Synthesis method and recycling method of metal organic structures

Abstract

The present specification provides a novel method for synthesizing metal-organic framework systems by vapor-phase addition of multiple ligands attached to a metal-organic framework, and a method for recycling metal-organic framework systems by stripping the ligands and re-adding the same ligands or adding different ligands to the metal-organic framework to provide a recycled or reused metal-organic framework system.

Description

Technical Field

[0001] [Cross - Reference to Related Applications] This application claims the priority and benefit of U.S. Provisional Application No. 62 / 706,389, filed on Aug. 13, 2020, the disclosure of which is incorporated herein by reference in its entirety. Background of the Invention

[0002] The present invention relates to a carbon dioxide absorbent including a metal - organic framework system, and more particularly, to a metal - organic framework system based on the MOF - 274 metal - organic framework having a diamine - appended ligand, and a method for manufacturing and recycling the same.

[0003] Amine - appended metal - organic frameworks based on the metal - organic framework MOF - 274 are promising candidates for the selective recovery of CO2 from exhaust gases. Conventionally, this material has been formed by dispersing a nascent metal - organic framework in an amine - containing non - coordinating solvent and then repeating the washing. Although various amines have been demonstrated, when quaternary amines are included, additional heating is required after addition to liberate excess amines and generate the desired loading. When successfully functionalized, these amine - appended metal - organic frameworks exhibit a unique V - type isotherm for CO2 and bind selectively over N2 or O2.

[0004] The conjugation of MOF - 274 containing salicylate cross - linked with an ethylenediimine core has the same properties as the MOF - 274 metal - organic framework and also has the ability to add amines to the backbone. Such an absorber material with added amines is useful for capturing CO2 from a stream containing carbon dioxide with high capacity and a V - type isotherm. Solvents with high boiling points or higher polarities such as diisopropylbenzene and butanol have also been used, but as a result, the crystallinity is dramatically reduced.

[0005] Furthermore, when the amine-added MOF is circulated, amine loss progresses over time, and the material is inactivated for the desired separation. In certain systems, when the metal-organic structure is contacted with vapor to desorb the bound CO2, the amine loss is accelerated. Additionally, some metal-organic structures in the MOF-274 family have low stability and decompose when exposed to a solvent, preventing successful amine addition and hindering their use for subsequent CO2 capture.

[0006] Furthermore, in CO2 capture applications, the metal-organic structure MOF-274 functionalized with diamine exhibits a desirable Type V isotherm. However, by installing different diamines, the properties of the adsorbent change, such as imparting vapor stability and changing the CO2 partial pressure / temperature required for CO2 adsorption. Due to this versatility, diamine-added MOF-274 metal-organic structures have the potential to be utilized for CO2 capture from various streams. However, once the selected amine is added to the metal-organic structure MOF-274, in the current paradigm, the material will remain in that specific form during its service life.

[0007] Little attention has been paid to recycling used diamine-added MOF-274 metal-organic structure systems or intentionally removing amines from metal-organic structure systems to fill with different diamines to achieve different performances. Additionally, when new and advantageous diamine-added MOF-274 metal-organic structure systems are discovered, the ability to upgrade the adsorbent system through the installation of new diamines eliminates de novo MOF synthesis and minimizes costs, waste, and adsorbent downtime.

[0008] Therefore, there is a need for a method of synthesizing new or existing metal-organic structures that can be circulated without amine loss over a long period of time and / or recycled and / or reused with different amines for use under the same or different CO2 capture conditions. SUMMARY OF THE INVENTION

[0009] This specification provides a method for synthesizing a metal-organic framework system comprising a metal-organic framework and a plurality of ligands added to the metal-organic framework in the gas phase. Also provided is a method for recycling and reusing the metal-organic framework system. The metal-organic framework has a plurality of one or more different metal elements and a plurality of linkers. Each of the plurality of one or more different metal elements is crosslinked by one or more of the plurality of linkers to form open metal sites. In one aspect, the metal-organic framework system comprises a diamine added to the open metal sites of the metal-organic framework. In one aspect, the plurality of one or more different metal elements comprises magnesium, zinc, nickel, copper, and / or combinations thereof. In one aspect, the different metal element is Mg. In one aspect, the plurality of ligands are amines or alcohols.

[0010] The method of the present invention comprises the following steps: (a) providing a metal-organic framework comprising at least one open metal site; and (b) adding a ligand to the metal-organic framework in the gas phase at the open metal site to form a metal-organic framework system.

[0011] Further provided herein is a method for manufacturing a metal-organic framework system, comprising the following steps: (a) manufacturing a metal-organic framework; (b) evaporating a plurality of ligands to generate a gas phase; and (c) in the gas phase, binding at least one of the plurality of ligands to at least one of the open metal sites of the metal-organic framework to form a metal-organic framework system. The metal-organic framework comprises a plurality of open metal sites, where a linker bridges at least one of the plurality of open metal sites to another. In another aspect, the method can further comprise suspending the metal-organic framework in a solvent. In one aspect, the method can further comprise filtering the solvent from the metal-organic framework. In one aspect, the method can further comprise a plurality of ligands heated to form a gas phase. In one aspect, the method can further comprise reducing the pressure such that the plurality of ligands form a gas phase. In one aspect, the method can further comprise an inert gas passing through the gas phase.

[0012] The novel method of the present invention forms a plurality of open metal sites added in the gas phase with 2-aminomethylpiperidine and / or N,N-dimethylethylenediamine Ethynediimine bis(salicylic acid) and can generate a novel metal-organic framework system comprising a metal-organic framework having metal ions bound together. Thus, a novel metal-organic framework system comprising a magnesium variant of the MOF-274 metal-organic framework with 2-aminomethylpiperidine and / or N,N-dimethylethylenediamine added is provided.

[0013] Further provided herein is a method for recycling or reusing a metal-organic framework system, comprising the following steps: (a) detaching a plurality of first additional ligands from the metal-organic framework system such that the structure of the metal-organic framework remains intact (either intact or) providing a remaining metal-organic framework; and (b) adding at least one of a plurality of second additional ligands to the metal-organic framework to generate a recycled metal-organic framework system. In certain aspects, the recycling method further includes sequentially immersing the metal-organic framework system and the metal-organic framework to provide a recycled metal-organic framework system. In certain aspects, these methods further include washing the metal-organic framework system in a solvent to remove a plurality of first additional ligands. In certain aspects, these methods further include adding at least one of a plurality of second additional ligands to the metal-organic framework in the gas phase. In certain aspects, the plurality of first additional ligands are used diamine additional ligands. In certain aspects, the plurality of second additional ligands are recycled from the plurality of first additional ligands. In certain aspects, the plurality of first attachment ligands are different from the plurality of second additional ligands.

[0014] In certain aspects, the linker is a polydentate organic ligand that includes a first binding site and a second binding site that are crosslinked together with a third binding site. In certain aspects, the first binding site and the second binding site of the polydentate organic ligand each include a salicylate moiety, and the third binding site includes a diamine moiety. In certain aspects, the polydentate organic linker is 5,5'-(((1E,2E)-ethane-1,2-diylidene)bis-(azanediylidene))bis(2-hydroxybenzoic acid). BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figures 1A and 1B are isotherms of the metal-organic framework of Example 1 performed at 50 °C. The metal-organic framework of Example 1 has added thereto the ligand N,N-dimethylethylenediamine, and the ligand 2-aminomethylpiperidine (2-ampd) is added to the metal-organic framework of Example 1. Figure 1A is an isotherm on a linear pressure scale. Figure 1B is on a logarithmic pressure scale.

[0016] Figure 2 shows the powder X-ray diffraction ("PXRD") patterns of the metal-organic framework (pristine) of Example 1 and the metal-organic framework system after amine impregnation in a solvent or vapor of the metal-organic framework of Example 1.

[0017] Figure 3 shows the PXRD data collected for the metal-organic framework system obtained after gas-phase amine addition to the metal-organic framework MOF-274, shown as the metal-organic frameworks MOF-274 and EMM-44.

[0018] Figure 4 shows the thermogravimetric analysis ("TGA") of the metal-organic framework prepared by adding 2-ampd to a 5% manganese, 95% magnesium MOF-274 structure, normalized to 100 °C considering the removal of entrapped solvent at low temperature.

[0019] Figure 5 shows the 1 1H NMR spectrum of Metal-organic framework 1 of Example 3 generated by gas-phase addition of 2-ampd.

[0020] Figure 6 shows the CO2 isotherm for the metal-organic framework system 1 of Example 3.

[0021] Figure 7 shows the PXRD data collected for the metal-organic framework MOF-274 and the metal-organic framework system 2 of Example 3 obtained after adding the ligand mmen to the gas-phase amine.

[0022] Figure 8 shows the 1 1H NMR spectrum of the metal-organic framework system 2 of Example 3.

[0023] Figure 9 shows the CO2 isotherm for the metal-organic framework system 2 of Example 3.

[0024] Figure 10 shows the CO2 isotherm of Figure 9 with the x-axis limited to clearly show the presence of type-V isotherm behavior.

[0025] Figure 11 is a display of the crystal structure of MOF-274 having diamine coordinated to an open metal site, artistically displayed on the right showing the chemical structure of the N,N'-dimethylethylenediamine ligand.

[0026] Figure 12 is the 1 1H NMR spectrum of the commercially available metal-organic framework system, mmen@MOF-274.

[0027] Figure 13 is the 1 1H NMR spectrum of the metal-organic framework system, mmen@MOF-274 after immersion in water.

[0028] Figure 14 is the 1 1H NMR spectrum of the metal-organic framework system, mmen@MOF-274 after immersion in methanol.

[0029] Figure 15 is the 1 1H NMR spectrum of the metal-organic framework system, mmen@MOF-274 after immersion in ethanol.

[0030] Figure 16 is a comparison of the powder X-ray diffraction patterns of the metal-organic framework systems, mmen@MOF-274 and MOF-274, in which the ligand mmen was exfoliated with water, methanol, or ethanol.

[0031] Figures 17A and 17B are the CO2 isobars for the metal-organic framework systems, mmen@MOF-274 from which mmen was exfoliated using water or methanol, and water and methanol, respectively, and the metal-organic frameworks after mmen was exfoliated.

[0032] Figure 18 is the 1 1H NMR spectrum of the recycled metal-organic framework system in which a plurality of first additional ligands, 2-ampd, of the metal-organic framework system were exfoliated using water and the metal-organic framework (MOF-274) was re-added with a plurality of second additional ligands, also 2-ampd.

[0033] Figure 19 shows the 1 1H NMR spectrum of a recycled metal-organic framework system obtained from a metal-organic framework system (MOF-274 with mmen) in which a plurality of first additional ligands, mmen, were exfoliated using methanol and a plurality of second additional ligands, 2-ampd, were added to the metal-organic framework. 1 1H NMR spectrum.

[0034] Figure 20 shows the 1 1H NMR of a metal-organic framework comprising a metal-organic framework system MOF-274 to which a plurality of first additional ligands, mmen, were added and a plurality of second additional ligands 2-ampd were re-added. 1 1H NMR.

[0035] Figure 21 shows the CO2 isotherm of the samples described in Example 5 and shown in Figures 18, 19, and 20.

DETAILED DESCRIPTION OF THE INVENTION

[0036] [Detailed Description of the Invention] For the purposes of the present disclosure, the following definitions apply:

[0037] As used herein, the articles “a” and “the” are understood to include the plural as well as the singular.

[0038] Unless otherwise specified, the term "aryl" means a polyunsaturated, aromatic substituent that can be monocyclic or have multiple fused or covalently bonded rings. In some aspects, the substituent has 1 to 11 rings, more specifically 1 to 3 rings. The term "heteroaryl" refers to an aryl substituent (or ring) containing 1 to 4 heteroatoms selected from N, O, and S, where the nitrogen and sulfur atoms may optionally be oxidized and the nitrogen atom(s) may optionally be quaternized. Exemplary heteroaryl groups are 6-membered azines such as pyridinyl, diazinyl, and triazinyl. The heteroaryl group can be attached to the remainder of the molecule through a heteroatom. Non-limiting examples of aryl and heteroaryl groups include phenyl, 1-naphthyl, 2-naphthyl, 4-biphenyl, 1-pyrrolyl, 2-pyrrolyl, 3-pyrrolyl, 3-pyrazolyl, 2-imidazolyl, 4-imidazolyl, pyrazinyl, 2-oxazolyl, 4-oxazolyl, 2-phenyl-4-oxazolyl, 5-oxazolyl, 3-isoxazolyl, 4-isoxazolyl, 5-isoxazolyl, 2-thiazolyl, 4-thiazolyl, 5-thiazolyl, 2-furyl, 3-furyl, 2-thienyl, 3-thienyl, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-pyrimidyl, 4-pyrimidyl, 5-benzothiazolyl, purinyl, 2-benzimidazolyl, 5-indolyl, 1-isoquinolyl, 5-isoquinolyl, 2-quinoxalinyl, 5-quinoxalinyl, 3-quinolyl, and 6-quinolyl. The substituents for each of the above aryl and heteroaryl ring systems are selected from the group of acceptable substituents described below.

[0039] As used herein, the terms "alkyl," "aryl," and "heteroaryl" may, optionally, include both substituted and unsubstituted forms of the indicated species. Substituents of aryl and heteroaryl groups are generally referred to as "aryl group substituents." Substituents are selected, for example, from: groups having a number from zero to the total number of open valences on the aromatic ring system and attached to the nucleus of the heteroaryl or heteroarene through a carbon or heteroatom (e.g., P, N, O, S, Si, or B), including, but not limited to, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted heterocycloalkyl, --OR’, =O, =NR’, =N--OR’, --NR’R’’, --SR’, -halogen, --SiR’R’’R’’’, --OC(O)R’, --C(O)R’, --CO2R’, --CONR’R’’, --OC(O)NR’R’’, --NR’’C(O)R’, --NR’--C(O)NR’’R’’’, --NR’’C(O)2R’, --NR--C(NR’R’’R’’’)NR’’’’, --NR--C(NR’R’’)=NR’’’, --S(O)R’, --S(O)R’, --S(O)NR’R’’, --NRSOR’, --CN, and --R’, --, --CH(Ph), fluoro(C1-C4)alkoxy, and fluoro(C1-C4)alkyl. Each of the above groups is attached to the aryl or heteroaryl nucleus either directly or through a heteroatom (e.g., P, N, O, S, Si, or B); where R’, R’’, R’’’, and R’’’’ are preferably independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl. When the compounds of the invention contain one or more R groups, for example, each of the R groups is independently selected in the same manner as each R’, R’’, R’’’, and R’’’’ group when one or more of these groups are present.

[0040] The term "alkyl", by itself or as part of another substituent, unless otherwise specified, means a straight-chain, branched-chain, or cyclic hydrocarbon radical, or combinations thereof, which may be fully saturated, mono- or polyunsaturated, and may include di-, tri- and polyvalent radicals, and has the specified number of carbon atoms (i.e., C1-C 10 which means from 1 to 10 carbon atoms). Examples of saturated hydrocarbon radicals include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, sec-butyl, cyclohexyl, (cyclohexyl)methyl, cyclopropylmethyl, and homologs and isomers such as, for example, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc. Unsaturated alkyl groups have one or more double or triple bonds. Examples of unsaturated alkyl groups include, but are not limited to, vinyl, 2-propenyl, crotyl, 2-isopentenyl, 2-(butadienyl), 2,4-pentadienyl, 3-(1,4-pentadienyl), ethynyl, 1- and 3-propynyl, 3-butynyl, and higher homologs and isomers thereof. The term "alkyl" is also intended to optionally include derivatives of alkyl as defined in detail below, such as "heteroalkyl", unless otherwise indicated.

[0041] As used herein, the term "heteroalkyl", by itself or in combination with another term, unless otherwise specified, means a stable straight, branched, or cyclic hydrocarbon radical of the indicated number of carbon atoms and at least one heteroatom selected from the group consisting of O, N, Si, and S, or combinations thereof, wherein the nitrogen and sulfur atoms may optionally be oxidized and the nitrogen heteroatom may optionally be quaternized. The heteroatom(s) O, N, S, and Si may be placed at any interior position of the heteroalkyl group or at the position at which the alkyl group is attached to the remainder of the molecule. Examples include, but are not limited to, --CH2--CH2--O--CH3, --CH2--CH2--NH--CH3, --CH2--CH2--N(CH3)--CH3, --CH2--S--CH2--CH3, --CH2--CH2--, --S(O)--CH3, --CH2--CH2--S(O)2--CH3, --CH=CH--O--CH3, --Si(CH3)3, --CH2-CH=N--OCH3, and --CH=CH--N(CH3)-CH3. Up to two heteroatoms may be consecutive, e.g., --CH2--NH--OCH3 and --CH2--O--Si(CH3)3. Similarly, the term "heteroalkylene", by itself or as part of another substituent, means a divalent radical derived from heteroalkyl, exemplified by, but not limited to, --CH2--CH2--S--CH2--CH2-- and --CH2--S--CH2--CH2--NH--CH2--. For heteroalkylene groups, the heteroatoms can also occupy either or both of the chain termini (e.g., alkyleneoxy, alkylenedioxy, alkylenamino, alkylenediamino, etc.). Further, for alkylene and heteroalkylene linking groups, the orientation of the linking group is not implied by the direction in which the formula of the linking group is written. For example, the formula --CO2R'-- represents both --C(O)OR' and --OC(O)R'.

[0042] As used herein, the term "heteroatom" includes oxygen (O), nitrogen (N), sulfur (S), and silicon (Si), boron (B), and phosphorus (P).

[0043] As used herein, the term "ligand" means a molecule containing one or more substituents that can function as a Lewis base (electron donor). In certain aspects provided herein, the ligand can be an amine or an amine containing from 1 to 10 amine groups.

[0044] The term "halo" or "halogen" means an atom of fluorine, chlorine, bromine or iodine, either alone or as part of another substituent, unless otherwise specified.

[0045] The symbol "R" is a general abbreviation representing a substituent selected from H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, and substituted or unsubstituted heterocycloalkyl groups.

[0046] As used herein, the term "periodic table" means the periodic table of the elements of the International Union of Pure and Applied Chemistry (IUPAC) as of December 2015.

[0047] As used herein, an "isotherm" shows the adsorption of an adsorbate as a function of concentration while the temperature of the system is held constant. In certain aspects, the adsorbate is CO2 and the concentration can be measured as the CO2 pressure. As described herein, the isotherm can be performed using various mathematical models applied to calculate the apparent surface area using a porous material. S. Brunauer, P. H. Emmett and E. Teller. J. Am. Chem. Soc. 1938, 60, 309 - 319; K. Walton and R. Q. Snurr, J. Am. Chem. Soc. 2007, 129, 8552 - 8556; I. Langmuir, J. Am. Chem. Soc. 1916, 38, 2221.

[0048] As used herein, the isotherm term "step", which is defined by a sigmoid absorption profile and is also known as the V-shaped isotherm, S.J. Gregg and K.S.W. Sing, Adsorption, Surface Area and Porosity, 2nd Ed. This step can generally be defined by the positive second derivative of the isotherm, followed by an inflection point, followed by the negative second derivative of the isotherm. This step occurs when the binding sites of the adsorbent become accessible only at a specific gas partial pressure, such as when CO2 is inserted into a metal-amine bond or when the pores of a dynamic structure are opened.

[0049] The term "salt(s)" includes salts of compounds prepared by neutralization of an acid or base, depending on the particular ligand or substituent found in the compounds described herein. When the compounds of the present invention contain relatively acidic functional groups, the base addition salts can be obtained by contacting the neutral form of such compounds with a sufficient amount of the desired base, neat or in a suitable inert solvent. Examples of base addition salts include sodium salts, potassium salts, calcium salts, ammonium salts, organic amino salts, or magnesium salts, or similar salts. Examples of acid addition salts include those obtained from inorganic acids such as hydrochloric acid, hydrobromic acid, nitric acid, carbonic acid, bicarbonic acid, phosphoric acid, monohydrogen phosphoric acid, dihydrogen phosphoric acid, sulfuric acid, monohydrogen sulfuric acid, hydriodic acid, or phosphorous acid. Similarly, salts obtained from relatively non-toxic organic acids such as acetic acid, propionic acid, isobutyric acid, butyric acid, maleic acid, malonic acid, benzoic acid, succinic acid, suberic acid, fumaric acid, lactic acid, mandelic acid, phthalic acid, benzenesulfonic, p-toluenesulfonic, citric acid, tartaric, methanesulfonic, etc. are included. Certain compounds of the present disclosure contain both basic and acidic functional groups that allow the compound to be converted into either a basic or an acid addition salt. Hydrates of salts are also included.

[0050] Metal-organic framework The metal-organic framework has a plurality of one or more different metal elements and a plurality of linkers, and each of the plurality of one or more different metal elements (metal ions) is bridged by one or more of the plurality of linkers. In certain embodiments, this forms an open metal site In some aspects, the plurality of one or more different metal elements are magnesium, zinc, nickel, copper, and / or combinations thereof including As described herein, the metal-organic framework is one or more distinct elements independently selected from the group of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn can include In some aspects, the distinct metal element is Mg.

[0051] The metal-organic framework can have the general structural formula I. M 1 x M 2 (2-x) (A) I where M 1 is a metal or a salt thereof, M 2 is a metal or a salt thereof, M 1 can be the same as M 2 , X is 1, or M 1 is not M 2 and X is a value from 0.01 to 1.99. A is an organic linker.

[0052] Suitable linkers (also referred to herein as "organic linkers") can be determined from symmetry operations that relate the structure of the metal-organic framework and the portion that binds to the metal nodes of the organic linker. Linkers that are chemically or structurally different but can be related by C2-axis symmetry in the metal-node binding region form metal-organic frameworks with the same topology. In one aspect, the organic linker is formed by two phenyl rings bonded at carbons 1,1', and a carboxylic acid can be present at carbon 3,3' and an alcohol at carbon 4,4'. Switching the positions of the carboxylic acid and the alcohol (e.g., "pc-H4DOBPDC" or "pc-MOF-274" described below) does not change the topology of the metal-organic framework.

[0053] Also, the linker is a first binding site and a second binding site that are crosslinked together with a third binding site including It can be a multi-dentate organic ligand. In some cases, the first binding site and the second binding site of the multi-dentate organic ligand are each salicylate moiety including , and the third binding site is a diamine moiety including . In some cases, the multi-dentate organic linker is 5 , 5’- ( ((1E,2E)-ethane-1,2-diylidene)bis-(azanediyl i diyl))bis(2-hydro benzoic acid ). Metal-organic framework system

[0054] As described herein, the metal-organic framework system contains a ligand attached to the metal-organic framework. Generally, the metal-organic framework system can have the general structural formula II. M 1 x M 2 (2-x) (A)(B) II

[0055] Here, M 1 is independently selected from Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M 2 is independently selected from Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M 1 can be the same as M 2 , X is 1, or M 1 is not M 2 , and X is a value from 0.01 to 1.99. A is an organic linker and B is a ligand. Generally, the number of ligands (B) will correspond to the number of metal sites. However, for polyamines such as those described in Example 5, the number of ligands can be less than 2, and ideally it is a ratio of two metals to one ligand.

[0056] As described herein, the ligand can be an amine or an alcohol. More specifically, the amine can be a diamine, cyclic diamine, triamine, and / or tetramine. Further, the metal-organic framework can exhibit a V-shaped step CO2 isotherm profile upon exposure to carbon dioxide. As described in U.S. Patent Application No. 62 / 839261, it is possible to adjust the V-shaped step by the choice of metal and / or the ratio of the metal incorporated into the metal-organic framework system. In one aspect, the metal-organic framework includes a diamine added to the metal-organic framework.

[0057] Further, an adsorbent is provided that includes one or more of the metal-organic frameworks described herein. The adsorbent of the present invention can be used in a method for removing carbon dioxide from various types of gas streams.

[0058] Conventional synthetic methods for producing metal-organic frameworks In conventional synthesis for producing metal-organic frameworks, the solid is completely dissolved in a solvent to form a reaction solution, and then the growth of the metal-organic framework is promoted at a high temperature. As a prerequisite for such synthesis, a large amount of solvent necessary for dissolving the reagent may be required. However, for crystal growth, the amount of solid reagent required to produce the metal-organic framework is often a limiting factor.

[0059] As referred to herein, conventional synthesis is typically an application reaction carried out by conventional electrical heating without parallel reactions. In traditional synthesis, the reaction temperature is a major parameter in the synthesis of metal-organic frameworks, and two temperature ranges, solvothermal and non-solvothermal, are usually distinguished and define the type of reaction setup to be used. Solvothermal reactions are generally carried out in a sealed container at an autogenous pressure of about the boiling point of the solvent used. Since non-solvothermal reactions are carried out at or below the boiling point under normal pressure, the requirements for synthesis are simplified. Non-solvothermal reactions can be further classified into room temperature and high temperature.

[0060] The synthesis of conventional metal-organic frameworks is carried out in a solvent at a temperature in the range from room temperature to about 250 °C. Heat is transferred by convection from an oven, which is a source of high temperature. Alternatively, potential, electromagnetic waves, mechanical waves (ultrasound), or mechanical energy can also be introduced. The energy source is closely related to the time, pressure, and energy per molecule introduced into the system, and each of these parameters can strongly affect the metal-organic framework formed and its morphology.

[0061] The synthesis of conventional metal-organic frameworks is described in McDonald, T., Mason, J., Kong, X. et al, Cooperative insertion of CO2 in diamine-appended metal-organic frameworks, Nature 519, 303 - 08 (2015), which is incorporated herein by reference. Generally, 0.10 mmol of linker, 0.25 mmol of metal salt, and 10 mL of solvent, namely methanol / dimethylformamide (“DMF”), are placed together in a 20 mL glass scintillation vial. Then, the vial is sealed and placed on a hot plate at 393 °K in a well plate with a depth of 2 cm for about 12 hours, after which powder is formed on the bottom and walls of the vial. Then, the metal-organic framework material is decanted, and the remaining powder is immersed three times in DMF and then three times in methanol. Then, the metal-organic framework is filtered and collected and completely desolvated by heating at 523 °K for 24 hours under dynamic vacuum (10 μbar or less). Using this specific methodology, in the conventional synthesis method, about 0.073 mmol of metal-organic framework, or a yield of 73% (comparing the mmol of the formed metal-organic framework with the initial mmol of the linker) or a volume-normalized mass-based yield of 2.7 grams per liter of the reaction solution can be obtained.

[0062] In addition to the conventional synthesis described in Nature, 2015, 519, 303 - 308, which is incorporated herein by reference, the synthesis for generating metal - organic frameworks is further described in Nature, J. Am. Chem. Soc. 2012, 134, 7056 - 7065; Chem. Sci. 2018, 9, 160 - 174; U.S. Patent No. 8,653,292 and U.S. Patent Application Publication Nos. 2007 / 0202038, 2010 / 0307336, and 2016 / 0031920.

[0063] In one aspect, the ligand can include other structural elements used to coordinate the ligand to one or more metals of the structural system, including, but not limited to, the following functional groups: carboxylate, triazolato, pyrazolato, tetrazolato, pyridine, amine, alkoxide, and / or sulfate group.

[0064] As an example, the amine - appended metal - organic framework can be prepared in a two - step process shown in Scheme 1 as follows:

Chemical formula

[0065] In step 1, suitable salts of M 1 and suitable salts of M 2 are combined with linker A in a suitable solvent and heated to provide a metal - organic framework system generally represented by formula I. For example, MnCl2 and Mg(NO3)2·6H2O are combined with 4,4’ - dioxido - 3,3’ - biphenyldicarboxylate (H4DOBPDC) in methanol and N,N’ - dimethylformamide (DMF) to provide a composition of formula I where M 1 is Mn, M 2 is Mg and A is DOBPDC.

[0066] In step 2, the metal - organic framework of formula I is combined with ligand (B) in a suitable solvent. For example, M 1 is Mn, M 2is Mg, A is DOBPDC, which is combined with 2-ampd in toluene to provide a mixed metal organic structure of Formula II, where M 1 is Mn, M 2 is Mg, A is DOBPDC, and B is 2-ampd. The number of amines will correspond to the number of metals.

[0067] Before disclosing and describing the novel methods and compositions, it should be understood that unless otherwise specified, the present invention is not limited to specific compounds, components, compositions, reactants, reaction conditions, ligands, catalyst structures, metallocene structures, etc., and such things can vary. Also, it should be understood that the terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting.

[0068] Gas-phase addition of ligands to metal-organic frameworks As described herein, current methods for manufacturing metal-organic framework systems are affected by the evaporation of the solvents used to manufacture the systems. By utilizing higher-boiling or more polar solvents, the evaporation of the solvents can be reduced, but the crystallinity of the materials may also decrease. Therefore, a new synthetic method has been developed in which ligands in the gas phase are brought into contact with the metal-organic framework and bound to the metal-organic framework to provide a metal-organic framework system. In this new approach, the crystallinity is maintained, and in some cases, an improvement in the signal intensity and peak width of the metal-organic framework is observed, indicating that the crystallinity is improved at a higher order. In fact, the adsorption isotherms of metal-organic frameworks with low crystallinity do not show the desired adsorption steps, indicating the superiority of this gas-phase approach.

[0069] Furthermore, when the amine-functionalized metal-organic framework is circulated, amine loss progresses over time, and the material for the desired separation may become inactivated. In certain systems, when the metal-organic framework is contacted with steam to desorb the bound CO2, amine loss is accelerated. In particular, some metal-organic frameworks of the MOF-274 family have low stability and decompose when exposed to solvents, resulting in unsuccessful amine addition and inability to be used for subsequent CO2 recovery. These problems are solved by contacting the metal-organic framework with amine in the gas phase. The amine is heated above its boiling point and passed over the metal-organic framework, adding the amine to the metal sites and generating the desired adsorbent. The metal-organic framework can be re-functionalized with amine by reproducing the original loading protocol, but in such an approach, it is necessary to completely remove the adsorbent from the process unit, resulting in costs and downtime. Also, a solution of amine dissolved in the adsorbent can be poured in. It can be synthesized with organic solvents, but a large amount of organic solvents need to be used, causing safety problems, an unnecessary flow of hazardous waste, and additional costs.

[0070] As described in the following examples, a novel method for synthesizing a metal-organic framework system includes the following steps: (a) providing a metal-organic framework comprising at least one open metal site; and (b) adding (bonding) a ligand in the gas phase to the metal-organic framework at the open metal site to form a metal-organic framework.

[0071] In one aspect, the method is a method for manufacturing a metal-organic framework system comprising the following steps: (a) creating a metal-organic framework; (b) evaporating a plurality of ligands to generate a gas phase; and (c) in the gas phase, binding at least one of the plurality of ligands to at least one of the open metal sites of the metal-organic framework to form a metal-organic framework system. The metal-organic framework includes a plurality of open metal sites, and a linker crosslinks at least one of the plurality of open metal sites to another. The method can further include suspending the metal-organic framework in a solvent. In one aspect, the method can further include filtering the solvent from the metal-organic framework. In one aspect, the method can further include heating the plurality of ligands to form a gas phase. In one aspect, the method can further include the plurality of ligands forming a gas phase under reduced pressure. In one aspect, the method can further include an inert gas passing through the gas phase.

[0072] An innovative new method for the production and regeneration of amine-functionalized metal-organic frameworks specialized for selective CO2 capture. The removal of the solvent from the process also facilitates the preparation of new material compositions, namely, various amine-functionalized forms of the MOF-274 metal-organic framework that cannot be prepared by conventional solution-phase amine-functionalization efforts. Importantly, as described in the examples, the desired Type-V CO2 isotherm is retained for materials prepared by the gas-phase addition approach.

[0073] Therefore, gas-phase addition of ligands, particularly amines, can produce novel metal-organic frameworks that were previously unstable system can be produced . New Regular metal-organic frameworks system are including a metal-organic framework, in which magnesium ions and / or cobalt ions are ethynediimine bis(salicylic acid) linked by to form a plurality of open metal sites, and a plurality of open metal sites are added in the gas phase to provide a metal-organic framework system is provided. More specifically, the novel metal-organic framework systemAs, it constitutes a MOF-274 metal-organic framework. Also, a plurality of open metal site is added with 2-aminomethylpiperidine and / or N,N-dimethylethylenediamine.

[0074] Recycling and / or reuse of the metal-organic framework As described above, the metal-organic framework, MOF-274, can be functionalized with diamines and forms a promising candidate for CO2 capture applications as it results in a desirable Type-V isotherm. By introducing different diamines, the properties of the adsorbent change, such as imparting vapor stability and changing the CO2 partial pressure and temperature required for CO2 adsorption. Due to this versatility, MOF-274 with added diamines can have potential utility for CO2 capture from a wide range of different streams.

[0075] Provided herein is a method for reusing a metal-organic framework system by (1) stripping a diamine from a MOF-274 metal-organic framework; and (2) filling the metal-organic framework with a different diamine for reuse of the metal-organic framework system in different streams containing CO2 referred to herein as "CO2 streams".

[0076] As described in the examples, the recycled diamine-added MOF-274 adsorbent (referred to as the "recycled metal-organic framework system") exhibits a desirable Type-V isotherm and shows surprising stability to successive immersion in the preparation solvent, as many metal-organic frameworks are known to decompose, collapse, or undergo pore blockage under similar conditions. Thus, there was a problem that recycled MOF-274 with added diamine could not be recycled or that MOF-274 with another added diamine could not be used under different CO2 recovery conditions. Therefore, this problem was solved by impregnating MOF-274 with added diamine into a coordinating solvent, exchanging this solvent with a non-coordinating solvent, and treating the stripped MOF-274 (the metal-organic framework without the original diamine) with a different diamine to obtain an entirely different adsorbent. In contrast, prior art solutions involve the synthesis of a new MOF-274 material followed by addition with the desired diamine.

[0077] As described in the examples, a method for recycling and / or reusing a metal-organic framework system includes the step of stripping (peeling off or removing by other means) at least one or more of a plurality of ligands from the metal-organic framework system. For the purpose of recycling the metal-organic framework, useful solvents include water, methanol, ethanol, or combinations thereof. The solvent can be compatible with the ligand for complete removal, while at the same time providing multiple options for process flexibility and optimization. To remove the ligand, the metal-organic framework is immersed in the solvent for at least about 10 minutes to about 18 hours.

[0078] The addition or re-addition of ligands to the metal-organic framework can be carried out in solution (liquid) or using the novel gas-phase method described herein. As taught in the following examples, the metal-organic framework can be added with different or the same plurality of ligands.

[0079] For example, when different diamines are installed in a metal-organic framework system, adsorbent properties change, such as the imparting of vapor stability or the change in the CO2 partial pressure and temperature required to affect CO2 adsorption. Due to such versatility, the metal-organic framework has potential usefulness for capturing CO2 from various different streams. However, as described herein, when the metal-organic framework is added with a selected amine, the current paradigm is that the metal-organic framework remains in its specific form during its period of use. Recycling of used metal-organic frameworks and intentionally stripping ligands from metal-organic frameworks for the purpose of obtaining different performances with different ligands have received little attention so far. Furthermore, if new advantageous amine-added metal-organic frameworks are discovered, the adsorbent system can be upgraded by installing new diamines, eliminating the need to newly synthesize the metal-organic framework, thus minimizing costs, waste, and the downtime of the adsorbent.

[0080] Recycling / reusing a metal-organic framework system, if carried out on a large scale, can bring significant benefits and can promote the subsequent recovery and reuse of ligands by various separation approaches such as distillation, adsorption beds, membranes, etc.

[0081] Synthesized, recycled, and reused metal-organic frameworks As described above, the metal-organic frameworks synthesized or recycled / reused by the novel method of the present invention can include variations and different aspects. For example, in one aspect, the method can provide metal-organic frameworks and metal-organic framework systems having linkers of the general formula:

Chemical formula

[0082] Examples of such linkers include the following:

Chemical formula

[0083] Examples of suitable organic linkers include 4,4’-dioxidobiphenyl-3,3’-dicarboxylate (H4DOBPDC); 4,4’’-dioxid-[1,1’:4’,1’’-terphenyl]-3,3’’-dicarboxylate (H4DOTPDC); and 3,3’-dioxidobiphenyl-4,4’-dicarboxylate (para-carboxylate H4DOBPDC, also called PC-DOBPDC) and the following compounds:

Chemical formula

[0084] In one embodiment, the linker has the following formula:

Chemical formula

[0085] In one embodiment, the linker has the following formula:

Chemical formula

[0086] Here, R 11 , R 12 , R 13 , R 14 , R 15 and R 16 are each independently selected from H, halogen, hydroxyl, methyl, and halogen-substituted methyl.

[0087] In one embodiment, the linker has the following formula:

Chemical formula

[0088] In one embodiment, the linker may have the following formula:

Chemical formula

[0089] In one embodiment, the organic linker includes a molecule having two (or more) phenyl rings, or a plurality of cross-linked aryl species such as two phenyl rings linked by vinyl or alkynyl.

[0090] Synthesized, recycled, reused metal-organic framework system As provided herein, the ligand can include one or more groups that can function as suitable Lewis bases (electron donors) such as oxygen, phosphorus, sulfur, or an amine having 1 to 10 amine groups. The method can provide a metal-organic framework system capable of adding various types of ligands to the metal-organic framework. In one embodiment, B is a ligand selected from the group consisting of:

Chemical formula

[0091] Here, Z is carbon, silicon, germanium, sulfur, or selenium, and R1, R2, R3, R4, R5, R6, R7, R8, R9 and R 10 are each independently selected from H, halogen, methyl, halogen-substituted methyl, and hydroxyl. In one embodiment, R1, R2, R3, R4, R5, R6, R7, R8, R9 and R 10 are each H, and Z is carbon.

[0092] Ligands suitable for the method of manufacturing the metal-organic framework system of the present invention can have (at least) two functional groups: 1) a functional group used to bind CO2; and 2) a functional group used to bind a metal. The second functional group for binding the metal can be an amine. Oxygen-containing groups such as alcohols, ethers or alkoxides, carbon groups such as carbenes or unsaturated bonds such as alkenes or alkynes, or other functional groups such as sulfur atoms can also be used.

[0093] The metal-organic framework systems described herein are useful as sorbents for various gas separations, including the separation of individual gases from streams of composite gases such as carbon dioxide / nitrogen, carbon dioxide / hydrogen, carbon dioxide / methane, carbon dioxide / oxygen, carbon monoxide / nitrogen, carbon monoxide / methane, carbon monoxide / hydrogen, hydrogen sulfide / methane, and hydrogen sulfide / nitrogen.

[0094] Among the main advantages of physical adsorption onto solid materials is the low regeneration energy compared to the regeneration energy required for aqueous amines. However, this advantage often comes at the expense of low capacity and poor selectivity. The metal-organic framework systems of the present invention provide sorbents that can bridge the two approaches by incorporating sites for binding CO2 by chemisorption onto solid materials. These materials can eliminate the need for aqueous solvents, significantly reduce the regeneration cost compared to conventional amine scrubbers, and maintain exceptional selectivity and high capacity for CO2 at low pressures.

[0095] All numerical values in the detailed description and claims of this specification are modified by "about" or "approximately" the indicated values, taking into account experimental error and variations.

[0096] For the sake of brevity, only specific ranges are explicitly disclosed in this specification. However, ranges starting from any lower limit can be combined with any upper limit to recite ranges that are not explicitly recited, and similarly, ranges starting from any lower limit can be combined with any other lower limit to recite ranges that are not explicitly recited, and similarly, ranges starting from any upper limit can be combined with any other upper limit to recite ranges that are not explicitly recited. Further, within a range, any point or individual value between its endpoints is included even if not explicitly described. Thus, all points or individual values can be combined with other points or individual values, or with other lower or upper limits, to function as their own lower or upper limits and describe ranges that are not explicitly explained.

[0097] The features of the present invention are described in the following non-limiting examples.

[0098] Example 1 Addition reaction of metal-organic frameworks by gas-phase method First, a metal-organic framework system was made by the conventional method described in this specification, and then a metal-organic framework system was made by adding a plurality of amine ligands to the metal-organic framework in the gas phase. Specifically, a mixed metal body of metal-organic frameworks described in US Pat. App. 62 / 839,261 was prepared before, suspended in toluene, and transferred to the upper part of a side-arm type filter funnel with a ground glass frit. An empty round-bottom flask was attached to the funnel, and the solvent was transferred to the empty round-bottom flask by vacuum filtration to create a uniform wet cake of the metal-organic framework on the glass frit. The filter was capped with a septum and vented with a needle. The discarded solvent was replaced with 2.5 molar equivalents of N,N'-dimethylethylenediamine (mmen) with respect to the amount of the metal-organic framework. Next, while passing nitrogen through the wet cake (metal-organic framework), the round-bottom flask was heated to 120 °C above the boiling point of the amine. Heating was continued until a plurality of amine ligands evaporated, and an absorber capable of capturing carbon dioxide was obtained.

[0099] Example 2 Characteristic evaluation of the adsorbent of Example 1 As described above, that of Example 1 adsorbent is obtained by synthesizing a metal-organic framework system capable of capturing carbon dioxide. This metal-organic framework system ethynediiminebissalicylic acid (hereinafter referred to as "EDBSA") linker and an open including a metal site contained a one-dimensional hexagonal metal-organic framework. Through the incorporation of di-amine appended ligands and tetra-amine appended ligands, a sharp adsorption of carbon dioxide was brought about stepwise.

[0100] Figures 1A and 1B show the effect of saturated amines on the metal-organic framework. The metal-organic framework showed a typical type 1 adsorption isotherm. The metal-organic framework with added amine (metal-organic framework system) showed a strong type 5 isotherm. Figures 1A and 1B are isotherm diagrams at 50 °C of the metal-organic framework, the metal-organic framework system with added N,N-dimethylethylenediamine ligand, and the metal-organic framework system with added 2-aminomethylpiperidine (2-ampd). In Figure 1A, the isotherm is shown on a linear pressure scale. In Figure 1B, the isotherm is shown on a logarithmic pressure scale.

[0101] Using the method of the present invention, the ligand (amine ligand) is heated above its boiling point, and the gas phase of the ligand is transported to the metal-organic framework using a carrier gas (such as nitrogen). The metal-organic framework was heated to a fairly high temperature in order to enable covalent bonding of the ligand with the amine and to prevent condensation and solidification of the ligand. As a result, it was confirmed that the crystallinity of the metal-organic framework was maintained. Figure 2 shows the powder X-ray diffraction patterns of samples obtained by treating the metal-organic framework system of Example 1 in a solvent and in a gas phase ("gas phase"). The sample treated in the gas phase shows improved signal intensity and peak width, and higher order and improved crystallinity are observed. In fact, the adsorption isotherm of a material with low crystallinity no longer shows a desirable adsorption step, demonstrating the advantage of adding the ligand in the gas phase.

[0102] Example 3 Gas-phase addition reaction of metal-organic framework MOF-274 The metal-organic framework with added amine, MOF-274, is a promising candidate for selective CO2 capture from exhaust gases. Conventionally, metal-organic framework systems have been formed by dispersing the nascent metal-organic framework MOF-274 in an amine-containing non-coordinating solvent and then repeating the washing. It has been demonstrated that various ligands consisting of amines, including tetraamines, release excess amines and require additional heating after addition to generate the desired loading. When successfully functionalized, these amine-added metal-organic frameworks exhibit a unique V-shaped isotherm for CO2 and bind them more selectively than nitrogen (N2) or oxygen (O2).

[0103] Specifically, the metal-organic framework described in US Patent Application No. 62 / 839,261, MOF-274, was suspended in toluene and transferred to the upper part of a side-arm filter funnel with a fritted glass. An empty round-bottom flask was attached to the funnel, and the solvent was transferred to the empty round-bottom flask by vacuum filtration to create a uniform wet cake of the metal-organic framework on the glass frit. The filter was capped with a septum and vented with a needle. The solvent was discarded and replaced with an appropriate amount of amine. Next, the round-bottom flask was heated above the boiling point of the amine, and a stream of nitrogen was passed through the side arm of the filter flask, passing the amine-containing metal-organic framework wet cake from the round-bottom flask. Heating was continued until all the amine had evaporated from the round-bottom flask. The resulting material showed the desired type V CO2 isotherm.

[0104] The amines used for gas-phase addition were 2-(aminomethyl)piperidine ("2-ampd") and N,N'-dimethylethylenediamine ("mmen") shown immediately below to generate Metal-organic framework system 1 and Metal-organic framework system 2, respectively.

Chemical formula

[0105] Example 4 Additional gas-phase addition reaction of metal-organic framework systems The metal-organic framework system 1 was prepared by gas-phase addition of 2-ampd. After amine addition, powder X-ray diffraction data were collected for the metal-organic framework and the metal-organic framework system, and are provided in Figure 3. As shown in Figure 3, the crystallinity of the metal-organic framework was maintained even after gas-phase amine addition of 2-ampd. Further, as shown in Figure 4, thermogravimetric analysis of the metal-organic framework system 1 prepared by adding the ligand (2-ampd) to the 5% manganese MOF-274 metal-organic framework system was performed and normalized to 100 °C considering the removal of the entrapped solvent at low temperature. As shown in the graph of Figure 4, the 42.6 wt% loss at 250-400 °C exactly matches the theoretical weight loss of the metal-organic framework system. Similarly, the 11.8 wt% loss at 100-250 °C indicates physically adsorbed 2-ampd remaining in the metal-organic framework channels after gas-phase loading. Figure 5 shows the 1 1H NMR of the metal-organic framework system 1. For the integration of a pair of protons (singlet, 7.95 ppm) on the linker, the integration of the four uppermost multiplets should be 12 if the metal-organic framework system is 100% added. In this example, summing the four uppermost multiplets gives 14, indicating that 117% of the amine has been added, which is consistent with the TGA data shown in Figure 4. As shown in Figure 6, the metal-organic framework system 1 also exhibited the desired type-V isothermal behavior.

[0106] The metal-organic framework system 2 was prepared by gas-phase addition of mmen, a ligand, to the metal-organic framework (MOF-274). Figure 7 provides the powder X-ray diffraction data collected for the metal-organic framework MOF-274 and the metal-organic framework system 2 obtained following gas-phase amine addition. This data indicates that the crystallinity was retained following gas-phase amine addition of the ligand.

[0107] As shown in Figure 8, the metal-organic framework system 2 1It was further analyzed by \(^1\)H NMR spectroscopy. In relation to the integration of the proton pair (singlet, 7.95 ppm) on the linker, the integration of the four most upfield multiplets should total 10 for 100% of the appended material. In this example, the sum was 11, indicating that 110% of the amine was added. The metal-organic framework system 2 also showed the desired type-V isotherm behavior (Figure 9). In Figure 10, the x-axis of the CO₂ isotherm of the metal-organic framework system 2 was restricted to 0 - 1 kPa to more clearly show the presence of type-V isotherm behavior.

[0108] As another method of amine addition, the entire apparatus was placed in an oven and heated to an appropriate temperature to vaporize the amine. By heating the entire system, the amine remained in the gas phase and did not condense or solidify on the frit of the funnel. This method is particularly effective for amines such as 2-ampd, spermine, and triethylenetetramine shown below.

Chemical formula

[0109] Example 5 Recycling of Metal-Organic Framework Systems Desorption of Diamine Ligands from Metal-Organic Framework MOF-274 As described herein, the metal-organic framework, MOF-274, can be functionalized with diamines and forms a promising candidate for CO₂ capture applications by providing the desired type-V isotherm. By introducing different diamines (ligands), the properties of the adsorbent can be changed, such as imparting vapor stability and changing the CO₂ partial pressure and temperature required for CO₂ adsorption. Due to this versatility, the metal-organic framework system (MOF-274) with added diamine has potential usefulness for capturing CO₂ from a wide range of different streams.

[0110] When the metal-organic framework MOF-274, a metal-organic structure, is added with the selected amine, the current paradigm is that the material remains in its specific form throughout its period of use. Little attention has been paid to recycling used diamine-added MOF-274, the metal-organic structure system, or intentionally peeling off and detaching ligands / amines from the metal-organic framework MOF-274 for the purpose of filling with different diamines to achieve different performances. Furthermore, when new advantageous diamine-added MOF-274 materials are discovered, the adsorbent system can be upgraded. By introducing new diamines, the synthesis of the metal-organic framework becomes unnecessary, and costs, waste, and the downtime of the adsorbent can be minimized.

[0111] In this example, diamine was peeled off from the metal-organic structure system and then different diamines were added (attached / bound) to the metal-organic structure. In this way, the recycled diamine-added MOF-274 adsorbent shows a desirable type V isotherm and exhibits surprising stability against continuous immersion in the conditioning solvent, since many MOFs are known to decompose, collapse, or cause pore blockage under similar conditions.

[0112] Specifically, the amine-functionalized metal-organic framework MOF-274 CO2 adsorbent had its amine removed while maintaining the integrity of the MOF-274 metal-organic structure, re-added with another ligand (diamine), and used for CO2 capture.

[0113] As shown in Fig. 11, the conventional amine - appended metal - organic framework system is mmen@MOF - 274, where mmen is N,N’ - dimethylethylenediamine. Siegelman, T.M. et al., Controlling Cooperative CO2 Adsorption in Diamine - Appended Mg2(dobpdc) Metal - Organic Frameworks, J. Am. Chem. 2017, 139, 1026 - 1053. In Fig. 11, the crystal structure of MOF - 274 with diamine coordinated to open metal sites is artistically depicted. On the right side of the metal - organic framework is the chemical structure of N,N’ - dimethylethylenediamine. Adding mmen to the metal - organic framework (MOF - 274) provides a metal - organic framework system denoted as mmen@MOF - 274 herein.

[0114] As shown in Fig. 12, the degree of amine loading of the metal - organic framework system mmen@MOF - 274 1 was determined by 1H NMR. The signature peaks from mmen (ligand) were located at approximately 3.25 and 2.55 ppm, where the theoretical integrals for aromatic protons on the linker were 8 and 12, respectively. Three downfield integrals with equal values of 2 were assigned to the aromatic protons of the linker. The experimental integrals of the mmen protons were 8 and 12.25, which are equivalent to the theoretical values, indicating that the amine coordination of was 100% of open gold metal site sites.

[0115] Samples of the metal - organic framework system, mmen@MOF - 274, were immersed in (1) water, (2) methanol, and (3) ethanol for 24 hours and recovered by centrifugation. Figs. 13, 14, and 15 show the respective 1H NMR spectra collected for the mmen@MOF - 274 materials after immersion and digestion. The peaks attributed to the ligand mmen are effectively removed, indicating that the ligand has been completely removed from the metal - organic framework system. 1

[0116] Specifically, Fig. 13 shows the 1 1 1H NMR of the metal-organic framework system mmen@MOF-274 after immersion in water. The peak of mmen is integrated to a value suggesting that more than 99.5% of the ligand has been removed. Fig. 14 shows the 1 1 1H NMR of this metal-organic framework system after immersion in methanol. The peak of the ligand mmen is integrated to a value suggesting that 99% of the amine has been removed. Fig. 15 shows the 1 1 1H NMR of the same metal-organic framework system (mmen@MOF-274) after immersion in ethanol. The peak of the ligand mmen is integrated to a value suggesting that 97.75% of the amine has been removed from the metal-organic framework system.

[0117] Fig. 16 shows a comparison of the powder X-ray diffraction data of the metal-organic framework system mmen@MOF-274 and the metal-organic framework MOF-274 after removing the ligand with water, methanol, and ethanol. The indistinguishable diffraction data indicates that the crystallinity of the metal-organic framework is maintained through the exfoliation process.

[0118] As shown in Fig. 17A, the CO2 adsorption performance of the metal-organic framework MOF-274 obtained by exfoliating mmen with water or methanol was evaluated by CO2 isotherms. Since the amine has been removed, the desired type V isotherm was not observed. The obtained CO2 capacity was shown to be 2.72 - 3.41 mmol CO2 / g MOF-274 (100 - 150 mg CO2 / g MOF-274) adsorbed at 40 °C or below, indicating that the surface area of the metal-organic framework is maintained. For mmen@MOF-274 exfoliated with ethanol, comparable data have not yet been obtained.

[0119] Figure 17B is the CO2 adsorption isobar of the mmen metal-organic framework MOF-274 exfoliated with water and methanol. In these cases, the coordination solvent was not washed away with a non-coordinating solvent (e.g., toluene). As a result, the capacity of the recycled metal-organic framework system was lower than the theoretical value, potentially due to the coordinating solvent in which H2O is more strongly bound than MeOH.

[0120] It has been demonstrated that multiple different exfoliating solvents are effective for diamine removal, and significant effects can be obtained when implemented on a large scale, which may facilitate the subsequent recovery and reuse of the coordinated diamine. The exfoliating solvent is prepared to completely remove the diamine and can simultaneously provide multiple options for process flexibility and optimization.

[0121] Example 6 Recycled metal-organic framework system After amine removal as described in Example 4, the metal-organic framework was immersed in a 20 vol% 2-aminomethylpiperidine ("2-ampd") ligand in toluene solution to generate a metal-organic framework system, 2-ampd@MOF-274. These samples (recycled metal-organic framework systems) were characterized by digestion and 1 1H NMR. The characteristic peaks of the recycled metal-organic framework system are located at 1.25 - 2.0 ppm and would have a theoretical integral value of 12 when completely filled within the metal-organic framework MOF-274.

[0122] As shown in Figures 18 - 20, the recycled metal-organic framework system was able to give a stoichiometric loading. Specifically, Figure 18 shows a recycled metal-organic framework system in which multiple first additional ligands, 2-ampd, were exfoliated with water and the metal-organic framework (MOF-274) was re-added with the same 2-ampd as multiple second additional ligands. 11H NMR is shown. The reference peak at 1.25 - 2.0 ppm was integrated to a value of 12.07, and 100.6% loading of the ligand 2-ampd onto the metal-organic structure was confirmed. The diamine 2-aminomethylpiperidine is shown in the spectrum.

[0123] Figure 19 shows the 1H NMR of a recycled metal-organic structure system (MOF-274 with mmen) obtained by exfoliating a plurality of first additional ligands mmen using methanol and then adding a plurality of second additional ligands 2-ampd to the metal-organic structure MOF-274. 1 1H NMR is shown. Integrating the reference peak at 1.25 - 2.0 ppm gave 12.36, confirming that the ligand 2-ampd was 103% loaded onto the metal-organic structure. Figure 20 shows the 1H NMR when the metal-organic structure system (a metal-organic structure system formed by adding a plurality of first additional ligands mmen to the metal-organic structure MOF-274) was exfoliated using ethanol and a plurality of second additional ligands 2-ampd were re-added. 1 1H NMR is shown. The reference peak at 1.25 - 2.0 ppm was 12.04, confirming that the ligand 2-ampd was 100.3% loaded onto the metal-organic structure MOF-274.

[0124] The CO2 isobars of the samples in Figures 18, 19, and 20 are as shown in Figure 21. As shown in Figure 21, the samples of the recycled metal-organic structure system showed an update close to the theoretical maximum of 4 mmol CO2 / g of the metal-organic structure. In all samples, the experimental CO2 uptake was just below the theoretical maximum of 4 mmol CO2 / g of the metal-organic structure system, indicating that the integrity of the structure was not affected by mmen exfoliation and 2-ampd addition, confirming the potential of this approach to convert the diamine-added MOF-274 metal-organic structure system into a recycled metal-organic structure system. The disclosure herein may include the following aspects. (Aspect 1) A method for synthesizing a metal-organic framework system comprising a metal-organic framework and a plurality of ligands added to the metal-organic framework, comprising: providing a metal-organic framework comprising at least one open metal site; and adding a ligand in the gas phase to the open metal site of the metal-organic framework to form a metal-organic framework system including the steps of, a method. (Aspect 2) A method for manufacturing a metal-organic framework system, comprising: manufacturing a metal-organic framework, wherein the metal-organic framework comprises a plurality of open metal sites and a linker crosslinks at least one of the plurality of open metal sites to another; evaporating a plurality of ligands to generate a gas phase; and in the gas phase, binding at least one of the plurality of ligands to at least one of the open metal sites of the metal-organic framework to form a metal-organic framework system including the steps of, a method. (Aspect 3) The method according to aspect 2, further comprising the step of suspending the metal-organic framework in a solvent. (Aspect 4) The method according to aspect 3, further comprising the step of filtering the solvent from the metal-organic framework. (Aspect 5) The method according to any one of aspects 1 to 4, wherein the ligand is heated to form a gas phase. (Aspect 6) The method according to any one of aspects 1 to 5, wherein an inert gas passes through the gas phase. (Aspect 7) The method according to aspect 6, wherein the inert gas is nitrogen. (Aspect 8) A metal-organic framework system produced by the method according to any one of Aspects 1 to 7, wherein the metal-organic framework system is linked with ethynediimine bis-salicylate to form a plurality of metal sites, and a plurality of metal sites added in the gas phase with 2-aminomethylpiperidine and / or N,N-dimethylethylenediamine, and includes a metal-organic framework containing magnesium ions and / or cobalt ions that provides the metal-organic framework system. (Aspect 9) A metal-organic framework system including a metal-organic framework of magnesium ions and / or cobalt ions that forms a plurality of open metal sites in conjunction with ethynediimine bis-salicylate, wherein 2-aminomethylpiperidine and / or N,N-dimethylethylenediamine are added to the plurality of open metal sites. (Aspect 10) A method for recycling a metal-organic framework system, comprising the steps of: detaching a plurality of first additional ligands from the metal-organic framework system to provide a metal-organic framework, wherein the structure of the metal-organic framework remains intact; and adding at least one of a plurality of second additional ligands to the metal-organic framework to provide a recycled metal-organic framework system. (Aspect 11) The method according to Aspect 10, further comprising the step of sequentially immersing the metal-organic framework system and the metal-organic framework to provide a recycled metal-organic framework system. (Aspect 12) The method according to Aspect 10, further comprising the step of washing the metal-organic framework system in a solvent to remove a plurality of first additional ligands. (Aspect 13) The method according to Aspect 10, further comprising the step of adding at least one of a plurality of second additional ligands to the metal-organic framework in the gas phase. (Aspect 14) The method according to any one of Aspects 1 to 13, wherein the plurality of first additional ligands are used diamine additional ligands. (Aspect 15) The method according to any one of Aspects 1 to 14, wherein the plurality of second additional ligands are the recycled plurality of first additional ligands. (Aspect 16) The method according to any one of Aspects 1 to 15, wherein the plurality of first additional ligands are different from the plurality of second additional ligands. (Aspect 17) The method according to any one of Aspects 1 to 16, wherein the metal-organic framework system includes a diamine added to the metal-organic framework. (Aspect 18) The method according to any one of aspects 1 to 17, wherein the metal-organic structure has a plurality of one or more distinct metal elements and a plurality of linkers, each of the plurality of one or more distinct metal elements being cross-linked by one or more of the plurality of linkers to form a metal site. (Aspect 19) The method according to any one of aspects 1 to 18, wherein the plurality of one or more distinct metal elements comprises magnesium, zinc, nickel, copper, and / or combinations thereof. (Aspect 20) The method according to any one of aspects 1 to 19, wherein the distinct metal element is Mg. (Aspect 21) The method according to any one of aspects 1 to 20, wherein the ligand is an amine. (Aspect 22) The method according to any one of aspects 1 to 21, wherein the plurality of ligands is an alcohol. (Aspect 23) The method according to any one of aspects 1 to 22, wherein the linker is a multidentate organic ligand comprising a first binding site and a second binding site cross-linked together with a third binding site. (Aspect 24) The method according to aspect 23, wherein the first binding site and the second binding site of the multidentate organic ligand each comprise a salicylate site, and the third binding site comprises a diamine group. (Aspect 25) The method according to aspect 24, wherein the multidentate organic linker is 5,5'-(((1E,2E)-ethane-1,2-diylidene)bis-(azanediylidene))bis(2-hydroxybenzoic acid).

Claims

1. A method for synthesizing a metal-organic framework system comprising a metal-organic framework and a plurality of ligands attached to the metal-organic framework, comprising: providing a metal-organic framework comprising at least one open metal site; and adding a ligand to the metal-organic framework at the open metal site in the gas phase to form a metal-organic framework system including the steps of the metal-organic framework has the following general structural formula I: M １ ｘ M ２ （２－ｘ） (A) I [wherein, M １ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M ２ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M １ is the same as M ２ where X is 1, or M １ is not M ２ but rather, X is a value from 0.01 to 1.99 A is a linker] having In the metal organic structure, M １ and M ２ at least one of which is cross-linked by a linker of A to form the open metal site, the metal-organic framework system has the following general structural formula II: M １ ｘ M ２ （２－ｘ） (A)(B) II [wherein, M １ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M ２ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M １ is the same as M ２ where X is 1, or M １ is not M ２ but rather X is a value from 0.01 to 1.99, A is the linker contained in the general structural formula I, B is a ligand] having a method.

2. A method for manufacturing a metal-organic framework system, comprising: manufacturing a metal-organic framework comprising a plurality of open metal sites; evaporating a plurality of ligands to generate a gas phase; and in the gas phase, bonding at least one of the plurality of ligands to at least one of the open metal sites of the metal-organic framework to form a metal-organic framework system including the steps of the metal-organic framework has the following general structural formula I: M １ ｘ M ２ （２－ｘ） (A) I [wherein, M １ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M ２ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M １ is the same as M ２ where X is 1, or M １ is not M ２ but rather, X has a value ranging from 0.01 to 1.99 A is a linker] having In the metal organic structure, M １ and M ２ at least one of which is crosslinked by a linker of A to form the open metal site, the metal-organic framework system has the following general structural formula II: M １ ｘ M ２ （２－ｘ） (A)(B) II [wherein, M １ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M ２ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M １ is the same as M ２ where X is 1, or M １ is not M ２ Instead, X has a value ranging from 0.01 to 1.99 A is the linker contained in the general structural formula I, B is a ligand] having a method.

3. The method according to claim 2, further comprising the steps of suspending the metal-organic framework in a solvent and filtering the solvent from the metal-organic framework.

4. The method according to any one of claims 1 to 3, wherein the ligand is heated to form a gas phase, or an inert gas passes through the gas phase, or a combination thereof.

5. A method for recycling a metal-organic framework system, comprising washing the metal-organic framework system in a solvent to remove a plurality of first additional ligands from the metal-organic framework system to provide a metal-organic framework, wherein the structure of the metal-organic framework remains the same; and adding at least one of a plurality of second additional ligands to the metal-organic framework in the gas phase to provide a recycled metal-organic framework system including the steps of the metal-organic framework system has the following general structural formula II: M １ ｘ M ２ （２－ｘ） (A)(B) II [wherein, M １ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M ２ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M １ is the same as M ２ where X is 1, or M １ is not M ２ but rather X has a value ranging from 0.01 to 1.99 A is a linker, B is a first additional ligand] having the metal-organic framework has the following general structural formula I: M １ ｘ M ２ （２－ｘ） (A) I [wherein, M １ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M ２ is independently selected from the group consisting of Mg, Ca, V, Mn, Cr, Fe, Co, Ni, Cu, and Zn, M １ is the same as M ２ where X is 1, or M １ is not M ２ but rather, X is a value from 0.01 to 1.99 A is the linker contained in the general structural formula II] A method having **Claim 6** The method according to claim 5, further comprising the step of sequentially immersing a metal-organic framework system and a metal-organic framework to provide a recycled metal-organic framework system. **Claim 7** M １ is independently selected from the group consisting of Mg, Ni, Cu, and Zn, M ２ is independently selected from the group consisting of Mg, Ni, Cu, and Zn, The method according to any one of claims 1 to 4 and 5 to 6. **Claim 8** The method according to any one of claims 1 to 4 and 5 to 7, wherein the linker is 5,5'-(((1E,2E)-ethane-1,2-diylidene)bis(azanediylidene))bis(2-hydroxybenzoic acid).

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