Patent Application
20230123029
A metal organic framework (MOF) is a relatively new hybrid organic-inorganic material which is a microporous crystalline material composed of metal atoms or metal clusters and organic ligands connecting them by coordination bonds. The pore size and physical/chemical properties of MOFs can be controlled by selection of appropriate metal atoms and organic ligands. Because of the special properties of these MOFs, they show potential applications as gas storage and/or absorption, catalysis, and separation membranes.
The zeolitic imidazolate framework (ZIF) is a sub-concept of MOF particles and has the advantage of allowing easy control of the particle surface area, pore size, and chemical properties by using organic ligands containing various functional groups.
The present disclosure provides a ZIF nanoparticle containing tri-ligands, the method of manufacturing the same, mixed matrix membrane comprising the same, and method of separating gas using the membrane, which has excellent CO2 separation performance, dispersibility, and compatibility with polymers, and it is designed to develop a CO2-selective high-performance hybrid membrane.
The present disclosure provides nanoparticles of a zeolitic imidazolate framework (ZIF) into which three kinds of ligands are introduced. The nanoparticles include metal ions; and an organic ligand bound to the metal ion, wherein the organic ligand comprises an imidazole-based first organic ligand, alkylamine-based second organic ligand, and third organic ligand comprising at least one amine group substituted on the ring.
In the organic ligand, the third organic ligand is 20 to 60 mol %.
The organic ligand includes 30 to 80 mol % of the first organic ligand, 3 to 15 mol % of the second organic ligand, and 20 to 60 mol % of the third organic ligand.
The first organic ligand, the second organic ligand, and the third organic ligand are each directly bonded to the metal ion nanoparticles.
The first organic ligand includes at least one of primary, secondary, and tertiary amines, and contains one or more selected from the group of alkylamines having an alkyl chain of any one length of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, propadecyl, butadecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, and nodadecyl.
The second organic ligand includes at least one selected from 2-methylimidazole, imidazole, ethylimidazole, nitroimidazole, chloromethylimidazole, dichloroimidazole, imidazole-4-carboxamide, aminobenzimidazole, benzimidazole, 5-chlorobenz imidazole, 5,6 dimethylbenzimidazole, methylbenzimidazole, bromobenzimidazole, and nitrobenzimidazole.
The third organic ligand includes at least one selected from amino-1,2,4-triazole, aminoimidazole, 2-aminobenzimidazole and 6-aminobenzimidazole.
The spacing between the (011) crystal planes of the nanoparticles is 12.06 to 11.95 Å, the IR peak of the amine-metal bond of the nanoparticles is 425.5 to 429.5 cm′, the specific surface area of the nanoparticles is 400 to 1000 m2 g−1, the pore volume is 0.2 to 0.65 cm3 and the size of the nanoparticles is 80 nm to 120 nm.
The present disclosure also provides a method of manufacturing nanoparticles of a zeolitic imidazolate framework (ZIF) into which three kinds of ligands are introduced. The method includes agitating a metal precursor, an imidazole-based first organic ligand, and an alkylamine-based second organic ligand in a first polar solvent to obtain raw nanoparticles; and substituting at least a portion of the first organic ligand and the second organic ligand of the raw nanoparticles with a third organic ligand comprising at least one amine group substituted on a ring.
The substituting is performed by agitating the raw nanoparticles and the third organic ligand in a second polar solvent.
The metal precursor includes an acetate salt of one or more metals selected from the group consisting of Co, Zn, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Lr, Rf, db, Sg, Bh, Hs, Mt, Ds, Rg, and Uub, the first polar solvent and the second polar solvent each independently include at least one selected from the group consisting of alcohol, methanol, ethanol, propanol, ethylene glycol, water, dimethylformamide, dimethyl sulfoxide, acetonitrile, and dimethylacetamide.
The present disclosure also provides a hybrid membrane comprising nanoparticles. The hybrid membrane includes 100 parts by weight of a polymer; and a hybrid membrane comprising 30 to 150 parts by weight of the nanoparticles according to anyone from claim 1 to claim 7.
The hybrid membrane has a CO2/N2 separation performance of 25 to 60, a CO2/CO separation performance of 15 to 60, and a CO2/CH4 separation performance of 24 to 50 at 1 atmospheric pressure and 35° C.
The present disclosure also provides a gas separation method including separating one or more gases from a mixed gas containing two or more gases using the hybrid membrane.
The difference in molecular size of the gases included in the mixed gas is 0.1 Å to 5 Å, and the mixed gas includes CO2.
In the following description, a ZIF into which three ligands are introduced is referred to as a “nanoparticle”, nanoparticles using 3-amino-1,2,4-triazole (Atz) as the third ligand are called “TAZIF” or “TAZIF8”.
In the following description, zinc as the metal particle, 2-methylimidazole (2mim) as the first ligand, tributylamine as the second ligand, and 3-amino-1,2,4-triazole (Atz) is illustrated by way of example, but the present invention is not limited thereto.
In addition, in the following description, the hybrid membrane is used as a hybrid membrane for separating CO2 gas, but the use of the hybrid membrane of the present invention is not limited thereto.
The present invention provides nanoparticles with three ligands, 1) by controlling the compatibility between nanoparticles and polymers and the pore size of nanoparticles using an alkyl amine modulator, and 2) by partially substituting a new organic ligand containing an amine group capable of selectively adsorbing CO2 gas in the nanoparticles. The hybrid separation membrane including nanoparticles has high permeability and high selectivity to CO2 gas.
Each of the three organic ligands may be connected to a metal ion by a coordination bond.
Nanoparticles introduced with amine groups by reforming have improved CO2 gas adsorption capacity, and at the same time, pore size is controlled by reforming, thereby enabling selective gas adsorption and permeation. When nanoparticles are synthesized using an amine modulator, the compatibility between the polymer and the nanoparticles is increased, the crystallinity of the nanoparticles is improved, and the pore size of the nanoparticles can be adjusted.
In the present invention, as shown in
The nanoparticles according to the present invention include a metal ion and an organic ligand bound thereto. The organic ligand includes an imidazole-based first organic ligand, an alkylamine-based second organic ligand, and a third organic ligand including at least one amine group substituted on a ring.
In the organic ligand, the third organic ligand may be 20 to 60 mol %, 25 to 55 mol %, or 25 to 60 mol %. Alternatively, the organic ligand may be composed of 30 to 80 mol % of the first organic ligand, 3 to 15 mol % of the second organic ligand, and 20 to 60 mol % of the third organic ligand.
Each of the first organic ligand, the second organic ligand, and the third organic ligand is directly bound to a metal ion.
The first organic ligand may include at least one selected from 2-methylimidazole, imidazole, ethylimidazole, nitroimidazole, chloromethylimidazole, dichloroimidazole, imidazole-4-carboxamide, aminobenzimidazole, benzimidazole, 5-chlorobenz imidazole, 5,6 dimethylbenzimidazole, methylbenzimidazole, bromobenzimidazole, and nitrobenzimidazole.
Alternatively, the first organic ligand may include one or more selected from imidazole-based compounds represented by the following Chemical Formula 1 or Chemical Formula 2 but is not limited thereto.
In each of Formula 1 and Formula 2,
R1, R2, R3, R4, R5, R6, R7, and R8 are each independently H, a C1 to C10 linear or branched alkyl group, a halogen, hydroxy, cyano, nitro, an aldehyde group, or a C1 to C10 group,
A1, A2, A3, and A4 are each independently C or N, with the provision that R5, R6, R7, and R8 are present only when A1 and A4 are C.
The second organic ligand may include at least one of primary, secondary, and tertiary amines, and may include one or more selected from the group of alkylamines having an alkyl chain of any one length of methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, propadecyl, butadecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, and nodadecyl.
The third organic ligand may include at least one selected from 3-amino-1,2,4-triazole, aminoimidazole, 2-aminobenzimidazole, and 6-aminobenzimidazole.
The size of the nanoparticles may be 10 nm to 100 nm or 5 nm to 50 nm, and the pore size of the nanoparticles may be 0.1 nm to 1 nm.
The nanoparticles have a (011) crystal plane spacing of 12.06 to 11.95 Å, the IR peak of the amine-metal bond of the nanoparticles is 425.5 to 429.5 cm−1, the specific surface area of the nanoparticles is 400 to 1000 m2 g−1, and the pore volume is 0.2 to 0.65 cm3 g−1, and the size of the nanoparticles may be 80 nm to 120 nm.
The method for preparing nanoparticles according to the present invention comprises the steps of (1) stirring a metal precursor, an imidazole-based first organic ligand, and an alkylamine-based second organic ligand in a first polar solvent to obtain raw nanoparticles; and (2) substituting at least a portion of the first organic ligand and the second organic ligand of the raw nanoparticles with a third organic ligand.
In the step of obtaining the raw nanoparticles, the molar ratio of the metal precursor: the first organic ligand: the second organic ligand: the first polar solvent may be 1:1-5:3-10:200-1000.
The mixing temperature is 40° C. to 80° C., and the mixture can be stirred for 2 hours to 20 hours. Thereafter, the obtained raw particles are dried.
In the substitution step, the molar ratio of the raw nanoparticles: the third organic ligand: the second polar solvent is 1:5 to 15:30 to 80, and the mixture is stirred. The mixing temperature is 30° C. to 80° C., and the mixture can be stirred for 2 hours to 20 hours.
After stirring, the precipitate is separated through centrifugation, and then purified and dried to obtain nanoparticles.
Metal precursors may include an acetate salt of one or more metals selected from the group consisting of Co, Zn, Sc, Ti, V, Cr, Mn, Fe, Ni, Cu, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Lr, Rf, db, Sg, Bh, Hs, Mt, Ds, Rg and Uub.
The first polar solvent and the second polar solvent may independently include one or more selected from the group consisting of alcohol, methanol, ethanol, propanol, ethylene glycol, water, dimethylformamide, dimethylsulfoxide, acetonitrile, and dimethylacetamide.
The hybrid membrane including nanoparticles includes a polymer matrix and nanoparticles dispersed in the polymer matrix. The polymer matrix may include any one selected from the group consisting of polyimide, polysulfone (PSF), polyisosulfone (PES), cellulose acetate (CA), polydimethylsiloxane (PDMS), and polyvinyl acetate (PVAc).
The hybrid membrane can separate gases having a molecular size difference of 0.1 Å to 5 Å from each other, and may be used to separate a gas mixture of a gas set selected from the group of gas sets consisting of C3H6/C3H8, C2H4/C2H6, CO2/CH4, CO2/CO, CO2/N2, N2/CH4, and n-C4/i-C4 (n-butane/iso-butane), H2/CH4, H2/C3H8 and H2/C3H6. In the separation method, by passing a mixed gas through a hybrid membrane, the gases are separated from each other using a difference in molecular size of the gases included in the mixed gas.
The thickness of the hybrid membrane may be 50 nm to 100 μm or 1 μm to 100 μm.
The hybrid membrane may include 100 parts by weight of a polymer and 30 to 150 parts by weight or 40 to 80 parts by weight of nanoparticles. Alternatively, the nanoparticles in the hybrid membrane may be 20 wt % to 80 wt %, 30 wt % to 70 wt %, or 30 wt % to 50 wt %.
The hybrid membrane may have a CO2/N2 separation performance of 25 to 60, a CO2/CO separation performance of 15 to 60, and a CO2/CH4 separation performance of 24 to 50 at 1 atmospheric pressure and 35° C.
Hereinafter, the present invention will be described in detail through experimental examples.
Preparation of Nanoparticles
In a round flask, zinc acetate-based metal salt, 2-methylimidazole (2mim), amine modulator (ie, tri-butyl amine, TBA), and methanol were mixed in a molar ratio of 1:2:5:500 at 65° C. The mixture was stirred at 700 rpm for 12 hours.
After 24 hours, the white precipitate formed was purified using methanol and a centrifuge.
Thereafter, the particles were dried at 100° C. and 200° C. under vacuum conditions for 12 hours each.
The obtained amine modulator-introduced raw nanoparticles (AZIF, AZIF8) were mixed with 3-amino-1,2,4-triazole (ie, Atz) and methanol in a molar ratio of 1:8:45 at 40° C. The mixture was stirred at 700 rpm for 6 hours, 6 hours 30 minutes, 6 hours 40 minutes, 7 hours, and 7 hours 30 minutes, respectively. After stirring, the white precipitate formed was purified using methanol and a centrifuge, and then dried at 100° C. and 120° C. under vacuum conditions for 12 hours, respectively, to obtain nanoparticles, that is, TAZIF (TAZIF8).
Analysis of Molar Ratio and Binding Form of Organic Ligands
The molar ratio of the organic ligand contained in the synthesized nanoparticles was calculated through 1H NMR analysis. As the equipment, Unity Inova (500 MHz) was used, and an analysis solution was prepared by dissolving each particle in a H2SO4/CDCl3 (10/90 v/v) solution.
As shown in Table 1, it was confirmed that the molar ratio of 2mim decreased and the molar ratio of Atz increased in the TAZIF8 particles stirred using Atz for up to 6 hours and 40 minutes without significant change in the amine modulator group in the organic ligand. However, in the TAZIF particles stirred for 7 hours and 7 hours 30 minutes, the molar ratio of 2mim and TBA compared to the raw nanoparticles rapidly decreased, confirming that most of the organic ligands in the nanoparticles were substituted with Atz. Particles subjected to Atz reaction for 6 hours, 6 hours 30 minutes, 6 hours 40 minutes, 7 hours, and 7 hours 30 minutes are named TAZIF8-30 mol %, TAZIF8-40 mol %, TAZIF8-50 mol %, TAZIF8-90 mol % and TAZIF8-99 mol %.
In order to check the presence or absence of precise coordination bond between Zn metal ions and organic ligands in TAZIF8 nanoparticles, by using time of flight secondary ion mass spectrometry (ToF-SIMS), the components and types of coordination bonds in the synthetic particles were confirmed. The instrument was applied with a 30 keV BI3+ cluster ion beam using IONI-TOF GmbH TOF SIMS 5. As shown in
Analysis of the Crystalline Structure of Nanoparticles
In order to determine the crystalline structure of the synthesized TAZIF8 particles, X-ray diffraction analysis (X-ray Diffraction, XRD) was used and compared with the raw nanoparticles (
Identification of Atz Organic Ligands within TAZIF
In order to confirm the presence of the introduced Atz organic ligand in the TAZIF8 particles, Fourier transform infrared spectroscopy (FT-IR) was analyzed. The instrument used Nicolet 380 FT-IR spectroscopy to scan a wavenumber of 4,000-400 cm−1 at a magnification of 2 cm−1. As the amount of Atz introduced increased, it was confirmed that the area of the detection peak at the wavenumbers of 3,500-3,000, 1,650, and 1,050 cm−1 representing the secondary amine group in the Atz group increased (
In addition, it was confirmed that the area of the detection peak at the wavenumbers of 3,100, 1,550-1,500, and 1,210 cm−1 representing the amino functional group (—NH—N—) group in Atz increased. As shown in
TAZIF Surface Area Analysis
For the surface area analysis of TAZIF8 nanoparticles introduced with the Atz group, the Brunauer-Emmett-Teller (BET) equation was used from the N2 adsorption isotherm and compared with the raw nanomaterials. The measurement was carried out under N2 77K conditions using Micromeritics ASAP 2020, and the particles were used after pretreatment for 3 hours under 120° C. vacuum condition before N2 adsorption measurement. As shown in
Scanning Electron Microscope Analysis
Crystal Plane Peak Analysis
To confirm the possibility of selective CO2 interaction and pore size change of TAZIF8 nanoparticles, a real-time X-ray diffraction analyzer (In-situ XRD) was used to adsorb CO2, N2, and CH4 gases under isothermal conditions at 1 atm and 35° C., and the changes in the peak values and the peak area values of the (011) crystal plane of the particles were compared. X'Pert Pro equipment was used and the conditions of 60 kV and 60 mA were applied. As shown in
As shown in Table 3, as a result of confirming the change in the (011) crystal plane peak value observed after exposing each nanoparticle to vacuum conditions, the raw nanoparticles showed a change of about 0.05 deg. whereas the TAZIF8 nanoparticles showed little change in the (011) crystal plane peak value even after exposure to vacuum conditions. This means that the pore size of the TAZIF8 nanoparticles was limited compared to the native nanoparticles. After exposing each nanoparticle exposed to vacuum conditions to CO2 gas (011), and the change in the crystal plane peak value was observed, in the case of raw nanoparticles, it shows a change of about 0.05 deg, whereas TAZIF8-30 mol % shows a change of 0.07 deg., and TAZIF8-40 mol % shows a change of 0.09 deg. This can be interpreted as an improvement in the amount of CO2 gas adsorption due to the amine group in the Atz group introduced into the TAZIF8 nanoparticles even though the TAZIF8 nanoparticles have a limited pore size compared to the original nanoparticles. On the other hand, TAZIF8-50 mol % is 0.05 deg., which can be interpreted as a decrease in the adsorption amount because the pore size in the nanoparticles is very limited, and CO2 gas does not penetrate into the particles despite having an amine group.
As shown in
On the other hand, in the case of N2 and CH4 gases, it was confirmed that the adsorption amount gradually decreased as the amount of Atz introduced increased. This is a result similar to the result of the N2 isothermal adsorption experiment, as the Atz group, which is larger than the 2mim organic ligand, was introduced, the specific surface area and pore volume of the particles decreased, and at the same time, it was shown that it was difficult for the gas to pass through the pores of the TAZIF8 particle due to the strong bonding force between the metal and the organic ligand. In addition, in the case of TAZIF8-50 mol % nanoparticles, the amount of CO2 adsorption decreased compared to TAZIF8-40 mol % nanoparticles; this indicates that when an excessive amount of Atz group is introduced, the amount of adsorption to CO2 gas can be decreased due to the above reasons.
Membrane Manufacturing and SEM Analysis
A hybrid membrane was prepared by mixing AZIF8, TAZIF8-30 mol %, TAZIF8-40 mol %, or TAZIF8-50 mol % with 6FDA-DAM polyimide (PI) polymer at a weight ratio of 60 (polymer)/40 (nanoparticle). AZIF8, TAZIF8-30 mol %, TAZIF8-40 mol %, and TAZIF8-50 mol % nanoparticles were mixed with a solvent (N-methyl-2-pyrrolidone, NMP) in a glass bottle for 1 hour, and each nanoparticle was uniformly dispersed in the solvent through an ultrasonic mill. Each nanoparticle was uniformly dispersed in the solvent for 30 seconds using a cone-shaped ultrasonicator. After mixing 6FDA-DAM polymer in a solvent in which each nanoparticle is uniformly dispersed and stirring through a roller for 12 hours, a glass bottle containing a uniformly dissolved polymer solution was placed in an ultrasonic grinder for 30 minutes to remove microbubbles in the solution, and the polymer solution was spread on a glass plate with a thin layer of 250 μm using a casting knife and dried under vacuum conditions at 120° C. for 12 hours. After 12 hours, the vitrified hybrid membrane was dried once again under vacuum conditions at 120° C. for 12 hours to remove residual solvent. The hybrid membrane obtained at this time exhibited a thickness of about 35 to 45 μm (
In order to observe the effect by the presence or absence of the second ligand, by using TAZIF8-40 mol % nanoparticles introduced with the second ligand and TZIF8-40 mol % nanoparticles omitting the second ligand, a hybrid membrane having 40 wt % nanoparticle was formed. As shown in
Measurement of Physical Properties of Hybrid Membranes
The mechanical properties of the hybrid membrane, Young's modulus and hardness, were measured using a nanoindenter. The mechanical properties were measured by pressing the Berkovich tip into the surface 5 times with a load of 2,500 uN using the TI-950 equipment. As shown in
Analysis of Gas Separation Performance of Hybrid Membrane
Table 4 shows the CO2, N2, CO, and CH4 single gas separation performance of all hybrid membranes prepared including PI polymer under isothermal conditions at 1 atm pressure and 35° C. The single gas permeability test of each hybrid membrane was evaluated using a fixed volume-variable permeation system. As a result of the experiment, it was confirmed that the CO2 permeability simultaneously increased as the amount of Atz introduced into the TAZIF8 particles increased, compared to the PI/AZIF8 hybrid membrane.
It is considered that selective CO2 permeation occurred through the interaction of the amine group in AZIF8-Atz with CO2 gas. On the other hand, as the amount of Atz introduced increases, the permeability of N2, CO, and CH4 gases gradually decreases, this means that it is difficult for all gases except CO2 to pass through the pores of the particle because the pore size of the particles becomes smaller after the introduction of the Atz organic ligand in AZIF8.
In the case of TAZIF8-40 mol % nanoparticles, the hybrid membrane containing a 40 weight % of nanoparticle had a CO2 permeability of 1638 Barrer, a CO2/N2 selectivity of 42.5, a CO2/CO selectivity of 28.7, and a CO2/CH4 selectivity of 44.2 without particle agglomeration, and it was confirmed that high selectivity is possible. On the other hand, in the case of the hybrid membrane containing TAZIF8-50 mol % of 40 nanoparticles weight %, the CO2/N2 selectivity was 54.6, the CO2/CO selectivity was 36.1, and the CO2/CH4 selectivity was 45.6, and it showed improved selectivity, but the CO2 permeability was lower than the PI/TAZIF8-40 mol % membrane containing the same weight ratio as 891.54 Barrer. This means that the excess Atz group introduced into the TAZIF8-50 mol % nanoparticles reduces the specific surface area and pore volume of the particles, at the same time, and this means that it is difficult for the gas to pass through the pores of the TAZIF8 particle due to the strong bonding force between the metal and the organic ligand.
In order to more accurately analyze the gas permeation/adsorption mechanism of TAZIF8 nanoparticles, a 35° C. isothermal adsorption experiment for CO2, N2, and CH4 gases of a hybrid membrane containing 40 weight % of nanoparticle was performed. As shown in
Based on the results of the isothermal adsorption experiment, the adsorption behavior of the developed hybrid membrane was analyzed using the dual mode model equation consisting of the sum of the Henry model and the Langmuir model.
Ci (cm3 (STP) cm−3 (polymer)) is the concentration of gas i in the hybrid membrane, pi is the partial pressure of gas i in the equilibrium state, CHi (cm3 (STP) cm−3 (polymer)) is the Langmuir adsorption constant for gas i, bi (atm−1) is the affinity constant for gas i, and kD,i (cm3 (STP) cm−3 (polymer) atm−1) is the Henry constant for gas i. All nanoparticles were dried at 35° C. for 12 hours under vacuum conditions prior to adsorption experiments. As shown in Table 5, the hybrid membrane including TAZIF8 nanoparticles with increased Atz introduction improved the selective interaction with CO2, so that all C′H, b, and kD variables continued to increase up to the PI/TAZIF8-40 mol % membrane, and these model parameters decrease again because the surface area and pores are significantly reduced in the PI/TAZIF8-50 mol % membrane. On the other hand, the variables for N2 and CH4 gases decrease the surface area and pore volume of nanoparticles as the amount of Atz is increased, and it was confirmed that all PI/TAZIF8 MMMs have reduced C′H compared to PI/AZIF8. This result indicates that TAZIF8 nanoparticles are capable of selective interaction with CO2 and decrease the adsorption amount without special interaction with respect to N2 and CH4.
In the dense polymer membrane, gas permeability (Pi) may be expressed as the product of diffusivity (Di), which is a dynamic factor, and solubility (Si), which is a thermodynamic factor.
P
i
=D
i
×S
i
Based on the adsorption amount for each gas calculated in
aDiffusivity
bSolubility
