CN106611653B - A kind of MOF composite materials and its preparation method and application - Google Patents

Abstract

The invention belongs to technical field of composite materials, provide a kind of novel MOF composite materials and its preparation method and application.The composite material includes MXene layer structures and is interspersed in MOF crystal structures therein.The material directly reacts generation MOF crystal with the organic ligand added as metal ion source using the metal A ions for etching MAX material generation, final MOF composite materials is directly obtained by single step reaction by " one-step method ".The material can be used for the field of lithium battery, super capacitor.The method of the invention is easy to operate and safe in preparation, with short production cycle, and production cost is low, yield height and basic no coupling product.It can be applied to lithium battery, super capacitor etc. and improve its storage energy and utilization ratio.

Description

A kind of MOF composite material and its preparation method and application

technical field

The invention belongs to the technical field of composite materials, relates to the preparation and application of organic-inorganic composite materials, and aims to obtain MOF/MXene composite materials, which can be applied to lithium batteries and supercapacitors, and improve the utilization efficiency of stored energy of devices.

Background technique

With the development of the global economy, the demand for energy is also increasing, but the traditional fossil energy is about to be exhausted. Moreover, the exploitation of a large amount of fossil energy has brought many problems to geology and the environment. The greenhouse effect caused by the carbon dioxide emitted by the burning of fossil fuels has brought great pressure to the environment in which we live. These have promoted researchers to find new materials and energy conversion methods to break the deadlock in energy. Efficiently converting the chemical energy of fuels into electrical energy and developing new technologies for electrical energy storage and conversion, so as to finally realize the use of electrical energy to replace the high-pollution and inefficient use of fossil fuels in daily life, has become a current hot spot. Compared with other common energy storage devices, supercapacitors have a series of advantages such as short charging time, long cycle life, high efficiency, and the ability to fully charge and fully discharge without affecting their performance and life. Heavy equipment, rail transit, new energy vehicles and military and other fields. However, due to the relatively immature technology, the energy density of supercapacitors is still relatively low compared with batteries, which greatly limits its further application in many fields. Even though the high-efficiency energy storage effect brought by supercapacitors has not reached the expected ideal state, people have seen huge research and development potential in it. Therefore, finding a new type of material to make supercapacitors for efficient energy storage has become one of the most important research directions now.

MAX (M stands for transition metal elements, A stands for main group elements, X stands for carbon or nitrogen) material is a new type of machinable ceramic material that has attracted much attention. This material includes more than fifty kinds of ternary carbides or nitrides, For example Ti ₃ SnC ₂ , Ti ₂ AlC, etc. Two-dimensional transition metal carbides or carbonitrides, or MXenes, are a new two-dimensional structure material discovered by Yury Gogotsi and Michel W.Barsoum et al. in 2011 (M.Naguib, et al.ACS NANO, 2012.6, 1322). Its general chemical formula can be represented by M _n+1 X _n T _z , wherein M refers to a transition metal, X refers to C or/and N, n is generally 1-3, and T _z refers to a surface group. At present, MXenes are mainly obtained by extracting weakly bound A-site elements (such as Al atoms) in the MAX phase by HF acid or a mixed solution of hydrochloric acid and fluoride. It has the characteristics of high specific surface area and high conductivity of graphene, flexible and adjustable components, and controllable minimum nano-layer thickness. It has shown great potential in the fields of energy storage, adsorption, sensors, and conductive fillers. .

Metal-organic framework (MOF) is a coordination polymer that has developed rapidly in the past ten years. It has a three-dimensional pore structure. Generally, metal ions are used as connection points, and organic ligands are supported to form a 3D extension of space. It is a new type of of crystalline porous materials, including nodes and connecting bridges. It has the advantages of high porosity, low density, large specific surface area, regular pore channels, adjustable pore size, and topological diversity and tailorability. It has broad applications in catalysis, energy storage and separation. However, there are still many deficiencies in the currently available MOF materials for energy storage, such as uneven structure, high cost, and low yield.

The present invention aims to find a new type of material to make supercapacitors to achieve high-efficiency energy storage. The MAX material is combined with the MOF material to form a new MOF/MXene nanocomposite material. This material will have the large specific surface area of MOF and the excellent electrical conductivity of MXene.

Contents of the invention

In order to solve the above-mentioned technical problems, the present invention provides a method for preparing novel MOF/MXene nanocomposites based on the process of preparing MXene from MAX materials, that is, the controllability of MXene structure is used to obtain MOF composites with uniform structure. The shortcomings of the traditional MOF composite preparation methods in terms of uniformity and yield have been overcome, and the new MOF/MXene nanocomposite material has great application prospects in supercapacitors as energy storage materials. New materials for supercapacitors. Concrete technical scheme of the present invention is as follows:

The invention provides a novel MOF composite material. The composite material includes a layered structure and MOF crystals, and the MOF crystals are interspersed on the layered structure and the surface of the material. The layered structure is an MXene layered structure made of MAX material; the MOF crystal is formed with free A ions generated when MAX material is used to prepare MXene as nodes and organic ligand molecules as connecting bridges.

The MAX material can be selected from Ti ₃ GaC ₂ , Ti ₂ AlC, Ti ₃ AlC ₂ , Ti ₃ SnC ₂ , Ti ₂ SnC, etc., and the organic ligand molecule can be selected from 1,4-naphthalene dicarboxylic acid, 1 ,3,5- Trimellitic acid and so on.

The present invention also provides a method for preparing the above-mentioned MOF composite material. The method is as follows: the MAX material is etched to remove the A-layer atoms in the MAX material to obtain the MXene material and free A ions, and organic ligand molecules are added while etching, The organic ligand molecules react with the above-mentioned A ions on the surface of the MXene material to form MOF crystals, so that a MOF/MXene composite material with a layered structure of MOF and MXene materials can be formed.

The MAX material can be selected from Ti ₃ GaC ₂ , Ti ₂ AlC, Ti ₃ AlC ₂ , Ti ₃ SnC ₂ , Ti ₂ SnC, and the organic ligand molecule can be selected from 1,4-naphthalene dicarboxylic acid, 1,3 , 5- Trimellitic acid and so on.

The above-mentioned MOF crystals are formed on the surface of the layered structure of MXene, so the MOF crystals are interspersed in the layered structure of MXene, making the composite material not just a simple superposition of the two structures, but a close combination of the two structures.

Due to the structural characteristics of MAX materials, the obtained MXene layered structure has the characteristics of uniform and uniform layer spacing distribution, and has high structural controllability. The MOF crystal based on the MXene layered structure is also more uniform and controllable in structure than traditional MOF materials, expanding its application in energy storage fields such as supercapacitors. By selecting MAX materials, the structural characteristics such as layer thickness and layer spacing of the MXene layered structure can be adjusted, thereby realizing the structural diversity and controllability of MOF/MXene composites.

The MOF/MXene composite material combines the advantages of the two structures, further increasing the specific surface area and porosity of the material, and the controllability of the structure also improves the utilization rate of the material, so that the composite material improves energy storage and utilization efficiency .

In a specific scheme, for example, Ti ₃ AlC ₂ and 1,4-naphthalene dicarboxylic acid are selected as MAX materials and organic ligand molecules, and Ti ₃ AlC ₂ is etched to remove Al ions to obtain MXene material Ti ₃ C ₂ and free Al ³⁺ , adding 1,4-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid and the above-mentioned Al ³⁺ self-assembled on the surface of Ti ₃ C ₂ to form Al as the node and 1,4-naphthalene dicarboxylic acid For the MOF crystals of the connecting bridges, MOF/MXene composites are finally obtained.

More specific above-mentioned preparation method comprises following three steps:

Step 1, MAX material pretreatment: Use a ball mill to grind the MAX material into a submicron-sized MAX material.

During ball milling, the MAX phase material is ball milled in an organic solvent or water, and after vacuum drying, the ball mill is sieved to obtain a submicron-sized MAX material. For example, Ti ₃ AlC ₂ is ball milled in ethanol, dried in vacuum and then sieved by ball milling to obtain submicron Ti ₃ AlC ₂ powder.

Step 2, generate MOF/MXene nanocomposites by "one-step method": add water, a small amount of HF or a mixture of hydrochloric acid and fluoride, organic ligand molecules and pretreated MAX materials to the reactor, at 120-200 1-10 hours under hydrothermal heating to obtain MOF/MXene nanocomposite material.

For example, add water, a small amount of HF, excess naphthalene dicarboxylic acid, and treated Ti ₃ AlC ₂ powder to the reactor, and heat it at 180°C for 6 hours, and HF will etch away the Ti ₃ AlC ₂ structure under hydrothermal conditions. The metal atom Al produces Ti ₃ C ₂ , and the obtained Al ion reacts with naphthalene dicarboxylic acid to obtain MOF [Al(μ ₂ -OH)(1,4-ndc) _n ], that is, MOF/MXene nanocomposite material.

Step 3, purifying and removing unreacted organic matter; washing, soaking the MOF/MXene nanocomposite material and drying.

For example, wash the sample with ethanol for 3 times, centrifuge the product, re-immerse in ethanol for 12 hours, then use ethanol for high-speed centrifugation and wash twice, and dry the product in vacuum at 100°C for 24 hours.

The method of the present invention adds etching acid and organic ligands at the same time, directly uses metal A ions generated by etching MAX as a metal ion source to generate MOF crystals, and obtains a final composite material through a one-step reaction. The method has the advantages of simple and safe operation in preparation, short production cycle, low production cost, high yield and basically no by-products.

The method of the present invention can form different kinds of MXene and MOF composite materials by changing MAX materials and organic ligands.

The present invention also provides references to the above-mentioned MOF composite material in the field of energy storage, and the MOF composite material can be used for lithium batteries or supercapacitors.

The present invention has the following beneficial effects: 1. The obtained MOF/MXene nanocomposite material has good structural controllability and diversity; 2. The method of the present invention has a simple preparation process, low cost, and is easy to use on a large scale; 3. The MOF/MXene nanocomposite material can be applied to lithium batteries, supercapacitors, etc. to improve their energy storage and utilization efficiency.

Description of drawings

Below in conjunction with accompanying drawing and specific application mode, the present invention is described in further detail:

Fig. 1 is a scanning electron micrograph of MAX (Ti ₃ AlC ₂ ) particles obtained after ball milling in Example 1 of the present invention;

Fig. 2 is the scanning electron microscope picture that obtains MOF composite material after one-step reaction in the embodiment of the present invention 1;

Fig. 3 is the transmission electron microscope picture of MOF composite material in the embodiment 1 of the present invention;

Fig. 4 is the cyclic voltammetry curve of the supercapacitor with MOF composite material as electrode in Example 1 of the present invention, and the scanning speed is 10mVs ^-1 ;

Fig. 5 is a scanning electron microscope image of the MOF composite material in Example 2 of the present invention.

Detailed ways

In order to better illustrate the technical solutions of the present invention, specific implementations are used below for illustration.

Example 1

The MOF/MXene composite material prepared in this example uses Ti ₃ AlC ₂ and 1,4-naphthalene dicarboxylic acid as the MAX material and organic ligand molecule, including MXene material Ti ₃ C ₂ with a layered structure, and interspersed with MOF crystals with layered structure and material surface with Al as nodes and 1,4-naphthalene dicarboxylic acid as connecting bridges.

The specific steps are:

Step 1, MAX material pretreatment: using a ball mill, ball mill Ti ₃ AlC ₂ in ethanol, vacuum dry and sieve the ball mill to obtain submicron Ti ₃ AlC ₂ powder.

Step 2, generate MOF/MXene nanocomposites by "one-step method": add water, a small amount of HF, excess naphthalene dicarboxylic acid and treated Ti ₃ AlC ₂ powder in the reaction kettle, heat at 180°C for 6 hours, Under thermal conditions, HF etches away the metal atom Al in the Ti ₃ AlC ₂ structure to obtain Ti ₃ C ₂ , and the obtained Al ions react with naphthalene dicarboxylic acid to obtain MOF[Al(μ ₂ -OH)(1,4- ndc) _n ], that is, MOF/MXene nanocomposites.

Step 3: Purify and remove unreacted organic matter; wash the sample 3 times with ethanol, centrifuge the product, re-immerse in ethanol for 12 hours, then use ethanol for high-speed centrifugation and wash twice, and vacuum-dry the product at 100°C for 24 hours.

The prepared MOF/MXene nanocomposite was carried out using an electrochemical workstation, and the cyclic voltammetry curve of the supercapacitor with the MOF composite as an electrode was scanned at a scanning speed of 10mVs ^-1 .

Fig. 1 is the SEM image of the MAX(Ti ₃ AlC ₂ ) particles obtained after ball milling in this example, and Fig. 2 is the SEM image of the MOF composite material obtained after one-step reaction in this example; Fig. 3 is the SEM image of the MOF composite obtained in this example Transmission electron microscope image of the MOF composite. It can be seen from Fig. 1 to Fig. 3 that the MOF composite material prepared in this embodiment includes a regular layered structure and a uniform crystal structure interspersed in the layered structure, and the layer thickness and layer spacing of the layered structure are uniform. is nanoscale, the diameter of the crystal structure is also a nanoscale structure.

Figure 4 is the cyclic voltammetry curve of the supercapacitor using the MOF composite material as the electrode in this example, and its scanning speed is 10mVs ^-1 , it can be seen from the figure that the MOF composite material has good energy storage characteristics, and the The characteristics are stable.

Example 2

The MOF/MXene composite material prepared in this example uses Ti ₂ AlC and 1,3,5-trimellitic acid as MAX materials and organic ligand molecules, including MXene material Ti ₂ C with a layered structure, and interspersed The MOF crystal with 1,3,5-trimesic acid as the node and Al as the connecting bridge between the layered structures, Fig. 5 is the scanning electron microscope image of the MOF composite material in this embodiment. .

The specific steps are: Step 1, MAX material pretreatment: use a ball mill to ball mill Ti ₂ AlC in ethanol, vacuum dry and sieve the ball mill to obtain submicron Ti ₂ AlC powder.

Step 2: Generate MOF/MXene nanocomposites by "one-step method": add water, HF, excess 1,3,5-trimesic acid and treated Ti ₂ AlC powder to the reactor, and hydrothermally heat it at 120°C For 8 hours, the metal atoms Al in the Ti ₂ AlC structure were etched away by HF under hydrothermal conditions to obtain a Ti ₂ C nanosheet structure, and the obtained Al ions reacted with 1,3,5-trimesic acid to obtain MOF [MIL-96], that is, MOF/MXene nanocomposites.

Step 3, purify and remove unreacted organic matter; wash the sample 3 times with ethanol, centrifuge the product, re-immerse in ethanol for 12 hours, then use ethanol for high-speed centrifugation and wash twice, and vacuum dry the product at 100°C for 24 hours. The prepared MOF/MXene nanocomposite was carried out using an electrochemical workstation, and the cyclic voltammetry curve of the supercapacitor with the MOF composite as an electrode was scanned at a scanning speed of 10mVs ^-1 .

Example 3

The MOF/MXene composite material prepared in this example uses Ti ₃ AlC ₂ and 1,4-naphthalene dicarboxylic acid as the MAX material and organic ligand molecule, including MXene material Ti ₃ C ₂ with a layered structure, and interspersed with MOF crystals with layered structure and material surface with Al as nodes and 1,4-naphthalene dicarboxylic acid as connecting bridges.

The specific steps are:

Step 1, MAX material pretreatment: using a ball mill, ball mill Ti ₃ AlC ₂ in ethanol, vacuum dry and sieve the ball mill to obtain submicron Ti ₃ AlC ₂ powder.

Step 2, generate MOF/MXene nanocomposites by "one-step method": add water, a small amount of HF, excess naphthalene dicarboxylic acid and treated Ti ₃ AlC ₂ powder to the reaction kettle, heat at 200°C for 1 hour, Under thermal conditions, HF etches away the metal atom Al in the Ti ₃ AlC ₂ structure to obtain Ti ₃ C ₂ , and the obtained Al ions react with naphthalene dicarboxylic acid to obtain MOF[Al(μ ₂ -OH)(1,4- ndc) _n ], that is, MOF/MXene nanocomposites.

Step 3: Purify and remove unreacted organic matter; wash the sample 3 times with ethanol, centrifuge the product, re-immerse in ethanol for 12 hours, then use ethanol for high-speed centrifugation and wash twice, and vacuum-dry the product at 100°C for 24 hours.

The prepared MOF/MXene nanocomposite was carried out using an electrochemical workstation, and the cyclic voltammetry curve of the supercapacitor with the MOF composite as an electrode was scanned at a scanning speed of 10mVs ^-1 .

Example 4

The MOF/MXene composite material prepared in this example uses Ti ₂ AlC and 1,3,5-trimellitic acid as MAX materials and organic ligand molecules, including MXene material Ti ₂ C with a layered structure, and interspersed The MOF crystal with 1,3,5-trimesic acid as the node and Al as the connecting bridge between the layered structures, Fig. 5 is the scanning electron microscope image of the MOF composite material in this embodiment.

The specific steps are: Step 1, MAX material pretreatment: use a ball mill to ball mill Ti ₂ AlC in ethanol, vacuum dry and sieve the ball mill to obtain submicron Ti ₂ AlC powder.

Step 2: Generate MOF/MXene nanocomposites by "one-step method": add water, HF, excess 1,3,5-trimesic acid and treated Ti ₂ AlC powder to the reactor, and hydrothermally heat it at 140°C For 10 hours, the metal atom Al in the Ti ₂ AlC structure was etched away by HF under hydrothermal conditions to obtain a Ti ₂ C nanosheet structure. At the same time, the obtained Al ions reacted with 1,3,5-trimesic acid to obtain MOF [MIL-96], that is, MOF/MXene nanocomposites.

Step 3, purify and remove unreacted organic matter; wash the sample 3 times with ethanol, centrifuge the product, re-immerse in ethanol for 12 hours, then use ethanol for high-speed centrifugation and wash twice, and vacuum dry the product at 100°C for 24 hours.

The prepared MOF/MXene nanocomposite was carried out using an electrochemical workstation, and the cyclic voltammetry curve of the supercapacitor with the MOF composite as an electrode was scanned at a scanning speed of 10mVs ^-1 .

Claims (8)

1. a kind of MOF composite materials, it is characterised in that：The composite material includes layer structure and MOF crystal, and the MOF is brilliant Body is interspersed in layer structure and material surface；Layered structure is the MXene layer structures as made from MAX material；The MOF The free A ions that crystal generates when preparing MXene using MAX material are formed as node using organic ligand molecule as bridge is coupled.

2. composite material according to claim 1, it is characterised in that：The MAX material may be selected from Ti₃GaC₂、Ti₂AlC、 Ti₃AlC₂Or Ti₃SnC₂, the organic ligand molecule may be selected from Isosorbide-5-Nitrae naphthalenedicarboxylic acid or 1,3,5- trimesic acids.

3. a kind of preparation method for preparing MOF composite materials as claimed in claim 1 or 2, it is characterised in that：The method For：The A layers atom being etched to MAX material in removal MAX material obtains MXene materials and free A ions, in etching Organic ligand molecule is added in simultaneously, the organic ligand molecule reacts to be formed in MXene material surfaces with above-mentioned A ions MOF crystal can thus form MOF with MXene materials with the MOF/MXene composite materials of the mutual iterative structure of stratiform.

4. preparation method according to claim 3, which is characterized in that above-mentioned preparation method includes following three step：

Step 1, MAX material pretreatment：MAX material is worn into the MAX material of submicrometer scale using ball mill；

Step 2 generates MOF/MXene nanocomposites by " one-step method "：Water, a small amount of HF or salt are added in a kettle Mixed liquor, organic ligand molecule and the pretreated MAX material of acid and fluoride, hydro-thermal 1-10 is small at 120-200 DEG C When, obtain MOF/MXene nanocomposites；

Step 3, purifying removal unreacted organic matter；Drying after MOF/MXene nanocomposites is impregnated in cleaning.

5. preparation method according to claim 3 or 4, which is characterized in that the MAX material may be selected from Ti₃GaC₂、 Ti₂AlC、Ti₃AlC₂、Ti₃SnC₂Or Ti₂SnC, the organic ligand molecule may be selected from Isosorbide-5-Nitrae naphthalenedicarboxylic acid or 1,3,5- equal benzene three Formic acid.

6. according to the method described in claim 4, it is characterized in that, in step 1, in ball milling, MAX phase materials are being had Ball milling is carried out in solvent or water, ball milling is sieved after vacuum drying, obtains the MAX material of submicrometer scale.

7. according to the method described in claim 4, it is characterized in that, in step 3, using ethyl alcohol washing sample 3 times, will produce After object centrifugation, it is soaked in ethyl alcohol 12 hours, is then cleaned 2 times using ethyl alcohol high speed centrifugation, product vacuum at 100 DEG C again It is 24 hours dry.

8. MOF composite materials as claimed in claim 1 or 2 are in the application in energy storage field, which is characterized in that the MOF is compound Material can be used for lithium battery or super capacitor.