阅读说明：本技术 一种快速、宏量制备高结晶半导体共价三嗪框架的方法 (Method for rapidly and massively preparing high-crystalline semiconductor covalent triazine framework ) 是由 徐宇曦 孙甜 于 2021-09-28 设计创作，主要内容包括：本发明公开了一种快速、宏量制备高结晶共价三嗪框架的方法。将单体和催化剂放入石英管中,液氮致冷后,在真空状态下进行熔融密封到密封管中；将密封管转移至微波炉中,在微波功率下加热反应；将反应完的产物进行溶剂洗涤得到块体结晶CTFs；将块体结晶CTFs进行物理剥离得到超薄纳米片。本发明所制备的CTFs具有高结晶性,丰富的氮含量,可剥离成超薄二维纳米片的特性以及合适的能带结构,具有优异的光催化制氢性能,在光催化制氢领域展现出极大的应用前景。(The invention discloses a method for quickly and massively preparing a high-crystallization covalent triazine framework. Putting the monomer and the catalyst into a quartz tube, refrigerating by liquid nitrogen, and melting and sealing the monomer and the catalyst into a sealing tube in a vacuum state; transferring the sealing tube into a microwave oven, and heating and reacting under microwave power; washing the reacted product with a solvent to obtain bulk crystalline CTFs; and (3) physically stripping the bulk crystalline CTFs to obtain the ultrathin nanosheet. The CTFs prepared by the method has high crystallinity and rich nitrogen content, has the characteristic of being capable of being stripped into ultrathin two-dimensional nanosheets and a proper energy band structure, has excellent photocatalytic hydrogen production performance, and shows great application prospects in the field of photocatalytic hydrogen production.)

1. A method for rapidly and massively preparing a high-crystallization covalent triazine framework is characterized in that:

the method comprises the following steps:

(1) putting a certain amount of monomer and a certain amount of catalyst into a quartz tube, refrigerating by liquid nitrogen, and melting and sealing the quartz tube into a sealing tube in a vacuum state;

(2) transferring the sealed tube obtained in the step (1) to a microwave oven, and heating for a period of time under certain microwave power to perform reaction;

(3) and (3) washing the product obtained in the step (2) by using a solvent to obtain the bulk crystalline CTFs.

2. The process according to claim 1 for the rapid, macro-preparation of highly crystalline covalent triazine frameworks, characterized in that: in the step (1), the liquid nitrogen is cooled for 2-20 min.

3. The process according to claim 1 for the rapid, macro-preparation of highly crystalline covalent triazine frameworks, characterized in that: in the step (1), the monomer dosage is 10mg-400mg, and the catalyst dosage is 0.02ml-2 ml.

4. The process according to claim 1 for the rapid, macro-preparation of highly crystalline covalent triazine frameworks, characterized in that: in the step (1), the monomer is one of 1, 4-terephthalonitrile, 4-biphenyldicarbonitrile and 1,3, 5-tricyanobenzene.

5. A rapid, macro-preparation of highly crystalline covalent triazine frameworks as claimed in claim 1The method of (2), characterized by: the catalyst is CF₃SO₃H。

6. The process according to claim 1 for the rapid, macro-preparation of highly crystalline covalent triazine frameworks, characterized in that: in the step (2), the power of the microwave oven is controlled at 220- & gt 1000W, and the reaction time is 10s-3 h.

7. The process according to claim 1 for the rapid, macro-preparation of highly crystalline covalent triazine frameworks, characterized in that: in the step (3), the adopted washing solvent is one or more of an ammonia water solution, absolute ethyl alcohol, N-Dimethylformamide (DMF), acetone and tetrahydrofuran.

8. The process according to claim 1 for the rapid, macro-preparation of highly crystalline covalent triazine frameworks, characterized in that: and (4) carrying out physical stripping on the bulk crystal CTFs obtained in the step (3) to obtain the ultrathin nanosheets.

9. The process according to claim 8 for the rapid, macro-preparation of highly crystalline covalent triazine frameworks, characterized in that: in the step (4), the physical stripping method is ultrasonic stripping or ball milling stripping.

10. Use of a covalent triazine framework prepared according to any of the claims 1-9, characterized in that: the covalent triazine framework is used for photocatalytic hydrogen production.

Technical Field

The invention relates to a preparation method of a covalent triazine framework, in particular to a method for quickly and massively preparing a high-crystallization covalent triazine framework and application of the high-crystallization covalent triazine framework in a photocatalytic hydrogen production direction.

Background

Covalent Triazine Frameworks (CTFs) are crystalline organic porous materials covalently linked by Triazine units, and have the characteristics of rich pore structures, high nitrogen content, excellent thermal stability and chemical stability and the like. These excellent properties make it widely applicable in the fields of gas separation, energy storage, optical, electrical, thermal catalysis, etc. However, the preparation of CTFs remains a great challenge, and most of the methods reported so far tend to give only amorphous or semi-crystalline products, mainly due to the low reversibility of the cyano (-CN) trimerization reaction. For the frame material, the improvement of crystallinity is often beneficial to the improvement of photoelectric characteristics, so that the preparation of high-crystalline semiconductor CTFs material is a long-sought goal of researchers.

The current methods for preparing crystalline CTFs are mainly divided into three types: (1) high temperature processes (400 ℃), including ionothermal processes and phosphorus pentoxide catalyzed processes. The method is characterized in that: the reaction temperature is high (400 ℃), the reaction time is long (more than or equal to 40 hours), the carbonization of products is serious, and the semiconductor characteristics are lost. (2) Superacid (trifluoromethanesulfonic acid, CF)₃SO₃H) A catalytic process. The products are mostly amorphous or semi-crystalline semiconductors, and have low specific surface area (less than 200) and limited application. (3) And (3) carrying out polycondensation reaction on the amidine salt. The method is characterized in that: the preparation method can be used for preparing semiconductor crystal products, but the required time is longer (more than or equal to 60 hours), and a large amount of organic solvent is required, so that the preparation method is not beneficial to large-scale preparation and industrial application. In addition, the polymerization mechanism of crystalline CTFs is not known, which greatly hinders the development of the field.

In order to solve the problems in the field, the invention provides a method for microwave-assisted rapid synthesis of high-crystalline CTFs. Using highly catalytically active and strongly polar CF₃SO₃H is simultaneously used as a wave absorbing agent and a catalyst, and is heated by using a household microwave oven as an energy source, so that a crystalline product can be obtained within a very short time (10 s). Meanwhile, a semi-in-situ characterization means (PXRD, FTIR) and the like are adopted to carry out mechanism research of the system, and an ordered polymerization mechanism of the crystalline CTFs is proposed. Meanwhile, the method can be used for quickly preparing a hectogram-level high-crystallization sample. The rapidly synthesized block CTFs is stripped to obtain an ultrathin nanosheet, and the ultrathin nanosheet is used in the field of photocatalytic hydrogen production and has excellent performance.

Disclosure of Invention

In order to solve the problems in the background art, the invention aims to provide a method for quickly and massively preparing a high-crystallization covalent triazine framework and application of the method in the field of photocatalytic hydrogen production.

The invention utilizes strong-polarity high-catalytic-activity CF₃SO₃The H is used as a wave absorbing agent and a catalyst, can effectively absorb microwave energy and quickly transfer the microwave energy to a monomer, and can also efficiently catalyze the trimerization cyclization reaction of the monomer to obtain a crystalline framework material. The prepared CTFs have high crystallinity and rich nitrogen content, can be stripped into ultrathin two-dimensional nanosheets, and has a proper energy band structure, so that the material has a great application prospect in the field of photocatalytic hydrogen production.

Due to the convenience of the method, the method can be used for preparing hectogram high-crystallinity CTFs and has higher specific surface area. In addition, the method can be expanded to the synthesis of the crystalline CTFs with different molecular structures.

The implementation method comprises the following steps:

(1) putting a certain amount of monomer and a certain amount of catalyst into a quartz tube, refrigerating by liquid nitrogen, and melting and sealing the quartz tube into a sealing tube in a vacuum state;

(2) transferring the sealed tube obtained in the step (1) to a microwave oven, and heating for a period of time under certain microwave power to perform reaction;

(3) and (3) washing the product after the reaction in the step (2) by using a solvent, removing residual catalyst, unreacted monomer and part of small molecular products to obtain bulk crystalline CTFs, and obtaining the covalent triazine framework.

In the step (1), the volume of the quartz tube is 5-50ml, and the liquid nitrogen cooling time is 2-20 min.

In the step (1), the monomer dosage is 10mg-400mg, and the catalyst dosage is 0.02ml-2 ml.

In the step (1), the monomer is one of 1, 4-terephthalonitrile, 4-biphenyldicarbonitrile and 1,3, 5-tricyanobenzene.

The catalyst is CF₃SO₃H。

In the step (2), the power of the microwave oven is controlled at 220-1000W, the reaction time is 10s-3h, the polymerization process conforms to an ordered polymerization mechanism, and hectogram-level high-crystalline CTFs can be prepared.

In the step (3), the adopted washing solvent is one or more of an ammonia water solution, absolute ethyl alcohol, N-Dimethylformamide (DMF), acetone and tetrahydrofuran.

In a specific embodiment, (4) may be further performed to physically exfoliate the bulk crystalline CTFs obtained in (3) above to obtain ultrathin nanosheets.

In the step (4), the physical stripping method is ultrasonic stripping or ball milling stripping.

The covalent triazine framework of the invention is used for photocatalytic hydrogen production.

The invention adopts strong-polarity high-catalytic-activity CF₃SO₃H is used as a catalyst, the catalyst can effectively absorb microwave energy and quickly transfer the microwave energy to the monomer, and can efficiently catalyze the trimerization cyclization reaction of the monomer to obtain a crystalline framework material. The prepared CTFs have high crystallinity and rich nitrogen content, can be stripped into ultrathin two-dimensional nanosheets, and has a great application prospect in the field of photocatalytic hydrogen production.

The invention has the beneficial effects that:

the invention aims to provide a technology for rapidly and massively preparing a high-crystallization covalent triazine framework. The method is simple in implementation process, and the prepared high-crystallization sample has higher specific surface area and semiconductor characteristics and can be used for hydrogen production by photolysis of water.

The invention rapidly prepares the high-crystalline CTFs by a household microwave oven auxiliary heating method. Highly catalytically active and strongly polar CF₃SO₃The H can rapidly absorb microwave energy and transfer the microwave energy to the cyano monomer to initiate the rapid and efficient polymerization of the monomer. As the process is carried out in a higher energy state, nucleation and crystallization energy barrier are overcome, and the crystallization product is quickly obtained.

The invention is characterized in that: (1) high efficiency and convenience; (2) universality (monomer expandable); (3) can be prepared in large quantity; (4) the stripped ultrathin nanosheet has excellent photocatalytic hydrogen production performance.

Drawings

FIG. 1 shows the molecular structure and powder XRD data of highly crystalline CTFs prepared rapidly in the examples, wherein (a), (b) and (c) in FIG. 1 are CTFs with three different structures prepared by rapid synthesis; (d) (e) powder XRD data and simulated stacking mode data corresponding to the three CTFs;

FIG. 2 shows the nitrogen adsorption-desorption isotherms and pore size distribution profiles in the examples, in FIG. 2, (a) the nitrogen adsorption-desorption isotherms of three different structures of CTFs; (b) an aperture distribution map;

fig. 3 shows a schematic diagram of data results for exfoliated ultrathin nanosheets, and in fig. 3, (a) a TEM image of ultrathin CTF-DCB nanosheets; (b) an AFM map and a height map of CTF-DCB nanoplates;

FIG. 4 shows a schematic diagram of data results of photocatalytic hydrogen production performance, specifically a comparison diagram of bulk CTF-DCB and CTF-DCB nanosheet photocatalytic performance. (a) The block CTF-DCB and the stripped nanosheet photocatalytic hydrogen production performance diagram; (b) the average hydrogen production rate per hour of the bulk CTF-DCB and the stripped nano-sheets is shown in the figure, and the corresponding dispersion liquid of the photocatalyst is shown in the figure.

FIG. 5 is a graphical representation of the results of ordered polymeric support data, in FIG. 5, (a) powder XRD data for different reaction times; (b) FTIR data for different reaction times;

fig. 6 is a schematic diagram of macro-fabrication of CTFs, and in fig. 6, (a) an optical photograph of a large-scale fabricated CTF-DCB; (b) mass-produced CTF-DCB weight plots; (c) XRD pattern of CTF-DCB powder prepared in large scale; (d) and the large-scale prepared CTF-DCB nitrogen adsorption-desorption isotherm and pore size distribution diagram.

Detailed Description

The present invention is further described below in conjunction with the following embodiments and the accompanying drawings, it being understood that the description of the figures and the following embodiments are only illustrative of the present invention and are not limiting.

The examples of the invention are as follows:

example 1

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.05ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min,and (4) melting and sealing. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 220W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone and tetrahydrofuran in turn, and is dried in vacuum at 120 ℃ to obtain a crystallized product. And further ball-milling the nano-particles for 2 hours to obtain CTF nano-particles for photocatalytic hydrolysis hydrogen production.

Example 2

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 220W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. And further ball-milling the nano-particles for 2 hours to obtain CTF nano-particles for photocatalytic hydrolysis hydrogen production.

Example 3

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.2ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 220W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. And further ball-milling the nano-particles for 2 hours to obtain CTF nano-particles for photocatalytic hydrolysis hydrogen production.

Example 4

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 220W, and reacting for 20 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. And further ball-milling the nano-particles for 2 hours to obtain CTF nano-particles for photocatalytic hydrolysis hydrogen production.

Example 5

Reacting monomeric terephthalonitrile (DCB)(200mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 220W, and reacting for 30 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. And further ball-milling the nano-particles for 2 hours to obtain CTF nano-particles for photocatalytic hydrolysis hydrogen production.

Example 6

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 440W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. And further ball-milling the nano-particles for 2 hours to obtain CTF nano-particles for photocatalytic hydrolysis hydrogen production.

Example 7

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube to a household microwave oven after the room temperature is recovered, controlling the reaction power to be 550W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. And further ball-milling the nano-particles for 2 hours to obtain CTF nano-particles for photocatalytic hydrolysis hydrogen production.

Example 8

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 800W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. The molecular structure of CTF-DCB is shown in FIG. 1(b), and is connected with triazine unitThe two-dimensional planar molecular structure, the prepared CTF-DCB has high crystallinity, as shown in figure 1(e), and is well matched with the simulated AA stacking model. The nitrogen adsorption-desorption isotherm thereof exhibited a characteristic of microporous adsorption, as shown in fig. 2 (a). The pore size distribution data is concentrated at 1.1 nm, as shown in FIG. 2(b), indicating that the prepared material has a fine pore distribution structure characteristic. In addition, the prepared bulk CTF-DCB can be stripped by ball milling to obtain a two-dimensional ultrathin CTF-DCB nanosheet, as shown in FIGS. 3(a) (b), with a thickness distribution range of 2-3 nm. Compared with bulk CTF-DCB, the CTF-DCB nanosheet has excellent photocatalytic hydrogen production performance, as shown in FIGS. 4(a) (b). The improvement of the performance mainly comes from the fact that the nano sheets can be better dispersed in water and fully contact with a reaction medium, and meanwhile, the two-dimensional nano sheet structure can expose more active sites and promote the catalytic process.

Example 9

Monomeric terephthalonitrile (DCB) (200mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. The sealed tube is transferred into a household microwave oven after being returned to the room temperature, the reaction power is controlled to be 800W, the reaction can be carried out for different time (10s-20min), products with different reaction time can be sequentially washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like, and a crystal product can be obtained after vacuum drying at 120 ℃, as shown in figure 5(a), the appearance of an ordered structure can be observed at the initial stage of the reaction for 10s and 30s, the crystallinity is gradually improved along with the extension of the reaction time, the ordered structure is followed, and the reversible repair mechanism is different from the reversible repair mechanism followed by most COFs. In addition, the FT-IR data, FIG. 5(b), shows that as the reaction time is extended, the cyano content gradually decreases, the monomer decreases, the trimerization cyclization reaction occurs rapidly, supporting the assumption of ordered polymerization.

Example 10

Monomeric 1,3, 5-Tricyanobenzene (TCB) (80mg) and catalyst CF were added₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 800W, and reacting for 10 min. The reaction product is treated by ammonia water and absolute ethyl alcohol,washing acetone, tetrahydrofuran and the like in sequence, and drying in vacuum at 120 ℃ to obtain a crystallized product. The molecular structure of the CTF-TCB is shown in figure 1(a) and is a two-dimensional planar molecular structure connected with triazine units, and the prepared CTF-TCB has better crystallinity as shown in figure 1(d) and is better matched with a simulated AA stacking model. The nitrogen adsorption-desorption isotherm thereof exhibited a characteristic of microporous adsorption, as shown in fig. 2 (a). The pore size distribution data is concentrated at 0.67 nm, as shown in fig. 2(b), indicating that the prepared material has a fine pore distribution structure characteristic.

Example 11

Monomeric 4, 4-biphenyldinitrile (DCBP) (100mg) and catalyst CF₃SO₃H (0.1ml) was put into a 10ml quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 800W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. The molecular structure of the CTF-DCBP is shown in figure 1(c) and is a two-dimensional planar molecular structure connected by triazine units, and the prepared CTF-DCBP has high crystallinity as shown in figure 1(f) and is well matched with a simulated AA stacking model. The nitrogen adsorption-desorption isotherm thereof exhibited a characteristic of microporous adsorption, as shown in fig. 2 (a). The pore size distribution data is concentrated at 2.0 nm, as shown in FIG. 2(b), indicating that the prepared material has a fine pore distribution structure characteristic.

Example 12

Monomeric terephthalonitrile (DCB) (128g) and catalyst CF₃SO₃H (100ml) was charged into a 1L quartz heat-resistant tube, followed by cooling in liquid nitrogen for 10min, and melt-sealed. And (4) transferring the sealed tube into a household microwave oven after the room temperature is recovered, controlling the reaction power to be 800W, and reacting for 10 min. The reaction product is washed by ammonia water, absolute ethyl alcohol, acetone, tetrahydrofuran and the like in sequence, and is dried in vacuum at 120 ℃ to obtain a crystallized product. The large-scale prepared sample of CTF-DCB is shown in (a) and (b) of FIG. 6, the large-scale prepared sample has better crystallinity, and as shown in (c) of FIG. 6, the nitrogen adsorption-desorption isotherm and the pore size distribution show that the large-scale prepared sample has definite and accurate pore structureAnd (4) distribution.

In conclusion, the invention can rapidly prepare (less than 20min) semiconductor CTFs with high crystallization and high specific surface area, the preparation speed of the semiconductor CTFs is far higher than that of the existing research, and the hectogram preparation of the semiconductor CTFs is realized for the first time. The prepared semiconductor CTFs has excellent photocatalytic hydrogen production performance through simple stripping, and has great application prospect in the field of photocatalytic application.