A microporous covalent organic framework material based on quinoxaline and imine linkage and a preparation method thereof

Abstract

The present application relates to a kind of microporous covalent organic framework material based on quinoline and imine bond connection and its preparation method, belong to covalent organic framework material technical field.The microporous covalent organic framework material is by 4,5- di (4-aminophenyl) -1,2-phenylenediamine with 4,4 '-di (4- formylphenyl) benzil or the formyl ortho substitution derivative of 4,4 '-di (4- formylphenyl) benzil by irreversible ring aromatization reaction and reversible Schiff base reaction one-pot method construction new binary COFs based on quinoline and imine bond connection, not only enrich the diversity of binary COFs variety, and the method will linear reaction and ring formation reaction of imine bond combination, effectively reduce the occurrence of competitive reaction, and the method is simple, provide new synthesis strategy for the construction of binary COFs.

Description

Technical Field

[0001] This invention relates to a microporous covalent organic framework material based on quinoxaline and imine bonds and its preparation method, belonging to the technical field of covalent organic framework materials. Background Technology

[0002] Covalent organic frameworks (COFs) are a class of well-defined crystalline porous materials, consisting of ordered, periodic two- or three-dimensional network structures formed by the precise assembly of organic structural units through covalent bonds. The diversity of building and connecting units, combined with the designability of functions, gives COFs well-defined structures, designable framework structures, permanent channels, and easily customizable functionality, attracting attention in many fields. COFs have wide applications in gas adsorption and separation, sensing, catalysis, energy storage and conversion, and drug delivery.

[0003] In the construction of COFs, the intrinsic properties of the chemical bonds at the linking sites formed by reversible covalent bonds play a crucial role in the stability, crystallinity, and properties of the resulting materials. Given the wide range of chemical reactions that can form these linking sites, introducing novel linking mechanisms to construct COF materials with unique properties and functions is essential. Since Yaghi's pioneering work in 2005, various COFs with different structures and functions have been reported. Most COFs use only one linking site, such as BO bonds, C=N bonds, imides, and C=C; only a very few examples have been reported of COFs with dual linking sites, all based on highly reversible BO bonds. These binary COFs with dual linking sites possess the physicochemical properties of two different linking sites, enriching the functionality of the resulting materials. However, the construction of COFs with dual linking sites still faces significant challenges, mainly due to the competition between two different types of covalent bond formation reactions. Therefore, balancing the competition between different linking site formation reactions and exploring new synthetic strategies for binary COFs is crucial. Summary of the Invention

[0004] To reconcile the conflicting reactions of two types of covalent bond formation in binary COFs with dual-linkage sites, this invention provides a microporous covalent organic framework material based on quinoxaline and imine bonds and its preparation method. The novel binary COFs based on quinoxaline and imine bonds are constructed via a one-pot method combining irreversible cycloaromatization and reversible Schiff base reactions, effectively reducing the occurrence of competing reactions between the two types of covalent bonds. This not only enriches the diversity of binary COFs but also provides a new synthetic strategy for their construction.

[0005] The objective of this invention is achieved through the following technical solutions.

[0006] A microporous covalent organic framework material based on quinoxaline and imine bonds has the following specific structural formula:

[0007]

[0008] The microporous covalent organic framework material is formed by a condensation reaction of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine (BABD) with 4,4'-bis(4-formylphenyl)benzoin or a formyl ortho-substituted derivative of 4,4'-bis(4-formylphenyl)benzoin. The substituent R in the material's structural formula is H or the same as the substituent at the formyl ortho position of 4,4'-bis(4-formylphenyl)benzoin. R is preferably H, F, CH3, OH, OCH3, OC2H5, or OC3H7.

[0009] The specific preparation steps of the microporous covalent organic framework material are as follows:

[0010] 4,5-bis(4-aminophenyl)-1,2-phenylenediamine (BABD), aromatic aldehyde compounds, catalysts and organic solvents were mixed and heated to 100-150°C in a closed environment for a solvothermal reaction for no less than 12 hours. After the reaction was completed, the temperature was lowered and the reaction products were collected to obtain a microporous covalent organic framework material based on quinoxaline and imine bonds.

[0011] The aromatic aldehyde compound is 4,4'-bis(4-formylphenyl)benzoin or a formyl ortho-substituted derivative of 4,4'-bis(4-formylphenyl)benzoin;

[0012] The catalyst is an aqueous solution of acetic acid, an aqueous solution of lactic acid, or Sc(OTF)3.

[0013] Preferably, the ortho-formyl derivative of 4,4'-bis(4-formylphenyl)benzoin is 4,4'-bis(3-fluoro-4-formylphenyl)benzoin (where R = F), 4,4'-bis(3-methyl-4-formylphenyl)benzoin (where R = CH3), 4,4'-bis(3-hydroxy-4-formylphenyl)benzoin (where R = OH), or 4,4'-bis(3-methoxy-4-formylphenyl)benzoin (where R = OCH3). More preferably, the aromatic aldehyde compound is 4,4'-bis(4-formylphenyl)benzoin (BFB) or 4,4'-bis(3-hydroxy-4-formylphenyl)benzoin (BHFB).

[0014] When the aromatic aldehyde compound is BFB, the organic solvent is preferably o-dichlorobenzene (o-DCB), mesitylene (Mes), N,N-dimethylacetamide (DMAc), a DMAc / Mes mixed solvent, a DMAc / o-DCB mixed solvent, or a DMAc / Dio (1,4-dioxane) mixed solvent; when the aromatic aldehyde compound is BHFB, the organic solvent is preferably DMAc, a DMAc / Mes mixed solvent, or a DMAc / o-DCB mixed solvent. Furthermore, in the above mixed solvents, the volume ratio of the two solvents is (1:9) to (9:1).

[0015] Preferably, the molar ratio of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine to the molar ratio of aromatic aldehyde compounds is (1:0.9) to (0.9:1).

[0016] Preferably, the molar ratio of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine to catalyst is 1:(6-25). Wherein, when the aromatic aldehyde compound is BFB, the molar ratio of BABD to catalyst is more preferably 1:(6-25); when the aromatic aldehyde compound is BHFB, the molar ratio of BABD to catalyst is more preferably 1:(6-15).

[0017] Preferably, the concentration of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine in the organic solvent is 0.05–0.15 mmol / mL.

[0018] Preferably, the reaction time is 12–84 h. When the aromatic aldehyde compound is BFB, the reaction time is more preferably 12–72 h; when the aromatic aldehyde compound is BHFB, the reaction time is more preferably 36–84 h.

[0019] Preferably, the reaction product is first collected by filtration, and then the filtered reaction product is soaked and washed with tetrahydrofuran 2-3 times, each time for 0.5-1h, or the filtered reaction product is extracted with dry tetrahydrofuran as solvent by Soxhlet extraction for 24-48h, and finally vacuum dried at 80-120℃ for 2-12h to obtain a microporous covalent organic framework material based on quinoxaline and imine bonds.

[0020] Beneficial effects:

[0021] (1) Quinoxaline modules were synthesized based on the aromatic cyclization reaction of aromatic aldehydes and amine monomers, achieving the connection between aldehyde and amino monomers. These A2B2-type bifunctional monomers exhibit similar chemical and thermodynamic stability to other bifunctional monomers. These bifunctional COFs are more stable than previously reported binary COFs formed based on BO and C=N bonds, and have potential for practical applications. Furthermore, the ortho-aldehyde position can be functionalized by modifying functional groups. For example, materials containing OH functional groups not only increase hydrophilicity and dispersibility, altering physical and chemical properties, but also provide possibilities for further post-synthetic modifications.

[0022] (2) The formation of COF materials is a thermodynamic process. The formation of COFs with dual-connection sites is more difficult than that with single-functional sites, mainly because the chemical reactions that form different functional sites are competitive. How to balance the two different reactions so that the reaction modules can be arranged efficiently and orderly to form crystalline porous materials is crucial and important. This invention utilizes the fact that both imine bonds and quinoxaline rings are based on the formation of imine bonds. The large potential energy difference between the two reduces the occurrence of competitive reactions, so o-phenylenediamine tends to bind with o-diketone. Moreover, the linear imine bond linkers formed by aromatic amino groups and aldehyde groups can also play a good repair role.

[0023] Taking CR-COF-3 as an example, its detailed formation mechanism is as follows: Aromatic amino compounds and aromatic aldehyde compounds first undergo a Schiff base reaction under acid catalysis, where the amino group and the aldehyde group or o-diketone group undergo a condensation reaction to obtain random polymer fragments. Driven by the cyclization of the o-phenylenediamine group and the o-diketone group, the imine bond eventually forms a quinoxaline ring during the reconstruction process, realizing the combination of aromatic amino compounds and aromatic aldehyde compounds, thereby achieving partial ordering of the polymer. The above polymer contains only linear imine bonds, which further achieve framework self-repair and error correction under solvothermal conditions, ultimately yielding a thermodynamically stable crystalline polymer.

[0024] (3) The microporous covalent organic framework material described in this invention has good solvent compatibility, but the preferred type of solvent is more conducive to crystallization and tends to obtain a more ordered material structure.

[0025] (4) In the preparation process of the microporous covalent organic framework material of the present invention, the concentration of the raw material in the solvent should not be too high. Too high a concentration is not conducive to crystallization. Moreover, the concentration of the raw material in the solvent has a certain influence on the morphology of the material. Therefore, the preferred concentration is more conducive to crystallization and obtaining a uniform morphology.

[0026] (5) This invention constructs novel binary COFs based on imine bonds and quinoxaline linkages through an irreversible cycloaromatization reaction and a reversible Schiff base reaction in a one-pot method. This not only enriches the diversity of binary COFs, but also combines the linear reaction of imine bond formation with the cyclization reaction, effectively reducing the occurrence of competing reactions. Furthermore, this method is simple to operate and provides a new synthetic strategy for the construction of binary COFs. Attached Figure Description

[0027] Figure 1 This is the chemical reaction formula for the reaction of BABD and BFB to generate CR-COF-3 in Example 1.

[0028] Figure 2 The image shows a comparison of the infrared spectra of CR-COF-3, BABD, and BFB prepared in Example 1 in different wavelength ranges; wherein, the wavelength range tested in Figure a is 4000–450 cm⁻¹. -1 The wavelength range tested in Figure b is 1800–600 cm. -1 .

[0029] Figure 3 The image shows the N1s X-ray photoelectron spectroscopy (XPS) spectrum of CR-COF-3 prepared in Example 1.

[0030] Figure 4 Comparison diagrams of experimental PXRD, refined PXRD, PXRD based on AA stacking simulation, and PXRD based on AB stacking simulation for CR-COF-3 prepared in Example 1.

[0031] Figure 5 This is a scanning electron microscope (SEM) image of CR-COF-3 prepared in Example 1.

[0032] Figure 6 This is a transmission electron microscope (TEM) image of CR-COF-3 prepared in Example 1.

[0033] Figure 7 The figures show a comparison of the nitrogen adsorption-desorption isotherms at 77 K for CR-COF-3 prepared in Example 1 and CR-COF-4 prepared in Example 2; where figure a is the nitrogen adsorption-desorption isotherm of Example 1 and figure b is the nitrogen adsorption-desorption isotherm of Example 2.

[0034] Figure 8 The figures show a comparison of the BET surface area fitting curves of CR-COF-3 prepared in Example 1 and CR-COF-4 prepared in Example 2; where figure a is the fitting curve of Example 1 and figure b is the fitting curve of Example 2.

[0035] Figure 9 The figures show a comparison of the pore size distributions of CR-COF-3 prepared in Example 1 and CR-COF-4 prepared in Example 2; where figure a is the pore size distribution of Example 1 and figure b is the pore size distribution of Example 2.

[0036] Figure 10 The thermogravimetric analysis curves of CR-COF-3 prepared in Example 1 and CR-COF-4 prepared in Example 2 are compared; wherein, Figure a is the thermogravimetric analysis curve of Example 1 and Figure b is the thermogravimetric analysis curve of Example 2.

[0037] Figure 11 The image shows the adsorption isotherms of CR-COF-3 prepared in Example 1 for methane, nitrogen, and carbon dioxide at 298 K.

[0038] Figure 12 This is the chemical reaction formula for the reaction of BABD and BHFB in Example 2 to generate CR-COF-4.

[0039] Figure 13 The image shows a comparison of the infrared spectra of CR-COF-4, BABD, and BHFB prepared in Example 2 in different wavelength ranges; wherein, the wavelength range tested in Figure a is 4000–450 cm⁻¹. -1 The wavelength range tested in Figure b is 1800–600 cm. -1 .

[0040] Figure 14 The image shows the N1s X-ray photoelectron spectroscopy (XPS) spectrum of CR-COF-4 prepared in Example 2.

[0041] Figure 15 Comparison diagrams of experimental PXRD, refined PXRD, PXRD based on AA stacking simulation, and PXRD based on AB stacking simulation for CR-COF-4 prepared in Example 2.

[0042] Figure 16 This is a scanning electron microscope (SEM) image of CR-COF-4 prepared in Example 2.

[0043] Figure 17 This is a transmission electron microscope (TEM) image of CR-COF-4 prepared in Example 2.

[0044] Figure 18 The image shows the adsorption isotherms of CR-COF-4 prepared in Example 2 for methane, nitrogen, and carbon dioxide at 298 K.

[0045] Figure 19 The CR-COF-3 prepared in Example 1 and the CR-COF-3 prepared in Example 3 in different solvents溶剂 '、CR-COF-3 溶剂 "and CR-COF-3 溶剂 Comparison of experimental PXRD values ​​for “”.

[0046] Figure 20 The CR-COF-4 prepared in Example 2 and the CR-COF-4 prepared in Example 4 溶剂 Comparison of experimental PXRD values.

[0047] Figure 21 The CR-COF-3 prepared in Example 1 and the CR-COF-3 prepared in Example 5 at different catalyst concentrations 催化剂 '、CR-COF-3 催化剂 "and CR-COF-3 催化剂 A comparison of experimental PXRD results for “”.

[0048] Figure 22 CR-COF-4 prepared in Example 2 and CR-COF-6 prepared in Example 6 at different catalyst concentrations 催化剂 '、CR-COF-6 催化剂 "and CR-COF-6 催化剂 A comparison of experimental PXRD results for “”.

[0049] Figure 23 Comparison of experimental PXRD values ​​of CR-COF-3 prepared in Example 1 and eight products prepared in Example 7 at different reaction times.

[0050] Figure 24 The CR-COF-4 prepared in Example 2 and the CR-COF-4 prepared in Example 8 at different reaction times 时间 'and CR-COF-4 时间 The experimental PXRD comparison chart.

[0051] Figure 25 CR-COF-4 prepared in different solvents in Example 9 溶剂 CR-COF-4 溶剂 "and CR-COF-4 溶剂 PXRD comparison chart of "".

[0052] Figure 26 CR-COF-3 prepared in Example 1 and CR-COF-3 prepared in Example 10 温度 Comparison of experimental PXRD values. Detailed Implementation

[0053] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are obtainable from publicly available commercial sources.

[0054] The main instruments used to characterize the prepared COF materials in the following examples are as follows:

[0055] Infrared spectrometer: Model Bruker ALPHA, wavelength range 400–4000 cm⁻¹ -1 Bruker Corporation, USA;

[0056] X-ray powder diffractometer: Model Bruker Foucus D8, Bruker Corporation, USA; powder sample scanning temperature 298K, pressure 40kV, current 50mA; X-ray radiation source: Cu-K. α ;

[0057] X-ray photoelectron spectrometer: Model T PHI 5000VersaProbe III, Al K as X-ray source (0.6eV);

[0058] Scanning electron microscope: Model JEOL S-4800, Hitachi, Japan; wherein, the sample is attached to the conductive adhesive on the cross-sectional sample stage, and the test voltage is 10.00kV;

[0059] Transmission electron microscope: Model FEI Tecnai G2 F30; The sample was ultrasonically dispersed in ethanol and then drop-coated onto a copper grid, with a test voltage of 300kV.

[0060] Gas adsorption apparatus: Model Quantachrome (ASiQMVH002-5), Quantachrome Corporation, USA; used to test the adsorption capacity of the prepared thin film material for different gases under standard atmospheric pressure (101 kPa), with the purity of the gases used being 99.999%; in this experiment, it was used to test the nitrogen adsorption at 77 K.

[0061] Thermogravimetric analyzer: Waters TGAQ500 thermogravimetric analyzer; Before thermogravimetric analysis, the sample needs to be thoroughly dried. The test is carried out in a nitrogen atmosphere with a heating rate of 10℃ / min and a test range from room temperature to 800℃.

[0062] Gas adsorption instrument: Model BELMaster Ver.7 (for MAX series); Before conducting gas adsorption experiments, the sample needs to be thoroughly dried, and the sample amount is approximately between 30 and 200 mg. It is mainly used to test gas adsorption in the range of -5 to 50°C, and the pressure test range is 0.001 to 1 atm.

[0063] Example 1

[0064] (1) Add 4,5-bis(4-aminophenyl)-1,2-phenylenediamine (BABD, 14.5 mg, 0.05 mmol) and 4,4'-bis(4-formylphenyl)benzoylan (BFB, 20.8 mg, 0.05 mmol) to a 10 mL sealing tube, then add o-dichlorobenzene (o-DCB, 1 mL) to the sealing tube and sonicate for 10 min. Then add acetic acid solution (6 M, 0.1 mL) to the sealing tube and continue sonicating for 10 min. Afterwards, seal under vacuum and heat to 120 °C and let stand for 72 h.

[0065] (2) After the reaction was completed, the mixture was cooled to room temperature, then soaked in tetrahydrofuran and filtered. The filtered reaction product was subjected to Soxhlet extraction for 48 hours using ultra-dry tetrahydrofuran as a solvent, and then vacuum dried at 120°C for 6 hours to obtain a yellow fluffy solid (23.8 mg, yield 75%), which is a microporous covalent organic framework material based on quinoxaline and imine bonds, abbreviated as CR-COF-3. Its chemical reaction formula is as follows: Figure 1 As shown.

[0066] Infrared spectra of CR-COF-3, BABD, and BFB were measured using an infrared spectrometer in different wavelength ranges, such as... Figure 1 As shown, the -NH2 in BABD ranges from 3433 to 3212 cm⁻¹. -1 The signal peaks within the range are attributed to the NH stretching vibration peak, and the -CHO peak of BFB is at 2856 cm⁻¹. -1 and 2754cm -1 The signal peaks at these locations are attributed to the CH bond stretching vibrations of aldehydes. Additionally, BFB peaks at 1691 and 1658 cm⁻¹... -1 The characteristic signal peak at this location is attributed to the stretching vibration peak of C=O. The characteristic signal peaks of the aforementioned monomers almost disappear in the infrared spectrum of CR-COF-3, while they are present at 1622 and 1195 cm⁻¹, respectively. -1 Characteristic signal peaks of the -C=N- bond were observed at 1462 and 1387 cm⁻¹. Furthermore, peaks were observed at 1462 and 1387 cm⁻¹. -1 Characteristic signal peaks of quinoxaline were observed. The above infrared spectroscopy results indicate that this embodiment successfully synthesized a COF material based on quinoxaline and imine bonds.

[0067] The XPS plot of N1s of CR-COF-3 was measured using X-ray photoelectron spectroscopy, as shown below. Figure 3 As shown, signal peaks for quinoxaline and imine N were observed at 399.73 eV and 398.87 eV, respectively, further confirming that the synthesized material is a COF material based on quinoxaline and imine bonds.

[0068] The CR-COF-3 was tested using an X-ray powder diffractometer. Meanwhile, a theoretical structure was established, and the structure of CR-COF-3 was simulated by MaterialStudio 7.0. Then, the structure was optimized using Forcite, and two crystal models based on AA stacking and AB stacking were obtained. Two theoretically predicted X-ray diffraction patterns were obtained using the software, denoted as the PXRD curve simulated based on AA stacking and the PXRD curve simulated based on AB stacking. Additionally, the Pawley refinement of the experimental powder diffraction data was performed on the basis of the theoretical structure in the Reflex module by selecting the Powder Refinement module. As Figure 4 shown, there is a strong diffraction peak (4.46°) and a weak diffraction peak (8.92°) in the solid line a, indicating the formation of a crystalline polymer material by the reaction. Comparing the solid line a of the experimental test with the curves c and d of the theoretical simulation, it shows that the intensity and position of the main signal peaks of the solid line a are consistent with the theoretical PXRD data of the single-hole COF simulated based on AA stacking (i.e., curve c), confirming that the experimentally obtained COF is consistent with the theoretically predicted results. In addition, the refined dashed line a almost coincides with the solid line a. Based on the refinement results, the diffraction peaks 4.46° and 8.92° observed in the solid line a were respectively assigned to the d(100) and d(200) crystal planes, and the unit cell parameters of CR-COF-3 obtained after refinement are α = β = 90°, γ = 109.68°, R p = 3.18%, R wp = 4.08%.

[0069] The microscopic morphology of CR-COF-3 was characterized using a scanning electron microscope and a transmission electron microscope. As can be seen from Figure 5 the SEM image, the morphology of CR-COF-3 is an aggregated structure of irregular spherical particles. As can be seen from Figure 6 the TEM image, the morphology of CR-COF-3 is an irregular spherical structure, and there are irregular lamellar structures attached to the edges.

[0070] The gas adsorption experiment of CR-COF-3 was carried out using a gas sorption analyzer. According to Figure 7 (a) the nitrogen adsorption curve, the BET specific surface area of CR-COF-3 was calculated to be 650 m 2 / g for the adsorption data in the low-pressure range (0.05 < P / P0 < 0.30) using the quenched solid density functional theory model (QSDFT) (as shown in Figure 8 (a)); the pore volume calculated at P / P0 = 0.99 is 0.509 cm 3 / g; the pore size distribution (PSD) was obtained by calculating the quenched solid density functional theory (QSDFT), as Figure 9 As shown in (a), the pore size distribution of CR-COF-3 is mainly concentrated at 1.67 nm.

[0071] The thermal stability of CR-COF-3 was evaluated using thermogravimetric analysis, with tests conducted under a nitrogen atmosphere. Figure 10 (a) shows that CR-COF-3 has very good thermal stability, with a thermal weight loss of only 5% when heated from room temperature to 553℃.

[0072] The adsorption performance of CR-COF-3 for methane, nitrogen, and carbon dioxide at 298 K was investigated. Figure 11 Test results show that CR-COF-3 is effective against methane (6.6 cm⁻¹). 3 / g) and carbon dioxide (20.2cm) 3 It has some adsorption capacity for g), but its adsorption capacity for nitrogen is very low (0.3 cm⁻¹). 3 / g).

[0073] Example 2

[0074] (1) Add 4,5-bis(4-aminophenyl)-1,2-phenylenediamine (BABD, 14.5 mg, 0.05 mmol) and 4,4'-bis(3-hydroxy-4-formylphenyl)benzoylan (BHFB, 22.5 mg, 0.05 mmol) to a 10 mL sealing tube, then add DMAc / Mes (v / v, 0.5 mL / 0.5 mL) to the sealing tube and sonicate for 10 min. Then add acetic acid solution (6 M, 0.1 mL) to the sealing tube and continue sonicating for 10 min. Then seal under vacuum and heat to 120 °C and let stand for 72 h.

[0075] (2) After the reaction was completed, the mixture was cooled to room temperature, then soaked in tetrahydrofuran and filtered. The filtered reaction product was subjected to Soxhlet extraction for 48 hours using ultra-dry tetrahydrofuran as a solvent, and then vacuum dried at 120°C for 6 hours to obtain a yellow fluffy solid (31 mg, yield 93%), which is a covalent organic framework material linked by quinoxaline and imine bonds, abbreviated as CR-COF-4. Its chemical reaction formula is as follows: Figure 12 As shown.

[0076] Infrared spectra of CR-COF-4, BABD, and BHFB were measured using an infrared spectrometer in different wavelength ranges, such as... Figure 13 As shown, the -NH2 in BABD ranges from 3433 to 3212 cm⁻¹. -1 The signal peaks within the range are attributed to the NH stretching vibration peak, and BHFB at 2864 cm⁻¹. -1 and 2760cm -1The characteristic signal peaks at these locations are attributed to the CH bond stretching vibration peaks of aldehydes. BHFB peaks are at 1666 and 1646 cm⁻¹. -1 The characteristic signal peak at this location is attributed to the stretching vibration peak of C=O. The characteristic signal peaks of the aforementioned monomers almost disappear in the infrared spectrum of CR-COF-4, while they are present at 1619 and 1193 cm⁻¹, respectively. -1 Characteristic signal peaks of the -C=N- bond were observed at [value missing]. Furthermore, peaks were observed at 1462 and 1356 cm⁻¹. -1 Characteristic signal peaks of quinoxaline were observed. The above infrared spectroscopy results indicate that this embodiment successfully synthesized a COF material based on quinoxaline and imine bonds.

[0077] The XPS plot of N1s of CR-COF-4 was measured using X-ray photoelectron spectroscopy, as shown below. Figure 14 As shown, signal peaks of quinoxaline and imine N1s were observed at 399.73 eV and 401.01 eV, respectively, further proving that the synthesized COF material is based on quinoxaline and imine bond linkage.

[0078] X-ray powder diffraction (XPD) was used to analyze CR-COF-4. Simultaneously, a theoretical structure was established, and the structure of CR-COF-4 was simulated using Material Studio 7.0. Then, Forcite was used for structural optimization, resulting in two crystal models: AA-packed and AB-packed. Two theoretical X-ray diffraction patterns were predicted using the software, denoted as: the PXRD curve based on the AA-packed simulation and the PXRD curve based on the AB-packed simulation, respectively. Furthermore, the Powder Refinement module in the Reflex module was used to perform Pawley refinement on the experimental powder diffraction data based on the theoretical structure. Figure 15 As shown, solid line a contains a strong diffraction peak (4.58°) and a weak diffraction peak (9.00°), indicating that the reaction formed a crystalline polymer material. Comparing the experimentally measured solid line a with the theoretically simulated curves c and d, the intensity and position of the main signal peaks in solid line a are consistent with the theoretical PXRD data (i.e., curve c) of the single-pore COF based on AA stacking simulation, confirming that the experimentally obtained COF is consistent with the theoretical prediction. Furthermore, the refined dashed line a almost overlaps with solid line a. Based on the refined results, the diffraction peaks 4.58° and 9.00° observed in solid line a are assigned to the d(100) and d(200) crystal planes, respectively. The refined cell parameters of CR-COF-4 are... α=β=90°, γ=109.68°, R p =2.54%, R wp =3.35%.

[0079] The microscopic morphology of CR-COF-4 was characterized using a scanning electron microscope and a transmission electron microscope. From Figure 16 the SEM image of Figure 17 it can be seen that the morphology of CR-COF-4 is a structure aggregated by irregular ellipsoidal particles. From

[0080] the TEM image of Figure 7 (b), it can be seen that the morphology of CR-COF-4 is a solid ellipsoidal structure. 2 / g (as shown in Figure 8 (b)); the pore volume calculated at P / P0 = 0.99 is 1.453 cm 3 / g; the pore size distribution (PSD) was obtained by calculating the quenched solid functional theory (QSDFT), as shown in Figure 9 (b), and the pore size distribution of CR-COF-4 mainly concentrates at 1.67 nm.

[0081] A thermogravimetric analyzer was used to evaluate the thermal stability of CR-COF-4, and the test was carried out under a nitrogen atmosphere. As shown in Figure 10 (b), CR-COF-4 has very good thermal stability, and the thermal weight loss from room temperature to 495 °C is only 5%.

[0082] The gas adsorption properties of CR-COF-4 for methane, nitrogen, and carbon dioxide at 298 K were studied. Figure 18 The test results of 3 show that, similar to CR-COF-3, CR-COF-4 has a certain adsorption for methane (6.3 cm 3 / g) and carbon dioxide (20.2 cm 3 / g), while the adsorption amount of nitrogen is very low (1.8 cm

[0083] Example 3

[0084] On the basis of Example 1, only 1 mL of o-DCB in step (1) was replaced with 1 mL of DMAc / o-DCB mixed solvent (v / v, 0.5 mL / 0.5 mL), 1 mL of DMAc / Mes mixed solvent (v / v, 0.5 mL / 0.5 mL), and 1 mL of DMAc / Dio (v / v, 0.5 mL / 0.5 mL) respectively. Other steps and conditions were the same as those in Example 1. Correspondingly, three products were obtained, which were briefly recorded as CR-COF-3 溶剂'、CR-COF-3 溶剂 CR-COF-3 溶剂 ”'.

[0085] For CR-COF-3 溶剂 '、CR-COF-3 溶剂 "and CR-COF-3 溶剂 "Perform PXRD tests separately, from..." Figure 19 The test results show that CR-COF-3 prepared with o-DCB as solvent and CR-COF-3 prepared with DMAc / o-DCB as solvent... 溶剂 'CR-COF-3 has high crystallinity and is prepared using DMAc / Mes as a solvent.' 溶剂 "and CR-COF-3 prepared using DMAc / Dio as solvent" 溶剂 "The crystallinity is low, but the target crystalline product with the same structure as in Example 1 was prepared in all three solvents mentioned above."

[0086] Example 4

[0087] Based on Example 2, except that in step (1), 1 mL of DMAc / Mes mixed solvent (v / v, 0.5 mL / 0.5 mL) was replaced with 1 mL of DMAc / o-DCB mixed solvent (v / v, 0.5 mL / 0.5 mL), all other steps and conditions were the same as in Example 2. Accordingly, a product was obtained, abbreviated as CR-COF-4. 溶剂 '.

[0088] For CR-COF-4 溶剂 Perform PXRD testing, from Figure 20 The test results show that a crystalline target product with the same structure as in Example 2 was prepared using DMAc / o-DCB as a solvent.

[0089] Example 5

[0090] Based on Example 1, only the concentration of the acetic acid solution in step (1) was changed from 6M to 3M, 9M, and 12M respectively. All other steps and conditions were the same as in Example 1. Accordingly, three products were obtained, which are abbreviated as CR-COF-3. 催化剂 '、CR-COF-3 催化剂 CR-COF-3 催化剂 ”'.

[0091] For CR-COF-3 催化剂 '、CR-COF-3 催化剂 "and CR-COF-3 催化剂 "Perform PXRD tests separately, from..." Figure 21 The test results show that the same crystalline target product with the same structure as in Example 1 can be prepared in different acetic acid solutions.

[0092] Example 6

[0093] Based on Example 2, only the concentration of the acetic acid solution in step (1) was changed from 6M to 3M, 9M, and 12M respectively. All other steps and conditions were the same as in Example 2. Accordingly, three products were obtained, which are abbreviated as CR-COF-4 respectively. 催化剂 '、CR-COF-4 催化剂 CR-COF-4 催化剂 ”'.

[0094] For CR-COF-4 催化剂 '、CR-COF-4 催化剂 "and CR-COF-4" 催化剂 "Perform PXRD tests separately, from..." Figure 22 The test results show that crystalline target products with the same structure as in Example 2 can be obtained using 3M and 6M acetic acid solutions, while no crystalline target products with the same structure as in Example 2 are generated in 9M and 12M acetic acid solutions.

[0095] Example 7

[0096] Based on Example 1, only the reaction time in step (1) was modified from 72h to 1h, 2h, 4h, 6h, 9h, 12h, 24h, and 48h respectively. All other steps and conditions were the same as in Example 1. Accordingly, eight products were obtained, which are abbreviated as CR-COF-3. 时间 '、CR-COF-3 时间 CR-COF-3 时间 '、CR-COF-3 时间 CR-COF-3 时间 CR-COF-3 时间 CR-COF-3 时间 CR-COF-3 时间 """".

[0097] The eight products prepared above were subjected to PXRD tests, from which... Figure 23 The test results show that crystallization begins after 2 hours of reaction, and its crystallinity increases with the extension of reaction time, reaching equilibrium after 24 hours. Further extension of reaction time does not significantly change the crystallinity. That is, no crystalline target product with the same structure as in Example 1 is generated after 1 hour of reaction, but crystalline target products with the same structure as in Example 1 are generated from 2 to 72 hours of reaction.

[0098] Example 8

[0099] Based on Example 2, only the reaction time in step (1) was changed from 72h to 24h and 48h respectively. All other steps and conditions were the same as in Example 2. Accordingly, two products were obtained, which are abbreviated as CR-COF-4 respectively. 时间 '、CR-COF-4 时间 ".

[0100] For CR-COF-4 时间 'and CR-COF-4 时间 "Perform PXRD tests separately, from..." Figure 24 The test results show that monomers containing hydroxyl groups are relatively difficult to crystallize. Crystallization begins after 24 hours of reaction, occurs after 48 hours, and a highly crystalline product is obtained after 72 hours. That is, no crystalline target product with the same structure as in Example 2 was generated after 24 hours of reaction, but crystalline target products with the same structure as in Example 2 were generated after 48 hours and 72 hours of reaction.

[0101] Example 9

[0102] Based on Example 2, the only difference is that in step (1), 1 mL of DMAc / Mes mixed solvent (v / v, 0.5 mL / 0.5 mL) is replaced with 1 mL of o-DCB, 1 mL of Mes, or 1 mL of o-DCB / Mes mixed solvent (v / v, 0.5 mL / 0.5 mL). All other steps and conditions are the same as in Example 2. Accordingly, three products are obtained, abbreviated as CR-COF-4. 溶剂 CR-COF-4 溶剂 '、CR-COF-4 溶剂 "".

[0103] For CR-COF-4 溶剂 CR-COF-4 溶剂 "and CR-COF-4 溶剂 "Perform PXRD tests separately, from..." Figure 25 The test results show that the product prepared with o-DCB as solvent is amorphous and does not produce the same crystalline target product as in Example 2; when Mes or o-DCB / Mes is used as solvent, the product contains the same crystalline target product as in Example 2.

[0104] Example 10

[0105] Based on Example 1, only the temperature of the static reaction in step (1) was changed from 120°C to 80°C. All other steps and conditions were the same as in Example 1. Accordingly, a product was obtained, abbreviated as CR-COF-3. 温度 '.

[0106] For CR-COF-3 温度 Perform PXRD testing, from Figure 26 The test results show that, after standing at 80°C, no crystalline target product with the same structure as in Example 1 was obtained.

[0107] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microporous covalent organic framework material based on quinoxaline and imine bonds, characterized in that: The specific structural formula is shown below: In the structural formula, R is H, F, CH3, OH, OCH3, OC2H5, or OC3H7.

2. A method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds as described in claim 1, characterized in that: The microporous covalent organic framework material is formed by a condensation reaction of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine with 4,4'-bis(4-formylphenyl)benzoin or a formyl ortho-substituted derivative of 4,4'-bis(4-formylphenyl)benzoin, wherein the substituent group at the formyl ortho position of 4,4'-bis(4-formylphenyl)benzoin is the same as the other substituent groups of R in the structural formula except for H.

3. The method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds according to claim 2, characterized in that: The specific preparation steps are as follows: 4,5-Di(4-aminophenyl)-1,2-phenylenediamine, aromatic aldehyde compounds, catalysts and organic solvents were mixed and heated to 100-150°C in a closed environment for a solvothermal reaction for no less than 12 hours. After the reaction was completed, the temperature was lowered and the reaction products were collected to obtain a microporous covalent organic framework material based on quinoxaline and imine bonds. The aromatic aldehyde compound is 4,4'-bis(4-formylphenyl)benzoin or a formyl ortho-substituted derivative of 4,4'-bis(4-formylphenyl)benzoin; The catalyst is an aqueous solution of acetic acid, an aqueous solution of lactic acid, or Sc(OTF)3.

4. The method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds according to claim 3, characterized in that: The ortho-formyl derivatives of 4,4'-bis(4-formylphenyl)benzoin are 4,4'-bis(3-fluoro-4-formylphenyl)benzoin, 4,4'-bis(3-methyl-4-formylphenyl)benzoin, 4,4'-bis(3-hydroxy-4-formylphenyl)benzoin, or 4,4'-bis(3-methoxy-4-formylphenyl)benzoin.

5. The method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds according to claim 3, characterized in that: When the aromatic aldehyde compound is 4,4'-bis(4-formylphenyl)benzoin, the organic solvent is o-dichlorobenzene, mesitylene, N,N-dimethylacetamide, a mixture of N,N-dimethylacetamide and mesitylene, a mixture of N,N-dimethylacetamide and o-dichlorobenzene, or a mixture of N,N-dimethylacetamide and 1,4-dioxane; when the aromatic aldehyde compound is 4,4'-bis(3-hydroxy-4-formylphenyl)benzoin, the organic solvent is N,N-dimethylacetamide, a mixture of N,N-dimethylacetamide and mesitylene, or a mixture of N,N-dimethylacetamide and o-dichlorobenzene.

6. The method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds according to claim 3, characterized in that: The molar ratio of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine to aromatic aldehyde compounds is (1:0.9) to (0.9:1).

7. The method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds according to claim 3, characterized in that: When the aromatic aldehyde compound is 4,4'-bis(4-formylphenyl)benzoin, the molar ratio of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine to the catalyst is 1:(6-25); when the aromatic aldehyde compound is 4,4'-bis(3-hydroxy-4-formylphenyl)benzoin, the molar ratio of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine to the catalyst is 1:(6-15).

8. The method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds according to claim 3, characterized in that: The concentration of 4,5-bis(4-aminophenyl)-1,2-phenylenediamine in organic solvents is 0.05–0.15 mmol / mL.

9. The method for preparing a microporous covalent organic framework material based on quinoxaline and imine bonds according to claim 3, characterized in that: When the aromatic aldehyde compound is 4,4'-bis(4-formylphenyl)benzoin, the reaction time is 12-72 h; when the aromatic aldehyde compound is 4,4'-bis(3-hydroxy-4-formylphenyl)benzoin, the reaction time is 36-84 h.

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