selectivity and capacity of MOFs, including pore size limitation, physical adsorption, and chemisorption. In addition, we discuss the advantages/disadvantages, challenges, and prospects of MOFs in the separation of light hydrocarbon.

A Microporous Zn(bdc)(ted)0.5 with Super High Ethane Uptake for Efficient Selective Adsorption and Separation of Light Hydrocarbons.

Separating light hydrocarbons (C2H6, C3H8, and C4H10) from CH4 is challenging but important for natural gas upgrading. A microporous metal-organic framework, Zn(bdc)(ted)0.5, based on terephthalic acid (bdc) and 1,4-diazabicyclo[2.2.2]octane (ted) ligands, is synthesized and characterized through various techniques, including powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and porosity analysis. The adsorption isotherms of light hydrocarbons on the material are measured and the isosteric adsorption heats of CH4, C2H6, C3H8, and C4H10 are calculated. The prediction of C2-4/C1 adsorption selectivities is accomplished using ideal adsorbed solution theory (IAST). The results indicate that the material exhibits exceptional characteristics, including a Brunauer-Emmett-Teller (BET) surface area of 1904 m2/g and a pore volume of 0.73 cm3/g. Notably, the material demonstrates remarkable C2H6 adsorption capacities (4.9 mmol/g), while CH4 uptake remains minimal at 0.4 mmol/g at 298 K and 100 kPa. These findings surpass those of most reported MOFs, highlighting the material's outstanding performance. The isosteric adsorption heats of C2H6, C3H8, and C4H10 on the Zn(bdc)(ted)0.5 are higher than CH4, suggesting a stronger interaction between C2H6, C3H8, and C4H10 molecules and Zn(bdc)(ted)0.5. The molecular simulation reveals that Zn(bdc)(ted)0.5 prefers to adsorb hydrocarbon molecules with richer C-H bonds and larger polarizability, which results in a stronger dispersion force generated by an adsorbent-adsorbate induced polarization effect. Therefore, the selectivity of C4H10/CH4 is up to 180 at 100 kPa, C3H8/CH4 selectivity is 67, and the selectivity of C2H6/CH4 is 13, showing a great potential for separating C2-4 over methane.

Metal-ion-tuned metal-organic frameworks for C2H2/CO2 separation

Adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) by adsorption is a viable method for producing high-purity C2H2 required for industrial applications. However, separating C2H2 and CO2 is challenging due to their extremely similar molecular sizes and physical properties. Metal-Organic Frameworks (MOFs), as a novel porous material with high specific surface area and tunable pore size, have shown great potential in the separation and purification of light hydrocarbons. Herein, we synthesized three isoreticular Al-MOFs (Al-TCPP, Al-TCPP(Co), and Al-TCPP(Fe)) by modulating metal ions at the porphyrin center, all of which can effectively separate C2H2/CO2. The addition of metal ions can regulate and improve the separation selectivity of C2H2/CO2. Compared with the parent Al-TCPP, the IAST selectivities of Al-TCPP(Co) and Al-TCPP(Fe) for equimolar C2H2/CO2 increased from 1.73 to 3.66 and 4.43, respectively. Breakthrough experiments validate their efficient separation of C2H2/CO2. Furthermore, they all exhibit excellent hydrothermal stability, laying the foundation for practical applications.

Highly Efficient Propyne/Propylene Separation in a "Flexible-Robust" and Hydrolytically Stable Cu(II)-MOF.

Propyne/propylene separation is important in the petrochemical industry but challenging due to their similar physical properties and close molecular sizes. Metal-organic frameworks (MOFs) are a class of promising adsorbents for light hydrocarbon separations. Among them, the so-called "flexible-robust" MOFs combine the advantages of flexibility and rigidity in structure and could show enhanced gas separation selectivity as well as improved gas uptake at low pressure. Interpenetrated MOFs offer a platform to explore the "flexible-robust" feature of MOFs based on their subnetwork displacement in the process of gas adsorption. Herein, we present two hydrolytically stable MOFs (BUT-308 and BUT-309) with interpenetrated structures and fascinating propyne/propylene separation performance. BUT-308 is composed of interpenetrated 2D Cu(BDC-NH2)BPB layers (H2BDC-NH2 = 2-aminobenzene-1,4-dicarboxylic acid; BPB = 1,4-bis(4-pyridyl)benzene), while BUT-309 consists of twofold interpenetrated 3D pillared-layer Cu2(BDC-NH2)2(BPB-CF3) nets (BPB-CF3 = 2-trifluoromethyl-1,4-bis(4-pyridyl)benzene). Gas adsorption measurements showed that BUT-309 was a "flexible-robust" adsorbent with multistep adsorption isotherms for C3H4 rather than C3H6 at a wide temperature range. The guest-dependent pore-opening behavior endows BUT-309 with high potential in the C3H4/C3H6 separation. The C3H4 adsorption measurements of BUT-309 at 273-323 K showed that the lowering of the temperature induced the pore-opening action at lower pressure. Column breakthrough experiments further confirmed the capability of BUT-309 for the efficient removal of C3H4 from a C3H4/C3H6 binary gas, and the C3H6 processing capacity at 273 K (15.7 cm3 g-1) was higher than that at 298 K (35.2 cm3 g-1). This work shows a rare example of "flexible-robust" MOFs and demonstrated its high potential for C3H4/C3H6 separation.

Polycrystalline Metal-Organic Framework Membranes for Separation of Light Hydrocarbons.

Due to facile designability and versatile nanospace, metal-organic frameworks (MOFs) have been considered as promising membrane materials. Compared to the mixed matrix membranes that incorporated with MOF particles, the polycrystalline MOF membranes demonstrates significant advantages in maximum utilizing the crystalline nanospace, and thus yielding a fruitful of achievements in the last twenty years. Although some reviews have summarized the development of MOF-based membranes, the theoretical framework for oriented design and preparation of polycrystalline MOF membranes for highly efficient separation of light hydrocarbons remains in infancy. Herein, in this review, the fabrication strategies of polycrystalline MOF membranes and the corresponding performance in the separation of light hydrocarbons were classified and summarized. Particularly, the MOF membranes with global and local dynamics have been proposed as an interesting topic promoted performance.

Process integration of light hydrocarbon separation and hydrate-based desalination for efficient and practical LNG cold energy recovery

Liquefied natural gas (LNG) regasification occurs over a wide temperature range, and LNG cold energy released from regasification cannot be fully utilized in a single process. Various studies have integrated individual processes to improve LNG cold energy utilization. However, each process has different temperature requirements, and it is challenging to integrate the geographical environment. This study presents a novel LNG cold energy multi-utilization process by integrating light hydrocarbon separation (LHS) and hydrate-based desalination (HYD) for efficient and practical LNG cold energy recovery. In the proposed process, light hydrocarbons in LNG are separated from LHS, which requires cryogenic energy. The remaining LNG cold energy is then utilized for HYD, which requires an operating temperature of 1 °C. Energy, exergy, and techno-economic analyses were compared to the base case, where cold energy was only used for desalination. The results show that a more efficient energy utilization process was achieved by reducing the exergy loss by 16.47 %. High-value materials could be recovered, such as liquefied ethane and liquefied petroleum gas, high-purity methane gas, and pure water. Despite additional equipment costs attributable to LHS, the net annual revenue based on the generated products was 6.66×107 USD/yr, with a payback period of 6.66 yr.

Metal confined in metal‐organic framework‐based mixed matrix membranes for efficient butadiene recognition separation

AbstractThe efficient separation of butadiene (1,3‐C4H6) from C4 hydrocarbons is a critical step in petrochemical processes. However, the traditional cryogenic distillation suffers from energy‐intensity and serious environmental stress, necessitating the development of alternative technologies for efficient 1,3‐C4H6 separation. Herein, a 1,3‐C4H6 recognition mixed matrix membrane is reported via incorporating metal copper encapsulated a metal‐organic framework (CuBTC@Cu) into elastic poly(dimethylsiloxane) (PDMS). The resulting CuBTC@Cu/PDMS membrane can efficient separate 1,3‐C4H6 from various C4 hydrocarbons including 1,3‐C4H6/n‐C4H8, 1,3‐C4H6/iso‐C4H8, 1,3‐C4H6/n‐C4H10 and 1,3‐C4H6/iso‐C4H10, yielding superior selectivity of 5.11, 6.35, 4.78, and 10.30, respectively, with 1,3‐C4H6 permeability of 53240 Barrer. Notably, the appropriate π‐complexation interaction between butadiene molecules and CuBTC@Cu as well as suitable transmission channel size enable the membrane only permeable to 1,3‐C4H6 and block the permeation of other C4 hydrocarbons, showing a unique 1,3‐C4H6 recognition behavior in membrane separation. The concept of affinity‐relying separation combining molecular sieving would open a new direction for designing gas membranes for efficient light hydrocarbon separations.

Sorption and Desorption of Vapor of n-Pentane by Porphyrin Aluminum Metal-Organic Framework: Mechanism of Bonding, Kinetics and Stoichiometry by Complementary In-Situ Time-Dependent and Ex-Situ Methods.

Metal-organic frameworks (MOFs) are highly nanostructured coordination polymers that contain metal cations and organic linkers and feature very large pore volumes and surface areas. The sorption and desorption of n-pentane vapor by porphyrin aluminum metal-organic framework Al-MOF-TCPPH2 where TCPPH2 is tetrakis(4-carboxyphenyl)porphyrin linker were studied by a novel method of in-situ time-dependent attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy in a controlled atmosphere and complementary in-situ and ex-situ methods. Sorption facilely occurs in the flow of dried air, and in the obtained adsorption complex the adsorbate molecules interact with phenyl and carboxylate groups of the linker and the O-H group. Sorption kinetics follows the pseudo-first-order rate law, as confirmed by in-situ time-dependent gravimetry. Further, an ex-situ (static) sorption of n-pentane vapor results in an adsorption complex with as much as 29.1 wt.% n-pentane with the stoichiometric formula [Al-MOF-TCPPH2]2(n-C5H12)7 and a distinct XRD pattern. Finally, in the flow of dried air, the adsorption complex gradually desorbed n-pentane, following the pseudo-first-order rate law. The reversibility of sorption and desorption makes porphyrin aluminum MOF promising for the separation of light hydrocarbons and chemo-sensing. In-situ time-dependent ATR-FTIR spectroscopy in a controlled atmosphere, in combination with in-situ time-dependent gravimetry, is a new approach for the determination of binding sites of sorbents with adsorbate molecules, the stoichiometry of complexes, and chemical kinetics of "solid-gas" interactions.

A stable microporous framework with multiple accessible adsorption sites for high capacity adsorption and efficient separation of light hydrocarbons

Metal-organic frameworks (MOFs), a type of designable porous materials, are effectively employed to realize light hydrocarbons storage and separation in favor of energy conservation and environmental protection, superior to traditional separation technology. Significantly, a novel MOF, Ni2(L)2(HCOO)2·4H2O (1) has been constructed from a bifunctional group ligand of 3-hydroxy-4-(4H-1,2,4-triazol-4-yl) benzoic acid ligand (HL). MOF 1 possesses stable porous structure with narrow channels functionalized with multiple accessible adsorption sites of hydroxy group, carboxyl oxygen atoms from the L− and HCOO−, exhibiting a well trade-off between good capacity and selectivity for light hydrocarbons. The single-component sorption isotherm results of Ni2+ based MOF not only shows good gas sorption capacity for light hydrocarbons of C2H2, C2H6, C2H4, C3H8, and greenhouse gas CO2, especially remarkable uptake for C2H2 (122.0 cm3 g−1 at ambient condition), but also favorable selectivity for binary mixtures of C2H2/CH4, C2H6/CH4, C3H8/CH4, C2H4/CH4, C2H2/C2H4 as well as C3H8/C2H6/CH4 ternary mixture, as confirmed by ideal adsorbed solution theory (IAST) calculations, and dynamic breakthrough experiment. Grand canonical Monte Carlo (GCMC) simulation reveals the multiple synergism of accessible adsorption sites including functional OH groups, carboxylate groups, HCOO− and π···π stacking interaction between guest molecules and host-pore are crucial to contribute selective gas adsorption of light hydrocarbons.