CN114752028A

CN114752028A - Solvent-free preparation method and application of covalent organic framework COFs film

Info

Publication number: CN114752028A
Application number: CN202210543071.0A
Authority: CN
Inventors: 李文琼; 陈寒雪; 陈朝阳; 何云; 梁晓光
Original assignee: Guangxi Normal University
Current assignee: Guangxi Normal University
Priority date: 2022-05-19
Filing date: 2022-05-19
Publication date: 2022-07-15
Anticipated expiration: 2042-05-19
Also published as: CN114752028B

Abstract

The invention discloses a solvent-free controllable preparation method of a covalent organic framework COFs film and application thereof, wherein during preparation, three-aldehyde phloroglucinol (Tp) and 5, 5-diamino-2, 2-bipyridine (Bpy) are taken to synthesize TpBpy; or collecting trialdehyde phloroglucinol (Tp) and triaminoguanidine hydrochloride (TG)_Cl) Synthesis of TpTG_Cl(ii) a Placing the monomer material in a high vacuumIn the coating machine, the organic evaporation source is set to have the required film thickness, and after a zinc sheet is taken as a receiving substrate, a thermal deposition method is adopted to uniformly deposit monomer raw materials on the surface layer of the zinc sheet to form a layer of COFs film with the required thickness. And the zinc sheet loaded with the COFs film is used as a zinc cathode and applied to a zinc-air battery. The preparation method has simple process, safety, environmental protection and easy operation, and the adopted thermal deposition method realizes the solvent-free and thickness-controllable preparation of the COFs film for the first time, namely the electrically neutral COFs film can be prepared, and the ionic COFs film can also be prepared. The prepared film material is attached to a zinc sheet and applied to a zinc-air battery, so that the zinc dendritic crystal inhibition effect is very obvious, the cycle life is prolonged, and the cycle is more stable.

Description

Solvent-free preparation method and application of covalent organic framework COFs film

Technical Field

The invention belongs to the synthesis of organic chemical materials by a pure physical method, and particularly relates to a solvent-free preparation method and application of a covalent organic framework COFs film.

Background

Covalent organic framework Compounds (COFs) are a class of porous crystalline materials connected by light elements such as carbon, hydrogen, oxygen, nitrogen, etc. through reversible covalent bonds. It has large specific surface area, uniform pore size distribution, and pore size capable of transmitting core required material of metal-air battery such as ion and water molecule. The existing preparation methods of COFs materials are mainly divided into seven types: solvothermal method, ionothermal method, microwave radiation method, interfacial growth method, mechanical grinding method, heating reflux method and normal temperature and pressure method. In different polymerization reactions, both the reaction conditions and the monomer composition affect the crystallinity and porosity of the COFs. Of the seven preparation methods, the solvothermal method and the ionothermal method have high preparation yield, and the finished product is powdery; the mechanical grinding method has a slightly reduced yield, but has a large amount of original monomers left and is complicated to purify. The finished product prepared by the interfacial growth method is a film, but the film has uneven thickness, is easy to crack when residual solvent is cleaned, and finally becomes powder. Almost all the finished products of the seven existing preparation methods are powder, and the finished product prepared by only one interface growth method is also a fragile thin-film material with uncontrollable thickness. If the COFs film is applied to the electrode of the battery, the required film thickness is high, and in a flexible device, the film cannot be a fragile powdery sample.

Therefore, a method for preparing COFs which has controllable thickness and smooth surface and is suitable for electrodes in batteries needs to be developed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a preparation method and application of a Covalent Organic Frameworks (COFs) film with controllable thickness and no solvent. The preparation method is simple in process, safe, environment-friendly and easy to operate. The thickness of the prepared COFs film material is accurate and controllable, and the surface layer of the film is smooth. And the second method can prepare the electrically neutral COFs film and the ionic COFs film. The prepared finished product can be applied to a zinc-air battery, and can effectively inhibit the growth of zinc dendrites on the surface of a zinc cathode, so that the service life of the battery is prolonged, and the high-performance effective time is prolonged.

The technical scheme for realizing the purpose of the invention is as follows:

the invention relates to a solvent-free preparation method of covalent organic framework COFs thin films, which can be prepared by using charge-neutral COFs materials and can also be prepared by using ionic COFs materials. The invention selects the material TpBpy of the electric neutral COFs and the material TpTG of the ionic COFs_ClTwo representative COFs materials were prepared.

The corresponding monomer materials for preparing the neutral COFs material TpBpy are respectively as follows: trihalo-meta-phenol (Tp), 5, 5-diamino-2, 2-bipyridine (Bpy).

The ionic COFs material TpTG_ClThe corresponding preparation monomers are respectively: triformylm-phenol (TP), triaminoguanidine hydrochloride (TG)_Cl)。

The invention discloses a solvent-free preparation method of a covalent organic framework COFs film, which comprises the following steps:

synthesizing TpBpy by taking trialdehyde phloroglucinol and 5, 5-diamino-2, 2-bipyridine;

synthesizing TpTG from trialdehyde phloroglucinol and triaminoguanidine hydrochloride_Cl；

Respectively placing the monomers in different quartz crucibles and respectively placing the monomers in two organic evaporation sources in a high vacuum coating machine; then, synchronously heating and evaporating the two monomers by adopting a thermal deposition method, taking a zinc sheet as a substrate, and carrying out condensation deposition on the surface of the substrate to form a COFs primary sample which is uniformly distributed and has a certain thickness; and finally, taking out the substrate, and carrying out heating treatment on the substrate to obtain the covalent organic framework COFs film with the required thickness.

In the preparation method, the more specific technical scheme is as follows:

the TpBpy comprises trialdehyde phloroglucinol and 5, 5-diamino, 2, 2-bipyridyl in parts by weight: (16-160): (27.9-279).

The TpTG_ClThe weight parts of the medium trialdehyde phloroglucinol and the triaminoguanidine hydrochloride are as follows: (21-210): (14-140).

The preferable weight parts of the trialdehyde phloroglucinol and the 5, 5-diamino, 2, 2-bipyridyl in the TpBpy are as follows: (90-160): (139-279).

The TpTG_ClThe preferred weight parts of the medium trialdehyde phloroglucinol and the triaminoguanidine hydrochloride are as follows: (126-210): (84-140).

The purity of the trialdehyde phloroglucinol is 99%, the purity of the 5, 5-diamino-2, 2-bipyridine is 98%, and the purity of the triaminoguanidine hydrochloride is 99%.

The vacuum degree required by the thermal deposition method is less than or equal to 1 multiplied by 10⁻⁴Pa, the evaporation temperature is 80-150 ℃, the substrate rotation rate is 5 r/min, and the used film thickness probe is a 6 MHz gold-plated crystal oscillator plate.

The evaporation temperature of each monomer in the thermal deposition method is as follows: trialdehyde phloroglucinol: 85-100 ℃,5, 5-diamino, 2, 2-bipyridine: 90-110 ℃, triaminoguanidine hydrochloride: 110-.

The temperature and the time length in the heating treatment are respectively as follows: 120 ℃ and 130 ℃ for 3-6 hours.

The invention also provides application of the zinc sheet loaded with the covalent organic framework COFs thin film prepared by the preparation method as a negative electrode material of a zinc-air battery, wherein the zinc-air battery is a semi-open zinc-air battery with a sandwich structure.

The invention discloses an application of a zinc sheet loaded with a Covalent Organic Frameworks (COFs) film as a negative electrode material of a zinc-air battery, which comprises the following steps: a layer of COFs film is added to the inner side of a negative electrode zinc sheet of the semi-open zinc-air battery with the sandwich structure, and the COFs film and the negative electrode zinc sheet are combined into a whole to serve as a new conductive negative electrode material.

The thermal deposition method has the advantage that the thickness of the film can be accurately controlled in the process of evaporating the thin film due to the program characteristics of the sample preparation device. The hot deposition method is mainly characterized in that solid substances are heated to be gasified and then condensed when being cooled, the surface of a formed film is smooth, and meanwhile, when two different organic substances are synchronously evaporated, the uniformity degree of the mixture of the two monomers is extremely high, so that the chemical reaction between the monomers is more convenient to generate. The whole evaporation and deposition process does not need the participation of a solvent, and the solvent-free preparation of the COFs thin film material can be realized.

Compared with the prior art, the COFs film prepared by the invention has various performances of the covalent organic framework material obtained by the seven preparation methods, and when the COFs film is formed for the first time, a solvent is not required to be used, and the thickness of the COFs film is controllable. The zinc sheet with the COFs film is used for replacing an original untreated zinc sheet to serve as a negative electrode material of a zinc-air battery, and the COFs film in the material belongs to a porous material, so that the COFs film has ion conductivity and water molecule permeability, and the aperture of the COFs film is about 0.1-3 nm.

The preparation method has simple process, safety, environmental protection and easy operation, adopts the thermal deposition technology to uniformly mix and deposit the original preparation monomers of the COFs on the surface of the substrate to form a layer of COFs thin film structure with controllable thickness and smooth surface, and the layer of structure perfectly shows various performances of the finished product prepared by the seven modes of the conventional COFs. The layer structure also embodies good performance in actual device testing, and has obvious zinc dendrite inhibition and cycle service life improvement in a sandwich structure device of a zinc-air battery.

Drawings

FIG. 1 is a schematic diagram of a COFs film prepared by the example.

FIG. 2 is an optical photograph of the COFs thin films prepared in the examples.

FIG. 3 is a comparative XRD characterization of COFs films prepared in the examples and COFs powder materials prepared by hydrothermal method.

FIG. 4 is an atomic force microscope thickness characterization of example COFs films.

FIG. 5 is a schematic view of a sandwich structure of an exemplary zinc-air cell;

wherein, 1 is carbon cloth, 2 is alkaline electrolyte, 3 is a COFs film layer, and 4 is metal zinc.

FIG. 6 shows zinc-air cell devices at 10 mA-cm with and without COFs film layers in examples⁻²A charge-discharge cycle test data chart of (1).

FIG. 7 shows zinc-air cell devices at 10 mA-cm with and without COFs film layers in examples⁻²SEM photograph (10 μm scale) of dendrite on the surface of the zinc negative electrode after the charge-discharge cycle test of (1).

Detailed Description

The technical solutions of the present invention will be described in detail below with reference to the examples and the accompanying drawings, but the present invention is not limited thereto.

Examples

Preparing a covalent organic framework material COFs film, referring to model figure 1, wherein the two crucibles are arranged below the figure 1, and the zinc sheet is arranged above the crucibles and used as a substrate; the preparation method comprises the following steps:

Weighing 90-160 mg of trialdehyde phloroglucinol (Tp) and 139-279 mg of 5, 5-diamino-2, 2-bipyridine (Bpy) into two quartz crucibles respectively;

placing the crucibles filled with Tp and Bpy in different thermal deposition organic evaporation sources;

cutting the zinc sheet into 2 × 5cm²Fixing the thin sheet on a sample preparation substrate, heating a Tp evaporation source to 85-100 ℃ and heating an Bpy evaporation source to 90-110 ℃ at a heating rate of 10 ℃/min; by means of a film thickness monitor, when the thickness of the film reaches the set required film thickness, the thermal deposition process is automatically closed; finally, a zinc sheet of the tpbppy film carrying crystalline COFs was obtained, as shown in fig. 2.

Similarly, 126-210 mg of trialdehyde phloroglucinol (Tp) and 84-140 mg of triaminoguanidine hydrochloride (TG) were weighed out separately_Cl) Respectively loading into two quartz crucibles;

will contain Tp and TG_ClThe crucibles are arranged on different thermal deposition organic evaporation sources;

cutting the zinc sheet into 2 × 5cm²Fixing the thin sheet on a substrate of vacuum coating, heating the Tp evaporation source to 85-100 ℃ at a heating rate of 10 ℃/min, and TG_ClHeating the evaporation source to 110-130 ℃; by means of a film thickness monitor, when the thickness of the film reaches the set required film thickness, the thermal deposition process is automatically closed; finally, the ionic COFs-loaded TpTG is obtained _ClZinc flakes of the film.

Comparative experimental example: preparing a Covalent Organic Frameworks (COFs) powder material by a hydrothermal method:

tp (90 mg) and Bpy (139 mg) were put into a 20 mL-volume branched-mouth tube, and dioxane, mesitylene and 36% acetic acid were added to the tube in a volume ratio of 9:1:1 (mL); then the mixture is subjected to sound wave treatment for 20 min in a branch pipe; the mixture was subjected to a cycle of freezing-degassing-thawing-filling with nitrogen gas three times by means of liquid nitrogen (77K) and double calandria; then sealing the orifice of the branch orifice pipe, and placing the sealed branch orifice pipe filled with the reaction mixture in an oil bath kettle at 120 ℃ for reaction for 72 hours to obtain powdery COFs material Tp-Bpy. And respectively carrying out centrifugal cleaning by using DMAc, deionized water and acetone, and drying for 12 h at the temperature of 90 ℃ to obtain powdery Tp-Bpy.

Similarly, Tp (126 mg) and TG were mixed_Cl(84 mg) into a 20 mL branched tube and adding dioxane and deionized water to the tube in a volume ratio of 6:1.8 (mL); then the mixture is subjected to sound wave treatment for 20 min in a branch pipe; the mixture was subjected to a cycle of freezing-degassing-thawing-filling with nitrogen gas three times by means of liquid nitrogen (77K) and double calandria; then sealing the orifice of the branch orifice tube, and placing the sealed branch orifice tube filled with the reaction mixture in an oil bath pan at 120 ℃ for storage for 3 days to obtain powdery COFs material TpTG _Cl. Respectively centrifugally cleaning with DMAc, deionized water and acetone, and drying at 90 ℃ for 12 h to obtain powdery TpTG_Cl。

The COFs thin film material prepared by the thermal deposition method and the COFs powder material prepared by the hydrothermal method are tested by XRD and are contrasted and characterized to judge whether the COFs thin film material is successfully prepared or not, the result is shown in figure 3, and all XRD characteristic peaks are uniform and correspond to each other.

For the measurement of the film thickness, as shown in FIG. 4, the error between the desired thickness and the initially set thickness is within. + -.10 nm.

Referring to fig. 5, preparation of the air electrode:

the carbon cloth 1 used for the air electrode is prepared by respectively cleaning the carbon cloth 1 in acetone, alcohol and deionized water for 30min, drying and coating cobaltosic oxide slurry on the surface of the carbon cloth 1.

The cobaltosic oxide slurry is prepared from cobaltosic oxide powder, conductive carbon black, deionized water, isopropanol and Nafion perfluororesin solution; the concrete mixture ratio is that slurry is prepared by mixing 9 mg of cobaltosic oxide and 21 mg of conductive carbon black and dissolving the mixture in 2.4 mL of deionized water, 0.6 mL of isopropanol and 0.3 mL of Nafion perfluororesin solution; the prepared slurry is ultrasonically processed for 20-30min, and is uniformly coated on a carbon cloth anode material by a liquid-transferring gun, and the loading capacity is about 0.2-1 mg cm ⁻²。

Referring to fig. 5, preparation of electrolyte 2:

200 mL of deionized water was measured, and 67.4 g of KOH and 7.2 g of anhydrous zinc acetate were added thereto, and stirred to a solution state free of precipitates.

Referring to fig. 5, preparation of the zinc electrode 4 and device assembly:

the zinc electrode 4 is made of pure zinc sheets with the thickness of 0.25-0.35 mm, the zinc sheets are cut into cuboid blocks with the length of 2-3 cm and the width of 1-2 cm, and the oxides on the surfaces of the cuboid blocks are ground by sand paper and used as a thermal evaporation receiving substrate of the COFs thin film 3 material.

The prepared air electrode is cut into a cuboid block with the length of 2-3 cm and the width of 1-2 cm, and then the zinc electrode 4, the COFs thin film layer 3, the electrolyte 2 and the air electrode 1 are assembled in sequence in a sandwich structure mode, as shown in figure 4.

The zinc-air cell using COFs thin film layer and the zinc-air cell not using the thin film layer were tested at 10 mA cm using Wuhan blue electric test system CT2001A⁻²Charging and discharging at a current density ofElectrical cycling tests, as shown in FIG. 6, show that in zinc-air cells without the COFs film layer of the present invention, the cycle duration started to fluctuate significantly only on the 100 hour side. In the zinc-air battery with the COFs film layer, the cycle time is over 700 hours, and the cycle is very stable in the whole cycle process. It can be seen that the service life of the zinc-air battery is improved by more than 5 times by adding the COFs film layer.

After the cycle test was completed, the zinc negative electrode in the device was removed, and the surface thereof was photographed by SEM, and as a result, as shown in fig. 7, it was found that the zinc sheet using the COFs thin film had very few dendrites on the surface and was uniformly distributed. The zinc sheet without the COFs film layer has extremely numerous and disordered dendrites on the surface.

Claims

1. A solvent-free preparation method of covalent organic framework COFs thin films is characterized by comprising the following steps:

taking trialdehyde phloroglucinol (Tp) and 5, 5-diamino-2, 2-bipyridine (Bpy) to synthesize TpBpy;

or taking trialdehyde phloroglucinol (Tp) and triaminoguanidine hydrochloride (TG)_Cl) Synthesis of TpTG_Cl；

Respectively placing the monomers in different quartz crucibles and in two organic evaporation sources in a high vacuum coating machine;

then, synchronously heating and evaporating the two monomers by adopting a thermal deposition method, taking a zinc sheet as a substrate, and carrying out condensation deposition on the surface of the substrate to form a COFs primary sample which is uniformly distributed and has a certain thickness;

and finally, taking out the substrate, and carrying out short-time heating treatment on the substrate to obtain the covalent organic framework COFs film with the required thickness.

2. The method of claim 1, wherein the Covalent Organic Frameworks (COFs) film are prepared by a solvent-free process, comprising:

the TpBpy comprises trialdehyde phloroglucinol and 5, 5-diamino, 2, 2-bipyridyl in parts by weight: (16-160): (27.9-279);

The TpTG_ClMiddle trialdehydeThe phloroglucinol and the triaminoguanidine hydrochloride are prepared from the following components in parts by weight: (21-210): (14-140);

3. The method of claim 2, wherein the Covalent Organic Frameworks (COFs) are prepared by a solvent-free process, comprising:

the TpBpy comprises trialdehyde phloroglucinol and 5, 5-diamino, 2, 2-bipyridyl in parts by weight: (90-160): (139-279);

the TpTG_ClThe weight parts of the medium trialdehyde phloroglucinol and the triaminoguanidine hydrochloride are as follows: (126-210): (84-140).

4. The method of claim 1, wherein the Covalent Organic Frameworks (COFs) film are prepared by a solvent-free process, comprising:

the required vacuum degree of the thermal deposition method is less than or equal to 1 multiplied by 10⁻⁴Pa, the evaporation temperature is 80-150 ℃, the substrate rotation rate is 5 r/min, and the used film thickness probe is a 6 MHz gold-plated crystal oscillator plate.

5. The method of claim 4, wherein the evaporation temperature of each monomer in the thermal deposition method is:

trialdehyde phloroglucinol: 85-100 ℃;

5, 5-diamino, 2, 2-bipyridine: 90-110 ℃;

Triaminoguanidine hydrochloride: 110-130 ℃.

6. The method of claim 1, wherein the Covalent Organic Frameworks (COFs) film are prepared by a solvent-free process, comprising:

7. The COFs film having an organic covalent organic skeleton produced by the production method according to any one of claims 1 to 6.

8. Use of covalent organic frameworks COFs thin films according to claim 7, characterized in that: the prepared zinc sheet loaded with the covalent organic framework COFs film replaces the original pure zinc sheet in the zinc-air battery to be used as a negative electrode material.

9. The use of claim 8, wherein: the zinc-air battery is a semi-open zinc-air battery with a sandwich structure.