Mixed metal strategy for rapid synthesis of metal-organic frameworks under ambient conditions

Abstract

Disclosed herein is a metal organic framework (MOF) having a UTSA-16 structure, wherein the composition includes: 0-80 mol% of all metals in the MOF is one or more first metals selected from the group consisting of Cr, Mn, Fe, Ni, Cu, and Co; and 20-100 mol% of all metals in the MOF is one or more second metals selected from the group consisting of Cd, Mn, and Zn.

Description

Technical Field

[0001] This invention relates to metal-organic frameworks (MOFs) having a UTSA-16 structure. In particular, this invention relates to MOFs with good CO2 capture performance, and a method for producing MOFs significantly faster under milder reaction conditions. Background Technology

[0002] Listing or discussing previously disclosed documents in this specification should not be construed as an admission that such documents are part of the prior art or common general knowledge.

[0003] Metal-organic frameworks (MOFs) are porous crystalline materials with modular synthetic chemistry. Due to their high compositional tunability, they are suitable for precise materials engineering, allowing for excellent performance in many commercially interesting applications. For example, certain MOFs have exhibited large CO2 absorption and capture, high CO2 selectivity, and extended stability that makes them excellent CO2 capture adsorbents. The development of scalable and sustainable solutions is a necessary step toward the practical commercial application of MOFs. This is because most anticipated MOF applications require large footprints (e.g., ~3000 tons of adsorbent for a capture unit integrated with a 500MW coal-based power plant). Consequently, environmental impact and manufacturing costs significantly affect the overall economic viability of the approach.

[0004] UTSA-16 is a promising MOF material for capturing CO2 by adsorption due to its isothermal characteristics, adsorption mechanism, and stability. Almost all reported syntheses of this material are based on the scheme in the Journal of the American Chemical Society 2005, 127(47), 16352-16353: where only the container and solvent volumes are adjusted to achieve the desired synthesis scale. The reported scheme involves mixing the precursor feedstock in a 50% / 50% ethanol-water mixture followed by isothermal heating at 120 °C for a fixed duration, corresponding to an autogenous pressure of 4 to 6 bar. This solvothermal synthesis method requires a specialized reactor that introduces additional capital costs to production and excludes the use of conventional glass equipment, typically operating at pressures below 2 bar. Continued attempts to scale up this material have been hampered by the inability to lower the synthesis temperature below the boiling point of the solvent. Furthermore, the prevailing scheme requires extended crystallization times (up to 2 days). The reaction efficiency, estimated by space-time yield, is 25 kg (m³). 3 sky) -1 This would require an increase of approximately tenfold to be commercially viable. The ternary phase equilibrium of deprotonated ligand salts in solution (i.e., tripotassium citrate + ethanol + water) involves liquid-liquid phase separation. In the presence of cobalt salts, viscous gelation occurs. It should be understood that mixing is adversely affected by high viscosity.

[0005] The transition from closed solvothermal conditions to open reflux synthesis using safe and inexpensive solvents is a significant step toward scalable solutions. Reflux synthesis of MOFs utilizes proven manufacturing techniques and has been demonstrated in tonne production of aluminum fumarate MOFs. When reflux synthesis replaces the solvothermal method, capital equipment costs, safety compliance costs, and energy costs can all be reduced.

[0006] Reaction optimization for MOFs is highly system-specific. Most reported reflux synthesis schemes described for low-valence and high-valence MOFs involve binary systems with a single metal precursor and a single organic linker. These schemes are unsuitable for the synthesis of materials with higher structural complexity. UTSA-16 possesses unique chemical characteristics, resulting in distinct coordination geometries for the metals within its differentiated structural motifs. Generally accepted crystal field theory predicts that one of these coordination geometries is significantly more favorable in terms of stability. This directly impacts synthesis, as conditions unfavorable to the formation of less stable motifs will substantially impair the kinetics, and thus the yield and efficiency of product formation.

[0007] Therefore, there is a need for improved materials and methods that can produce USTA-16 in a milder reaction at a faster time while retaining good CO2 capture performance. Summary of the Invention

[0008] Surprisingly, the introduction of a second metal component yielded UTSA-16 analogs with improved CO2 capture performance, which could be formed under significantly milder conditions and in a shorter time. This ensured the use of conventional laboratory equipment and open reflux synthesis. The optimized scheme is more compatible with industrial production, paving the way for the mass production of these promising materials.

[0009] Aspects and embodiments of the present invention are listed in the following numbered entries.

[0010] 1. A metal-organic framework (MOF) having a UTSA-16 structure, wherein the composition includes:

[0011] Of the total metals in the MOF, 0–80 mol% are selected from one or more first metals chosen from the group consisting of Cr, Mn, Fe, Ni, Cu, and Co; and

[0012] Of the total metals in the MOF, 20–100 mol% are one or more second metals selected from the group consisting of Cd, Mn, and Zn.

[0013] 2. The MOF according to item 1, wherein the second metal is Zn.

[0014] 3. The MOF according to item 1 or 2, wherein the second metal is present in an amount of 25 to 100 mol% of all metals present in the MOF.

[0015] 4. The MOF according to item 3, wherein the second metal is present in an amount of 50 to 75 mol% of all metals present in the MOF.

[0016] 5. The MOF according to any one of the preceding entries, wherein the first metal is selected from Fe and Co.

[0017] 6. The MOF as described in item 5, wherein the first metal is Co.

[0018] 7. The MOF according to any one of the preceding entries, wherein the first metal is present in an amount of 25 to 50 mol% of all metals present in the MOF.

[0019] 8. The MOF according to any one of the preceding entries, wherein the second metal preferentially occupies tetrahedral metal sites within the MOF.

[0020] 9. The MOF according to any one of the preceding entries, wherein the first metal, when present, occupies a majority of the octahedral metal sites within the MOF.

[0021] 10. The MOF according to any one of the preceding entries, wherein the first metal and the second metal, when present, preferentially occupy the octahedral metal sites and tetrahedral metal sites within the MOF, respectively.

[0022] 11. The MOF according to any one of the preceding entries, wherein the saturated CO2 absorption of the MOF is at most 5.0 mmol / g, optionally wherein the saturated CO2 absorption of the MOF is 2.5 to 4.5 mmol / g, for example 3.39 to 3.50 mmol / g.

[0023] 12. The MOF according to any one of the preceding entries, wherein the working capacity of said MOF to penetrate CO2 is at most 2.2 mmol / g, for example 1.0 to 1.8 mmol / g, for example 1.65 to 1.70 mmol / g.

[0024] 13. A method for forming a MOF according to any one of the preceding items, wherein the method comprises aging a mixture comprising a first metal precursor, a second metal precursor, a base, citric acid, a first solvent, and a second solvent at a temperature of 15–200°C for a period of time, wherein:

[0025] The first metallic precursor is selected from one or more of the group consisting of Cr, Mn, Fe, Ni, Cu and Co;

[0026] The second metallic precursor is selected from one or more of the group consisting of Cd, Mn, and Zn; and

[0027] The metal in the first metal precursor is present in an amount of 0 to 80 mol% of the total metal in the mixture; and

[0028] The metal in the second metal precursor is present in an amount of 20 to 100 mol% of the total metal in the mixture.

[0029] 14. The method according to item 13, wherein the temperature is 20 to 150°C.

[0030] 15. The method according to item 14, wherein the temperature is 40 to 120°C, for example, 60 to 80°C.

[0031] 16. The method according to item 15, wherein the temperature used causes one solvent to reflux or both solvents to reflux.

[0032] 17. The method according to any one of items 13 to 16, wherein:

[0033] (a) The first solvent is water and the second solvent is an alkyl alcohol (e.g., methanol, propanol, or, more particularly, ethanol); and / or

[0034] (b) The base is a metal hydroxide (e.g., the base is KOH); and / or

[0035] (c) The method is performed under ambient atmospheric conditions (e.g., standard pressure).

[0036] 18. The method according to any one of items 13 to 17, wherein the first metal precursor and the second metal precursor are metal salts and their hydrates, wherein the metal is in the form of a cation and is balanced by one or more counter ions selected from one or more of halide (e.g., chloride), nitrate, sulfate, hydroxide, oxo, and acetate anions.

[0037] 19. The method according to any one of items 13 to 18, wherein:

[0038] (a) The second metal precursor is Zn(OAc)2 or its hydrate (e.g., Zn(OAc)2·2H2O); and / or

[0039] (b) The metal in the second metal precursor is present in an amount of 25 to 100 mol%, for example 50 to 75 mol%, of all the metals present in the mixture.

[0040] 20. The method according to any one of items 13 to 19, wherein:

[0041] (a) The first metal precursor is Fe(OAc)2, Co(OAc)2 or its hydrate (e.g., Co(OAc)2·4H2O); and / or

[0042] (b) The metal in the first metal precursor is present in an amount of 25 to 50 mol%, for example 50 to 75 mol%, of all the metals present in the mixture.

[0043] 21. A method for capturing CO2, comprising the step of exposing a material comprising an MOF according to any one of items 1 to 12 to an environment containing CO2. Attached Figure Description

[0044] Figure 1 (a) Representation of the inorganic constituent units within UTSA-16 and their respective formation trends when using different metal precursors. (b) Representation of single-metal and mixed-metal synthesis methods for synthesizing UTSA-16 with different formation kinetics.

[0045] Figure 2 (a) PXRD patterns of mixed metal UTSA-16 MOFs with varying Zn loading (x represents the feed mole fraction of Zn in the mixed Zn / Co precursor). (b) Reported Co-O bond distances for tetrahedral and octahedral Co motifs in UTSA-16. k-bonds collected at the Co K-edge (c) and Zn K-edge (d). 3 - Fourier transform of weighted EXAFS data. (e) Location of the first peak maximum of the FT-EXAFS data as a function of Zn load x. Upward triangle: data from CO K-edge. Downward triangle: data from Zn K-edge. (f) Fraction Y of any metallic substance occupying a tetrahedral site. Co,tet and Y Zn,tet As a function of Zn load x. Note that, based on SCXRD data, Y Co,tet (x=0) and Y Zn,tet (x=1) is 0.33.

[0046] Figure 3(a) PXRD patterns of UTSA-16-Zn-0 obtained after culturing at different temperatures for 24 hours. (b) PXRD patterns of UTSA-16-Zn-0.50 obtained after culturing at different temperatures for 24 hours. (c) Growth kinetics of UTSA-16-Zn-x based on ex-situ experiments. An S-shaped fit (solid line) is presented to guide the eye.

[0047] Figure 4 (a) CO2 isotherm of UTSA-16-Zn-x at 298 K. (b) Breakthrough curve of wet CO2 (relative humidity: 85%) of UTSA-16-Zn-x at 298 K. (c) Isoheat absorption of CO2 by UTSA-16-Zn-x. (d) IAST selectivity of UTSA-16-Zn-x for 10:90 CO2 / N2 mixture at 298 K under different feed pressures.

[0048] Figure 5 Optical micrographs of UTSA-16-Zn-0.25 (a, b, scale bar: 50 μm) and UTSA-16(Co) (c, d, scale bar: 200 μm). The droplets are liquid / gels with relatively high viscosity.

[0049] Figure 6 FTIR spectrum of UTSA-16-Zn-x: 400-4000 cm⁻¹ -1 (Left) and 1000-1800cm -1 (right).

[0050] Figure 7 DSLF fitting of CO2 isotherms at 273 and 298 K for UTSA-16-Zn-x material.

[0051] Figure 8 Comparison of TGA thermograms of UTSA-16-Zn-x materials (recorded in air, 150-800℃, heating rate 5℃ / min).

[0052] Figure 9 Photographs of UTSA-16-Zn-x held against white A4 paper: (from left to right) x = 0 (pure Co), 0.25, 0.50, 0.75, 1.00 (pure Zn).

[0053] Figure 10 XANES spectra of Co K-edge and Zn K-edge of bimetallic UTSA-16-Zn-x material.

[0054] Figure 11 The results of the EXAFS fitting. Experimental data are shown as white circles, and the fitted curve is shown as a solid line.

[0055] Figure 12 The composition of the self-made penetration device used in this study.

[0056] Figure 13 Uncorrected penetration curves of UTSA-16-Zn-x material under different conditions. Empty symbol – N2, solid symbol – CO2. Detailed Implementation

[0057] Surprisingly, the introduction of the second metal described herein provides mixed-metal UTSA-16 analogs that can be prepared under milder conditions compared to monometallic UTSA-16. These compounds exhibit an asymmetric site distribution of the first and second metals and benefit from an expanded reaction space and faster reaction kinetics. Furthermore, the materials disclosed herein can possess improved gas separation properties while retaining the underlying structure of UTSA-16.

[0058] Therefore, in a first aspect of the invention, a metal-organic framework (MOF) having a UTSA-16 structure is provided, wherein the composition includes:

[0059] Of the total metals in the MOF, 0–80 mol% are selected from one or more first metals chosen from the group consisting of Cr, Mn, Fe, Ni, Cu, and Co; and

[0060] Of the total metals in the MOF, 20–100 mol% are one or more second metals selected from the group consisting of Cd, Mn, and Zn.

[0061] In the embodiments described herein, the word "comprising" can be interpreted as requiring the mentioned features, but not limiting the presence of other features. Optionally, the word "comprising" can also refer to the situation where only the listed components / features are intended to be present (e.g., the word "comprising" can be replaced by the phrases "consisting of" or "substantially consisting of"). It is explicitly understood that both broad and narrow interpretations can be applied to all aspects and embodiments of the invention. In other words, the word "comprising" and its synonyms can be replaced by the phrases "consisting of" or "substantially consisting of" or their synonyms, and vice versa.

[0062] The phrase “consistently made of” or its synonyms can be interpreted in this text as referring to materials that may contain small amounts of impurities. For example, the material can be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greater than 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure.

[0063] As used herein, the term USTA-16 refers to MOFs that share a structure similar to that disclosed in the microporous cobalt citrate framework of USTA-16 (University of Texas at San Antonio-16). However, to avoid ambiguity, compounds disclosed herein use different constituent components.

[0064] As mentioned above, the first metal present can be selected from one or more of the group consisting of Cr, Mn, Fe, Ni, Cu, and Co. For example, the first metal (in its presence) can be selected from one or both of Fe and Co, or, more particularly, the first metal (in its presence) can be Co. It can be understood from the above that the first metal may or may not be present in the MOF of the present invention. When the MOF is present, the first metal can represent up to 80 mol% of all metals present in the MOF. In a particular embodiment of the present invention, when the first metal is present, it can represent 25–50 mol% of all metals present in the MOF.

[0065] As mentioned herein, the second metal can be one or more selected from the group consisting of Cd, Mn, and Zn. In a more particular embodiment that may be mentioned herein, the second metal can be Zn.

[0066] As will be understood, the second metal may be the only metal present in the MOF (i.e., the first metal represents 0 mol% of all metals in the MOF and the second metal represents 100 mol%), but it may more typically exist in combination with the first metal. Therefore, in embodiments of the invention, the second metal may represent 20–80 mol% of all metals in the MOF, for example 25–100 mol%, for example 50–75 mol%.

[0067] Therefore, in embodiments of the present invention, the MOF may include:

[0068] (a) 0 mol% of the first metal and 100 mol% of the second metal;

[0069] (b) 25 mol% of the first metal and 75 mol% of the second metal;

[0070] (c) 50 mol% of the first metal and 50 mol% of the second metal;

[0071] (d) 75 mol% of the first metal and 25 mol% of the second metal; and

[0072] (e) 80 mol% of the first metal and 20 mol% of the second metal,

[0073] 100 mol% represents all the metals in the MOF.

[0074] Within the microporous cobalt citrate framework USTA-16, there are tetra[Co4] clusters and single [Co(O2CR)4] units, with the Co(II) species employing octahedral and tetrahedral coordination environments, respectively.

[0075] In embodiments of the invention where only the second metal is present, by analogy, both octahedral and tetrahedral coordination environments will be occupied simultaneously. The second metal will occupy both octahedral and tetrahedral coordination environments. However, when the first metal is also present, the second metal will preferentially occupy tetrahedral metal sites within the MOF. For example, a majority of the second metal can occupy tetrahedral metal sites within the MOF. When used herein, "majority" can mean 51 mol% of the second metal, such as 55 mol%, 60 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, 95 mol%, or 99 mol% occupying tetrahedral metal sites.

[0076] Similarly, when only a small amount of the second metal is present (e.g., 20 mol%), the first metal can occupy both octahedral and tetrahedral coordination environments. However, the first metal can exhibit preferential octahedral metal site occupancy. For example, a majority of the first metal, in its presence, can occupy octahedral metal sites within the MOF. When used herein, "majority" can mean 51 mol% of the first metal, for example, 55 mol%, 60 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, 95 mol%, or 99 mol% occupying octahedral metal sites.

[0077] Therefore, in embodiments of the present invention in which the first and second metals coexist, the first metal and the second metal preferentially occupy the octahedral metal sites and tetrahedral metal sites within the MOF, respectively.

[0078] For example, when a 50:50 mixture of Zn and Co, which are respectively the second and first metals, is present, 65 mol% of Zn can occupy tetrahedral metal sites. Furthermore, when a 25:75 mixture of Zn and Co, which are respectively the second and first metals, is present, 82 mol% of Zn can occupy tetrahedral metal sites.

[0079] The specific surface area of ​​the MOF disclosed in this article can be 300–1500 m². 2 g -1 For example, 500-1000m 2 g -1 For example, 691–863m 2 g -1 .

[0080] The MOFs disclosed herein can be used for CO2 capture. Accordingly, the MOFs of the present invention can exhibit a saturated CO2 absorption of up to 5.0 mmol / g, optionally wherein the saturated CO2 absorption of the MOF is 2.5 to 4.5 mmol / g, for example 3.39 to 3.50 mmol / g. Alternatively or optionally, the CO2 penetration capacity of the MOFs of the present invention can be up to 2.2 mmol / g, for example 1.0 to 1.8 mmol / g, for example 1.65 to 1.70 mmol / g.

[0081] The MOFs disclosed herein can be readily prepared. As mentioned above, the MOFs disclosed herein can be formed under milder conditions (e.g., lower temperatures or pressures). Therefore, in a second aspect of the invention, a method for forming the MOFs described herein is provided, wherein the method comprises aging a mixture comprising a first metal precursor, a second metal precursor, a base, citric acid, a first solvent, and a second solvent at a temperature of 15–200°C for a period of time, wherein:

[0082] The first metallic precursor is one or more selected from the group consisting of Cr, Mn, Fe, Ni, Cu and Co;

[0083] The second metallic precursor is selected from one or more of the group consisting of Cd, Mn, and Zn; and

[0084] The metal in the first metal precursor is present in an amount of 0 to 80 mol% of the total metal in the mixture; and

[0085] The metal in the second metal precursor is present in an amount of 20 to 100 mol% of the total metal in the mixture.

[0086] Any suitable temperature in the range of 15 to 200°C can be used. For example, the temperature can be 20 to 150°C, such as 40 to 120°C, or 60 to 80°C. In other embodiments, the temperature can be room temperature (i.e., 20 to 30°C, such as about 25°C).

[0087] As mentioned above, this method utilizes both first and second solvents. Accordingly, the temperature used for preparation can result in either reflux of one solvent or reflux of both solvents. Compared to solvothermal methods, using reflux synthesis can reduce equipment costs, safety compliance costs, and energy costs.

[0088] Any suitable solvent can be used as the first and second solvents. For example, the first solvent can be water and the second solvent can be an alkyl alcohol (e.g., methanol, propanol, or, more particularly, ethanol).

[0089] Any suitable base can be used in the methods disclosed herein. For example, the base can be a metal hydroxide (e.g., KOH).

[0090] The above method can be performed under any suitable pressure. For example, it can be performed under ambient atmospheric conditions (e.g., standard pressure). Furthermore, this can reduce the costs associated with the preparation of MOFs.

[0091] Any suitable chemical may be used as the first and second metal precursors. As will be understood, the selected chemical will need to include a first and / or second metal capable of acting as a precursor. In embodiments of the invention that may be mentioned herein, the first and second metal precursors may be metal salts and their hydrates, wherein the metal is in cationic form and is balanced by one or more counterions selected from one or more of halide (e.g., chloride), nitrate, sulfate, hydroxide, oxo, and acetate anions.

[0092] In certain embodiments that may be mentioned herein, the second metal precursor may be Zn(OAc)2 or its hydrate (e.g., Zn(OAc)2·2H2O). Alternatively or additionally, the metal in the second metal precursor may be present in an amount of 25–100 mol%, for example, 50–75 mol%, of all metals present in the mixture.

[0093] In specific embodiments that may be mentioned herein, the first metal precursor is Fe(OAc)2, Co(OAc)2, or its hydrate (e.g., Co(OAc)2·4H2O). Alternatively or additionally, the metal in the first metal precursor may be present in an amount of 25–50 mol%, for example 50–75 mol%, of all metals present in the mixture.

[0094] As mentioned above, the MOFs disclosed herein can be used to capture CO2. Therefore, in a third aspect of the invention, a method for capturing CO2 is provided, comprising the step of exposing a material including the MOFs disclosed herein to an environment containing CO2.

[0095] Further aspects and embodiments of the invention will now be described with reference to the following non-limiting examples.

[0096] Example

[0097] The original UTSA-16(Co) contains tetra[Co4] clusters and a single [Co(O2CR)4] unit coexisting in the framework, where Co IIThe species employ octahedral and tetrahedral coordination environments, respectively. In turn, these units form nodes with octahedral and triangular connectivity, resulting in anatase-type networks. According to crystal field theory, the presence of weakly field ligands such as carboxylate groups and solvent molecules largely favors Co in octahedral coordination. II As a result, tetrahedral Co under the prevailing reaction conditions... II The low thermodynamic stability of the material can reduce the driving force for the formation of the corresponding [Co(O2CR)4] motif, and thus kinetically limit the formation process of the material. Figure 1 a). We assume that Zn is included. II As a second metallic component, it can generate structurally similar [Zn(O2CR)4] motifs in the framework, since Zn is known to be... II In several systems, it exhibits a tetrahedral geometry. In mixed metal formulations, a one-pot combination of two metal sources favors the formation of [Co4] and [Zn(O2CR)4] due to their specific coordination preferences. Importantly, cation partitioning decouples the formation rates of the two motifs from the octahedral-tetrahedral equilibrium of the individual precursors, leading to accelerated MOF formation kinetics. Figure 1 b). Based on this, mixed metal formulations were prepared and analyzed.

[0098] Materials and methods

[0099] All reagents were commercially available and used without further purification. The reagents were prepared using PU... + Ultrapure water supplied by the purification system (VWR).

[0100] Table 1. List of Chemicals

[0101] chemicals source Citric acid, >98% TCI Singapore Cobalt acetate tetrahydrate, 98% Alfa Aesar Zinc acetate dihydrate, 98+% ACS Strem Chemicals Potassium hydroxide, reagent, 98% flakes Sigma Aldrich Ethanol, >99.8% ACS VWR Methanol, >99.8% ACS VWR

[0102] Powder X-ray diffraction. For phase analysis, Cu K₂ was used on a Bruker D8 Advance instrument. α radiation PXRD patterns were collected in the 2θ range of 5–40°. Data were collected at a scan rate of 2° / min. FWHM data derived for kinetic experiments were collected on a Rigaku Miniflex 600 diffractometer, also using Cu K0... α radiation Patterns were collected from the 2θ range of 5–15° at a scanning speed of 2° / min.

[0103] The metallic composition of the mixed metal UTSA-16 MOF was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES, Optima 7300DV, Perkin Elmer). The UTSA-16 sample was digested in a 5% aqueous HNO3 solution, which allowed for complete dissolution of the MOF. The solution was transferred to a low-density polyethylene tube (Fisher Scientific) for further testing.

[0104] FTIR-ATR spectroscopy. Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectra were recorded on a Bruker Vertex 70 spectrometer.

[0105] UV-Vis spectra. Solid-state UV-Vis spectra were collected using a Shimadzu UV-2450 spectrophotometer in the 400-800 nm range with BaSO4 as the standard.

[0106] XPS analysis was performed on a Kratos Axis Ultra XPS system (Kratos Analytical) at 15 kV using monochromatic Al K. α Photoelectron spectra (XPS) were collected using radiation (hν = 1286.71 eV). The measured binding energies (BEs) were referenced to the C1s peak corresponding to the C-C bond (BE set at 284.5 eV). Fitting of the high-resolution Co spectra took into account sites with octahedral coordination environments (O). h ), sites with tetrahedral coordination environment (T) d The remaining contributions are concentrated in the individual satellite signals after Shirley background subtraction. Simultaneously, the Co 2p peaks are analyzed. 3 / 2 and Co 2p 1 / 2 Orbits were fitted. The full width at half maximum (FWHM) was constrained to be identical for any orbit, while the area ratio was constrained to 2:1 based on spin-orbit splitting. A similar fit was performed on the Zn 2p region, but without satellite contributions.

[0107] TGA experiments. Thermogravimetric analysis (TGA) data were collected using a Shimadzu DTG-60AH at an air flow rate of 30 mL / min. The samples were heated to 900 °C at a heating rate of 10 °C / min.

[0108] EXAFS analysis. X-ray absorption fine structure (XAFS) spectra were collected in transmission mode at room temperature under the XAFCA beamline at the Singapore Synchrotron Light Source. Co and Zn K-edge spectra were processed using the IFEFT package according to standard procedures.

[0109] Synthesis and activation procedures

[0110] General Procedure 1. Solvothermal Synthesis of UTSA-16-Zn-x Material

[0111] UTSA-16(Co) (or UTSA-16-Zn-0) was synthesized according to those reported in the Journal of the American Chemical Society 2005, 127(47), 16352-16353. Briefly, Co(OAc)₂·4H₂O (1 mmol), KOH (3 mmol), and citric acid (1 mmol) were mixed in H₂O (2.5 mL) to obtain a homogeneous aqueous solution. The solution was transferred to a Teflon-lined reaction vessel (15 mL). Next, anhydrous ethanol (2.5 mL) was introduced while manually stirring the contents of the vessel. To prepare the bimetallic UTSA-16-Zn-x material, different amounts of Co(OAc)₂·4H₂O were replaced with Zn(OAc)₂·2H₂O, maintaining the total stoichiometry of the metal precursor relative to the ligand and KOH. The reaction mixture was introduced into a preheated oven (Memmert UF) at 120 °C and maintained at this temperature for 2 days, followed by recovery and cooling to room temperature. This method produces large single crystals (UTSA-16-Co) or powder, which are recovered by centrifugation at 5000 rpm and washed with a large amount of anhydrous methanol.

[0112] General Procedure 2. Growth of UTSA-16-Zn-x Single Crystals

[0113] UTSA-16-Zn-x single crystals can be grown at lower temperatures.

[0114] To grow UTSA-16-Zn-1.00 single crystals, 500 μL of an aqueous solution of 0.8 M Zn(OAc)₂·2H₂O was mixed with 500 μL of an aqueous solution of 0.8 M tripotassium citrate to produce a clear solution. Then, 500 μL of a 1% (v / v) aqueous ethanol solution was added. The homogeneous reaction mixture was transferred to a loosely capped scintillation vial and incubated in a preheated oven at 80 °C. Crystals observable by an optical microscope were recovered after approximately 24 hours and retained in the mother solution prior to SCXRD characterization.

[0115] To grow UTSA-16-Zn-0.25 single crystals, 375 μL of a 0.8 M Co(OAc)₂·4H₂O aqueous solution was first mixed with 500 μL of a 0.8 M tripotassium citrate aqueous solution. Next, 125 μL of a 0.8 M Zn(OAc)₂·2H₂O aqueous solution and 500 μL of a 1 vol% ethanol aqueous solution were added sequentially. The same heating and storage scheme was used for UTSA-16-Zn-1.00 (ICP results: 63.3% Co and 36.7% Zn).

[0116] It is important to note that the single-crystal formulation involves an open system in which the solvent is lost through evaporation. Therefore, the measured Co / Zn composition can reasonably vary with the feed and under different synthesis conditions. However, strong site occupancy was observed in all cases.

[0117] General Procedure 3. Activation of UTSA-16-Zn-x Material

[0118] The powder sample was exchanged daily with fresh methanol to dissolve excess ligands or metal precursors. The sample was dried at room temperature under dynamic vacuum for 24 hours to produce a dry solid product. All samples tested in the absorption measurements were activated (see Examples 6 and 7). For characterization, the samples were pre-activated but may be exposed to the environment or solvents during the characterization process.

[0119] Example 1. Synthesis and characterization of UTSA-16-Zn-x material

[0120] Mixed metal MOF samples containing Co and Zn – denoted as UTSA-16-Zn-x, where x represents the feed molar fraction of Zn in the mixed Zn / Co precursor, and x = 0, 0.25, 0.50, 0.75 or 1.00 – are prepared by a one-pot synthesis method according to general procedure 1.

[0121] Structural characterization

[0122] Bulk phase characterization confirmed that all samples possessed the same phase. Powder X-ray diffraction (PXRD) measurements confirmed a unique crystalline phase identical to that of UTSA-16. Figure 2 a). Fourier transform infrared (FTIR) spectroscopy data also confirmed the successful synthesis of the UTSA-16 type MOF. Figure 6 The elemental distribution measured by inductively coupled plasma optical emission spectrometry (ICP-OES) relative to the Co and Zn standards was in good agreement with the feed composition (Table 2).

[0123] Consistent with the color of the changing sample ( Figure 9XPS and UV-Vis spectral data together indicate that the distribution of octahedral-tetrahedral species is a function of the metallic composition of the mixed metal MOF.

[0124] XPS analysis supports T when Zn load increases from 0% to 50%. d Spectral contribution relative to O h And decrease.

[0125] · Octahedral Co 2+ The band position appears at approximately 540 nm (indicating red-pink), while the tetrahedral Co... 2+ The band position appears at approximately 650 nm. The F(R) of the single-metal Zn compound (x = 1.00) is close to zero. The F(R) of the single-metal Co compound (x = 0) includes contributions from both octahedral and tetrahedral Co, consistent with the crystal structure. For the case of x = 0.50, the contribution near λ = 625 nm decreases significantly. This is consistent with Co. tet From Zn tet The alternative is consistent because the latter has a very small spectral contribution.

[0126] Site occupancy within the bulk mixed metal MOF was assessed by measuring room-temperature extended X-ray absorption fine structure (EXAFS) spectra at the Co and Zn K- edges of mixed metal samples with different Zn loadings (x = 0, 0.25, 0.50, 0.75, 1.00). X-ray absorption near-edge structure (XANES) spectra were also performed. Figure 10 This indicates that the samples have similar valence states.

[0127] The BET method was used to determine the specific surface area of ​​UTSA-16-Zn-x material. Adsorption data were collected at 77 K. The obtained specific surface areas are shown in Table 3 below.

[0128] Table 2 (Table S.4.1) shows the calculated Co-Zn ratios of UTSA-16-Zn-x materials from ICP-OES compositional analysis.

[0129]

[0130] Table 3. Calculated BET surface area of ​​UTSA-16-Zn-x material

[0131] x <![CDATA[BET S.A.(m 2 g -1 )]]> 0.00 691 0.25 791 0.50 863 0.75 670 1.00 834

[0132] Example 2. Asymmetric site distribution of Co and Zn in UTSA-16-Zn-x

[0133] The asymmetric site distribution of Co and Zn within UTSA-16-Zn-x was demonstrated using X-ray absorption spectroscopy.

[0134] Fourier transform EXAFS data of all MOF samples at the Co and Zn K- edges are shown in Figure 2 In c and d. In The overall similarity of peak profiles within the R range indicates that the coordination environments employed by Co and Zn in the mixed metal MOF are essentially similar. On the other hand, the peak positions of the mixed metal samples are significantly divergent, extending across the K- edges of Co and Zn. Figure 2 e). With respect to the 1.53(6) of each monometallic MOF and In comparison, the peak maximum value falls within the following range: for CoK-edges... And for Zn K-edge is These are statistically significant biases. Because the average bond lengths of tetracoordinate and hexacoordinate cobalt in UTSA-16 are significantly different ( Figure 2 b) In the preserved crystal structure, the corrected shift of the peak position of any element in the opposite direction indicates the Co shift at a specific site by doping with Zn.

[0135] Based on previous processing of metal site doping in oxide materials, the quantification of site distribution based on EXAFS data was performed by simultaneously fitting the Co and Zn K-edges of the mixed metal sample (Physical Review B 2002, 66(22), 224405). Path amplitude was calculated using the Y-occupying tetrahedral sites. Co,tet and Y Zn,tet The parameters are parameterized based on the number of any metal species. Amplitude parameters are referenced from single-metal Co and Zn samples, whose site occupancy has been previously established by SCXRD (Journal of the American Chemical Society 2005, 127(47), 16352-16353). Other parameters are defined as follows. The results of EXAFS fitting of the combined eight independent datasets are presented in... Figure 11 The results are shown in Tables 4 and 5, and the values ​​of the obtained fitting parameters are reported therein. The fitting shows satisfactory overall agreement with the experimental data. The obtained Y... Co,tet This indicates that most of the Co species are located in the octahedral sites of the mixed metal sample, while Y... Zn,tet It has been proven that Zn has strong tetrahedral preference. Figure 2 f). At x = 0.25, Zn occupies 60.3% of the tetrahedral sites. When the x value increases to 0.50 and 0.75, respectively, this value increases to 84.4% and 93.5%. This strongly indicates an asymmetric site distribution in the mixed metallic material.

[0136] Fitting Parameterization

[0137] Input reported and collected crystal data for UTSA-16(Co) and UTSA-16(Zn), and generate relevant scattering paths using the FEFF program. Consider lengths less than... The path is fitted. For each path, four path parameters S0 are considered. 2 E0, ΔR and σ 2 Path degeneracy N is maintained as specified by the FEFF software.

[0138] A single global E0 is specified as a refineable parameter for each edge.

[0139] In single-metal samples, i.e., x = 0 and x = 1, S0 2 Parameterized into a single, refinable parameter. Co tet —O and Co oct The contributions of the —O single scattering paths are weighted by 0.33 and 0.67 respectively according to their stoichiometry within the resolved crystal structure. A similar weighting scheme is specified for UTSA-16-Zn-x (x=1).

[0140] In the bimetallic sample, the distribution parameterization between octahedral and tetrahedral sites in the structure is denoted by Y. Co,tet (x=0.25), Y Zn,tet (x=0.25), etc., and introduced as weighting parameters. These are then referenced to the S0 of the single-metal sample. 2 In other words, Co in x = 0.25 tet —S0 of the O scatterer 2 Defined as (S0) 2 ,x＝0 ×Y Co,tet (x=0.25)), while Co oct —S0 of the O scatterer 2 For [S0] 2 ,x＝0 ×(1-Y Co,tet (x=0.25)).

[0141] ΔR is parameterized as a single, refinable parameter for each edge, derived from the individual R values ​​of each path. eff Weighted.

[0142] Co tet —O、Co oct —O、Zn tet —O、Zn oct —O’s Debye-Waller factors are reasonably expected to be distinct, and a single refineable parameter is defined for each factor.

[0143] All parameters change freely during the simultaneous fitting of all eight datasets, leading to the calculation of the global R-factor.

[0144] Fitted ΔR and σ 2 The convergence to a physically reasonable value is summarized below. Note the amplitude reduction factor (S0). 2 It is slightly higher than the typical range (0.7–1.1) at the two edges.

[0145] Table 4. Parameters obtained by fitting a combination of eight datasets on the Co and Zn K-edges.

[0146]

[0147] Table 5. Goodness-of-fit information for each of the eight datasets on the Co and Zn K-edges.

[0148]

[0149] Example 3. Synthesis and characterization of UTSA-16-Zn-0.25 and UTSA-16-Zn-1.00 materials

[0150] Further possibilities for determining site occupancy by SCXRD arise due to the three-electron difference between Co and Zn introduced into the sample. A modified scheme was employed to prepare samples of suitable size for SCXRD data collection. Specifically, large single crystals of UTSA-16-Zn-1.00 and UTSA-16-Zn-0.25 were grown according to general procedure 2.

[0151] Unconstrained refinement of the occupancy factors in both octahedral and tetrahedral sites indicates near-complete occupancy of the tetrahedral sites due to Zn, while for UTSA-16-Zn-0.25, Zn occupancy in the octahedral sites is approximately 20%. This model agrees well with the diffraction data (see Table 6). The regressed occupancy corresponds to a bulk composition of 68.3% Co and 31.7% Zn within the single crystal (ICP results: 63.3% Co and 36.7% Zn).

[0152] Single-crystal X-ray diffraction (SCXRD)

[0153] Single-crystal X-ray diffraction data for UTSA-16-Zn-1.00 and UTSA-16-Zn-0.25 were collected at 100 K on a Bruker D8 Venture diffractometer. Data integration and summarization were performed using SAINT software. Multiscan absorption correction was applied to the collected reflectances. The structure was resolved using SHELXTL via a direct method and refined at F2 using the SHELXL-2014 / 7 package within the WINGX program via full-matrix least squares techniques. Refinement was performed anisotropically for all non-hydrogen atoms. All hydrogen atoms were located in a continuous difference Fourier plot and treated as riding atoms using SHELXL default parameters. The structure was checked using the PLATON Adsym subroutine to ensure that additional symmetries were not applied to the model.

[0154] Table 6. Crystal data and structural refinement of UTSA-16-Zn-1.00 and UTSA-16-Zn-0.25

[0155]

[0156]

[0157] Example 4. Effect of Zn loading on temperature-dependent crystallization

[0158] Compare the temperature-dependent crystallization of UTSA-16(Co) (i.e., UTSA-16-Zn-0) and UTSA-16-Zn-0.50.

[0159] Temperature-dependent crystallization

[0160] Except for heating in a preheated oven at a specified temperature (60, 80, 100°C) or at room temperature (25°C) for 24 hours, the reaction mixtures (corresponding to UTSA-16-Zn-0 and UTSA-16-Zn-0.50) were prepared according to general procedure 1.

[0161] The sample was recovered by centrifugation at 5000 rpm, washed with a large amount of anhydrous MeOH, and then dried in a vacuum oven for PXRD testing. Due to the significant Co content in the sample, it exhibited a high signal-to-noise ratio due to X-ray absorption when using a Cu Kα radiation source (Rigaku Miniflex). Therefore, the sample was processed using the instrument's accompanying software (RigakuPDXL) with background subtraction and filtering via the Savitsky-Golay function. Figure 3 All samples in 3a and 3b were treated using the same method. Due to absorption phenomena, the intensity measurements of samples with different compositions are not directly comparable.

[0162] result

[0163] In the case of a single-metal parent MOF (UTSA-16-Zn-0), a viscous gel was deposited, from which purple prismatic crystals were revealed. XRD patterns were collected from products crystallized after incubation at 25, 60, 80, and 100 °C for 24 hours. Figure 3 a) indicates that the solids obtained at low temperatures (25°C and 60°C) are primarily amorphous. When the temperature is increased to 80°C, a peak corresponding to UTSA-16 appears after 24 hours. At 100°C, large single crystals, observable by an optical microscope, begin to form. Figure 5 For UTSA-16-Zn-0.50, the characteristic PXRD peaks can even be observed by allowing the reaction mixture to stand at room temperature for 24 hours. Figure 3 b).

[0164] Example 5: Effect of Zn loading on induction time

[0165] The effect of Zn loading on formation kinetics was estimated using ex-situ PXRD studies. MOF formation kinetics were estimated by the reciprocal of the full width at half maximum (FWHM) of the main PXRD peak at ca. 7.5°, which was further normalized by long-term averages of comparable Zn loadings.

[0166] method

[0167] To accurately estimate the induction time, the composition is optimized to ensure a homogeneous starting solution. Given the salting-out effect, the solvent composition needs to be balanced to suppress liquid-liquid phase separation. Here, M is used. II Starting solution of (acetic acid)-K3 (citric acid) (0.4 M, in 15 vol% EtOH aqueous solution).

[0168] The final composition of the 10 mL solution includes 1.5 mL EtOH, 8.5 mL H2O, and 4 mmol M. II Acetic acid and 4 mmol of citric acid neutralized with 12 mmol KOH. 4 mmol of M II Acetic acid will further partition between the two metals, keeping all other reagent amounts constant. For example, a 50 / 50 solution (x = 0.5) can be prepared with 2 mmol of Co(OAc)₂·4H₂O and 2 mmol of Zn(OAc)₂·2H₂O, neutralized with 4 mmol of citric acid in 12 mmol of KOH in 5 mL of H₂O as solvent. Then, 1.5 mL of EtOH + 3.5 mL of H₂O solution is added to initiate the experiment. Different relative amounts of Co / Zn can be achieved by adjusting M... IIThe relative proportion of (acetic acid) was varied without changing the total molar amount. For example, mixtures of 25 / 75 (x = 0.75) and 75 / 25 (x = 0.25) could be prepared using 1 mmol of Co(OAc)₂·4H₂O and 3 mmol of Zn(OAc)₂·2H₂O, or 3 mmol of Co(OAc)₂·4H₂O and 1 mmol of Zn(OAc)₂·2H₂O, respectively. The concentration of EtOH strongly corresponds to the solid precipitation; to avoid immediate solid formation, EtOH was added as a dilute solution (<30%) in water. Samples were incubated in a preheated oven at 65 °C, removed at fixed intervals, and ice-quenched. The products were centrifuged (8,000 rpm, 3 min), vacuum dried at room temperature, and PXRD measurements were performed. The product recovery time was minimized and kept constant between samples with different Zn loadings. For samples that did not separate into solids after centrifugation, FWHM reported a value of 0.

[0169] result

[0170] Figure 3 c indicates that the induction time (defined as the time it takes for the product to exhibit significant crystallinity) decreases significantly with increasing Zn content in the system. Even a moderate Zn loading (x = 0.25) can drastically reduce the induction time to approximately 70 minutes. These results demonstrate the feasibility of obtaining mixed-metal UTSA-16 materials under ambient pressure for a reasonable synthesis duration (<48 hours).

[0171] exist Figure 3 In step c, the experiment was conducted at T = 65°C. The product crystallized in less than one hour. This temperature is below the boiling point of the solvent, which allows the reaction to be operated under ambient pressure using a simple reflux apparatus. From Figure 3 As is clear in section c, reaction time can be manipulated by adjusting the structural composition. By adapting appropriate process trade-offs, this property can be used to manipulate other parameters besides reaction time, such as temperature.

[0172] Example 6. Carbon capture performance of UTSA-16-Zn-x

[0173] Gas adsorption experiment

[0174] Gas isotherms were measured up to 1 bar using a Micromeritics ASAP 2020 surface area and pore size analyzer. Prior to measurement, the sample was subjected to a reduced pressure (<10 °C) at 150 °C. –2Degassing was performed at 1000 Pa until the degassing rate was below 5 μm Hg / min. UHP-grade N2 and CO2 were used for gas adsorption measurements. An oil-free vacuum pump and an oil-free pressure regulator were used to prevent sample contamination during the degassing process and isotherm measurements. Temperatures of 77 K, 273 K, and 298 K were maintained using a liquid nitrogen bath, an ice-water bath, and at room temperature, respectively.

[0175] Fitting of CO2 isotherm

[0176] The measured CO2 isotherms were fitted using the two-site Langmuir Freundlich (DSLF) isotherm model.

[0177]

[0178] The model attributes site heterogeneity to the definition of two adsorption sites, A and B, with different saturation capacities and affinity parameters.

[0179] Here, q represents the amount of gas adsorbed. sat Saturated gas adsorption capacity (mmol g) -1 b is the Langmuir-Freundlich affinity parameter (kPa). -1 ), and α is a dimensionless exponent.

[0180] Simultaneous fitting at 298K and 273K was performed using a built-in solver function in Microsoft Excel, where temperature dependence was described by a separate b term.

[0181] Table 7. DSLF isotherm parameters of UTSA-16-Zn-x material

[0182] x <![CDATA[q sat,A ]]> <![CDATA[b A,298 ]]> <![CDATA[b A,273 ]]> <![CDATA[α A ]]> <![CDATA[q sat,B ]]> <![CDATA[b B,298 ]]> <![CDATA[b B,273 ]]> <![CDATA[α B ]]> 0.25 2.367 0.028 0.222 1.528 2.754 0.028 0.064 0.684 0.50 2.158 0.029 0.220 1.530 2.752 0.029 0.064 0.681 0.75 2.173 0.030 0.237 1.514 2.706 0.030 0.067 0.678 1.00 2.449 0.027 0.213 1.562 2.716 0.027 0.063 0.703

[0183] Fitting of N2 isotherm

[0184] The measured N2 isotherm was fitted using a unit-point Langmuir (SSL) isotherm model.

[0185]

[0186] Due to the low curvature of the isotherms, independent fitting of samples with different Zn loads leads to large variations in the obtained parameters. To reduce the number of free parameters, the q values ​​of each UTSA-16-Zn-x sample were... sat The values ​​are limited to common values ​​scaled by their N2 absorption at 100 kPa. This limitation is supported by the isotherms, their isomorphic nature, and their largely consistent adsorption behavior with that of CO2.

[0187] Table 8. SSL isotherm parameters of UTSA-16-Zn-x material

[0188] x <![CDATA[q sat (mmol g -1 )]]> <![CDATA[b(kPa -1 )]]> 0.25 1.3322 0.00156 0.50 1.1947 0.00166 0.75 1.2387 0.00153 1.00 1.2599 0.00154

[0189] result

[0190] Single-component CO2 and N2 isotherms were collected for UTSA-16-Zn-x at 273 K and 298 K. The shape of the CO2 isotherm and the total CO2 absorption at 1 bar are substantially similar to those of the parent CO isotherm. Additionally, several other parameters obtained through isotherm analysis, such as the isothermal heat of CO2 adsorption (Q), were also analyzed. st Furthermore, the CO2 / N2 selectivity calculated using the Ideal Adsorption Solution Theory (IAST) is also the same. Figure 4 ; Figure 7 (See Table 9), which shows that UTSA-16-Zn-x and UTSA-16(Co) have similar CO2 capture performance.

[0191] Table 9: Summary of CO2 adsorption and capture performance indicators at 298 K

[0192]

[0193] Example 7. Competitive adsorption of UTSA-16-Zn-x under dynamic conditions

[0194] The breakthrough experiment also used simulated exhaust gas (15 / 85 CO2 / N2 feed) to analyze competitive adsorption under dynamic conditions.

[0195] Penetration test

[0196] Penetration test Figure 12 The homemade setup shown was performed. MOF sample (700–900 mg) was packed into a stainless steel column (L = 7 cm, D = 0.46 cm) and held in place using quartz wool and steel mesh.

[0197] The feed flow rate during the experiment was controlled using a mass flow controller (error: 0.1 sccm). The total flow rate through the column was set to 3 sccm. These were stabilized using a bypass line and switched to flow through the adsorption column immediately before the experiment.

[0198] The gas composition at the column outlet was determined using a Hiden QGA mass spectrometer. To accurately determine the flow rate, Ar was introduced into the outflow gas at a fixed flow rate of 3 sccm as an internal reference to correct for the mass flow rate. Upstream and downstream pressures were recorded. The original breakthrough plot was obtained as a relative composition over time, which was then converted to a normalized molar composition plot at the inlet relative to the over time plot.

[0199] Performance evaluation is based on three experiments:

[0200] • Dry feeding (RH = 0%) –

[0201] The column was activated by purging it with a constant He flow of 10 sccm at 120°C for 24 hours. The feed gas was a (15±1) / (85±1) CO2 / N2 mixture prepared by mixing the dry gas upstream of the column.

[0202] • Wet feeding (RH = 85%) –

[0203] The column was activated by purging it with a constant He flow of 10 sccm at 120°C for 24 hours. The feed gas was a (15±1) / (85±1) CO2 / N2 mixture with a relative humidity of approximately 85%; moisture was introduced at room temperature by passing the N2 flow through a water bubbler prior to mixing.

[0204] • Water-saturated adsorbent bed (saturated column) –

[0205] The column was activated by purging it with a constant He flow of 10 sccm at 120 °C for 24 hours. For pre-saturation, the wet purge flow was prepared by passing an N2 stream through a water bubbler at room temperature before mixing. The purge flow was passed through the column for 72 hours until a stable water signal was detected by the mass spectrometer. The column was then briefly activated at room temperature with a constant He flow (10 sccm). We observed that this condition enabled almost complete desorption of N2 / CO2, but minimal desorption of adsorbed H2O. Experiments were then conducted using “wet feed” conditions. Under these conditions, the MOF-packed column showed negligible absorption for either component.

[0206] The average residence time within the adsorption column is obtained by mass balancing using the inlet and outlet gas molar flow rates, i.e.

[0207]

[0208] The obtained residence time was corrected for the residence time in a control experiment using a blank tube under the same pressure drop and feed conditions. The validity of this correction depends on the linear additive relationship between the residence time and the experimental band broadening characteristics. Uncorrected breakthrough curve ( Figure 13 The corrected dwell times are listed in Table 10.

[0209] result

[0210] The saturated CO2 absorption of UTSA-16-Zn-x is 1.65–1.70 mmol g. -1Within a certain range, it exhibits strong moisture resistance. Figure 4 In a similar manner to the results of static CO2 uptake, these were slightly lower than the parental Co MOF (1.82 mmol g). -1 ).

[0211] The maximum productivity of CO2 (q) max ) and single-component static absorption (1.8 mmol g for x = 0.5 and 1, respectively) -1 and 1.94 mmol g -1 Good consistency. Typically, when switching from dry to RH=85% feed, the capacity is slightly lower (-2.3%) due to competitive adsorption of H2O.

[0212] Table 10. Dynamic adsorption parameters obtained from column breakthrough measurements

[0213]

[0214] Summarize

[0215] In summary, we have shown that replacing the rate-limiting tetrahedral Co species within UTSA-16 with Zn can significantly accelerate the formation kinetics of these MOFs, providing mild synthetic conditions suitable for the large-scale production of these materials. The new UTSA-16 type MOFs exhibit the same CO2-capturing properties as the parent Co species, with significant moisture resistance.

[0216] This invention generates hybrid metal composites from known binary (monometal / monolinker) MOFs with suitable structures, exhibiting improved synthetic robustness compared to monometallic materials. Optimizations derived from this strategy are more compatible with scale-up production, which will accelerate the process development of related materials for various commercial applications.

Claims

1. A metal-organic framework (MOF) having a UTSA-16 structure, wherein the MOF comprises: The first metal in the MOF (Metal-Oxide-Facility) is greater than 0 mol% and less than 80 mol%, wherein the first metal is Co; and A second metal comprising more than 20 mol% and less than 80 mol% of all metals in a MOF, wherein the second metal is Zn. The sum of the amounts of the first metal and the second metal is 100 mol% of all metals present in the MOF. The second metal occupies 51 mol%, or 55 mol%, or 60 mol%, or 70 mol%, or 75 mol%, or 80 mol%, or 85 mol%, or 90 mol%, or 95 mol%, or 99 mol% of the tetrahedral metal sites within the MOF. The first metal occupies 51 mol%, or 55 mol%, or 60 mol%, or 70 mol%, or 75 mol%, or 80 mol%, or 85 mol%, or 90 mol%, or 95 mol%, or 99 mol% of the octahedral metal sites within the MOF.

2. The MOF according to claim 1, wherein the second metal is present in an amount of 25 mol% or more and 80 mol% or less of all metals present in the MOF.

3. The MOF according to claim 2, wherein the second metal is present in an amount of 50 to 75 mol% of all metals present in the MOF.

4. The MOF according to claim 1, wherein the first metal is present in an amount of 25 to 50 mol% of all metals present in the MOF.

5. The MOF according to claim 1, wherein the saturated CO2 absorption of the MOF is at most 5.0 mmol / g.

6. The MOF according to claim 1, wherein the CO2 penetration capacity of the MOF is at most 2.2 mmol / g.

7. A method for forming a MOF according to any one of the preceding claims, wherein the method comprises aging a mixture comprising a first metal precursor, a second metal precursor, a base, citric acid, a first solvent, and a second solvent at a temperature of 15–200°C for a period of time, wherein: The first metal precursor is Co; The second metallic precursor is Zn; and The metal in the first metal precursor is present in an amount greater than 0 mol% and less than 80 mol% of the total metal in the mixture; and The metal in the second metal precursor is present in an amount of 20 mol% or more and 80 mol% or less of the total metal in the mixture. The sum of the amounts of metal in the first metal precursor and the metal in the second metal precursor is 100 mol of the total amount of metal in the mixture.

8. The method according to claim 7, wherein the temperature is 20 to 150°C.

9. The method according to claim 8, wherein the temperature is 40–120°C.

10. The method of claim 9, wherein the temperature used causes one solvent to reflux or both solvents to reflux.

11. The method according to any one of claims 7 to 10, wherein: (a) The first solvent is water and the second solvent is an alkyl alcohol; and / or (b) The base is a metal hydroxide; and / or (c) The method is carried out under ambient atmospheric conditions.

12. The method according to any one of claims 7 to 10, wherein the first metal precursor and the second metal precursor are metal salts or their hydrates, wherein the metal is in the form of a cation and is balanced by one or more counter ions, wherein the counter ions are selected from one or more of halide anions, nitrate anions, sulfate anions, hydroxide anions, oxo anions, and acetate anions.

13. The method according to any one of claims 7 to 10, wherein: (a) The second metal precursor is Zn(OAc)₂ or its hydrate; and / or (b) The metal in the second metal precursor is present in an amount of more than 25 mol% and less than 80 mol% of all metals present in the mixture.

14. The method according to any one of claims 7 to 10, wherein: (a) The first metal precursor is Co(OAc)₂ or its hydrate; and / or (b) The metal in the first metal precursor is present in an amount of 25 to 50 mol% of all the metals present in the mixture.

15. A method for capturing CO2, comprising the step of exposing a material comprising an MOF according to any one of claims 1 to 6 to an environment containing CO2.

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