Metal organic frameworks for gas separation applications
11607665 · 2023-03-21
Assignee
Inventors
Cpc classification
B01J20/226
PERFORMING OPERATIONS; TRANSPORTING
B01J20/28033
PERFORMING OPERATIONS; TRANSPORTING
C10L2290/542
CHEMISTRY; METALLURGY
International classification
C10L3/10
CHEMISTRY; METALLURGY
B01J20/28
PERFORMING OPERATIONS; TRANSPORTING
B01J31/16
PERFORMING OPERATIONS; TRANSPORTING
C07F5/00
CHEMISTRY; METALLURGY
Abstract
Embodiments of the present disclose provide a method of sorbing one or more compounds from a fluid, wherein the method may include contacting a M-soc-MOF composition with a fluid containing at least H.sub.2S and one or more of CO.sub.2 and CH.sub.4; and sorbing at least H.sub.2S from the fluid. Embodiments of the present disclosure provide a membrane that may include a metal-organic framework (MOF) composition, wherein the MOF composition includes a M-soc-MOF composition, where M is a metal and soc is a square-octahedral topology, and wherein the M-soc-MOF composition is a continuous thin film on a support.
Claims
1. A membrane comprising: a metal-organic framework (MOF) composition, wherein the MOF composition includes a M-soc-MOF composition, where M is a metal that includes Al.sup.+3 and soc is a square-octahedral topology, and wherein the M-soc-MOF composition is a continuous thin film on a support.
2. The membrane of claim 1, wherein the metal of the M-soc-MOF composition includes In.sup.3+.
3. The membrane of claim 1, wherein the metal of the M-soc-MOF composition includes Fe.sup.3+.
4. The membrane of claim 1, wherein the metal of the M-soc-MOF composition includes Ga.sup.3+.
5. The membrane of claim 1, wherein the M-soc-MOF includes 3,3′,5,5′-azobenzenetetracarboxylate (ABTC) as a ligand.
6. The membrane of claim 1, wherein the M-soc-MOF composition includes an extra-framework counter-ion selected from the group consisting of NO.sup.3−, Cl.sup.−, Br.sup.−, and OH.sup.−, or a combination thereof.
7. The membrane of claim 1, wherein the M-soc-MOF composition includes Fe-soc-MOF.
8. The membrane of claim 1, wherein the M-soc-MOF composition includes Ga-soc-MOF.
Description
BRIEF DESCRIPTION OF DRAWINGS
(1) This written disclosure describes illustrative embodiments that are non-limiting and non-exhaustive. In the drawings, which are not necessarily drawn to scale, like numerals describe substantially similar components throughout the several views. Like numerals having different letter suffixes represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
(2) Reference is made to illustrative embodiments that are depicted in the figures, in which:
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DETAILED DESCRIPTION
(65) The invention of the present disclosure relates to methods of separating one or more compounds using sorbent materials based on a series of isostructural metal-organic frameworks with soc topology. The series of isostructural metal-organic frameworks with soc topology (M-soc-MOFs) may include one or more trivalent metals, including, but not limited to, one or more of In.sup.3+, Fe.sup.3+, Ga.sup.3+, and Al.sup.3+. The M-soc-MOFs may host one or more extra-framework counter-ions, including, but not limited to, one or more of NO.sub.3.sup.−, Cl.sup.−, Br.sup.−, and OH.sup.−. The ability to select the intra-framework metal and/or extra-framework counter-ion permits fine-tuning and fabrication of equilibrium-based M-soc-MOFs with unprecedented dual chemical stability and gas/vapor selectivity suitable for upgrading various gas feedstocks, such as refinery-off gases (ROG) and natural gas (NG). For example, in some embodiments, the M-soc-MOFs may be used for separation-based production of high-quality hydrocarbons (CH.sub.4, C.sub.3H.sub.8, and n-C.sub.4H.sub.10) and olefins from H.sub.2S-containing gas streams. In other embodiments, the M-soc-MOFs may be used for the selective adsorption of H.sub.2S in CO.sub.2- and CH.sub.4-containing gas streams. In this way, the M-soc-MOFs of the present disclosure may be tuned to meet the requirements of a variety of gas separation/purification applications.
(66) In general, metal organic frameworks (MOFs) are a versatile and promising class of crystalline solid state materials which allow porosity and functionality to be tailored towards various applications. For example, MOF materials exhibit exceptionally high specific surface area, in addition to tunable pore size and functionality (e.g., permselectivity toward mono-branched and n-paraffins), which make them suitable for many applications including gas storage, gas separation, catalysis, drug delivery, light-emitting devices, and sensing.
(67) MOFs comprise a network of nodes and ligands, wherein a node has a connectivity capability at two or more functional sites, and a ligand has a connectivity capability at least at two functional sites, each of which connect to a node. Nodes are typically metal ions or metal containing clusters. In some instances, ligands with node connectivity capability at two or more functional sites can also be characterized as nodes. In some instances, ligands can include two functional sites capable of each connecting to a node, and optionally one or more additional functional sites which do not connect to nodes within a particular framework. In some embodiments, ligands can be poly-functional, or polytopic, and comprise two or more functional sites capable of each connecting to a node. In some embodiments, polytopic ligands can be heteropolytopic, wherein at least one of the two or more functional sites differ from another functional site.
(68) A MOF can comprise a metal-based node and an organic ligand which extrapolate to form a coordination network. Such coordination networks have advantageous crystalline and porous characteristics affecting structural integrity and interaction with foreign species (e.g., hydrocarbons). The particular combination of nodes and ligands within a framework will dictate the framework topology and functionality. Through ligand modification or functionalization, the environment in the internal pores can be modified to suit specific applications.
(69) MOF can be represented by the formula [(node)a(ligand)b(solvent)c]n, wherein n represents the number of molecular building blocks. Solvent represents a guest molecule occupying pores within the MOF, for example as a result of MOF synthesis, and can be evacuated after synthesis to provide a MOF with unoccupied pores. Accordingly, the value of c can vary down to zero, without changing the definitional framework of the MOF. Therefore, in many instances, MOFs can be defined as [(node)a(ligand)b]n, without reference to a solvent or guest molecule component.
(70) The M-soc-MOFs of the present disclosure offer several key attributes that are attractive for gas upgrading/separations: (i) high chemical and thermal stability associated with its relatively high porosity; (ii) the presence of accessible open metal sites that are appropriate for tuning and enhancing the strength of interactions with acid gases, particularly H.sub.2S; and (iii) the presence of extra-framework anions within the cavities, which is ideal for further tuning the adsorption properties of the soc-MOF adsorbent. The M-soc-MOFs of the present disclosure as described in greater detail below thus may be used to sorb one or more compounds from a fluid.
(71)
(72) In one embodiment, sorbing 102 comprises absorbing. In one embodiment, sorbing 102 comprises adsorbing. In one embodiment, sorbing 102 comprises a combination of adsorbing and absorbing. Sorbing 102 can include selective sorption (i.e., sorption of a single compound), or simultaneous sorption (e.g., sorption of a plurality of compounds). The M-soc-MOF compositions can sorb about 1% to about 99.9%, about 1% to about 90%, about 1% to about 50% or about 1% to about 30% of one or more compounds in a fluid. Sorbing 102 can occur at ambient temperature, at an elevated temperature, at a cooled temperature, or over a temperature range. In one embodiment, a temperature can be selectively changed to manipulate sorption and/or desorption of different compounds. Sorbing 102 can occur at ambient pressure, at an elevated pressure, at a cooled pressure, or over a pressure range. In one embodiment, pressure can be selectively changed to manipulate sorption and/or desorption of different compounds. In addition to or in the alternative to, a concentration of one or more M-soc-MOF compositions can be varied to affect a rate and/or magnitude of sorbing 102. One or more of temperature, pressure and M-soc-MOF concentration can be regulated to produce a simultaneous sorption of compounds, or a subsequent, step-wise sorption (i.e., in series) of compounds from a fluid. In series sorption generally includes sorbing a quantity of a first compound via a MOF, and subsequently sorbing a quantity of a second compound via the same MOF while at least a portion of the quantity of the first compound remains sorbed. Simultaneous sorption generally includes contacting a plurality of compounds with an MOF, and sorbing a quantity of each of the two compounds with the MOF.
(73) In some embodiments, the M-soc-MOFs may be used for separation-based production of high-quality hydrocarbons (CH.sub.4, C.sub.3H.sub.8, and n-C.sub.4H.sub.10) and olefins from H.sub.2S-containing gas streams. See, for example,
(74) The fluid (e.g., H.sub.2S-containing fluid) may contain one or more of H.sub.2S, one or more C.sub.2+ compounds, and one or more other chemical species. The one or more C.sub.2+ compounds may include one or more of C.sub.2H.sub.6, C.sub.2H.sub.4, C.sub.3H.sub.6, C.sub.3H.sub.8, and n-C.sub.4H.sub.10. The one or more other chemical species may include one or more of H.sub.2, CH.sub.4, and N.sub.2. In many embodiments, the M-soc-MOFs exhibit a selectivity for the one or more C.sub.2+ compounds over the one or more other chemical species. For example, the M-soc-MOFs may exhibit a selectivity for (e.g., sorb) one or more C.sub.2+ compounds over one or more of CH.sub.4, H.sub.2, and N.sub.2. In many embodiments, the M-soc-MOFs exhibit a high tolerance and/or chemical stability in the presence of H.sub.2S. For example, the M-soc-MOFs may maintain their structural integrities and separation performances upon exposure to H.sub.2S. In other embodiments, the M-soc-MOFs exhibit a selectivity for the one or more C.sub.2+ compounds and H.sub.2S over the one or more other chemical species. For example, the M-soc-MOFs may exhibit a selectivity for one or more C.sub.2+ compounds and H.sub.2S over one or more of CH.sub.4, H.sub.2, and N.sub.2.
(75) In some embodiments, the M-soc-MOFs may be used for the selective adsorption of H.sub.2S in CO.sub.2- and CH.sub.4-containing gas streams, such as ROG and NG. See, for example,
(76) The fluid (e.g., CO.sub.2- and/or CH.sub.4-containing fluid) may contain one or more of H.sub.2S, CO.sub.2, and CH.sub.4. In an embodiment, the fluid is a CO.sub.2-containing fluid that further includes H.sub.2S. In an embodiment, the fluid is a CH.sub.4-containing fluid that further includes H.sub.2S. In an embodiment, the fluid is a CO.sub.2- and CH.sub.4-containing stream that further includes H.sub.2S. In many embodiments, the M-soc-MOFs exhibit a selectivity for H.sub.2S over one or more of CO.sub.2 and CH.sub.4. For example, the M-soc-MOF may exhibit a selectivity for H.sub.2S over CO.sub.2 in a CO.sub.2-containing stream. The M-soc-MOF may exhibit a selectivity for H.sub.2S over CH.sub.4 in a CH.sub.4-containing stream. The M-soc-MOF may exhibit a selectivity for H.sub.2S over CO.sub.2 and CH.sub.4 in a CO.sub.2- and CH.sub.4-containing stream. In addition or in the alternative, in many embodiments, the M-soc-MOFs exhibit a high tolerance and/or chemical stability in the presence of H.sub.2S. In some embodiments, the M-soc-MOFs exhibit a selectivity for H.sub.2S and/or CO.sub.2 over CH.sub.4. For example, the M-soc-MOF may exhibit a selectivity for H.sub.2S>CO.sub.2>>CH.sub.4. In these embodiments, the M-soc-MOF may be used for the subsequent removal of H.sub.2S and CO.sub.2.
(77) Embodiments of the present disclosure also describe M-soc-MOFs suitable for any of the methods of the present disclosure. The M-soc-MOFs may include one or more metals or metal clusters, and one or more ligands. In many embodiments, the metals (M) of the M-soc-MOF may include one or more trivalent metals (e.g., methods capable of exhibiting a 3+ oxidation state). For example, M of the M-soc-MOF may include one or more of In.sup.3+, Fe.sup.3+, Ga.sup.3+, and Al.sup.3+. In many embodiments, the M-soc-MOFs include one or more counter-ions. For example, the counter-ions may include one or more of NO.sub.3.sup.−, Cl.sup.−, Br.sup.−, and OH.sup.−. In many embodiments, the M-soc-MOFs include a tetracarboxylate ligand. For example, the ligand may include 3,3′,5,5′-azobenzenetetracarboxylate (ABTC.sup.4−) ligands. Any combination of the M, counter-ions, and ligands described in the present disclosure may be used to construct M-soc-MOFs suitable for any of the methods of the present disclosure.
(78) In an embodiment, the M-soc-MOFs include a series of isostructural soc-MOFs (
(79) In an embodiment, the M-soc-MOF is In-soc-MOF, wherein a counter-ion is NO.sub.3.sup.− (In-soc-MOF-1a). In an embodiment, the M-soc-MOF is In-soc-MOF, wherein a counter-ion is Cl.sup.− (In-soc-MOF-1b). In an embodiment, the M-soc-MOF is In-soc-MOF, where a counter-ion is Br.sup.− (In-soc-MOF-1c). In an embodiment, the M-soc-MOF is Fe-soc-MOF, wherein a counter-ion is NO.sub.3.sup.− (Fe-soc-MOF-1a). In an embodiment, the M-soc-MOF is Fe-soc-MOF, wherein a counter-ion is Cl.sup.− (Fe-soc-MOF-1b). In an embodiment, the M-soc-MOF is Ga-soc-MOF, wherein a counter-ion NO.sub.3.sup.− (Ga-soc-MOF-1a). In an embodiment, the M-soc-MOF is Al-soc-MOF-, wherein a counter-ion is OH.sup.− (Al-soc-MOE-1d).
(80) In a preferred embodiment, the M-soc-MOF is one or more of Fe-soc-MOF, Ga-soc-MOF, and Al-soc-MOF. Each of these M-soc-MOFs may exhibit enhanced C.sub.2+/CH.sub.4 and/or H.sub.2S/CO.sub.2 and/or H.sub.2S/CH.sub.4 adsorption selectivities. For example, in an embodiment, each of these M-soc-MOFs may exhibit enhanced selectivity for one or more of C.sub.2+ compounds (e.g., C.sub.2H.sub.4, C.sub.3H.sub.6, and n-C.sub.4H.sub.10) over one or more of CH.sub.4, H.sub.2, and N.sub.2. In an embodiment, each of these M-soc-MOFs may exhibit enhanced selectivity for H.sub.2S over one or more of CO.sub.2 and CH.sub.4, or for H.sub.2S and/or CO.sub.2 over CH.sub.4. In another preferred embodiment, the M-soc-MOF is one or more of Ga-soc-MOF and Al-soc-MOF. Each of these M-soc-MOFs may maintain structural integrity and separation performance upon exposure to H.sub.2S. For example, in an embodiment, Ga-soc-MOF and Al-soc-MOF may exhibit enhanced selectivity for C.sub.2+ over other chemical species and maintain chemical stability in the presence of H.sub.2S. In another preferred embodiment, the M-soc-MOF is Ga-soc-MOF as it exhibits a selectivity for H.sub.2S and/or CO.sub.2 over CH.sub.4. While preferred embodiments are disclosed herein, such disclosure shall not be limiting, as any of the M-soc-MOFs described herein are capable of providing a selectivity and chemical stability suitable for any of the methods described herein.
(81) Embodiments of the present disclosure further describe thin-film membranes based on any of the M-soc-MOFs described in the present disclosure and methods of fabricating the same.
(82) Embodiments of the present invention further provide the use of stable MOFs and MOF compositions, particularly M-soc-MOFs, for the subsequent (i.e., in series) or simultaneous removal of CO.sub.2, H.sub.2S, and condensable hydrocarbons. Embodiments as described have the potential to reduce the number of processes in the natural gas or biogas overall treatment scheme. It is expected that the regeneration of M-soc-MOF compositions will be cost effective in comparison to conventional amine scrubbing. M-soc-MOF compositions also exhibit high affinity for condensable hydrocarbons (C.sub.2H.sub.6, C.sub.3H.sub.8, etc.) at the inverse of zeolites and activated carbons.
(83)
(84) One compound which can be sorbed by an M-soc-MOF from a fluid is CO.sub.2. CO.sub.2 can be sorbed from a fluid comprising H.sub.2O and/or CH.sub.4 by an M-soc-MOF with selectivity over one or more of H.sub.2O and CH.sub.4. One compound which can be sorbed by an M-soc-MOF from a fluid is H.sub.2S. H.sub.2S can be sorbed from a fluid comprising H.sub.2O and/or CH.sub.4 by an M-soc-MOF with selectivity over one or more of H.sub.2O and CH.sub.4. CO.sub.2 and H.sub.2S can be simultaneously sorbed from a fluid comprising H.sub.2O and/or CH.sub.4 by an M-soc-MOF with selectivity over one or more of H.sub.2O and CH.sub.4. CO.sub.2 and H.sub.2S can be sorbed from a fluid comprising H.sub.2O and/or CH.sub.4 in series by an M-soc-MOF with selectivity over one or more of H.sub.2O and CH.sub.4. In a specific embodiment, CO.sub.2 and H.sub.2S can be simultaneously sorbed from natural gas and/or biogas by an M-soc-MOF with selectivity over other one or more of H.sub.2O and CH.sub.4. In a specific embodiment, CO.sub.2 and H.sub.2S can be sorbed from a fluid comprising H.sub.2O and/or CH.sub.4 in series by an M-soc-MOF with selectivity over other one or more of H.sub.2O and CH.sub.4. Generally, the above sorption abilities and stability in the presence of water of suitable M-soc-MOFs as disclosed herein is an advantageous aspect unavailable from other M-soc-MOFs and industrial materials such as zeolites and activated carbon.
(85) Condensable hydrocarbons can be sorbed by an M-soc-MOF from a fluid. Examples of condensable hydrocarbons include ethane, propane, butane, pentane, and hexane. In some embodiments, examples of condensable hydrocarbons include straight chained alkanes with 6 carbons or less. Condensable hydrocarbons and one or more of CO.sub.2 and H.sub.2S can be simultaneously sorbed from a fluid, with selectivity over other one or more of H.sub.2O and CH.sub.4. Condensable hydrocarbons and one or more of CO.sub.2 and H.sub.2S can be sorbed in series from a fluid, with selectivity over other one or more of H.sub.2O and CH.sub.4. The ability to sorb condensable hydrocarbons is one advantageous aspect of suitable M-soc-MOFs as disclosed herein over other materials such as zeolites and activated carbon.
(86) M-soc-MOFs suitable for the methods disclosed herein include M-soc-MOFs comprising one or more trimer molecular building blocks (TMBB), as shown in
(87) Suitable metals (M) include trivalent metals (i.e., metals capable of exhibiting a +3 oxidation state). Trivalent metals include aluminum, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, germanium, arsenic, yittrium, zirconium, niobium, molybdenum, palladium, silver, indium, tin, antimony, lanthanum, cerium, praseodymium, samarium, europium gadolinium, terbium, erbium, thulium, ytterbium, lutetium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, lead, and bismuth. Particularly suitable trivalent metals include gallium, indium, iron, scandium, and aluminum. The three trivalent metals yield an overall cationic framework (+1 per formula unit) that is balanced by [NO.sub.3].sup.−1 ions. The disordered [NO.sub.3].sup.−1 ions occupy statistically two positions on the threefold axis with equal probability. A broad range of suitable trivalent metals advantageously allows for M-soc-MOFs to be customized for particular purposes. For example, lighter trivalent metals can provide an M-soc-MOF with increased sorption uptake per unit volume.
(88) Each TMBB unit is linked by six separate organic ligands, as shown in
(89) One particular suitable ligand is 3,3′,5,5′-azobenzenetetracarboxylate:
(90) ##STR00001##
(91)
(92) Other interesting structural features of the crystalline structure are its two types of infinite channels. The first type is hydrophilic, due to the water molecules coordinated to the indium centers which are pointed inside these channels. Guest water molecules occupy the remaining free volume in these channels and form hydrogen bonds with coordinated water molecules. The second type of channels can be guest free, and have an approximately 1 nm diameter.
(93) M-soc-MOFs can have a BET surface area of at least about 800 m.sup.2/g, at least about 900 m.sup.2/g, at least about 1,000 m.sup.2/g, at least about 1,200 m.sup.2/g, at least about 1,400 m.sup.2/g, or at least about 1,600 m.sup.2/g. In a specific embodiment, an M-soc-MOF has a BET surface area of at least about 800 m.sup.2/g. In a specific embodiment, an M-soc-MOF has a BET surface area of about 1,000 m.sup.2/g. In a specific embodiment, an M-soc-MOF has a BET surface area of about 1,000 m.sup.2/g to about 1,600 m.sup.2/g.
(94) M-soc-MOFs can have an average pore volume of at least about 0.2 cm.sup.3/g, at least about 0.25 cm.sup.3/g, at least about 0.3 cm.sup.3/g, at least about 0.45 cm.sup.3/g, at least about 0.6 cm.sup.3/g, or at least about 0.65 cm.sup.3/g. In a specific embodiment, an M-soc-MOF has an average pore volume of at least about 0.2 cm.sup.3/g. In a specific embodiment, an M-soc-MOF has an average pore volume of about 0.3 cm.sup.3/g. In a specific embodiment, an M-soc-MOF has an average pore volume of about 0.3 cm.sup.3/g to about 0.65 cm.sup.3/g.
(95) The following Examples are intended to illustrate the above invention and should not be construed as to narrow its scope. One skilled in the art will readily recognize that the Examiners suggest many other ways in which the invention could be practiced. It should be understand that numerous variations and modifications may be made while remaining within the scope of the invention.
Example 1
(96) The following Example describes a cooperative experimental/modeling strategy that was used to unveil the structure/gas separation performance relationship for a series of isostructural metal-organic frameworks (MOFs) with soc-topology (square-octahedral) hosting different extra-framework counter ions (NO.sub.3.sup.−, Cl.sup.− and Br.sup.−). In.sup.3+—, Fe.sup.3+—, Ga.sup.3+— and the newly isolated Al(III)-based isostructural soc-MOF were extensively studied and evaluated for the separation-based production of high-quality fuels (i.e., CH.sub.4, C.sub.3H.sub.8 and n-C.sub.4H.sub.10) and olefins. The structural/chemical fine-tuning of the soc-MOF platform promoted equilibrium-based selectivity toward C.sub.2+ (C.sub.2H.sub.6, C.sub.2H.sub.4, C.sub.3H.sub.6 C.sub.3H.sub.8, and n-C.sub.4H.sub.10) and conferred the desired chemical stability toward H.sub.2S. The noted dual chemical stability and gas/vapor selectivity, which have rarely been reported for equilibrium-based separation agents, are essential for the production of high-purity H.sub.2, CH.sub.4 and C.sub.2+ fractions in high yields. Interestingly, the evaluated soc-MOF analogues exhibited high selectivity for C.sub.2H.sub.4, C.sub.3H.sub.6 and n-C.sub.4H.sub.10. In particular, the Fe, Ga and Al analogues presented relatively enhanced C.sub.2+/CH.sub.4 adsorption selectivities. Notably, the Ga and Al analogues were found to be technically preferable because their structural integrities and separation performances were maintained upon exposure to H.sub.2S, indicating that these materials are highly tolerant to H.sub.2S. Therefore, the Ga-soc-MOF was further examined for the selective adsorption of H.sub.2S in the presence of CO.sub.2- and CH.sub.4-containing streams, such as refinery-off gases (ROG) and natural gas (NG). Grand canonical Monte Carlo (GCMC) simulations based on a specific force field describing the interactions between the guest molecules and the Ga sites supported and con-firmed the considerably higher affinity of the Ga-soc-MOF for C.sub.2+ (as exemplified by n-C.sub.4H.sub.10) than for CH.sub.4. The careful selection of an appropriate metal for the trinuclear inorganic molecular building block (MBB), i.e., a Ga metal center, imbues the soc-MOF platform with the requisite hydrolytic stability, H.sub.2S stability, and exceptional gas selectivity for ROG and NG upgrading. Finally, the soc-MOF was deployed as a continuous film on a porous support, and its gas permeation properties as a membrane were evaluated.
(97) Materials and Methods
(98) Organic Synthesis
(99) 3,3′,5,5′-azabenzene tetracarboxylic acid (ABTC) was synthesized in our lab by recently published procedure (Scheme 1). Briefly, A mixture of 5-nitroisophthalic acid (19 g, 90 mmol) and NaOH (50 g, 1250 mmol) in 250 ml of reverse osmosis water was placed into a 1 L 3-neck round bottom flask and stirred vigorously at 333 K. To this slurry 100 g of D-glucose dissolved in 150 ml of reverse osmosis water was slowly added. The resulted brown mixture was cooled down to room temperature and air was bubbled through reaction mixture overnight always under stirring. The reaction mixture was cooled with an ice bath and the sodium salt of 3,3′,5,5′-azobenzene tetracarboxylic acid was recovered by filtration and washed with small amount of cold water. The resulting yellow solid was then dissolved in 200 ml of reverse osmosis water and this solution was acidified to pH=1 by the addition of conc. HCl. The resulting orange solid was collected by filtration on the fritted funnel, washed with reverse osmosis water and dried in vacuum oven at 373 K to provide 10.5 g of target compound. Yield 70%. .sup.1H and .sup.13C NMR data are in a good agreement with previously reported data.
(100) ##STR00002##
Other Chemicals and Solvents
(101) All other chemicals and solvents were used as received unless otherwise stated from Fisher Scientific, Acros Organics, Sigma-Aldrich, Combi Blocks or TCI America. DMF was dried over CaH.sub.2. DI water=deionized water. .sup.1H and .sup.13C NMR spectra were recorded at room temperature with Bruker Avance 500 and 600 MHz spectrometers using CDCl.sub.3 or DMSO-d.sub.6 as the solvents, and referenced to the corresponding solvent peaks (7.26 and 77.16 ppm for CDCl.sub.3, and 2.50 and 39.52 ppm for DMSO-d.sub.6, respectively).
(102) Synthesis and X-ray Crystal Structure Analysis
(103) The In.sup.3+-, Fe.sup.3+-, and Ga.sup.3+-soc-MOF analogues were synthesized following the published procedure. The synthesis of the Al-soc-MOF-1d analogue was substantially more tedious because of the challenges in growing suitable crystals for single-crystal determination. After countless attempts using different conditions, the introduction of a modulator—acetic acid—was found to be crucial for isolating the targeted Al-soc-MOF-1d (see the synthetic procedure presented below).
(104) Single-Crystal Conditions for the Al-Soc-MOF-1d
(105) A solution of AlCl.sub.3.6H.sub.2O (13 mg, 0.054 mmol) and 3,3′,5,5′ azobenzenetetracarboxylic acid (10 mg, 0.028 mmol) in N,N-dimethylformamide (DMF) (2 mL), acetonitrile (CH.sub.3CN) (2 mL), and acetic acid (1 mL) was prepared in a Pyrex vial with a polytetrafluoroethylene (PTFE)-lined phenolic cap and subsequently placed into a preheated oven at 150° C. for 3 days to yield pure orange crystals (
(106) Scale-Up Conditions for the Al-Soc-MOF-1d
(107) A solution of AlCl.sub.3.6H.sub.2O (265.6 mg, 1.1 mmol) and 3,3′,5,5′ azobenzenetetracarboxylic acid (200 mg, 0.56 mmol) in DMF (40 mL), acetonitrile (CH.sub.3CN) (40 mL), and acetic acid (20 mL) was prepared in a round-bottom pressure flask and subsequently placed into a pre-heated oven at 150° C. for 3 days to give pure orange crystals. The Al-soc-MOF-1d was activated by first washing the as-synthesized crystals with 3×20 mL of DMF, followed by solvent exchange with acetonitrile for 6 days in a 65° C. oven. The adsorption studies were generally conducted on a freshly isolated MOF; typically, 30 to 40 mg of each activated sample was transferred (dry) to a 6-mm large bulb glass sample cell. Then, the sample was evacuated at room temperature using a turbomolecular vacuum pump (residual pressure below 10-7 mbar), kept at 220° C. for 24 h, then gradually heated to 220° C. at a rate of 1° C./min, and finally cooled to room temperature.
(108) Instrumentation and Procedures
(109) Single-crystal X-ray diffraction data were collected using a Bruker X8 PROSPECTOR APEX2 CCD diffractometer (Cu Kα, λ=1.54178 Å). Indexing was performed using APEX2 (Difference Vectors method). Data integration and reduction were performed using SaintPlus 6.01. Absorption correction was performed by multi-scan method implemented in SADABS. Space groups were determined using XPREP implemented in APEX2.1 Structure was solved using SHELXS-97 (direct methods) and refined using SHELXL-97 (full-matrix least-squares on F2) contained in APEX2.
(110) Powder X-ray diffraction (PXRD) measurements were carried out at room temperature on a PANalytical X'Pert PRO diffractometer 45 kV, 40 mA for Cu Kα (λ=1.5418 Å), with a step size of 0.05° in 2θ.
(111) Quantachrome Low-pressure gas N.sub.2 sorption measurements were performed on a fully automated autosorb-1 high resolution gas adsorption analyzer (Quantachrome) at relative pressures up to 1 atm. The cryogenic temperatures were controlled using liquid nitrogen and argon baths at 77 K.
(112) 3FLEX Low-pressure gas sorption measurements at 298K. Low pressure gas adsorption measurements at 298 K were performed on 3-Flex Surface Characterization Analyzer (Micromeritics) at relative pressures up to 1 atm.
(113) C.sub.4H.sub.10/CH.sub.4 Column breakthrough test. The homemade set-up for adsorption column breakthrough testing is composed of a stainless steel column. The column is 27 mm in length with 4 mm of inner (6.4 mm outer) diameter. The gas composition downstream the column is monitored using a hidden mass spectrometer. In a typical experiment, 0.1-0.4 g of adsorbent was treated at 403-433 K overnight in vacuum (in oven). After backfill with argon, the column is then transferred to a thermostatic chamber where helium is flushed trough the column at 3.5 cm.sup.3 min.sup.−1. The gas flow is then switched to the desired n-C.sub.4H.sub.10/CH.sub.4 (2/98) gas mixture at the same flow rate. The complete breakthrough of n-C.sub.4H.sub.10 and CH.sub.4 were indicated by the downstream gas composition reaching that of the feed gas.
(114) H.sub.2S/CO.sub.2/CH.sub.4 Column breakthrough tests. For H.sub.2S containing gases, the mixed gas testing measurements were carried out using custom made column breakthrough set-up, designed in collaboration with L&C (Hilleah, Fla. USA). The stainless steel column used in the breakthrough test with a capacity of packing up to 2 g of materials. The column downstream is monitored using a MKS mass spectrometer. In a typical experiment, 0.1-0.4 g of adsorbent was treated at 403-433 K overnight in vacuum (in situ). The gas flow is then switched to the desired CO.sub.2/H.sub.2S/CH.sub.4:5/5/90 gas mixture at the same flow rate (10 cm.sup.3/min). The complete breakthrough of CH.sub.4, CO.sub.2 and H.sub.2S were indicated by the downstream gas composition reaching that of the feed gas.
(115) In-situ FTIR. Fourier Transform InfraRed (FTIR) spectra were measured using Thermo Nicolet 6700 series spectrometer equipped with quantum Mercuric Cadmium Telluride (MCT-A) detector operating at liquid nitrogen temperature. Each IR spectrum was the average of 128 spectra recorded in the 4000-650 cm.sup.−1 spectral range with a resolution of 4 cm.sup.−1.
(116) Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments were performed using Praying Mantis module equipped with a dome sealed reaction chamber (ZnSe window) allowing a controlled in situ environment.
(117) KBr powder was used to collect the background spectrum. Sample was mixed with KBr (1 wt %) for sample spectrum collection. KBr and KBr+sample powders were dried at 200° C. under ultrahigh vacuum (<1 mTorr) prior transferring to the reaction chamber in glovebox environment. Before measurement sample was heated at 200° C. under vacuum (1 torr) in the sealed reaction chamber.
(118) TG-DSC. Enthalpy of adsorption for CO.sub.2 was measured using SENSYS evo TG-DSC from Setaram Instrumentation that can carry out simultaneous high resolution DSC and TGA experiments. In a typical experiment, the sample was activated in-situ 403-433 K under continuous dry N.sub.2 flow at the rate of 15 ml/min. For sorption experiment, baseline was obtained under dry N.sub.2 flow at the rate of 15 ml/min at 25° C. The desired gas was connected at auxiliary gas port and gas was changed from N.sub.2 to CH.sub.4, C.sub.3H.sub.8 and n-C.sub.4H.sub.10 exactly after 1 hour and TGA and DSC signal were monitored for few hours to obtain uptake and heat of sorption respectively.
(119) High-pressure gas sorption measurements. Adsorption equilibrium measurements of pure gases were performed using a Rubotherm gravimetric-densimetric apparatus (Bochum, Germany) (
Ω=m.sub.absolute−ρ.sub.gas(V.sub.adsorbent+V.sub.ss+V.sub.adsorbed-phase) (1)
Ω=m.sub.excess−ρ.sub.gas(V.sub.adsorbent+V.sub.SS) (2)
(120) The buoyancy effect resulting from the adsorbed phase may be taken into account via correlation with the pore volume or with the theoretical density of the sample.
(121) These volumes are determined using the helium isotherm method by assuming that helium penetrates in all open pores of the materials without being adsorbed. The density of the gas is determined using the Refprop equation of state (EOS) database and checked experimentally using a volume-calibrated titanium cylinder. By weighing this calibrated volume in the gas atmosphere, the local density of the gas is also determined. Simultaneous measurement of adsorption capacity and gas-phase density as a function of pressure and temperature is therefore possible.
(122) The pressure is measured using two Drucks high pressure transmitters ranging from 0.5 to 34 bar and 1 to 200 bar, respectively, and one low pressure transmitter ranging from 0 to 1 bar. Prior to each adsorption experiment, about 200 mg of sample is outgassed at 473 K at a residual pressure of 10.sup.−6 mbar. The temperature during adsorption measurements is held constant by using a thermostat-controlled circulating fluid.
(123) Results and Discussion
(124) The M-soc-MOFs of the present disclosure offer several key attributes that make it attractive for gas upgrading/separations: (i) high chemical and thermal stability associated with its relatively high porosity; (ii) the presence of accessible open metal sites that are appropriate for tuning and enhancing the strength of interactions with acid gases, particularly H.sub.2S; and (iii) the presence of extra-framework anions within the cavities, which is ideal for further tuning the adsorption properties of the soc-MOF adsorbent.
(125) Accordingly, the effect of different intra-framework metals on soc-MOF stability upon exposure to H.sub.2S and the associated adsorption properties of H.sub.2, CH.sub.4, C.sub.2H.sub.4, C.sub.3H.sub.6 and C.sub.2+ (C.sub.2H.sub.6, C.sub.3H.sub.8 and n-C.sub.4H.sub.10) were evaluated. In an embodiment, the Ga-based soc-MOF analogue (Ga-soc-MOF-1a) exhibited outstanding equilibrium-based separation performance for CH.sub.4/n-C.sub.4H.sub.10, H.sub.2S/CO.sub.2, and H.sub.2S/CH.sub.4 mixtures based on real co-adsorption measurements. To gain better insight into the adsorption mechanisms governing the separation of CH.sub.4 from n-C.sub.4H.sub.10, molecular simulations integrating advanced quantum and force field-based tools were conducted on Ga-soc-MOF-1a. A relatively inexpensive and newly isolated aluminum-based soc-MOF (Al-soc-MOF-1d) was further considered as a cost-effective material for various separation applications. Finally, to expand the applicability of the soc-MOF platform and broaden its scope to cover membrane technology, a pure soc-MOF continuous membrane on a porous alumina support was successfully fabricated for the first time and its performance evaluated for select gas separations.
(126) Adsorption Properties of In.sup.3+, Fe.sup.3+ and Ga.sup.3+ Isostructural Soc-MOFs
(127) Early results based on studies of the parent soc-MOF (In-soc-MOF-1a, based on the indium trimer [In.sub.3O(O.sub.2C—).sub.6] and the ABTC ligand) revealed the impact/importance of the localized charge density in a contracted pore system of approximately 1 nm for enhancing the strength of the interactions between the adsorbed H.sub.2 molecules and the host adsorbent. Therefore, the unique properties of M-soc-MOF-1 were explored, namely, the confined space associated with a localized charge density, on the adsorption of relatively polarizable light hydrocarbons, such as CH.sub.4 and C.sub.2+, and acid gases (CO.sub.2 and H.sub.2S). The apparent surface area and pore volume estimated for the evaluated M-soc-MOF-1, where M=In.sup.3+, Fe.sup.3+, Ga.sup.3+ or Al.sup.3+, are summarized in Table 3. Recognizing the importance of the selected metal center for the chemical stability, adsorption properties, and subsequent practical deployment of the associated MOF, the effects of the metal and counter-anion on the performances of the soc-MOF for ROG- and NG-related separations were investigated. In this context, the single-gas adsorption of various probe molecules, including CH.sub.4, C.sub.2H.sub.6, C.sub.3H.sub.8, C.sub.4H.sub.10 and H.sub.2, was first investigated in detail for the In.sup.3+, Fe.sup.3+ and Ga.sup.3+ analogues (
(128) TABLE-US-00003 TABLE 3 Summary of the assigned naming system denoting the counter-ion present in each of the soc-MOF analogues described herein and their corresponding BET areas and pore volumes Compound BET area Pore volume Abbreviation Counter-ion (m.sup.3/g) cm.sup.3/g In-soc-MOF-1a NO.sub.y 1220 0.50 In-soc-MOF-1b Cl.sup.− 1240 0.50 In-soc-MOF 1c Br.sup.− 1240 0.50 Fe-soc-MOF-1a NO.sub.y 1700 0.69 Fe-soc-MOF-1b Cl.sup.− 1650 0.65 Ga-soc-MOF- 1a NO.sub.y 1350 0.48 Al-soc-MOF-1d OH.sup.− 1500 0.56
(129) Therefore, the impact of the nature of the metal contained in the soc-MOF on the separation performances relevant to ROG and NG upgrading, e.g., C.sub.3H.sub.8 over CH.sub.4 was evaluated. Analyzing of the single-gas adsorption data of C.sub.3H.sub.8 and CH.sub.4 (
(130) TABLE-US-00004 TABLE 4 Comparison of C.sub.3H.sub.8/CH.sub.4 selectivity of soc-MOF adsorbents as compared to best conventional MOFs IAST C.sub.3H.sub.8/CH.sub.4 MOF selectivity at 1 bar Composition 13X 158 5/95 MFM-202a 90 50/50 RE-1,4- NDC- fcu-MOFs 325 5/95 tbo-MOF-2 140 5/95 Ga-soc-MOF-1a 370 5/95 In-soc-MOF-1c 500 5/95 Fe-soc-MOF-1b 800 5/95
(131) Encouraged by the high C.sub.3H.sub.8/CH.sub.4 separation factor, the potential of the soc-MOF platform for C.sub.2+/CH.sub.4 separations was explored. Comparing the C.sub.3H.sub.6 (
(132) TABLE-US-00005 TABLE 5 Polarizability of major common gases containing in NG and ROG Gas Polarizability × 10.sup.25/cm.sup.3 H.sub.2 08.00 N.sub.2 17.40 O.sub.2 15.80 CH.sub.4 25.93 C.sub.2H.sub.6 44.50 C.sub.2H.sub.4 42.50 C.sub.3H.sub.8 64.00 C.sub.3H.sub.6 62.60 n-C.sub.4H.sub.10 82.00
(133) Analyzing the single-gas adsorption data of C.sub.3H.sub.8 and N.sub.2 using the combination of the Toth and IAST models revealed very high C.sub.3H.sub.8/N.sub.2 selectivities (
(134) To better understand the observed C.sub.2+/CH.sub.4 equilibrium selectivity, the heats of adsorption of CH.sub.4, C.sub.3H.sub.8 and n-C.sub.4H.sub.10 were experimentally determined using a thermogravimetry-differential scanning calorimetry (TG-DSC) setup for the Ga-soc-MOF-1a. Interestingly, the C.sub.3H.sub.8 and n-C.sub.4H.sub.10 heats of adsorption were 40.3 and 50.1 kJ/mol, respectively, whereas that of CH.sub.4 was substantially lower and more difficult to quantify using the TG-DSC measurements (26±5 kJ/mol) due to the low uptake of CH.sub.4. The relatively open soc-MOF framework, which has an estimated channel size of 5.2-6.5 Å that favors non-resistant diffusion, suggested that the C.sub.2+ and CH.sub.4 separation was mainly governed by the adsorption equilibrium, which led to relatively strong interactions and uptake of C.sub.2+ compared to CH.sub.4 and, thus, supported the observed selectivity toward C.sub.2+, as exemplified by the C.sub.3H.sub.8/CH.sub.4 gas mixture (
(135) TABLE-US-00006 TABLE 6 Toth parameters for adsorption on soc-MOF analogues Gases Parameters CH.sub.4 C.sub.2H.sub.6 C.sub.3H.sub.8 n-C.sub.4H.sub.10 CO.sub.2 N.sub.2 In-soc-MOF-1a n.sub.s 5.4 4.04 4.2 — 8.23 5.2 K* 0.107 5.7 77.7 — 0.32 0.03 m 1.06 1.01 0.59 — 1.04 0.82 In-soc-MOF-1b n.sub.s 5.9 4.77 4.7 — 9.14 4.99 K* 0.12 3.23 393 — 0.32 0.04 m 1.03 0.99 0.42 — 1.05 1.05 In-soc-MOF-1c ns 5.49 5.04 4.63 — 8.25 4.7 K* 0.13 0.43 599 — 0.43 0.08 m 1.04 1 0.41 — 1 0.79 Fe-soc-MOF-1a n.sub.s 7.65 7.01 6.13 — 11.64 6.35 K* 0.12 2.84 1716 — 0.34 0.043 m 1.02 1.01 0.52 — 1.06 0.967 Fe-soc-MOF-1b n.sub.s 8.33 7.54 6.52 2 12.5 8.43 K* 0.102 2.61 1957 193 0.33 0.03 m 1.06 0.35 0.35 0.55 1.06 0.84 Ga-soc-MOF-1a n.sub.s 6.04 5.99 5 3.99 8.8621 4.71 K* 0.12 4.58 315 3600 0.308 0.09 m 1.003 0.78 0.47 0.33 1.24 0.8 Al-soc-MOF-1d n.sub.s 8 6.34 5.7 4.89 — — K* 0.14 3.37 80.4 1116 — — m 0.92 1.21 0.77 0.61 — — *parameter K has direct relation to the heat of adsorption
(136) The performance of the soc-MOF analogues, which was determined by performing single-gas adsorption and calorimetric studies and making macroscopic mixed-gas predictions for C.sub.2+/CH.sub.4 gas pair systems, was further experimentally confirmed by n-C.sub.4H.sub.10/CH.sub.4 (2/98) mixed-gas adsorption on Fe-soc-MOF-1b and column breakthrough studies.
(137) Microscopic Mechanisms of Separation in Soc-MOFs
(138) Since the treatment of high-spin state (d elements) cations (e.g. Fe.sup.3+) was still much more challenging using quantum calculation, computational work, regarding the separation mechanism, focused on the Ga.sup.3+ (p element) analogue. In this work, Grand canonical Monte Carlo (GCMC) simulations based on the use of a new density functional theory (DFT)-derived guest/Ga(III) force fields (see the SI) were employed to shed light on the equilibrium adsorption mechanism responsible for the high C.sub.2+/CH.sub.4 selectivity. As a preliminary step, these calculations reasonably reproduced the adsorption isotherms for CH.sub.4 and n-C.sub.4H.sub.10 (
(139) Interestingly, the simulation studies predicted that the Ga-soc-MOF-1 would be thermodynamically selective toward n-C.sub.4H.sub.10 over CH.sub.4 at pressures up to 1 bar for a molar mixture composition of n-C.sub.4H.sub.10/CH.sub.4 of 02/98. The GCMC-simulated n-C.sub.4H.sub.10/CH.sub.4 selectivity of 186 at 298 K and 1 bar was slightly lower than that obtained by applying the IAST model (˜300). This deviation was associated with an over-estimation of the simulated CH.sub.4 uptake in the gas mixture because of the possibility that this guest molecule occupied the cages, as shown in
(140) H.sub.2S Removal from ROG and NG Using the Soc-MOF Platform
(141) One of challenging upgrading steps in the treatment of ROG and NG is the handling of H.sub.2S that is generally present in ROG and NG at various compositions ranging from ppm to percentage levels. The removal of H.sub.2S is necessary to avoid poisoning of both the adsorbents used in different processes of the upgrading procedure and the catalyst involved in the subsequent utilization of H.sub.2 and CH.sub.4. The exceptional capabilities of the soc-MOF platform for removing C.sub.2+ from important commodities, such as CH.sub.4, led to exploring the suitability of this MOF platform to effectively remove H.sub.2S. Notably, depending on the compositions of ROG and NG, which dictate the stage at which H.sub.2S must be removed and the nature of the process selected, specific requirements for the separation agents regarding their affinities for H.sub.2S vs. CH.sub.4, C.sub.2+ and CO.sub.2 should be considered.
(142) The investigation of the use of various soc-MOF analogues revealed that the In.sup.3+ and Fe.sup.3+ analogues exhibited low tolerances to H.sub.2S and a loss of crystallinity, as evidenced by the powder X-ray diffraction (PXRD) patterns collected for In-soc-MOF-1a (
(143) Accordingly, single-component H.sub.2S gas adsorption was performed at 298 K on Ga-soc-MOF-1a (
(144) Furthermore, the favorable selectivity toward H.sub.2S and performance stability were confirmed by repetitive column breakthrough tests (the 1st cycle is represented in
(145) Using a CO.sub.2/H.sub.2S/CH.sub.4:5/5/90 mixture at a flow rate of 10 cm.sup.3/min and 25° C. in TSR mode, H.sub.2S and CO.sub.2 were retained in the column for nearly 40 and 5 min, respectively. In contrast, as expected, CH.sub.4 passed through the column almost instantly, reflecting the favorable selectivity for H.sub.2S over CH.sub.4 and CO.sub.2 (H.sub.2S/CH.sub.4 and H.sub.2S/CO.sub.2) (
(146) Heating the adsorption column during the second TSR cycle decreased the retention times to 24 and 3 min/g for H.sub.2S and CO.sub.2, respectively (
(147) Cost Optimization of Soc-MOFs
(148) To reduce the cost of adsorbents, MOFs based on the trinuclear aluminum(III) cluster were deliberately targeted. Importantly, MOFs based on the trinuclear Al(III) cluster [Al.sub.3(μ.sub.3-O)(O.sub.2C—).sub.6], i.e., 6-connected MBBs, are very scarce, and only a few examples have been reported in the literature because of challenges in identifying reaction conditions that allow the in situ formation of the inorganic MBB. After countless attempts, the appropriate reaction conditions, as described herein, that consistently allow the in situ formation of the desired trinuclear aluminum(III) MBB (i.e., [Al.sub.3(μ.sub.3-O)(O.sub.2C—).sub.6]) and, consequently, the aluminum soc-MOF analogue with the following formula: [Al.sub.3O(ABTC)1.5(OH)(H.sub.2O).sub.2], were successfully isolated. In this case, the counter ion was not chloride, as was anticipated, but OH—, as evidenced by energy-dispersive X-ray spectroscopy (EDX) and in situ Fourier transform infrared (FTIR) studies (
(149) Nitrogen (N.sub.2) adsorption measurements at 77 K were conducted on the acetonitrile exchanged samples and generated a fully reversible type-I isotherm representative of porous materials with permanent microporosity (
(150) Soc-MOF Thin-Film Membrane
(151) In adsorption technology, adsorbents are employed in bulk crystal/pellet forms or as particles in a fixed or moving bed column. The application of suitable separation agents as thin films, as in membrane technology, is another promising pathway that could offer many benefits, particularly with regard to enhancing the productivity and reducing the footprint/capital costs. Non-porous or low-porosity polymeric materials have been successfully fabricated as membranes and proven to be easily deployed in many challenging gas separation applications. In contrast, only a limited number of studies have addressed the fabrication of continuous MOF thin films as membranes, although MOF thin films have been reported for many other applications. Given the interesting separation properties of the soc-MOF platform, efforts were dedicated to fabricating soc-MOF based membranes and evaluating their associated properties for gas separations in general and for ROG in particular. As a proof of concept, the crystal intergrowth approach was employed for the film fabrication of the Fe(III) (
(152) The Fe-soc-MOF-1b thin-film membrane was selected as a case study for gas permeation measurements and evaluations of the associated gas transport properties. The permeation results for H.sub.2, O.sub.2, N.sub.2, CH.sub.4, CO.sub.2, C.sub.2H.sub.4, C.sub.2H.sub.6, C.sub.3H.sub.6, C.sub.3H.sub.8 and C.sub.4H.sub.10 on various Fe-soc-MOF-1b membranes were determined to be reproducible. Notably, the permeability decreased as the Leonard-Jones diameter of the molecules increased from H.sub.2 to CH.sub.4. However, as the boiling point of the component increased, as exemplified by C.sub.2H.sub.4, C.sub.2H.sub.6, C.sub.3H.sub.6, C.sub.3H.sub.8 and n-C.sub.4H.sub.10, the permeability increased (
(153) TABLE-US-00007 TABLE 7 Ideal selectivity for different gas mixtures calculated from single gas permeabilities Gas mixture Ideal selectivity H.sub.2/CO.sub.2 4.6 H.sub.2/N.sub.2 3.8 CO.sub.2/CH.sub.4 1.8 C.sub.2H.sub.6/C.sub.2H.sub.4 1.1 C.sub.3H.sub.8/C.sub.3H.sub.6 1.3 C.sub.4H.sub.10/CH.sub.4 2.2
(154) In sum, for the first time, the structure/separation property relationships for a series of isostructural MOFs with soc-topology were elucidated. In.sup.3+-, Fe.sup.3+-, Ga.sup.3+- and Al.sup.3+-based soc-MOFs were extensively studied as adsorbents and thin-film membranes for the separation-based production of high-quality hydrocarbons (CH.sub.4, C.sub.3H.sub.8 and n-C.sub.4H.sub.10) and olefins from H.sub.2S-containing gas streams. The combined features, which are rarely found in a single equilibrium-based separation agent, are necessary to fulfill the strict stability and selectivity requirements for producing high-purity H.sub.2, CH.sub.4 and C.sub.2+ fractions at high rates. All of the soc-MOF analogues were shown to exhibit high selectivity for C.sub.2H.sub.4, C.sub.3H.sub.6 and n-C.sub.4H.sub.10. In particular, the Fe(III), Ga(III) and Al(III) analogues showed relatively enhanced C.sub.2+/CH.sub.4 adsorption selectivities. This finding was confirmed by GCMC simulations performed for the n-C.sub.4H.sub.10/CH.sub.4 mixture, which indicated that the separation was mainly thermodynamically driven. Importantly, the Ga(III) and Al(III) analogues may be preferable given their high tolerance to H.sub.2S. The Ga-soc-MOF-analogue was further examined for the selective adsorption of H.sub.2S in CO.sub.2- and CH.sub.4-containing streams, such as ROG and NG. Furthermore, the successful formation of a soc-MOF-1 separation agent based on abundant and inexpensive aluminum metal was described Subsequently, the possibility of scaling this material at a relatively low cost was thus practical. Additionally, it was determined that the judicious selection of an appropriate intra-framework metal for the construction of the soc-MOF adsorbent was vital for tuning the gas selectivity and tolerance to H.sub.2S, which are prerequisites in various stages of ROG and NG upgrading. Finally, various soc-MOF analogues were deposited on a porous alumina support to produce continuous and defect-free films, and their gas permeation properties were evaluated. Notably, the permeation studies on the soc-MOF films are the first to offer insight into the structure/property relationships for MOF membranes in terms of the observed properties of bulk MOF adsorbents.
(155) TABLE-US-00008 TABLE 8 Crystal datea and refinement conditions of Al-soc-MOF-1d Identification code Al-soc-MOF-1d Empirical formula C.sub.24H.sub.17Al.sub.3N.sub.3O.sub.17.5 Formula weight 708.34 Crystal system, space group Cubic, P
Example 2
Synthesis of Indium-Soc-MOF
(156) In this example, an In-soc-MOF formulated as [In.sub.3O(C.sub.16N2O.sub.8H.sub.6).sub.1.5(H.sub.2O).sub.3](H.sub.2O).sub.3(NO.sub.3) was synthesized by reacting 3,3′,5,5′-azobenzenetetracarboxylic acid and In(NO.sub.3).sub.3.2H.sub.2O in a N,N-dimethylformamide (DMF)/CH.sub.3CN solution in the presence of piperazine. The resulting In-soc-MOF consisted of orange polyhedral crystals. It's structure included indium trimer building blocks, each trimer containing three {InO.sub.5(H.sub.2O)} octahedra sharing one central m3-oxo anions, and networked by six separate 3,3′,5,5′-azobenzenetetracarboxylate ligands. The total solvent-accessible volume for the In-soc-MOF was determined to be 57.2% by summing voxels more than 1.2 Å away from the framework using PLATON software.
(157) Other interesting structural features of the crystalline In-soc-MOF structure are the two types of infinite channels. The first type is hydrophilic, because the water molecules coordinated to the indium centers are pointed inside these channels. Guest water molecules occupy the remaining free volume in these channels and form hydrogen bonds with coordinated water molecules. The second type of channels have a diameter of approximately 1 nm diameter, and are guest-free as-synthesized.
(158) The synthesis methods of this study are generally applicable to similar M-soc-MOFs, including those with lighter trivalent metals.
Example 3
CO.SUB.2 .and H.SUB.2 .Sorption by Gallium-Soc-MOF
(159) This example utilizes use of metal organic frameworks as sorbents for use in simultaneous or subsequent removal of CO.sub.2 and H.sub.2S. The Ga-soc-MOF in question is constructed based on the assembly of Gallium-carboxylate trimer molecular building block (TMBB) and 3,3′,5,5′-azobenzenetetracarboxylate. The oxygen-centered gallium-carboxylate TMBB, [Ga.sub.3O(CO.sub.2).sub.6(H.sub.2O).sub.3] comprises a 6-connected node having trigonal-prismatic geometry networked by 3,3′,5,5′-azobenzenetetracarboxylate tetradentate ligands.
(160)
(161) Other embodiments of the present disclosure are possible. Although the description above contains much specificity, these should not be construed as limiting the scope of the disclosure, but as merely providing illustrations of some of the presently preferred embodiments of this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of this disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form various embodiments. Thus, it is intended that the scope of at least some of the present disclosure should not be limited by the particular disclosed embodiments described above.
(162) Thus the scope of this disclosure should be determined by the appended claims and their legal equivalents. Therefore, it will be appreciated that the scope of the present disclosure fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present disclosure, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims.
(163) The foregoing description of various preferred embodiments of the disclosure have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise embodiments, and obviously many modifications and variations are possible in light of the above teaching. The example embodiments, as described above, were chosen and described in order to best explain the principles of the disclosure and its practical application to thereby enable others skilled in the art to best utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the claims appended hereto
(164) Various examples have been described. These and other examples are within the scope of the following claims.