Zinc methyl-triazolate oxalate metal-organic framework sorbents, synthesis, and use

Abstract

Zinc-containing methyl-triazolate oxalate metal-organic framework (MOF) sorbents, its method of synthesis and use for sorptive gas separation applications.

Description

[0001] ZINC METHYL-TRIAZOLATE OXALATE METAL-ORGANIC FRAMEWORK SORBENTS, SYNTHESIS, AND USE

[0002] Field

[0003] The present invention relates to zinc-containing methyl-triazolate oxalate metal-organic framework sorbents, its method of synthesis and use. More particularly, the present invention relates to a zinc-containing methyl-triazolate oxalate metal-organic framework sorbent with a 3 (or 5)-methyl-triazolate ligand and an oxalate ligand, its method of synthesis and use for gas separation of an acid gas, such as CO2 from a multicomponent gas including, for example, the atmosphere, a flue gas, a process gas, and other gases containing an acid gas.

[0004] Background

[0005] Metal-organic frameworks (herein referred as “MOFs”) are a class of network solids composed of organic spacers linking metal ions or metal ion clusters. These materials are useful because of their high surface area and properties of the complexed metal including an ordered (crystalline) structures permeated by pores. The regularity of these materials allows their structures to be readily characterized by X-ray diffraction techniques. The properties are of particular interest for rapid adsorption of gases. This class of material is proposed for sorbing and separating gasses, for example, separation of an acid gas such as carbon dioxide (herein referred as “CO2”) from a multicomponent gas including, for example, the atmosphere, a combustion or flue gas, a process gas, and other gases containing an acid gas.

[0006] U.S. Patent 9,782,745, issued October 10, 2017 titled “METAL ORGANIC FRAMEWORK, PRODUCTION AND USE THEREOF”, discloses certain Zn MOFs which exhibit high CO2 adsorption capacity with high selectivity for adsorption of CO2 compared to nitrogen and moreover exhibit good thermal stability and good stability to water. The MOF described therein could be subjected to a plurality of adsorption and desorption cycles with near complete reversibility. U.S. Patent 11 ,230,562, issued January 25, 2022 titled “SYNTHESIS OF ZINC MOF MATERIALS”, teaches an improvement on the synthesis technique for preparing the Zn MOF disclosed in US patent 9,782,745.

[0007] Both U.S. Patent 9,782,745 and U.S. Patent 11 ,230,562 disclose a metalorganic framework solid (herein referred as “MOF”) having pores and wherein the framework includes zinc ions, oxalate, and a cycloazocarbyl compound. The cycloazocarbyl compound of the MOF therein is described as at least bidentate, having 2, 3 or 4 nitrogen atoms, typically as part of a 5-membered ring. Examples of cycloazocarbyl compounds described therein include imidazolates, triazolates and tetrazolates, and more particularly 1 ,2,4-triazolate, 1 H-1 ,2,4-triazolate-1-carboxamidine, 3-amino-1 ,2,4-triazolate, imidazolate, 4-fluoroimidazolate, 2-methyl-imidazolate and 1 ,2,3,4-tetrazolate. Of particular interest therein is a Zn (II) material designated CALF- 20, with the chemical formula Zn2Tz20x (where, Tz=1 ,2,4-triazolate, and Ox=oxalate).

[0008] U.S. Patent 9,782,745 exemplifies the synthesis of a particular example within this family of Zn MOF identified as CALF-20 which is performed as a batch process solvothermally in a sealed autoclave at a pressure above ambient pressure. In this procedure, Zn(ll) oxalate and a stoichiometric excess of 1 ,2,4-triazole with respect to both Zn and oxalate is added to water and methanol in a polytetrafluoroethylene (PTFE)-lined autoclave. The mixture is subsequently heated in the sealed autoclave to 180°C for 48 hours (i.e. , at high pressure) and washed with water. The space-time yield for this process is relatively low, of the order of about 40 kg / m3 / h, resulting in a cost of synthesis that is a significant limiting factor for CALF-20 and related MOFs. The reaction can also be carried out in pure methanol or ethanol. Subsequently, it has been found that in some cases, CALF-20 prepared by the autoclave method contains zinc oxide as an impurity as assessed by PXRD (powder X-ray diffraction), that is fully removed by an annealing process comprising two steps of heating to 200°C for 24 hours for each step, with a cooling and washing step in between. This purification step, however, adds additional time and cost to the synthesis of CALF-20.

[0009] U.S. Patent 11 ,230,562 discloses an improvement in the synthesis technique for preparing CALF-20 at reduced temperature and pressure. This method relies on forming a compound of cycloazocarbyl and oxalate or oxalate mixed with an additional chelating ligand prior to adding a zinc salt into the reaction medium. The disclosure also exemplifies the use of a solvent comprised of a small quantity of alcohol plus water in a mixture.

[0010] PCT International Publication WO 2022 / 175927 titled “SYNTHESIS METHOD OF ZINC METAL ORGANIC FRAMEWORK MATERIALS”, teaches an improvement on the synthesis technique disclosed in US Patent 11 ,230,562 for preparing the Zn MOF disclosed in US Patent 9,782,745. This method uses water as a solvent with a reduced reaction time.

[0011] CALF-20 is a desirable sorbent for certain gas separation applications, for example, separation of an acid gas, such as CO2, from a multi-component gas stream where the concentration of the target component is moderate or high, for example, greater than about 15 mole% (hereafter all gas percentages are listed as mole% which is approximately equivalent to volume %), as CALF-20 offers a desirable level of capture or sorption capacity and durability when exposed to water and / or oxygen at elevated temperatures.

[0012] For applications where the concentration of the target component is at a reduced concentration or dilute, for example, less than about 15%, conventional sorbents, for example, amines and KAUST-7, can have a desirable sorptive capacity. However, these sorbents typically are unstable when exposed to water and / or oxygen, resulting in an undesirably low durability over time for a wide range of industrial applications.

[0013] In certain gas separation applications and processes where the multicomponent gas has a dilute concentration of the target component, for example, less than about 40% concentration, with reduced levels of moisture, for example, less than about 5% relative humidity (herein referred to as “RH”), and where the sorbent is at least periodical exposed to steam, oxygen, contaminants (for example, SOx and NOx), and elevated temperatures (for example, 80°C to 120°C), during the gas separation process, conventional sorbents have a limited sorptive capacity and durability. Example applications include but are not limited to gas separation of CO2 from a flue or combustion gas stream produced by a combustor using a fossil fuel, such as a natural gas combined cycle (NGCC) application which can produce a flue gas stream with about 3-5% CO2 concentration or up to about 10% CO2 concentration with exhaust gas recirculation". Under certain gas separation conditions including those described above, there is a requirement for a sorbent with a desirable sorptive capacity and durability which overcomes the restrictions of the prior art. A method of synthesis of the sorbent is also required.

[0014] Summary

[0015] A methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent comprising an oxalate ligand, a methyl-triazolate ligand, a triazolate ligand, and a metal ion wherein the metal ion is zinc is disclosed herein.

[0016] In a broad aspect, a method of preparing a methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent comprises:

[0017] (a) adding a plurality of reactants and a solvent together, wherein the plurality of reactants comprises a (methyl) triazole / triazolate; a triazole or a salt format of an alkaline metal triazolate, or zinc triazolate; oxalic acid, or salt format alkalate metal oxalate, or zinc oxalate; if the triazolate or oxalate does not contain zinc, a zinc carbonate, a zinc oxide, or a zinc salt of acetate to form a reactant mixture;

[0018] (b) agitating the reactant mixture at a desired raised temperature; and

[0019] (c) forming a slurry of the reactant mixture.

[0020] In another broad aspect, a sorptive process for separating a multicomponent gas, said multi-component gas comprising at least a first component and a second component, comprises:

[0021] (a) providing a contactor comprising the methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent;

[0022] (b) admitting the multi-component gas as a feed stream into the contactor, sorbing at least a portion of the first component on and / or in the MTz-MOF sorbent, producing a first product stream depleted in the first component relative to the feed stream, and recovering the first product stream from the contactor; and

[0023] (c) desorbing at least a portion of the first component sorbed in and / or onto the MTz-MOF sorbent, producing a second product stream enriched in the first component relative to the feed stream, and recovering the second product stream from the contactor.

[0024] Brief Description of the Drawings

[0025] Figure 1 is a process flow diagram of an embodiment of the present invention, illustrating a sorptive process for separating a first component from a multicomponent gas using a contactor having a methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent, wherein the sorptive process employs a first regenerating step;

[0026] Figure 2 is a process flow diagram of an embodiment of the present invention, illustrating a sorptive process for separating a first component from a multicomponent gas using a contactor with a methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent, wherein the sorptive process is similar to the sorptive process in Fig. 1 , but employs an additional step such as second regenerating step; and

[0027] Figure 3 is a column chart illustrating carbon dioxide sorption capacities of various zinc methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbents (SMOF-8, SMOF-9, and SMOF-16) compared to a CALF-20 sorbent, at a concentration of 4% CO2, a temperature of 50°C, and at 0%, 10% and 20% relative humidities, the carbon dioxide sorption capacities were measured by dynamic vapor sorption (DVS).

[0028] Description

[0029] Definitions

[0030] CO2: carbon dioxide

[0031] MOF: metal-organic framework

[0032] SMOF: Svante metal-organic framework

[0033] Triazolate: 1 ,2,4-triazolate

[0034] MTz: methyl-triazolate, 3-methyl-triazolate, or 5-methyl-triazolate, 3(or 5)- methyl-1 ,2,4-triazolate

[0035] Methyl-ligand: can be a 3-methyl-triazolate ligand, a 5-methyl-triazolate ligand, a 3(or 5)-methyl-1 ,2,4-triazolate ligand, or a 3(or 5)-methyl-1 ,2,4- triazolate ligand 3(or 5)-methyl: 3-methyl or 5-methyl

[0036] 3(or 5)-methyl-triazolate: 3-methyl-triazolate or 5-methyl-triazolate

[0037] Ox: oxalate or oxalic acid

[0038] MTz-MOF: methyl-triazolate oxalate metal-organic framework

[0039] NOx: nitrogen oxides (e.g. NO, NO2, NO3)

[0040] SOx: sulfur oxides (e.g. SO2, SO3)

[0041] RH: relative humidity

[0042] Zn: zinc kg / m3 / d: kilogram per cubic meter per day, or kilogram per cubic metre per day

[0043] %: Mol% (or volume%) unless otherwise stated

[0044] As disclosed below, embodiments of a methyl-triazolate oxalate metalorganic framework (MTz-MOF) sorbents with a methyl triazolate ligand, an oxalate ligand, and zinc as a metal ion, and its method of synthesis and use are disclosed herein. The MTz-MOF sorbents can be used for but are not limited to gas separation of a target component, for example, an acid gas such as CO2, from a multi-component gas including, for example, the atmosphere, a flue gas, a process gas, and other gases containing an acid gas.

[0045] Methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbents

[0046] In embodiments, a methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent comprises a methyl-triazolate ligand and an oxalate ligand, and Zinc as a metal ion. In further embodiments, a MTz-MOF sorbent comprise a methyl- triazolate ligand and an oxalate ligand, where the methyl-triazolate ligand is 3 (or 5)- methyl and triazolate is or 1 ,2,4-triazolate, and the metal ion is zinc. In one aspect the MTz-MOF sorbents are zinc 3 (or 5)-methyl-1 ,2,4-triazolate oxalates.

[0047] In embodiments, the MTz-MOF sorbent comprise zinc as a metal ion, an oxalate ligand with a methyl-triazolate ligand, and a triazolate ligand, where the molar ratio of the methyl-triazolate ligand is equal to or less than about 99.5% and / or the triazolate ligand is equal to or greater than about 0.5%; the methyl-triazolate ligand is equal to or less than about 95% and / or the triazolate ligand is equal to or greater than about 5%; the methyl-triazolate ligand is equal to or less than about 90% and / or the triazolate ligand is equal to or greater than about 10%; the methyl-triazolate ligand is equal to or less than about 80% and / or the triazolate ligand is equal to or greater than about 20%; or the methyl-triazolate ligand is equal to or less than about 75% and / or the triazolate ligand is equal to or greater than about 25%.

[0048] In embodiments, the MTz-MOF sorbent comprise zinc as a metal ion and an oxalate ligand, a 3 (or 5)-methyl-triazolate ligand and a 1 ,2,4-triazolate ligand, where the molar ratio of the 3 (or 5)-methyl-triazolate ligand is equal to or less than about 99.5% and / or the 1 ,2,4-triazolate ligand is equal to or greater than about 0.5%; the 3(or 5)-methyl-triazolate ligand is equal to or less than about 95% and / or 1 ,2,4-triazolate ligand is equal to or greater than about 5%; the 3 (or 5)-methyl-triazolate ligand is equal to or less than about 90% and / or the 1 ,2,4-triazolate ligand is equal to or greater than about 10%; the 3 (or 5)-methyl-triazolate ligand is equal to or less than about 80% and / or the 1 ,2,4-triazolate ligand is equal to or greater than about 20%; or the 3 (or 5)- methyl-triazolate ligand is equal to or less than about 75% and / or the 1 ,2,4-triazolate ligand is equal to or greater than about 25%.

[0049] In further embodiments, the MTz-MOF sorbent comprises zinc as a metal ion, an oxalate ligand, a 3 (or 5)-methyl-1 ,2,4-triazolate ligand and a 1 ,2,4-triazolate ligand, where the molar ratio of the 3 (or 5)-methyl-1 ,2,4-triazolate ligand is equal to or less than about 99.5% and / or the 1 ,2,4-triazolate ligand is equal to or greater than about 0.5%; the 3 (or 5)-methyl-1 ,2,4-triazolate ligand is equal to or less than about 90% and / or the 1 ,2,4-triazolate ligand is equal to or greater than about 10%; the 3 (or 5)- methyl-1 ,2,4-triazolate ligand is equal to or less than about 80% and / or the 1 ,2,4- triazolate ligand is equal to or greater than about 20%; or the 3 (or 5)-methyl-1 ,2,4- triazolate ligand is equal to or less than about 75% and / or the 1 ,2,4-triazolate ligand is equal to or greater than about 25%.

[0050] A methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent with zinc as a metal ion offers the advantages of increasing the hydrophobicity and water stability relative to conventional sorbents. In applications and conditions where the multi-component gas exhibits a low RH, for example, less than about 5% RH, and a concentration of a target component in the multicomponent gas is at a reduced or dilute concentration, for example, less than about 15% concentration, the MTz-MOF sorbent having zinc as a metal ion, an oxalate ligand and at least one of a methyl-triazolate ligand and a triazolate ligand; a 3 (or 5)-methyl-1 ,2,4-triazolate ligand and a 1 ,2,4- triazolate ligand; or a 3 (or 5)-methyl-1 ,2,4-triazolate ligand, offers the advantages relative to conventional sorbents including a greater capture or sorptive capacity for the target component while maintaining a desirable stability and durability when exposed to water, oxygen, hot air (for example, between about 80°C - 150°C), and contaminants, for example, NOXand SOX.

[0051] Synthesis methods of methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbents

[0052] In synthesis embodiments, synthesis methods of the methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent having Zinc as a metal ion as described above, the synthesis method comprises:

[0053] 1 . Preparing a reactant mixture by dosing or adding a plurality of reactants and a solvent together in solution, wherein the plurality of reactants comprises (methyl) triazole / triazolate; triazole, a salt format of an alkaline metal triazolate, or zinc triazolate; oxalic acid, salt format of an alkaline metal, or zinc oxalate; if the triazolate or oxalate does not contain zinc, a zinc carbonate, a zinc oxide, or a zinc salt of acetate need to be added. In one aspect, the molar ratio of triazole / oxalic / zinc is 2 / 1 / 1 . In a preferred embodiment, the solvent consists substantially water or is water, for example, deionized water, demineralized water, distilled water, or other suitable water. In alternative embodiments, the solvent can be organic or alcohol based, and optionally combined with water. In particular embodiments, the reactant mixture has an equivalent ratio of MTz / (MTz + Tz) equal to or greater than about 5%, equal to or greater than about 10%, equal to or greater than about 20%, equal to or greater than about 20%, equal to or greater than about 30%, equal to or greater than about 40%, equal to or greater than about 50%, equal to or greater than about 60%, equal to or greater than about 70%, equal to or greater than about 75%, or equal to or greater than about 80%, equal to or greater than about 90%, or equal to or greater than about 99.5%. Dosing or adding the plurality of reactants and the solvent can be performed in a random sequence, in a predetermined sequence, or other suitable sequence. Preparation of the reactant mixture can be performed at a temperature equal to room or ambient temperature or not greater than about 50°C, and preferably at a pressure of about atmospheric pressure.

[0054] 2. Raising a temperature of the reactant mixture to a raised temperature such as a temperature in a range between about 20°C and the temperature at which the reactant mixture boils, for example, about 100°C, at about atmosphere pressure or preferably at atmospheric pressure.

[0055] 3. Agitating the reactant mixture at a raised temperature for a period of time, for example, equal to or greater than about 0.5 hours, equal to or greater than about 1 hour, equal to or greater than about 2 hours, or equal to or greater than about 3 hours to affect the construction of MTz-MOFs, and subsequently terminating of the agitation and / or reactions of the reactant mixture.

[0056] 4. Forming a slurry of the reactant mixture.

[0057] In aspects, the synthesis method further includes producing the MTz-MOF sorbent at a space-time-yield (STY) equal to or greater than about 500 kg / m3 / d.

[0058] In further embodiments, the above steps 2 and 3 can be performed substantially concurrently or sequentially. For example, the step of agitating the reactant mixture can occur concurrently with the step of raising the temperature of the reactant mixture, the step of raising the temperature of the reactant mixture is followed by the step of agitating the reactant mixture, or the step of agitating the reactant mixture is followed by the step of raising the temperature of the reactant mixture. The agitating of the reactant mixture can be performed at a raised temperature such as a temperature in a range between about 20°C and a temperature at which the reactant mixture boils, for example, at about 100°C, or in a range between about 50°C and a temperature at which the reactant mixture boils, for example, about 100°C. In one aspect, the steps of raising the temperature of the reactant mixture and / or agitating the reacting mixture can be performed for a period in time and the steps terminated after measuring and / or determining a change in sorptive capacity of a latest sample of the slurry is equal to or less than about 10%, equal to or less than about 5%, equal to or less than about 2%, than a sorptive capacity of a previous sample of the slurry.

[0059] In other embodiments of the synthesis method, after the step of forming a slurry, the synthesis method can further comprise forming a supported sorbent or an unsupported sorbent from the slurry; or forming a powder by at least one of filtering and drying of the slurry, and forming a supported sorbent or an unsupported sorbent from the powder. The MTz-MOF sorbent can be incorporated into macroscopic sorption structures such as laminated sheets on woven or non-woven substrates and passages in a monolith or other suitable structure, and which are capable of large scale capture of acid gasses such as CO2 from flue gases, process gasses, or from the ambient atmosphere.

[0060] The synthesis methods of the MTz-MOF sorbent with Zinc as a metal ion as described herein offers the advantages of an environmentally friendly synthesis process by producing the sorbent without the use of organic or alcohol based solvents (and associated disadvantages of using hazardous and toxic solvents, for example, added complexity and associated costs from handling, processing and disposal; producing the sorbent at a high space-time-yield, and enabling the use of zinc oxide as a reactant and a zinc source.

[0061] Methods of use of methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbents

[0062] The methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent having zinc as a metal ion, an oxalate ligand a methyl-triazolate ligand and a triazolate ligand disclosed herein and its resulting sorption properties can be used for the purpose of separating a first component, for example, an acid gas component such as carbon dioxide, from a multi-component gas stream, for example, the atmosphere, a flue gas, a process gas, and other gases containing an acid gas. The MTz-MOF sorbent can be used for industrial or utility deleterious effluent reduction and to provide a concentrated stream of the first component, for example, CO2, that can be further utilized for sequestration or other industrial usage.

[0063] In embodiments, a gas separator and / or a contactor of the present invention can be used in a sorptive process for separating a first component, for example, an acid gas component such as carbon dioxide from a multi-component gas stream. Embodiments of the gas separator and / or contractor can be provided where the contactor comprises the MTz-MOF sorbent with zinc as a metal ion disclosed herein. In one aspect, the contactor can be a parallel passage contactor, a monolithic contactor with passages for gas flow into the sorbent, or a packed-bed contactor.

[0064] In a process embodiment, a sorptive process for sorptive gas separation of a multi-component gas or stream comprising at least a first component, for example, an acid gas component such as carbon dioxide is provided. In one such embodiment, the sorptive process can separate at least a portion of the first component from the multi-component fluid gas or stream.

[0065] Fig. 1 illustrates a process embodiment, showing a sorptive process 10 for separation of a multi-component fluid gas or stream comprising at least a first component, for example, an acid gas component such as carbon dioxide, and at least one of a second component, for example, nitrogen, a third component, for example, water, and a fourth component, for example, oxygen. Sorptive process 10 comprise the steps of a providing step 12, a sorbing step 20 and a first regenerating step 30, where sorbing step 20 and a first regenerating step 30 can be repeated sequentially until sorptive process 10 is terminated.

[0066] Providing step 12, comprises providing a gas separator and / or contractor where the contactor comprising a MTz-MOF sorbent with Zinc as a metal ion disclosed herein. In one aspect, the contactor is a parallel passage contactor or a packed-bed contactor.

[0067] Sorbing step 20, comprise admitting a multi-component gas or stream, containing at least a first component, for example, an acid gas component such as carbon dioxide, and a second component, as a feed stream into the gas separator and / or the contactor; flowing the feed stream through the contactor and contacting the feed stream with the MTz-MOF sorbent; sorbing at least a portion of the first component of the feed stream in and / or onto the MTz-MOF sorbent, separating the first component from the feed stream, and forming a first product stream at least partially depleted in the first component relative to the feed stream; and recovering the first product stream from the contactor and / or gas separator. Although not specifically shown, the remaining components that are not sorbed in and / or onto the MTz-MOF sorbent, for example, the second component such as nitrogen, can substantially flow through the contactor and exit the contactor and gas separator as the first product stream. In embodiments, a concentration of the first component in the feed stream is equal to or less than about 50% concentration, equal to or less than about 15% concentration, equal to or less than about 10% concentration, or equal to or less than about 5% concentration; and a relative humidity of the feed stream is equal to or less than about 10% RH, or equal to or less than about 5% RH.

[0068] In applications and processes where the multicomponent gas or feed stream have a low or dilute concentration of the first component, for example, equal to or less than about 15% concentration and a low relative humidity, for example, equal to or less than about 10% RH, a gas separator with and employing the MTz-MOF sorbent with Zinc as a metal ion offers the advantages of a high sorption or sorptive capacity for the target or first component, with a high stability and durability when exposed to water, oxygen, hot air (for example, between about 80°C - 150°C), and flue gas contaminants, for example, NOx and SOx, relative to conventional sorbents.

[0069] First regenerating step 30, comprises desorbing at least a portion of the first component sorbed in and / or onto the MTz-MOF sorbent, by at least one of a temperature swing mechanism, a pressure swing mechanism, and a partial pressure swing mechanism; forming a second product stream at least partially enriched in the first component relative to the feed stream, and recovering the second product stream from the contactor and / or gas separator.

[0070] In optional embodiments, first regenerating step 30 optionally comprises admitting a first regeneration stream (such as steam) into the gas separator and / or contactor for contacting the MTz-MOF sorbent as the first regeneration stream flows through the contactor; desorbing the first component sorbed in and / or onto the MTz- MOF sorbent; forming a second product stream at least partially enriched in the first component relative to the feed stream; and recovering the second product stream from the contactor and / or gas separator. Heat from the first regenerating stream and / or at least a portion of the first regeneration stream (such as water from the steam) can sorb in and / or onto the MTz-MOF sorbent, assisting in desorbing the first component sorbed in and / or onto the MTz-MOF sorbent.

[0071] In Fig. 1 , sorbing step 20 and a first regenerating step 30 can be repeated sequentially until sorptive process 10 is terminated.

[0072] In alternative embodiments, a pressure swing sorptive process can be employed where sorbing step 20 is performed at an elevated pressure above atmospheric pressure, for example, greater than about 3 bar absolute, greater than about 5 bar absolute, or greater than about 10 bar absolute, and first regenerating step 30 is performed by reducing the pressure to a pressure less than the elevated pressure during sorbing step 20.

[0073] Fig. 2 illustrates a process embodiment, with a sorptive process 11 for separation of a multi-component fluid gas or stream comprising at least a first component, for example, an acid gas component such as carbon dioxide, and a second component. Sorptive process 11 comprises the steps of providing step 12, sorbing step 20 and first regenerating step 30, as shown in Fig. 1 . However, sorptive process 11 further comprise a second regenerating step 40, and sorbing step 20, first regenerating step 30 and second regenerating step 40 can be repeated sequentially until the sorptive process 11 is terminated.

[0074] During an optional second regenerating step 40, the water component sorbed in and / or onto the MTz-MOF sorbent can be desorbed from the MTz-MOF sorbent by admitting a second regeneration stream, such as a gas stream with a low partial pressure of water, or a relative humidity less than a relative humidity within the contactor. In embodiments, desorption of the water component sorbed in and / or on the MTz-MOF sorbent can be performed or assisted by applying a vacuum and reducing a pressure within the contactor to a pressure below a saturation pressure of the steam within the contactor. Components desorbed from the MTz-MOF sorbents during the second regenerating step 40, can form a third product stream which can be recovered from the contactor.

[0075] Additional optional subsequent steps (not shown in Figs. 1 and 2) can follow, for example, a cooling step where a temperature of the MTz-MOF sorbent can be reduced prior to repeating the sorbing step 20. The cycle of sorbing step 20, first regenerating step 730, and optional second regenerating step 40 (and optional subsequent steps) can be repeated as desired.

[0076] Synthesis Example 1 : SMOF-9

[0077] Preparation of the reactant mixture was performed in a 250 mL 3-neck- round-bottom flask equipped with over-head stirrer, thermocouple, condenser and heating mantle, and charged with oxalic acid dihydrate 15.84 g (0.125 mol), 1 ,2,4- triazole 8.73 g (0.125 mol) and MTZ 10.6 g (0.125 mol) and deionized (herein referred as “DI”) water 90 g at atmospheric pressure and at room temperature or about 20°C. Mixing of the reactant mixture was conducted for 1 .5 h at 150 rpm, followed by adding 28.2 g (0.25 mol) of basic zinc carbonate in portions during a 7 minute period. The reactant mixture was heated to about 100°C and the temperature was kept steady for about 5 hours. Occasionally, water was sprinkled in the flask to rinse down any solids on the wall of the flask. A slurry was recovered from the flask prior to separating solids from the slurry by suction filtration. The solids were then washed with DI water until the solids or filtrate reached a conductivity of less than 100 microsiemens / cm. Powder was collected and dried in a convection oven at 110°C overnight. The yield of the product was more than 95% where the loss was mainly due to handling losses from static charge.

[0078] Synthesis Example 2: SMOF-16

[0079] Preparation of the reactant mixture was performed in a 250 mL 3-neck- round-bottom flask equipped with an over-head stirrer, thermocouple, condenser and heating mantle, and charged with 15.84 g (0.125 mol) of oxalic acid dihydrate, 4.365 g(0.0625 mol) of 1 ,2,4-triazole, 15.9 g (0.1875 mol) of MTZ, and 50 g of DI water at atmospheric pressure and at room temperature or about 20°C. Mixing of the reactant mixture was conducted for 30 min at 150 rpm, 28.2 g (0.25 mol) of zinc carbonate basic was added in portions over a 30 min. period. The reactant mixture was heated to about 100°C and maintained at that temperature for about 7 hours. Occasionally, water was sprinkled in the flask to rinse down any solids on the wall of the flask. A slurry was recovered from the flask prior to separating solids from the slurry by suction filtration. The solids were washed with DI water until the solids or filtrate reached a conductivity of less than 100 microsiemens / cm. Powder was collected and dried in a convection oven at 110°C overnight. The yield of the product was more than 95%.

[0080] Comparative Synthesis Example 3: SMOF-8 HT (HT=high temperature)

[0081] Preparation of the reactant mixture was performed in a 100 ml PTFE flask with a PTFE-covered magnetic stir bar in an autoclave and 17 g DI water and 17 g of methanol was added followed by 7.62 g (0.06 mol) of oxalic acid dihydrate and 10.088 g (0.12 mol) of 3-methyl-1 ,2,4-triazole (MTz), each in a single dose. After the reactant mixture was mixed for about 90 mins, at 250 rpm, 13.435 g (0.12 mol) of basic zinc carbonate salt was added in portions over the reaction period of about 90 mins. The slurry in the autoclave was diluted with 18 ml mixed solvent of water and methanol with a molar ratio of 1 / 1 and mixed for an additional 90 mins. The flask was sealed and placed into programmable-oven and heated to 180°C for 48 h, before slowly cooling, for example, about 8 to 12 hours, to room temperature. The slurry was recovered from the flask prior to separating the solids from the slurry by suction filtration. The solids were washed with DI water until the conductivity of the solids or filtrate was less than 100 microsiemens / cm. Powder was collected and dried in a convection oven at 110°C overnight. The yield of the reactant mixture was more than 95%, where the loss was mainly due to handling losses from static charge.

[0082] Molar ratios of 3-methyl-1 ,2,4-triazole to 1 ,2,4-triazole of the example MTz-MOF sorbents described above are shown in Table 1 below.

[0083] Table 1 Nomination of CALF-20 and methyl-triazolate oxalate metal-organic frameworks (MTz-MOFs) Fig. 3 is a column chart illustrating carbon dioxide sorption capacities of various zinc methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbents (SMOF-8, SMOF-9, and SMOF-16) compared to the CALF-20 sorbent, at a concentration of 4% CO2, a temperature of 50°C, and at 0%, 10% and 20% relative humidity’s. The x-axis shows sorptive capacity for CO2 in weight%, where weight% = (mass of sorbed gas / mass of sorbent) x 100. The carbon dioxide sorption capacities were measured by dynamic vapor sorption (DVS). For the SMOF-8, SMOF-9, SMOF- 16, and CALF-20 sorbents, their respective CO2 sorptive capacity increased as the relative humidity decreased from 20% to 10% to 0%. SMOF-16 with 75% 3-methyl- 1 ,2,4-triazolate ligands and 25% 1 ,2,4-triazolate ligands, exhibits a greater sorptive capacity for CO2 sorption than SMOF-8 and CALF-20 at 0% RH, while SMOF-8 with 100% 3-methyl-1 ,2,4-triazolate ligands and 0% 1 ,2,4-triazolate ligands, exhibits a greater sorptive capacity for CO2 than CALF-20 at 0% RH.

Claims

WHAT IS CLAIMED IS:1 . A methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent comprising an oxalate ligand, a methyl-triazolate ligand, a triazolate ligand, and a metal ion wherein the metal ion is Zinc.

2. The MTz-MOF sorbent of claim 1 , further comprising a molar ratio of the methyl-triazolate ligand is equal to or less than 99.5% and / or the triazolate ligand is equal to or greater than 0.5%.

3. The MTz-MOF sorbent of claim 1 , wherein the methyl-triazolate ligand is 3(or 5)-methyl-triazolate, and the triazolate is 1 ,2,4-triazolate.

4. The MTz-MOF sorbent of claim 3, further comprising a molar ratio of the 3 (or 5)-methyl-triazolate ligand is equal to or less than 99.5% and / or the 1 ,2,4- triazolate ligand is equal to or greater than 0.5%.

5. The MTz-MOF sorbent of claim 1 , wherein the MTz-MOF sorbent is Zinc 3 (or 5)-methyl-1 ,2,4-triazolate oxalates.

6. The MTz-MOF sorbent of claim 5, further comprising a molar ratio of the 3 (or 5)-methyl-1 ,2,4-triazolate ligand is equal to or less than 99.5% and / or the1 ,2,4-triazolate ligand is equal to or greater than 0.5%.

7. A method of preparing the methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent of any one of claims 1 to 6, the method comprising:(a) adding a plurality of reactants and a solvent together, wherein the plurality of reactants comprises a (methyl) triazole / triazolate; a triazole or a salt format of an alkaline metal triazolate, or zinc triazolate; oxalic acid, or salt format alkalate metal oxalate, or zinc oxalate; if the triazolate or oxalate does not contain zinc, a zinc carbonate, a zinc oxide, or a zinc salt of acetate to form a reactant mixture;(b) agitating the reactant mixture at a raised temperature, and(c) forming a slurry of the reactant mixture.

8. The method of claim 7, wherein the raised temperature is in a range between 20°C and a boiling temperature of the reactant mixture.

9. The method of claims 7 or 8, wherein the molar ratio of triazole:oxalic:zinc is 2:1 :1 .

10. The method of any one of claims 7 to 9, wherein the solvent is water.11 . The method of any one of claims 7 to 10, further comprising agitating the reactant mixture for a period between 0.5 hours to 12 hours.

12. The method of any one of claims 7 to 11 , further comprising adding the reactants and the solvent, and agitating the reactant mixture together, at atmospheric pressure.

13. The method of any one of claims 7 to 12, further comprising forming a powder.

14. The method of any one of claims 7 to 13, further comprising forming a supported sorbent or an unsupported sorbent.

15. A sorptive process for separating a multi-component gas, said multi-component gas comprising at least a first component and a second component, the process comprising:(a) providing a contactor comprising the methyl-triazolate oxalate metal-organic framework (MTz-MOF) sorbent of any one of claims 1 to 14;(b) admitting the multi-component gas as a feed stream into the contactor, sorbing at least a portion of the first component on and / or in the MTz-MOF sorbent, producing a first product stream depleted in the first component relative to the feed stream, and recovering the first product stream from the contactor, and(c) desorbing at least a portion of the first component sorbed in and / or onto the MTz-MOF sorbent, producing a second product stream enriched in the first component relative to the feed stream, and recovering the second product stream from the contactor.

16. The process of claim 15, wherein a concentration of the first component in the feed stream is equal to or less than 50% concentration.

17. The process of claim 15 or 16, wherein a relative humidity of the feed stream is equal to or less than 10% relative humidity.

18. The process of any one of claims 15 to 17, wherein the first component is at least one of an acid gas and carbon dioxide.

19. The process of any one of claims 15 to 18, wherein the second component is nitrogen.

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