Method for repairing lattice defects in porous coordination polymer and application of method in ethylene / ethane separation

Abstract

The invention relates to a method for repairing lattice defects in a porous coordination polymer and application of the method in ethylene / ethane separation, and belongs to the technical field of coordination chemical materials. According to the invention, a porous crystal with connector defects is successfully repaired through a directional repair strategy, so that a complete frame structure is obtained. Lattice linker defects caused by steric hindrance of an adjacent carboxylic acid group of isonicotinic acid INA in NTU-70D are successfully repaired by installing additional INA along a specific direction under the assistance of formic acid. In-situ infrared analysis shows that the repaired NTU-70P has more contactable OINA sites in a regular and smooth nano channel, so that the C2H6 adsorption capacity and the C2H6 / C2H4 selectivity of the repaired NTU-70P are remarkably improved, and meanwhile, the repaired NTU-70P shows the capability of efficiently producing high-purity C2H4 (as high as 46.4 mLg <-1 >) from a mixture containing C2H6.

Description

Technical Field

[0001] The invention relates to a method for repairing lattice defects in a porous coordination polymer and application in ethylene / ethane separation, belonging to the technical field of coordination chemical materials. Background Art

[0002] As an emerging family of crystalline materials, porous coordination polymers (PCPs) can be synthesized from a variety of organic blocks and metal ion / cluster matrices and can be easily tuned to obtain tailored pore sizes, shapes, and surface functionalities for selective gas capture. According to classical nucleation theory, the crystallization process of PCPs can be divided into two major categories: nucleation and crystal growth. However, the combination of synthetic systems, thermodynamic / kinetic factors, steric hindrance, topological incompatibility, variability of building blocks, and environmental conditions may affect the crystal growth process, resulting in irregular arrangements or missing connectors / nodes in the final crystals.

[0003] Structural repair has been demonstrated to improve performance (Non-Patent Literature 1), for example: MIL-125-X (node ​​post-installation) (Non-Patent Literature 2) and HIAM-410 (linker post-installation) (Non-Patent Literature 3). However, effective control of pore chemistry and repair of such lattice defects in isostructural frameworks poses significant challenges, as PCPs typically have complex internal structures with interconnected voids or channels, resulting in limited accessibility to repair agents. In addition, the understanding and control of these further tailored nanospaces remains to be demonstrated, which hinders the design of advanced adsorbents.

[0004] Non-patent literature 1: S. Daliran, A. R. Oveisi, C. W. Kung, U. Sen, A. Dhakshinamoorthy, C. H. Chuang, M. Khajeh, M. Erkartal, J. T. Hupp, Chem. Soc. Rev. 2024, 53, 6244-6294.

[0005] Non-patent literature 2: Y. Han, W. Huang, M. He, B. An, Y. Chen, X. Han, L. An, M. Kippax-Jones, J. Li, Y. Yang, M. D. Frogley, C. Li, D. Crawshaw, P. Manuel, S. Y.Cheng,I.Silverwood,LLDaemen,AJRamirez-Cuesta,SJDay,SPThompson,BFSpencer,M.Nikiel,D.Lee,M. S.Yang,Nat.Mater.2024,23,1531-1538;

[0006] Non-patent document 3: FA Guo, J. Wang, CLChen, XL Dong, XY Li, H. Wang, P. Guo, Y. Han, J. Li, Angew. Chem. Int. Ed. 2023, 62, e202303527. Summary of the invention

[0007] The purpose of the present invention is to repair atomic-scale lattice defects in porous crystals. The linker defect framework (NTU-70D) was repaired by a directional strategy to obtain a perfect framework (NTU-70P). The lattice linker defect in NTU-70D caused by steric hindrance and supplemented by water molecules was determined by single crystal analysis. With the assistance of formic acid, this defect was repaired in new porous crystals of NTU-70P by installing additional isonicotinic acid INA in a prescribed direction. The complete coordination connection helps NTU-70P to show regular and smooth nanochannels.

[0008] The technical solution is:

[0009] A method for repairing lattice defects in a porous coordination polymer. The porous coordination polymer is a Co-based coordination polymer obtained by adding a repair ligand during a solvent thermal reaction between a ligand and a metal salt.

[0010] The repair ligand is formic acid, the ligand is isonicotinic acid, and the metal salt is cobalt nitrate.

[0011] The molar ratio of the ligand, the metal salt and the repair ligand is 1:0.8-0.9:0.45-0.55.

[0012] The solvent used in the reaction is a mixed solvent of DMF, water and methanol.

[0013] The volume ratio of DMF, water and methanol ranges from 4-7:0.5-1.5:0.2-0.4.

[0014] The reaction conditions are 80-110°C for 500-2000 min.

[0015] After the reaction is completed, the obtained porous coordination polymer is activated in methanol.

[0016] The porous coordination polymer obtained by the above method.

[0017] The porous coordination polymer mentioned above is 2 H 6 and C 2 H 4Use in separation.

[0018] Beneficial Effects

[0019] The present invention successfully repaired a porous crystal with a linker defect through a directional repair strategy, thereby obtaining a complete framework structure. The lattice linker defect in NTU-70D caused by the steric hindrance of the adjacent carboxylic acid groups of isonicotinic acid INA was successfully repaired by installing additional INA along a specific direction with the assistance of formic acid. In situ infrared analysis showed that the repaired NTU-70P had more accessible O in regular and smooth nanochannels. INA site, which makes its C 2 H 6 Adsorption amount and C 2 H 6 / C 2 H 4 The selectivity was significantly improved, and the 2 H 6 Efficient production of high purity C from mixtures 2 H 4 (up to 46.4mLg -1 ) ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 :Used to enhance the inverse C 2 H 6 / C 2 H 4 Schematic diagram of the repair of lattice connector defects in isolated PCPs.

[0021] Figure 2 : Synthesis route and structure of NTU-70D: synthesis route (a), lattice linker defect framework (b), Y-shaped nanochannel with narrow neck (c), and cage structure connected by channels (d). Hypothesis of directional linker installation: available sites for formic acid coordination (highlighted in green) (e), and its replacement by INA (f), possible coordination view of formic acid on Co4-Co4 cluster (g). Synthesis route and structure of NTU-70P: synthesis route (h), repaired framework (i), comparison of connection modes of two types of clusters in NTU-70D and NTU-70P (kl and mn), Y-shaped nanochannel with narrow neck (o), and isolated cage structure (p). The probe radius accessible to the inner surface is

[0022] Figure 3 :N for NTU-70D and NTU-70P 2 (77K) adsorption isotherm (a), C 2 H 6 and C 2H 4 (298K) adsorption isotherms (b). The C 2 H 6 Adsorption amount and C 2 H 6 / C 2 H 4 Selectivity (low pressure) comparison (c). Adsorption kinetics and kinetic selectivity of these two PCPs (298K) (d).

[0023] Figure 4 : In situ infrared spectra of NTU-70D (a: full spectrum, cd: magnified range) and NTU-70P (b: full spectrum, cd: magnified range) at 298K. The gas pressure is about 10kPa. The bottom lines in a and b show the spectra of the corresponding PCPs. The top two lines in each panel represent the difference spectra obtained by referencing the spectra of the activated samples. DETAILED DESCRIPTION

[0024] Example 1 Synthesis of NTU-70D

[0025] INA (40.0 mg, 0.325 mmol) and Co(NO 3 ) 2 6H 2 O (80.1 mg, 0.275 mmol) was added to DMF / H 2 Crystals were prepared by solvothermal reaction in O / MeOH (6 / 1 / 0.3, v / v / v, 7.3 mL) solution. The mixture was then sealed in a 20 mL Teflon-lined autoclave and heated at 95 °C for 1000 min. After cooling, the pink crystals were collected and washed with DMF.

[0026] Example 2 Synthesis of NTU-70P

[0027] INA (40.0 mg, 0.325 mmol) and Co(NO 3 ) 2 6H 2 Crystals were prepared by solvothermal reaction of O (80.1 mg, 0.275 mmol) and HCOOH (7.36 mg, 0.160 mmol), which was added to DMF / H 2 O / MeOH (6 / 1 / 0.3, v / v / v, 7.3 mL) solution. The mixture was then sealed in a 20 mL Teflon-lined autoclave and heated at 95°C for 1000 min. After cooling, the pink crystals were collected and washed with DMF.

[0028] Example 3 Activation of samples

[0029] Activated Crystals NTU-70 Series Crystals Solvent exchange crystals were prepared by immersing the synthesized sample in dry methanol for 3 days to remove non-volatile solvents, dialyzing the extract and replacing fresh methanol every 8 hours. Fully activated samples were obtained by heating the solvent exchange sample at 25°C for 2 hours under dynamic high vacuum and then at 75°C for another 8 hours.

[0030] Sample structure

[0031] INA and Co 2+ In DMF / H 2 Solvothermal reaction in O / MeOH produced pink crystals (NTU-70D). Single crystal X-ray diffraction analysis showed that it crystallized in the monoclinic system with I2 / m space group ( Figure 2 Based on this model, the connections of the two binuclear clusters are reduced to five and six, respectively, forming an open framework with high porosity (calculated by Platon: 57.6%, Figure 2 In addition, a Y-shaped nanochannel (approx. ), whose narrow neck is Vertical holes on the channel path The hole connects an open octahedral cage ( Figure 2 c and d). Since C 2 H 6 and C 2 H 4 The vacancies in the linker lead to an increase in the pore size and a decrease in the number of supramolecular O sites, allowing the unhindered passage of the two gases with minimal molecular differences.

[0032] After the introduction of formic acid during the synthesis of NTU-70D, a new crystal (NTU-70P) was obtained ( Figure 2 h and i). Crystal analysis shows that it crystallizes in the monoclinic system with a P2 / n space group. Similarly, the structure includes three binuclear Co clusters (Co1-Co2, Co3-Co3, and Co4-Co4) and a mononuclear Co5 node. The coordination environment of the single Co node is the same as that of NTU-70D, but the binuclear clusters exhibit different geometries. As expected, NINA coordinates to the Co3 and Co4 atoms of the two binuclear clusters, while COOINA binds to the eutectic on the Co1-CO2 cluster, forming a defined linker installation ( Figure 2 In addition, an INA around the Co1-Co2 cluster changes its orientation to match this geometric stoichiometry ( Figure 2The m and n of are highlighted in cyan). Therefore, the lattice connector defects are repaired, resulting in a fully connected NTU-70P. The structure also features a Y-shaped nanochannel with a narrow neck. However, the associated vertical pores are completely blocked, forming an isolated octahedral cage ( Figure 2 o and p). Therefore, the porosity of the entire skeleton is reduced to 49.8%.

[0033] Binary C 2 H 6 / C 2 H 4 Calculation of Selectivity of Mixture Adsorption

[0034] Ideal adsorption solution theory (IAST) was used to predict the adsorption of binary mixtures from the experimental pure gas isotherms. The C 2 H 6 / C 2 H 4 Selectivity, the single component isotherm should be fitted by an appropriate model. The two-site Langmuir-Frendlich equation is used to fit the experimental data:

[0035]

[0036] In equation (1), q is the amount of adsorption per mass of adsorbent (mol / kg), P is the pressure of the bulk gas in equilibrium with the adsorbed phase (kPa), qm1 and qm2 are the saturation capacities of sites 1 and 2 (mol / kg), b1 and b2 are the affinity coefficients for site 1 (1 / kPa), and n1 and n2 represent the deviations from an ideal uniform surface. The R values ​​for all fitted isotherms are 2 The values ​​are all over 0.99999.

[0037] The porosity of NTU-70D and NTU-70P was evaluated by N2 adsorption at 77 K. They both exhibited type I adsorption isotherms with fully reversible desorption behavior, indicating that they are microporous in nature ( Figure 3 a). When P / P0=1, the maximum N2 absorption of NTU-70P reaches 221.0cm 3 ·g -1 , lower than the maximum N of NTU-70D 2 Adsorption capacity (311.9cm3·gl, Figure 2 a). Therefore, compared with NTU-70D (1159m 2 ·g -1 and 0.4824cm 3 ·g -1), the calculated BET surface area and pore volume of NTU-70P are smaller (855m 2 ·g -l and 0.3411cm 3 ·g -l In addition, the pore size distribution of NTU-70P is concentrated in a very narrow range of 0.6 nm, while the pore size distribution of NTU-70D is broadened (from 0.62 to 0.8 nm). These observations are in good agreement with the structure. To verify the functionality of the repaired nanoprobes, single-component C 2 H 6 and C 2 H 4 Adsorption isotherm ( Figure 3 b). Under the full pressure of NTU-70D at 298K, C 2 H 6 The absorption rate is higher than that of C 2 H 4 , at a pressure of 100 kPa, the maximum C 2 H 6 and C 2 H 4 The absorption rates are 51.0cm 3 ·g -1 and 47.7 cm3·gl. In contrast, NTU-70P has a 2 H 6 and C 2 H 4 The maximum absorption capacity is up to 90.2cm 3 ·g -1 and 83.8 cm3·gl, which are 1.7–1.8 times that of NTU-70D, despite its larger surface area and pore volume. 2 H 6 and C 2 H 4 The adsorption-desorption of is completely reversible, indicating that there is no oligomerization of the gas blocking the channel. 2 H 6 Selective adsorbents.

[0038] To evaluate the separation potential, the adsorption selectivity was calculated using ideal adsorption solution theory (IAST) after fitting the isotherms with great accuracy. 2 H 6 / C 2 H 4 The ratio of the NTU-70D to the NTU-70D was changed (1 / 15, 1 / 9, and 1 / 1, v / v), but NTU-70D showed a relatively low C of about 1.6 at low pressure and 298 K. 2 H6 / C 2 H 4 The value of NTU-70P was increased to 2.6. Therefore, the repaired structure of NTU-70P not only showed an enhanced absorption capacity, but also showed C 2 H 6 / C 2 H 4 Improved selectivity.

[0039] To better understand the NTU-70D and NTU-70P in C 2 H 4 Selective adsorption of C 2 H 6 The in situ infrared (IR) spectra were collected at 298 K. Figure 4 ). After activation, a reference spectrum of empty PCP was recorded. 2 H 6 and C 2 H 4 The gas loading spectra were obtained by introducing the samples into Figure 4 a and b). At 2873-3022cm -1 There are multiple absorption peaks in the C 2 H 6 Load and C 2 H 4 The 2964-3119 cm-1 values ​​observed in the loaded PCP should be assigned to C 2 H 6 (CH 3 ) vibration absorption peak and C 2 H 4 (CH 2 ) vibration absorption peak. During the gas adsorption process of the two PCPs, the νs(COO-) in the two PCPs was at 1319 cm -1 The characteristic peaks of ν(OH) and ν(OH) are at 3645cm -1 The characteristic peaks of INA shifted to lower wavenumbers, indicating that the accessible OCOO and coordinated water of INA would interact with C 2 H 6 or C 2 H 4 Form hydrogen bonds. Usually, C 2 H 6 The adsorption of NTU-70P makes the νs(COO-) of NTU-70P at 1312cm -1 A clear peak is formed at 2 H 4 When the two gases were introduced into NTU-70D, very similar disturbances were observed ( Figure 4d and f). This means that further supplementation of OCOO in the nanospace repaired by NTU-70P will enhance the ability to distinguish the two gases. At the same time, after gas adsorption, the relatively large red shift of the characteristic peak of ν(OH) in NTU-70P compared with NTU-70D indicates that the coordinated water in the relatively small nanospace also contributes to the selective adsorption of C 2 H 6 Played a positive role ( Figure 4 c and e).

Claims

1. A method for repairing lattice defects in a porous coordination polymer, wherein the porous coordination polymer is a Co-based coordination polymer, characterized in that: The compound is obtained by adding a repair ligand during the solvothermal reaction between the ligand and the metal salt.

2. The method for repairing lattice defects in a porous coordination polymer according to claim 1, characterized in that: The repair ligand is formic acid, the ligand is isonicotinic acid, and the metal salt is cobalt nitrate.

3. The method for repairing lattice defects in a porous coordination polymer according to claim 1, characterized in that: The molar ratio of the ligand, the metal salt and the repair ligand is 1:0.8-0.9:0.45-0.

55.

4. The method for repairing lattice defects in a porous coordination polymer according to claim 1, characterized in that: The solvent used in the reaction is a mixed solvent of DMF, water and methanol.

5. The method for repairing lattice defects in a porous coordination polymer according to claim 1, characterized in that: The volume ratio of DMF, water and methanol ranges from 4-7:0.5-1.5:0.2-0.

4.

6. The method for repairing lattice defects in a porous coordination polymer according to claim 1, characterized in that: The reaction conditions are 80-110°C for 500-2000 min.

7. The method for repairing lattice defects in a porous coordination polymer according to claim 1, characterized in that: After the reaction is completed, the obtained porous coordination polymer is activated in methanol.

8. The porous coordination polymer obtained by the repair method according to claim 1.

9. Use of the porous coordination polymer according to claim 8 in the separation of C2H6 and C2H4.

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