Method for preparing two-dimensional olefin covalent organic framework material through acid-induced nitrogen protonation

Abstract

The invention discloses a method for preparing a two-dimensional olefin covalent organic framework material through acid-induced nitrogen protonation. The preparation method of the two-dimensional olefin covalent organic framework material comprises the following steps: 1) sequentially freezing and vacuumizing a monomer with nitrogen atoms, a monomer with aldehyde groups and acid in a closed container; and 2) heating the system obtained in the step 1) for reaction to obtain the two-dimensional olefin covalent organic framework material. According to the invention, acid is used for inducing N protonation to successfully construct, and a new thought and method are provided for preparation of olefin COFs; by adjusting the types of the acid catalysts, various two-dimensional olefin covalent organic framework materials can be effectively prepared, and the preparation process is simple. The two-dimensional olefin covalent organic framework material prepared by the invention has high crystallinity, high specific surface area, good chemical and thermal stability, porosity and regular ordered pore structure, and has wide application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of two-dimensional materials, and particularly relates to a method for preparing two-dimensional olefin covalent organic framework materials by acid-induced nitrogen protonation. Background Art

[0002] Covalent organic frameworks (COFs) are a new type of organic porous crystalline polymer materials with highly designed structures, high porosity, and ordered pores. They can be constructed with different physical structures and chemical properties by changing building blocks and connection modes to understand the relationship between structure and performance. Since COFs were reported by Yaghi et al. in 2005, COFs have been widely used in various fields, such as adsorption and separation, catalysis, energy storage, and semiconductor materials. Among them, sp 2 carbon-linked COFs (sp 2 -COFs) are considered ideal candidates for organic optoelectronic materials due to their all-π-conjugated structure and excellent stability. So far, the reported reactions for synthesizing sp 2 -COFs include Knoevenagel polycondensation, Aldol polycondensation, and Horner-Wads worth-Emmons reaction. The key to these reactions is still to construct multiple α-C with sufficient electron deficiency to effectively generate carbanion intermediates. Therefore, electron-withdrawing groups or strongly electronegative atoms are introduced into the building blocks, such as cyano groups. However, researchers have found that the introduction of cyano groups may make the cyanovinylene bond reversible, and at the same time, the steric collision between the cyano group and the adjacent aromatic ring will cause out-of-plane distortion, which may lead to an amorphous or low-crystalline structure of the synthesized COFs, thus limiting the further development and practical application of COF materials. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing two-dimensional olefin covalent organic framework materials by acid-induced nitrogen protonation, which is successfully constructed by acid-induced N protonation, providing new ideas and methods for the preparation of olefin COFs.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for preparing two-dimensional olefin covalent organic framework materials, comprising the following steps:

[0006] 1) Placing a monomer with a nitrogen atom, a monomer with an aldehyde group, and an acid in a closed container, and successively performing freezing and vacuum pumping;

[0007] 2) Heating the system obtained in step 1) for reaction to obtain the two-dimensional olefin covalent organic framework materials.

[0008] In the above method for preparing the two-dimensional olefin covalent organic framework material, the monomer having a nitrogen atom may be 2,4,6-trimethylpyridine (TMP) or 2,4,6-trimethyl-1,3,5-triazine (TMT);

[0009] The monomer having an aldehyde group may be terephthalaldehyde (TPA), 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde (TFPT) or 2,5-dimethoxybenzene-1,4-dicarbaldehyde (DMTA);

[0010] As an example, in step 1), the monomers may specifically be any of the following combinations:

[0011] 1) The monomer having a nitrogen atom is TMP, and the monomer having an aldehyde group is TPA;

[0012] 2) The monomer having a nitrogen atom is TMP, and the monomer having an aldehyde group is TFPT;

[0013] 3) The monomer having a nitrogen atom is TMP, and the monomer having an aldehyde group is DMTA;

[0014] 4) The monomer having a nitrogen atom is TMT, and the monomer having an aldehyde group is TPA;

[0015] 5) The monomer having a nitrogen atom is TMT, and the monomer having an aldehyde group is TFPT.

[0016] In the above method for preparing the two-dimensional olefin covalent organic framework material, the molar ratio of the monomer having a nitrogen atom to the monomer having an aldehyde group may be 1.0:(1.0 - 1.5). For example, for TMP or TMT and TPFT, it may specifically be 1.0:1.0; for TMP or TMT and TPA, it may specifically be 1.0:1.5; for TMP and DMTA, it may specifically be 1.0:1.5.

[0017] In the above method for preparing the two-dimensional olefin covalent organic framework material, the acid may be any one of benzoic acid, acetic acid, propionic acid and butyric acid.

[0018] In the above method for preparing the two-dimensional olefin covalent organic framework material, the molar ratio of the monomer having a nitrogen atom to the acid may be 1.0:(0.5 - 4.0). For example, for the TMP monomer, the molar ratio of the monomer to the acid may specifically be 1.0:2.0; for the TMT monomer, the molar ratio of the monomer to the acid may specifically be 1.0:3.0 or 1.0:4.0;

[0019] In the above method for preparing the two-dimensional olefin covalent organic framework material, the freezing temperature is 77K, such as freezing with liquid nitrogen;

[0020] The freezing time is 2 to 10 minutes, such as 2 minutes;

[0021] The vacuum pumping time is 2 to 10 minutes, such as 2 minutes or 10 minutes;

[0022] The freezing and vacuum pumping steps can be cycled 1 to 6 times, that is, freezing and vacuum pumping are repeated after the freezing and vacuum pumping steps, specifically 3 times.

[0023] In the above method for preparing the two-dimensional olefin covalent organic framework material, the closed container can specifically be a closed glass container.

[0024] In the above method for preparing the two-dimensional olefin covalent organic framework material, the reaction temperature can be 120°C to 400°C, specifically 120 to 180°C, 120°C, 150°C or 180°C, and the time is 3d to 15d, specifically 3d.

[0025] Furthermore, after the reaction, the method further includes the following steps:

[0026] 3) Cooling to room temperature, soaking the precipitate in a mixed solution composed of an alkali solution and an alcohol, and collecting the powder;

[0027] 4) Subjecting the powder to Soxhlet extraction with a detergent, and then drying under vacuum to obtain the two-dimensional olefin covalent organic framework material.

[0028] Preferably, in step 3), the alcohol is methanol;

[0029] The alkali solution is an aqueous NaOH solution;

[0030] The concentration of the alkali solution is 1M;

[0031] The volume ratio of the alkali solution to the alcohol is 1:1.

[0032] Preferably, in step 4), the detergent is at least one of methanol, dichloromethane, tetrahydrofuran, and ethanol, such as washing sequentially with any two of methanol, dichloromethane, tetrahydrofuran, and ethanol.

[0033] In the present invention, the room temperature is 15 to 30°C, such as 20 to 25°C.

[0034] Even further, in step 3), the alkali solution can be an aqueous solution of sodium hydroxide with a concentration of 1.0M; the alcohol can be methanol; the volume ratio of the alkali solution to the alcohol can be 1:1;

[0035] In step 4), the detergent can specifically be methanol and tetrahydrofuran, and wash sequentially;

[0036] The Soxhlet extraction time can be 3d.

[0037] The present invention further provides a two-dimensional olefin covalent organic framework material obtained by the preparation method described in any one of the above.

[0038] The application of the two-dimensional olefin covalent organic framework material in at least one of catalysis and as a semiconductor material is also within the protection scope of the present invention.

[0039] In the above application, the catalysis can specifically be visible light photocatalytic hydrogen evolution.

[0040] As an example, a mixture containing the two-dimensional olefin covalent organic framework material, the ascorbic acid aqueous solution, and H2PtCl6 is ultrasonically treated and then irradiated with a Xe lamp to achieve the visible light photocatalytic hydrogen evolution.

[0041] The present invention has the following beneficial effects:

[0042] 1. By adjusting the type of acid catalyst, the present invention can effectively prepare various two-dimensional olefin covalent organic framework materials, and the preparation process is simple.

[0043] 2. The two-dimensional olefin covalent organic framework materials TMPCOFs and TMTCOFs prepared by the present invention both have high crystallinity, high specific surface area, good chemical and thermal stability, porosity, and regular ordered pore structures.

[0044] 3. The TMP-TPACOF material prepared by the present invention has good application in catalysis. Under the irradiation of a 300W Xe lamp (λ>420nm), visible light photocatalytic hydrogen evolution experiments were carried out on TMPCOFs and TMTCOFs with similar structures and different nitrogen positions, and the results showed stable H2 production. TMP-TPACOF has excellent photocatalytic performance. Description of the Drawings

[0045] Figure 1 It is the synthesis route diagram of the two-dimensional olefin covalent organic framework TMP-TPACOF material in Example 1;

[0046] Figure 2 It is the synthesis route diagram of the two-dimensional olefin covalent organic framework TMP-TFPTCOF material in Example 2;

[0047] Figure 3 It is the synthesis route diagram of the two-dimensional olefin covalent organic framework TMP-DMTACOF material in Example 3;

[0048] Figure 4 It is the synthesis route diagram of the two-dimensional olefin covalent organic framework TMT-TPACOF material in Example 4;

[0049] Figure 5 Synthesis route diagram of the two-dimensional olefin covalent organic framework TMT-TFPTCOF material in Example 5;

[0050] Figure 6 XRD patterns of the TMP-TPACOF material (a) prepared in Example 1, the TMP-TFPTCOF material (b) prepared in Example 2, the TMP-DMTACOF material (c) prepared in Example 3, the TMT-TPACOF material (d) prepared in Example 4, and the TMT-TFPTCOF material (e) prepared in Example 5;

[0051] Figure 7 Infrared spectra of the TMP-TPACOF material (a) prepared in Example 1, the TMP-TFPTCOF material (b) prepared in Example 2, the TMP-DMTACOF material (c) prepared in Example 3, the TMT-TPACOF material (d) prepared in Example 4, and the TMT-TFPTCOF material (e) prepared in Example 5;

[0052] Figure 8 Thermogravimetric curves of the TMP-TPACOF material (a) prepared in Example 1, the TMP-TFPTCOF material (b) prepared in Example 2, the TMP-DMTACOF material (c) prepared in Example 3, the TMT-TPACOF material (d) prepared in Example 4, and the TMT-TFPTCOF material (e) prepared in Example 5;

[0053] Figure 9 N2 adsorption-desorption curves of the TMP-TPACOF material (a) prepared in Example 1, the TMP-TFPTCOF material (b) prepared in Example 2, the TMP-DMTACOF material (c) prepared in Example 3, the TMT-TPACOF material (d) prepared in Example 4, and the TMT-TFPTCOF material (e) prepared in Example 5.

[0054] Figure 10 Transmission electron micrographs (scale bar is 100 nm) of the TMP-TPACOF material (a) prepared in Example 1, the TMP-TFPTCOF material (b) prepared in Example 2, the TMP-DMTACOF material (c) prepared in Example 3, the TMT-TPACOF material (d) prepared in Example 4, and the TMT-TFPTCOF material (e) prepared in Example 5.

[0055] Figure 11 Photocatalytic performance of different COFs. Detailed implementation manners

[0056] The present invention will be further described in detail below in conjunction with specific embodiments. The provided embodiments are only for clarifying the present invention and not for limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements, and do not constitute any limitation to the present invention in any way.

[0057] Unless otherwise specified, the methods used in the following examples are all conventional methods, carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0058] The monomers in the following examples are all represented by abbreviations, and the specific substances they represent are as follows:

[0059] The TMP monomer is 2,4,6-trimethylpyridine;

[0060] The TMT monomer is 2,4,6-trimethyl-1,3,5-triazine;

[0061] The TPA monomer is terephthalaldehyde;

[0062] The TFPT monomer is 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde;

[0063] The DMTA monomer is 2,5-dimethoxybenzene-1,4-dicarboxaldehyde.

[0064] Example 1. Synthesis of TMP-TFPT COF

[0065] According to Figure 1 the synthesis route diagram of the two-dimensional olefin covalent organic framework TMP-TPACOF material shown, the specific steps are as follows:

[0066] 1) Weigh 1.0 mmol (121.2 mg) of the monomer TMP, 1.5 mmol (201.2 mg) of the monomer TPA, and 2.0 mmol (244.24 mg) of benzoic acid and place them in a sealed glassware;

[0067] 2) Freeze the sealed glassware at 77 K (liquid nitrogen) for 2 min, evacuate for 10 min (freezing-evacuation, cycle 3 times), and seal with a flame. Heat to make the reaction proceed at 180 °C for 3 d to obtain a yellow solid;

[0068] 3) After cooling to room temperature, soak the precipitate in a mixed solution of NaOH (1 M aqueous solution) and methanol (v / v = 1 / 1). Extract the obtained powder successively with tetrahydrofuran and methanol in a Soxhlet extractor at 120 °C for three days. Finally, dry the powder under vacuum at 90 °C to obtain TMP-TPACOF.

[0069] Figure 6 a is the XRD pattern of the TMP-TPACOF material prepared in Example 1. Diffraction peaks appeared at 4.70°, 8.12°, 9.37°, 12.38° and 26° (red line, upper), which were consistent with the simulated XRD (blue line, lower), indicating the successful preparation of TMP-TPACOF; Figure 7 a is the infrared spectrum of the TMP-TPACOF material prepared in Example 1. The adsorption bands of –CH3 and –CHO groups in the building block were located at 2916 cm -1 and 1698 cm -1 respectively. However, after polymerization, the adsorption bands decreased sharply or even disappeared, and new characteristic bending vibrations appeared at 965 and 1630 cm -1 for the -HC=CH- bond, indicating the successful preparation of TMP-TPACOF; Figure 8 a is the thermogravimetric curve of the TMP-TPACOF material prepared in Example 1. Thermogravimetric analysis showed that under a nitrogen atmosphere, TMP-TPACOF retained more than 97% of its weight at temperatures up to 400 °C, indicating that they also had excellent thermal stability. Figure 9 a is the N2 adsorption-desorption isotherm curve of the TMP-TPACOF material prepared in Example 1. The surface area of TMP-TPACOF was 1446 m 2 g -1 , indicating that TMP-TPACOF had good crystallinity. Figure 10 a is the high-magnification transmission image of the TMP-TPACOF material prepared in Example 1. The pore structure of TMP-TPACOF could be seen from the transmission image, indicating high crystallinity.

[0070] Example 2. Synthesis of TMP-TFPTCOF

[0071] According to Figure 2 the synthesis route diagram of the two-dimensional olefin covalent organic framework TMP-TFPTCOF material shown, the preparation was carried out as follows:

[0072] 1) Weigh 1.0 mmol (121.2 mg) of monomer TMP, 1.0 mmol (393.39 mg) of monomer TFPT and 3.0 mmol (366.36 mg) of benzoic acid and place them in a sealed glassware;

[0073] 2) Freeze the sealed glassware at 77 K (liquid nitrogen) for 2 min, evacuate for 2 min (freezing-evacuation, cycle 3 times), and seal with a flame. Heat to make the reaction proceed at 180 °C for 3 d to obtain a yellow solid;

[0074] 3) After cooling to room temperature, the precipitate was soaked in a mixed solution of NaOH (aqueous solution 1.0 M) and methanol (v / v = 1 / 1). The resulting powder was subjected to Soxhlet extraction with tetrahydrofuran and methanol successively for three days. Finally, the powder was dried under vacuum at 90 °C to obtain TMP-TFPTCOF.

[0075] Figure 6 b is the XRD pattern of the TMP-TFPTCOF material prepared in Example 2. Diffraction peaks appeared at 5.65°, 9.78°, 11.30°, 15.00° and 26° (red line, upper), which were consistent with the simulated XRD (blue line, lower), indicating the successful preparation of TMP-TPACOF; Figure 7 b is the infrared spectrum of the TMP-TFPTCOF material prepared in Example 2. The adsorption bands of the –CH3 and –CHO groups in the building block were located at 2916 cm -1 and 1698 cm -1 respectively. However, after polymerization, the adsorption bands decreased sharply or even disappeared, and new characteristic bending vibrations appeared at 965 and 1630 cm -1 for the -HC=CH- bond, indicating the successful preparation of TMP-TFPTCOF; Figure 8 b is the thermogravimetric curve of the TMP-TFPTCOF material prepared in Example 2. Under a nitrogen atmosphere, TMP-TFPTCOF retained more than 97% of its weight at temperatures up to 400 °C, indicating that they also have excellent thermal stability; Figure 9 b is the N2 adsorption-desorption curve of the TMP-TFPTCOF material prepared in Example 2. The surface area of TMP-TFPTCOF was 1476 m 2 g -1 , indicating that TMP-TPACOF has good crystallinity. Figure 10 b is the high-magnification transmission image of the TMP-TFPTCOF material prepared in Example 2. From the transmission image, the pore structure of TMP-TFPTCOF can be seen, indicating high crystallinity.

[0076] Example 3. Synthesis of TMP-DMTACOF

[0077] According to Figure 3 the synthesis route diagram of the two-dimensional olefin covalent organic framework TMP-DMTACOF material shown, the preparation was carried out as follows:

[0078] 1) Weigh 1.0 mmol (121.2 mg) of monomer TMP, 1.5 mmol (291.27 mg) of monomer DMTA and 2.0 mmol (244.24 mg) of benzoic acid and place them in a sealed glassware;

[0079] 2) The sealed glassware was frozen at 77 K (liquid nitrogen) for 2 min, evacuated for 2 min (freezing-evacuation, 3 cycles), and flame-sealed. It was heated to make the reaction proceed at 180 °C for 3 d to obtain a dark brown solid;

[0080] 3) After cooling to room temperature, the precipitate was soaked in a mixed solution of NaOH (aqueous solution 1.0 M) and methanol (v / v = 1 / 1). The resulting powder was subjected to Soxhlet extraction with tetrahydrofuran and methanol for three days. Finally, the powder was dried under vacuum at 90 °C to obtain TMP-DMTACOF.

[0081] Figure 6 c is the XRD pattern of the TMP-DMTACOF material prepared in Example 3. Diffraction peaks appeared at 4.76°, 8.24°, 9.53° and 12.61° (red line, upper), which is consistent with the simulated XRD (blue line, lower), indicating the successful preparation of TMP-DMTACOF; Figure 7 c is the infrared spectrum of the TMP-DMTACOF material prepared in Example 3. The adsorption bands of –CH3 and –CHO groups in the building block are located at 2916 cm -1 and 1698 cm -1 respectively. However, after polymerization, the adsorption bands decreased sharply or even disappeared, and new characteristic bending vibrations of the -HC=CH- bond appeared at 965 and 1630 cm -1 respectively, indicating the successful preparation of TMP-DMTACOF; Figure 8 c is the thermogravimetric curve of the TMP-DMTACOF material prepared in Example 3. Under a nitrogen atmosphere, TMP-DMTACOF retained more than 97% of its weight at temperatures up to 400 °C, indicating that they also have excellent thermal stability; Figure 9 c is the N2 adsorption-desorption isotherm of the TMP-DMTACOF material prepared in Example 3. The surface area of TMP-DMTACOF is 701 m 2 g -1 , indicating that TMP-TPACOF has good crystallinity. Figure 10 c is the high-magnification transmission image of the TMP-DMTACOF material prepared in Example 3. The pore structure of TMP-DMTACOF can be seen from the transmission image, indicating high crystallinity.

[0082] Example 4. Synthesis of TMT-TPACOF

[0083] According to Figure 4 the synthesis roadmap of the two-dimensional olefin covalent organic framework TMT-TPACOF material shown, the preparation was carried out as follows:

[0084] 1) Weigh 1.0 mmol (123.2 mg) of monomer TMT, 1.5 mmol (201.2 mg) of monomer TPA, and 3 mmol (366.36 mg) of benzoic acid and place them in a sealed glass vessel A;

[0085] 2) Freeze the sealed glass vessel at 77 K (liquid nitrogen) for 2 min, evacuate for 2 min (freezing - evacuation, cycle 3 times), and seal with a flame. Heat to carry out the reaction at 120 °C for 3 d to obtain a yellow solid;

[0086] 3) After cooling to room temperature, soak the precipitate in a mixed solution of NaOH (aqueous solution 1.0 M) and methanol (v / v = 1 / 1). Perform Soxhlet extraction on the obtained powder with tetrahydrofuran and methanol for three days. Finally, dry the powder under vacuum at 90 °C to obtain TMT - TPACOF.

[0087] Figure 6 d is the XRD pattern of the TMT - TPACOF material prepared in Example 4. Diffraction peaks appear at 4.79°, 8.31°, 9.62°, and 12.70° (red line, upper), which are consistent with the simulated XRD (blue line, lower), indicating the successful preparation of TMT - TPACOF; Figure 7 d is the infrared spectrum of the TMT - TPACOF material prepared in Example 4. The adsorption bands of the –CH3 and –CHO groups in the building blocks are located at 2916 cm -1 and 1698 cm -1 respectively. However, after polymerization, the adsorption bands decrease sharply or even disappear, and new characteristic bending vibrations appear at 965 and 1630 cm -1 for the -HC=CH- bond, indicating the successful preparation of TMT - TPACOF; Figure 8 d is the thermogravimetric curve of the TMT - TPACOF material prepared in Example 4. Under a nitrogen atmosphere, TMT - TPACOF retains more than 97% of its weight at temperatures up to 400 °C, indicating that they also have excellent thermal stability; Figure 9 d is the N2 adsorption - desorption curve of the TMT - TPACOF material prepared in Example 4. The surface area of TMT - TPACOF is 844 m 2 g -1 , indicating that TMT - TPACOF has good crystallinity. Figure 10 d is the high - magnification transmission image of the TMT - TPACOF material prepared in Example 4. From the transmission image, the pore structure of TMT - TPACOF can be seen, indicating high crystallinity.

[0088] Example 5. Synthesis of TMT - TFPTCOF

[0089] According to Figure 5Prepare according to the synthesis route diagram of the shown two-dimensional olefin covalent organic framework TMT-TFPTCOF material. The specific steps are as follows:

[0090] 1) Weigh 1.0 mmol (123.2 mg) of monomer TMT, 1.0 mmol (393.39 mg) of monomer TFPT, and 4.0 mmol (488.48 mg) of benzoic acid and place them in a sealed glassware;

[0091] 2) Freeze the sealed glassware at 77 K (liquid nitrogen) for 2 min, evacuate for 2 min (freezing-evacuation, cycle 3 times), and seal with a flame. Heat to make the reaction proceed at 180 °C for 3 d to obtain a yellow solid;

[0092] 3) After cooling to room temperature, immerse the precipitate in a mixed solution of NaOH (aqueous solution 1.0 M) and methanol (v / v = 1 / 1). Soxhlet extract the obtained powder with tetrahydrofuran and methanol successively for three days. Finally, dry the powder under vacuum at 90 °C to obtain TMT-TFPTCOF.

[0093] Figure 6 e is the XRD pattern of the TMT-TFPTCOF material prepared in Example 5. Diffraction peaks appear at 5.72°, 9.93°, 11.48°, and 15.20° (red line, upper), which is consistent with the simulated XRD (blue line, lower), indicating the successful preparation of TMT-TFPTCOF; Figure 7 e is the infrared spectrum of the TMT-TFPTCOF material prepared in Example 53. The adsorption bands of the –CH3 and –CHO groups in the building block are located at 2916 cm -1 and 1698 cm -1 respectively. However, after polymerization, the adsorption bands decrease sharply or even disappear, and new characteristic bending vibrations appear at 965 and 1630 cm -1 for the -HC=CH- bond, indicating the successful preparation of TMT-TFPTCOF; Figure 8 e is the thermogravimetric curve of the TMT-TFPTCOF material prepared in Example 5. Under a nitrogen atmosphere, TMT-TPACOF retains more than 97% of its weight at a temperature up to 400 °C, indicating that they also have excellent thermal stability; Figure 9 e is the N2 adsorption-desorption curve of the TMT-TFPTCOF material prepared in Example 5. The surface area of TMT-TFPTCOF is 952 m 2 g -1 , indicating that TMT-TFPTCOF has good crystallinity. Figure 10 e is the high-magnification transmission image of the TMT-TFPTCOF material prepared in Example 5. It can be seen from the transmission image that the pore structure of TMT-TFPTCOF indicates high crystallinity.

[0094] As can be seen from Examples 1-5, the two-dimensional olefin covalent organic framework materials TMPCOFs and TMTCOFs successfully prepared by acid-induced nitrogen protonation of the present invention both have high crystallinity, porosity and regular ordered pore structures. The two-dimensional olefin covalent organic framework materials of the present invention have different pore sizes, high crystallinity, good chemical stability and thermal stability.

[0095] Example 6, visible light photocatalytic hydrogen evolution

[0096] Under the irradiation of a 300W Xe lamp (λ>420nm), visible light photocatalytic hydrogen evolution experiments were carried out on TMPCOFs and TMTCOFs with similar structures and different nitrogen positions. The specific steps are as follows:

[0097] Photocatalytic hydrogen production using TMPCOFs and TMTCOFs as catalysts. For the photocatalytic hydrogen evolution experiment, sample powder (5mg), 0.1M aqueous ascorbic acid solution (50mL), and a certain amount of H2PtCl6 (0.8wt% Pt in H2O) were added to the flask as a co-catalyst. The mixture was sonicated for 5 minutes, degassed, and then irradiated with a 300W Xe lamp equipped with a 420nm long-pass filter. The temperature of the reaction system was maintained at 6 °C by a cooling water stream, and the generated gas sample was analyzed by an on-line gas chromatograph (TCD detector). The results showed stable H2 production under visible light irradiation (λ>420nm), and the mass-normalized HER rate was 83 mmol g -1 h -1 。

[0098] Figure 11 It is a photocatalytic hydrogen production performance diagram of Example 6, and the results show that TMP-TPACOF has excellent photocatalytic performance.

[0099] The present invention has been described in detail above. For those skilled in the art, the present invention can be implemented within a relatively wide range under the same parameters, concentrations and conditions without departing from the purpose and scope of the present invention. Although specific examples of the present invention are given, it should be understood that the present invention can be further improved. In short, according to the principle of the present invention, this application intends to include any changes, uses or improvements to the present invention, including changes made by using conventional techniques known in the art that are outside the scope disclosed in this application.

Claims

1. A method for preparing a two-dimensional olefin covalent organic framework material, comprising the following steps: 1) Freezing and evacuating in sequence a monomer having a nitrogen atom, a monomer having an aldehyde group, and an acid in a closed container; 2) Heating the system obtained in step 1) to carry out a reaction to obtain the two-dimensional olefin covalent organic framework material.

2. The preparation method of the two-dimensional olefin covalent organic framework material according to claim 1, wherein: The monomer having a nitrogen atom is 2,4,6-trimethylpyridine (TMP) or 2,4,6-trimethyl-1,3,5-triazine (TMT); The monomer having an aldehyde group is terephthalaldehyde (TPA), 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde (TFPT), or 2,5-dimethoxybenzene-1,4-dialdehyde (DMTA).

3. The preparation method of the two-dimensional olefin covalent organic framework material according to any one of claims 1-2, characterized in that: The molar ratio of the monomer having a nitrogen atom to the monomer having an aldehyde group is 1.0:(1.0 - 1.5).

4. The preparation method of the two-dimensional olefin covalent organic framework material according to any one of claims 1-3, characterized in that: The acid is any one of benzoic acid, acetic acid, propionic acid, and butyric acid.

5. The preparation method of the two-dimensional olefin covalent organic framework material according to any one of claims 1-4, characterized in that: The molar ratio of the monomer having a nitrogen atom to the acid is 1:(0.5 - 4.0).

6. The preparation method of the two-dimensional olefin covalent organic framework material according to any one of claims 1-5, characterized in that: The temperature of the freezing is 77K; The time of the freezing is 2 - 10 minutes; The time of the evacuation is 2 - 10 minutes; The steps of freezing and evacuating are cycled 1 - 6 times.

7. The preparation method of the two-dimensional olefin covalent organic framework material according to any one of claims 1-6, characterized in that: The temperature of the reaction is 120°C - 400°C, and the time is 3d - 15d.

8. The preparation method of the two-dimensional olefin covalent organic framework material according to any one of claims 1-7, characterized in that: The method further comprises the following steps after the reaction: 3) Cooling to room temperature, soaking the precipitate in a mixed solution of sodium hydroxide solution and methanol, and collecting the powder; 4) Subjecting the powder to Soxhlet extraction with a detergent, and then drying in vacuo to obtain the two-dimensional olefin covalent organic framework material; The detergent is at least one of methanol, dichloromethane, tetrahydrofuran, and ethanol.

9. The two-dimensional olefin covalent organic framework material obtained by the preparation method according to any one of claims 1 - 8.

10. Application of the two-dimensional olefin covalent organic framework material according to claim 9 in at least one of catalysis and as a semiconductor material.

Images