A triptycene-modified β-ketoenamine covalent organic framework, preparation method thereof and use thereof

Abstract

The present invention discloses a triptycene-modified β-ketoenamine covalent organic framework, a preparation method thereof, and its use. The triptycene-modified β-ketoenamine covalent organic framework is prepared by polycondensation of a polyaminotriptycene monomer, a 1,3,5-trialdehyde phloroglucinol monomer, and an enamine monomer. The triptycene-modified β-ketoenamine covalent organic framework of the present invention has excellent photocatalytic water decomposition and hydrogen production performance and is reusable. The preparation method provided by the present invention has a simple process, mild conditions, short time consumption, environmental friendliness, and is easy to industrialize.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic materials, and in particular relates to a triptycene-modified β-ketoenamine covalent organic framework, a preparation method thereof and uses thereof. Background Art

[0002] Energy crises and environmental pollution are serious challenges facing countries around the world today. Solar energy and hydrogen, as renewable, clean energy sources, hold great promise as alternatives to fossil fuels. Harnessing sunlight to catalytically split water to produce hydrogen is a key approach to converting solar energy into green hydrogen. Therefore, the search for new, green, efficient, and cost-effective semiconductor catalysts is of great significance.

[0003] Covalent organic framework materials (COFs) are a new type of organic polymer materials composed of light elements such as C, H, N, O, and B. Their atoms form an ordered porous framework structure through covalent bonds. They have been the frontier and hot topic in the field of photocatalysis research in recent years.

[0004] Among them, β-ketoenamine covalent organic frameworks (COFs) have shown great potential in photocatalytic research and application due to their good thermal and chemical stability, strong visible light absorption, suitable energy band structure, and porous structural characteristics. However, due to the large difference in electronegativity between carbon and nitrogen atoms in the COFs skeleton, the degree of electron delocalization in the conjugated system is low (electrons tend to be enriched around nitrogen atoms), the conjugated system is not fully expanded, the mobility of photogenerated charges is low, and they are easy to recombine, resulting in low quantum efficiency of photocatalytic reactions. Summary of the Invention

[0005] The present invention provides a triptycene-modified β-ketoenamine covalent organic framework, a preparation method and uses thereof. The carriers in the triptycene-modified β-ketoenamine covalent organic framework provided by the present invention have high migration and interface transfer efficiency, thereby improving the efficiency of the photocatalytic reaction.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A triptycene-modified β-ketoenamine covalent organic framework is prepared by polycondensation of polyaminotriptycene monomers, 1,3,5-trialdehyde phloroglucinol monomers and enamine monomers.

[0008] After the conjugated polymerization of β-ketoenamine covalent organic framework and triptycene, the increase in conjugated carbon content increases the degree of electron delocalization, accelerates the rapid transfer of photogenerated electrons on the β-ketoenamine covalent organic framework to triptycene, effectively improves the separation efficiency of photogenerated electron-hole pairs, and enhances the photocatalytic performance of the triptycene-modified β-ketoenamine covalent organic framework.

[0009] In order to further improve the hydrogen production activity, the mass ratio of polyaminotriptycene, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer is (5-40): (30-60): (15-45), and more preferably (10-25): (45-55): (25-43).

[0010] The β-ketoenamine serves as the basic connecting unit of this type of covalent organic framework. The aldehyde group of the β-ketoenamine covalent organic framework and the amino group of the triaminotriptycene monomer achieve conjugated polymerization through a Schiff base condensation reaction.

[0011] To further enhance hydrogen production activity, the enamine monomer is at least one of p-phenylenediamine (PDA), 2,5-diaminobenzonitrile (DBN), or 5,5'-diamino-2,2'-bipyridine (Bpy). More preferably, the enamine monomer is 2,5-diaminobenzonitrile (DBN).

[0012] Preferably, the mass amount of the polyaminotriptycene monomer is 5 to 40% of the total mass of the polyaminotriptycene monomer, the 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer.

[0013] When the enamine monomer is p-phenylenediamine (PDA), the mass amount of the polyaminotriptycene monomer is 10-40% of the total mass of the polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer, more preferably 10-30%.

[0014] When the enamine monomer is 2,5-diaminobenzonitrile (DBN), the mass amount of the polyaminotriptycene monomer is 10-40% of the total mass of the polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer, more preferably 10-30%.

[0015] When the enamine monomer is 5,5'-diamino-2,2'-bipyridine (Bpy), the mass amount of the polyaminotriptycene monomer is 5-30% of the total mass of the polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer, more preferably 5-20%.

[0016] When the enamine monomer is p-phenylenediamine (PDA), the obtained triptycene-modified β-ketoenamine covalent organic framework is abbreviated as Tp-PDA-TATP; when the enamine monomer is 2,5-diaminobenzonitrile (DBN), the obtained triptycene-modified β-ketoenamine covalent organic framework is abbreviated as Tp-DBN-TATP; when the enamine monomer is 5,5'-diamino-2,2'-bipyridine (Bpy), the obtained triptycene-modified β-ketoenamine covalent organic framework is abbreviated as Tp-Bpy-TATP.

[0017] The polyaminotriptycene monomer contains three or more amino groups, and preferably has three or six amino groups.

[0018] In order to further improve the catalytic activity, the polyaminotriptycene monomer includes at least one of 2,6,14-triaminotriptycene, 2,7,14-triaminotriptycene, 1,7,13-triaminotriptycene, 2,7,13-triaminotriptycene or 2,3,6,7,14,15-hexaminotriptycene, more preferably 2,6,14-triaminotriptycene (TATP).

[0019] In the present invention, unless otherwise specified, all raw materials used are conventional commercially available products.

[0020] The preferred structural formula of the triptycene-modified β-ketoenamine covalent organic framework is:

[0021]

[0022] At least one of .

[0023] The above structural formula represents the smallest structural unit, and the wavy lines represent omitted repeated structural units. The structure is infinitely extended.

[0024] The synthetic route of the above-mentioned triptycene-modified β-ketoenamine covalent organic framework is as follows:

[0025]

[0026] The triptycene-modified β-ketoenamine covalent organic framework is prepared by polycondensation reaction of polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer at room temperature for 8 to 12 hours.

[0027] The mass dosage of the polyaminotriptycene monomer is 5-40% of the total mass of the polyaminotriptycene monomer, the 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer.

[0028] When the enamine monomer is p-phenylenediamine (PDA), the mass amount of the polyaminotriptycene monomer is 10-40% of the total mass of the polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer, more preferably 10-30%.

[0029] When the enamine monomer is 2,5-diaminobenzonitrile (DBN), the mass amount of the polyaminotriptycene monomer is 10-40% of the total mass of the polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer, more preferably 10-30%.

[0030] When the enamine monomer is 5,5'-diamino-2,2'-bipyridine (Bpy), the mass amount of the polyaminotriptycene monomer is 5-30% of the total mass of the polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer, more preferably 5-20%.

[0031] The preparation method is simple, employs mild, controllable conditions, and is time-efficient. After conjugated polymerization of the β-ketoenamine covalent organic framework (BECAF) with triptycene, the delocalization of the π electrons within the BECAF framework increases, enhancing the separation, migration, and interfacial transfer efficiency of charge carriers within the BECAF bulk. This significantly improves charge separation and enhances the photocatalytic performance of the triptycene-modified BECAF.

[0032] As one specific implementation scheme, the preparation method of the triptycene-modified β-ketoenamine covalent organic framework comprises the following steps:

[0033] 1) placing 1,3,5-trialdehyde-meta-triphenol monomer and p-toluenesulfonic acid in a mixture of trimethylbenzene, 1,4-dioxane and acetic acid solution in a volume ratio of (2-3):(2-3):1, and ultrasonically dispersing to obtain liquid 1; the mass amount of p-toluenesulfonic acid used is 0.5-0.7 times the mass of 1,3,5-trialdehyde-meta-triphenol;

[0034] 2) placing the polyaminotriptycene monomer in a tetrahydrofuran solution and ultrasonically dispersing the mixture to obtain a second liquid;

[0035] 3) Liquid 1 and Liquid 2 are placed in a ball mill, enamine monomer is added, argon protective gas is introduced, and ball milling is performed at room temperature at a rotation speed of 300-500 rpm for 8-12 hours. The resulting product is centrifuged, washed, and dried to obtain a triptycene-modified β-ketoenamine covalent organic framework.

[0036] In the above step 1), p-toluenesulfonic acid is used as a catalyst and a dehydrating agent.

[0037] In the above step 3), the drying temperature is 50-60° C. and the drying time is 8-12 hours.

[0038] The polycondensation reaction is carried out under a protective atmosphere, which may be argon, nitrogen or other inert gases, to prevent the reactants and products from being decomposed by moisture and oxidation.

[0039] In step 3), the centrifugation speed was 11,000 rpm for 5 minutes, and then the mixture was washed with anhydrous tetrahydrofuran. The centrifugation and washing steps were repeated three times (one wash followed by centrifugation with tetrahydrofuran was considered one repetition, and this was repeated three times). Finally, the resulting product was dried in a vacuum drying oven at 60° C. for 12 hours.

[0040] The above-mentioned triptycene-modified β-ketoenamine covalent organic framework is used for photocatalytic water decomposition to produce hydrogen.

[0041] Photocatalytic decomposition of water to produce hydrogen preferably includes the following steps:

[0042] (1) mixing a triptycene-modified β-ketoenamine covalent organic framework, sodium ascorbate, chloroplatinic acid, and water to obtain a reaction solution; the mass amount of the triptycene-modified β-ketoenamine covalent organic framework is 0.1-0.2‰ of the mass of water; and the mass ratio of the triptycene-modified β-ketoenamine covalent organic framework, sodium ascorbate, and chloroplatinic acid is 20:(90-100):(0.04-0.06);

[0043] (2) The reaction solution is subjected to a photocatalytic reaction under vacuum conditions. The temperature of the photocatalytic reaction is preferably 5 to 8°C, more preferably 6°C.

[0044] In the above step 1), the triptycene-modified β-ketoenamine covalent organic framework, sodium ascorbate, chloroplatinic acid and water are mixed and ultrasonicated at a power of 50 to 150 W for 5 to 10 minutes to obtain a reaction solution; the power of the above ultrasonication is more preferably 90 to 110 W.

[0045] The present invention has no particular limitation on the dissolution, as long as the dissolution is complete.

[0046] In the above step (2), before the photocatalytic reaction, it is preferably further included: passing high-purity argon gas into the reaction solution, the purity of the high-purity argon gas is preferably above 99.999%; the flow rate of the high-purity argon gas is preferably 10 to 30 mL / min, more preferably 20 mL / min; the time for passing the high-purity argon gas is preferably 0.5 to 1.5 hours, more preferably 1 hour.

[0047] The purpose of introducing high-purity argon into the reaction solution in the present invention is to remove dissolved oxygen in the reaction solution.

[0048] In the above step (2), the light source for the photocatalytic reaction is preferably a xenon lamp, and the xenon lamp is preferably a CEL-HXUV300 model produced by Beijing Zhongjiao Jinyuan Company; when the xenon lamp is used as the light source in the present invention, a high-pass filter is preferably used to filter out light with a wavelength less than 420nm.

[0049] In step (2), the photocatalytic reaction is preferably carried out under vacuum conditions, and the vacuum degree of the vacuum conditions is preferably -0.08 to -0.12 MPa, more preferably -0.1 MPa.

[0050] In the present invention, the photocatalytic reaction is preferably accompanied by stirring; the stirring is preferably magnetic stirring; and the stirring speed is preferably 100 to 500 rpm, more preferably 300 rpm.

[0051] The present invention has no special limitation on the device for the photocatalytic reaction. In the embodiment of the present invention, a CEL-SPH2N photocatalytic water decomposition hydrogen production system produced by Beijing Zhongjiao Jinyuan Company is used to perform photocatalytic water decomposition hydrogen production.

[0052] From the composition and structure of the β-ketoenamine covalent organic framework, the C atoms in the structure are sp 2 Hybrid form, N in sp 2 or sp 3 The hybrid forms together form a stable two-dimensional porous conjugated system. Due to the difference in electronegativity between carbon and nitrogen atoms, most of the delocalized π electrons are enriched around the nitrogen atoms (i.e., the electron cloud density near the nitrogen atoms is higher). The π electron conjugated system is not fully expanded and the charge mobility is low. This is the fundamental reason for the low quantum yield of the photocatalytic reaction of the β-ketoenamine covalent organic framework. In the present invention, the aldehyde group of the β-ketoenamine covalent organic framework is doped with triaminotriptycene through a Schiff base condensation reaction, which increases the degree of delocalization of the π electrons on the β-ketoenamine covalent organic framework, improves the separation, migration and interface transfer efficiency of the carriers in the bulk phase of the β-ketoenamine covalent organic framework, and enhances the photocatalytic performance of the triptycene-modified β-ketoenamine covalent organic framework.

[0053] The technologies not mentioned in this invention are all referred to the prior art.

[0054] The triptycene-modified β-ketoenamine covalent organic framework of the present invention has excellent photocatalytic water decomposition and hydrogen production performance and is reusable. The preparation method provided by the present invention is simple, requires mild conditions, is time-saving, is environmentally friendly, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The SEM images of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3 are shown;

[0056] Figure 2 The samples prepared in Examples 1 to 3 are 13 C NMR spectrum;

[0057] Figure 3 The transient fluorescence spectra of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3 are shown;

[0058] Figure 4 Transient photocurrent diagrams of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3;

[0059] Figure 5 This is a comparison chart of the photocatalytic hydrogen production activities of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0060] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0061] In each case, polyaminotriptycene and 1,3,5-trialdehyde phloroglucinol were of analytical grade; ball milling was performed using a planetary ball mill; the purity of the protective atmosphere argon was 99.999%; and water was deionized water.

[0062] Example 1

[0063] To a centrifuge tube, 190 mg of 1,3,5-trialdehyde-m-trisphenol, 130 mg of p-toluenesulfonic acid, 3 mL of mesitylene, 3 mL of 1,4-dioxane, and 1 mL of 6M acetic acid were added. The mixture was sonicated at room temperature for 10 minutes to obtain a uniformly dispersed suspension. 72 mg of 2,6,14-triaminotriptycene was dissolved in 2 mL of tetrahydrofuran and sonicated at room temperature for 10 minutes to obtain a uniformly dispersed suspension. The two solutions were added to a ball mill, followed by 98 mg of p-phenylenediamine. Argon was introduced at 20 mL / min and the mixture was ball milled for 12 hours to obtain the product. The product was collected by centrifugation (11,000 rpm for 5 minutes) and washed with anhydrous tetrahydrofuran. The centrifugation and washing steps were repeated three times. Finally, the product was dried in a vacuum oven at 60°C for 12 hours to obtain a red powder, referred to as Tp-PDA-TATP. 0.2 .

[0064] Example 2

[0065] To a centrifuge tube, 190 mg of 1,3,5-trialdehyde-m-trisphenol, 130 mg of p-toluenesulfonic acid, 3 mL of mesitylene, 3 mL of 1,4-dioxane, and 1 mL of 6M acetic acid were added. The mixture was sonicated at room temperature for 10 minutes to obtain a uniformly dispersed suspension. 77.5 mg of 2,6,14-triaminotriptycene was dissolved in 2 mL of tetrahydrofuran and sonicated at room temperature for 10 minutes to obtain a uniformly dispersed suspension. The two solutions were added to a ball mill, followed by 120 mg of 2,5-diaminobenzonitrile. Argon was introduced at 20 mL / min and the mixture was ball milled for 12 hours to obtain the product. The product was collected by centrifugation (11,000 rpm for 5 minutes) and washed with anhydrous tetrahydrofuran. The centrifugation and washing steps were repeated three times. Finally, the product was dried in a vacuum oven at 60°C for 12 hours to obtain a red powder, referred to as Tp-DBN-TATP. 0.2 .

[0066] Example 3

[0067] To a centrifuge tube, 190 mg of 1,3,5-trialdehyde-m-trisphenol, 130 mg of p-toluenesulfonic acid, 3 mL of mesitylene, 3 mL of 1,4-dioxane, and 1 mL of 6 M acetic acid were added. The mixture was sonicated at room temperature for 10 minutes to obtain a uniformly dispersed suspension. 39.8 mg of 2,6,14-triaminotriptycene was dissolved in 2 mL of tetrahydrofuran and sonicated at room temperature for 10 minutes to obtain a uniformly dispersed suspension. The two solutions were added to a ball mill, followed by 168 mg of 5,5'-diamino-2,2'-bipyridine. Argon was introduced at 20 mL / min and the mixture was ball milled for 12 hours to obtain the product. The product was collected by centrifugation (11000 rpm, 5 minutes) and washed with anhydrous tetrahydrofuran. The centrifugation and washing steps were repeated three times. Finally, the product was dried in a vacuum oven at 60°C for 12 hours to obtain a red powder, referred to as Tp-Bpy-TATP. 0.1 .

[0068] Comparative Example 1

[0069] The only difference from Example 1 is that 2,6,14-triaminotriptycene is not added during the preparation process, and the rest is the same as in Example 1. Tp-PDA is obtained.

[0070] Comparative Example 2

[0071] The only difference from Example 2 is that 2,6,14-triaminotriptycene is not added during the preparation process, and the rest is the same as in Example 2. Tp-DBN is obtained.

[0072] Comparative Example 3

[0073] The only difference from Example 3 is that 2,6,14-triaminotriptycene is not added during the preparation process, and the rest is the same as in Example 3. Tp-Bpy is obtained.

[0074] The morphologies of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were observed using a S-3500N scanning electron microscope (SEM) manufactured by Hitachi, Japan. The operating voltage of the instrument was 20 kV, and the vacuum degree of the sample chamber was less than 3.0 × 10 - 5 Pa. Get SEM pictures, such as Figure 1 As shown, after triptycene modification, the particle size of samples in Examples 1 to 3 was reduced, and many small spherical particles were added to the samples. This indicates that the condensation doping of triptycene can significantly inhibit the orderly growth of the β-ketoenamine covalent organic framework structural units. The resulting triptycene-modified β-ketoenamine covalent organic framework has a smaller particle size. The small spherical particles attached to the surface are mainly caused by the grafting of triptycene onto the surface of the β-ketoenamine covalent organic framework. This facilitates more complete contact between the catalyst and the reactants, thereby promoting catalytic action.

[0075] The samples obtained in Examples 1 to 3 were analyzed using an Avance III 500 solid-state nuclear magnetic resonance spectrometer (NMR) produced by Bruker, Germany. 13 C NMR test, the spectrum obtained is as follows Figure 2 As shown. Analysis of the sample of Example 1 shows that the chemical shift values ​​of δ = 205.6ppm (a), δ = 141.6ppm (b) and δ = 126.1ppm (f) correspond to the carbon atom signals of the carbonyl group, carbon-nitrogen single bond and carbon-carbon double bond in the six-membered ring, respectively, and the chemical shift values ​​of δ = 140.4ppm (c), δ = 131.5ppm (d) and δ = 19.7ppm (e) are the signals of the substituted, meta and ortho carbon atoms on the benzene ring. The chemical shifts of the above carbon atoms are consistent with those of Tp-PDA-TATP. 0.2 In addition, a tertiary carbon atom peak appeared at δ = 51.9 ppm (h), which is a characteristic peak of the carbon of triptycene. Compared with the sample of Example 1, the sample of Example 2 showed characteristic peaks of cyano group and triptycene tertiary carbon at δ = 104.0 ppm (g) and δ = 53.0 ppm (h), respectively. 0.2 The peaks of other carbon atoms relative to Tp-PDA-TATP 0.2 There is a slight shift, indicating that there is a strong electronic conjugation between cyano and triptycene and the main framework, which affects the chemical shift of adjacent carbon atoms; similarly, the analysis of the sample in Example 3 shows that in addition to the characteristic peaks of carbon atoms containing Tp and Bpy motifs, Tp-Bpy-TATP 0.1 The sample also exhibited a characteristic peak of tertiary carbon of conjugated triptycene at δ = 51.5 ppm (h), indicating that triptycene was covalently conjugated with the β-ketoenamine covalent organic framework, forming a good electron transfer channel.

[0076] The transient fluorescence lifetimes of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured using a FLS920 fluorescence spectrometer produced by Edinburgh, UK (excitation wavelength 402.8 nm, scanning step length 1 nm), and transient fluorescence spectra were obtained, as shown in FIG. Figure 3 As shown. Figure 3 It can be seen that compared with Tp-PDA, Tp-DBN and Tp-Bpy, Tp-PDA-TATP 0.2 , Tp-DBN-TATP 0.2 and Tp-Bpy-TATP 0.1The transient fluorescence decay changes more slowly, and its fluorescence lifetime is significantly prolonged. The fluorescence lifetime curve was fitted using the double exponential decay kinetics method. The fitting results are shown in Table 1. There are short-lived and long-lived fluorescence emissions on the surface of the β-ketoenamine covalent organic framework, corresponding to the bulk recombination and surface recombination of photogenerated carriers, respectively. After conjugation with triptycene, the lifetimes of both types of fluorescence are extended, and the proportion of short-lived fluorescence decreases, while the proportion of long-lived fluorescence increases. This shows that the introduction of triptycene effectively inhibits the bulk recombination of photogenerated carriers. The conjugation between triptycene and the β-ketoenamine covalent organic framework increases the degree of electron delocalization on the β-ketoenamine covalent organic framework, accelerates the separation, migration and interface transfer rate of photogenerated electrons, effectively reduces the recombination probability of photogenerated carriers, and is beneficial to improving the photocatalytic activity of the triptycene-modified β-ketoenamine covalent organic framework.

[0077] Table 1 Fitting results of fluorescence lifetime test using samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3

[0078]

[0079] Photocatalytic hydrolysis hydrogen production performance test:

[0080] Changing the amount of 2,6,14-triaminotriptycene in Example 1, the rest were referred to Example 1 to obtain Tp-PDA-TATP. 0.1 , Tp-PDA-TATP 0.3 and Tp-PDA-TATP 0.4 Among them, Tp-PDA-TATP 0.1 It indicates that the mass dosage of polyaminotriptycene is 10% of the total mass of polyaminotriptycene, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer. The rest are similarly expressed and have similar meanings.

[0081] Changing the amount of 2,6,14-triaminotriptycene in Example 2, the rest are referred to Example 2 to obtain Tp-DBN-TATP. 0.1 , Tp-DBN-TATP 0.3 and Tp-DBN-TATP 0.4 Among them, Tp-DBN-TATP 0.1 It indicates that the mass dosage of polyaminotriptycene is 10% of the total mass of polyaminotriptycene, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer. The rest are similarly expressed and have similar meanings.

[0082] Changing the amount of 2,6,14-triaminotriptycene in Example 3, the rest are referred to Example 3, and Tp-Bpy-TATP is obtained respectively. 0.05 , Tp-Bpy-TATP 0.2and Tp-Bpy-TATP 0.3 Among them, Tp-Bpy-TATP 0.1 It indicates that the mass dosage of polyaminotriptycene is 10% of the total mass of polyaminotriptycene, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer. The rest are similarly expressed and have similar meanings.

[0083] 20 mg of the samples prepared in Examples 1 to 3 and Comparative Examples 1 to 3, 0.1 g of sodium ascorbate, 60 μL of a 1 mg / mL aqueous solution of chloroplatinic acid, and 100 mL of deionized water were respectively ultrasonicated at a power of 100 W for 5 min to obtain a reaction solution;

[0084] Each reaction solution was added to a reaction bottle of a photocatalytic water decomposition hydrogen production system (CEL-SPH2N photocatalytic water decomposition hydrogen production system produced by Beijing Zhongjiao Jinyuan Company), the circulating condenser of the reaction system was turned on to stabilize the system temperature at 5°C, argon gas with a purity of 99.999% was introduced into the reaction solution at a flow rate of 20mL / min for 1 hour, the sealing cover of the reactor was covered, and the reaction system was evacuated to a vacuum degree of -0.1MPa. A CEL-HXUV300 xenon lamp produced by Beijing Zhongjiao Jinyuan Company was used as a light source, and a high-pass filter was used to filter out light with a wavelength less than 420nm, and the photocatalytic water decomposition hydrogen production reaction was carried out under magnetic stirring. Every 1 hour, the concentration of the prepared hydrogen was automatically sampled and analyzed using a 2014C online gas chromatograph produced by Shimadzu Corporation of Japan. The results are shown as follows: Figure 5 shown.

[0085] like Figure 5 As shown in a, after a certain proportion of triptycene is added to the raw materials for modification, the hydrogen production activity of the β-ketoenamine covalent organic framework is significantly improved. 0.2 The optimal hydrogen production rate of the sample is 5.77 mmol·h -1 ·g -1 , which is 9.3 times the activity of the Tp-PDA sample prepared in Example 1; Tp-DBN-TATP prepared in Example 2 0.2 The optimal hydrogen production rate of the sample is 17.81 mmol·h -1 ·g -1 , which is 5.6 times the activity of the Tp-DBN sample prepared in Example 2; Tp-Bpy-TATP prepared in Example 3 0.1 The optimal hydrogen production rate of the sample is 13.55 mmol·h -1 ·g -1 , which is 2.1 times the activity of the Tp-Bpy sample prepared in Comparative Example 3.

[0086] The triptycene-modified β-ketoenamine covalent organic framework prepared in Examples 1 to 3 was subjected to a cyclic activity stability test according to the above-mentioned photocatalytic hydrolysis hydrogen production performance evaluation protocol. After each reaction, the sample was centrifuged three times (12000 rpm) and washed with deionized water, then dried at 110°C. 20 mg of sample (the insufficient amount was supplemented by the samples prepared in the corresponding Examples 1 to 3 and Comparative Examples 1 to 3), 0.1 g of sodium ascorbate, and 100 mL of deionized water were ultrasonically treated at a power of 100 W for 5 minutes to obtain a reaction solution. The illumination, vacuum, and cyclic condensation conditions were based on the above-mentioned photocatalytic hydrolysis hydrogen production performance evaluation protocol. The hydrogen production rate was detected every 1 hour, and the reaction was repeated for 5 hours each time. The cycle was repeated 4 times. The results are listed in Table 2.

[0087] According to Table 2, a dotted line graph of the hydrogen production rate of the photocatalytic hydrolysis hydrogen production using the triptycene-modified β-ketoenamine covalent organic framework prepared in Examples 1 to 3 is drawn, as shown in FIG. Figure 5 As shown in b.

[0088] Combined with Table 2 and Figure 5 b It can be seen that the photocatalytic hydrogen production activity of the triptycene-modified β-ketoenamine covalent organic framework provided by the present invention is significantly improved compared with the β-ketoenamine covalent organic framework, and the hydrogen production activity is stable. In the 20-hour cycle test, the triptycene-modified β-ketoenamine covalent organic framework has no obvious deactivation.

[0089] Table 2 Hydrogen production rate of the samples prepared by Examples 1 to 3 and Comparative Examples 1 to 3 by photocatalytic water decomposition cycle

[0090]

[0091]

[0092] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A triptycene-modified β-ketoenamine covalent organic framework, characterized in that: It is prepared by polycondensation of polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer; The mass ratio of polyaminotriptycene, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer is (5-40): (30-60): (15-45); The enamine monomer is at least one of p-phenylenediamine, 2,5-diaminobenzonitrile or 5,5'-diamino-2,2'-bipyridine; The polyaminotriptycene monomer is 2,6,14-triaminotriptycene.

2. The triptycene-modified β-ketoenamine covalent organic framework according to claim 1, characterized in that: Its structural formula is: At least one of .

3. A method for preparing the triptycene-modified β-ketoenamine covalent organic framework according to claim 1 or 2, characterized in that: The following steps are involved: It is prepared by polycondensation reaction of polyaminotriptycene monomer, 1,3,5-trialdehyde phloroglucinol monomer and enamine monomer at room temperature for 8 to 12 hours. The mass dosage of the polyaminotriptycene monomer is 5-40% of the total mass of the polyaminotriptycene monomer, the 1,3,5-trialdehyde phloroglucinol monomer and the enamine monomer.

4. The preparation method according to claim 3, wherein: The steps include: 1) placing 1,3,5-trialdehyde-meta-triphenol monomer and p-toluenesulfonic acid in a mixture of trimethylbenzene, 1,4-dioxane and acetic acid solution in a volume ratio of (2-3):(2-3):1, and ultrasonically dispersing to obtain liquid 1; the mass amount of p-toluenesulfonic acid used is 0.5-0.7 times the mass of 1,3,5-trialdehyde-meta-triphenol; 2) placing the polyaminotriptycene monomer in a tetrahydrofuran solution and ultrasonically dispersing the mixture to obtain a second liquid; 3) Liquid 1 and Liquid 2 are placed in a ball mill, enamine monomer is added, protective gas is introduced, and ball milling is performed at room temperature at a rotation speed of 300-500 rpm for 8-12 hours. The resulting product is centrifuged, washed, and dried to obtain a triptycene-modified β-ketoenamine covalent organic framework.

5. Use of the triptycene-modified β-ketoenamine covalent organic framework according to claim 1 or 2, characterized in that: Used for photocatalytic decomposition of water to produce hydrogen.

6. The use according to claim 5, characterized in that: Photocatalytic water decomposition to produce hydrogen includes the following steps: 1) mixing a triptycene-modified β-ketoenamine covalent organic framework, sodium ascorbate, chloroplatinic acid, and water to obtain a reaction solution; the mass amount of the triptycene-modified β-ketoenamine covalent organic framework is 0.1-0.2‰ of the mass of water; and the mass ratio of the triptycene-modified β-ketoenamine covalent organic framework, sodium ascorbate, and chloroplatinic acid is 20:(90-100):(0.04-0.06); 2) The reaction solution is subjected to a photocatalytic reaction under vacuum conditions at a temperature of 5 to 8°C.

7. The use according to claim 6, characterized in that: In step 2), before the photocatalytic reaction, the process also includes: introducing high-purity argon gas into the reaction solution, wherein the purity of the high-purity argon gas is greater than 99.999%; the flow rate of the high-purity argon gas is 10 to 30 mL / min; the time for introducing the high-purity argon gas is 0.5 to 1.5 hours; the light source for the photocatalytic reaction is a xenon lamp, and a high-pass filter is used to filter out light with a wavelength less than 420 nm.

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