CN113058650B - A kind of composite metal organic framework and its preparation and application - Google Patents

Abstract

The invention relates to a preparation method of a composite metal organic framework, which is characterized in that a conductive metal organic framework (TM-CAT, CAT is a metal organic framework formed by hexahydroxy triphenyl and transition metal TM, different types of the metal organic framework are distinguished by the transition metal TM) is modified on the surface of an iron-based metal organic framework (MIL-xx, MIL is short for a metal organic framework material, different types of the metal organic framework are distinguished by a number xx) to obtain the composite metal organic framework (MIL-xx @ TM-CAT). MIL-xx @ TM-CAT can be directly used as an electrolytic water or a secondary zinc-air battery oxygen electrode oxygen precipitation electrocatalyst, compared with independent TM-CAT or MIL-xx (Fe), MIL-xx @ TM-CAT makes up the defect that the cost of TM-CAT is too high, solves the problem of poor conductivity of MIL-xx, and can regulate and control the electrocatalytic activity according to the interaction of metals in the TM-CAT and the MIL-xx; meanwhile, the preparation process is simple, and the raw materials are easy to obtain, so that the application prospect is wide.

Description

A kind of composite metal organic framework and its preparation and application

technical field

The invention belongs to the technical field of catalysts and preparations thereof, and relates to electrocatalysts for electrolysis of water or oxygen electrodes of secondary zinc-air batteries for oxygen evolution.

Background technique

Metal-organic frameworks have been widely used in electrocatalyst and electrode materials research due to their advantages of high specific surface, rich metal content, easy control of structural components, and good stability.

However, conventional metal-organic frameworks generally do not have conductive properties, and additional conductive agents (carbon nanotubes, graphene, etc.) need to be added in the electrode preparation process, thereby reducing the density of active materials in the electrode and increasing the complexity of the process. A novel metal-organic framework (TM-CAT) with 2,3,6,7,10,11-hexahydroxytriphenyl as a ligand has excellent electrical conductivity, but the ligand is expensive, and TM-CAT is directly used The cost as an electrocatalyst is high. In addition, the metal-organic framework composed of a single metal cannot meet the requirements in terms of performance. In bimetallic or multimetallic metal-organic frameworks, the catalytic activity can be greatly improved due to the interaction between different metals.

SUMMARY OF THE INVENTION

Common metal-organic frameworks are directly used as catalysts, which have problems such as poor conductivity and low catalytic activity. Aiming at these deficiencies, the present invention proposes a method for preparing a composite metal organic framework. It is distinguished by the transition metal TM) modified on the surface of the iron-based metal-organic framework (MIL-xx, MIL is the abbreviation of a class of metal-organic framework materials, and its different types are distinguished by the number xx) to obtain a composite metal-organic framework (MIL- xx@TM-CAT). MIL-xx@TM-CAT can be directly used as electrocatalyst for oxygen evolution of oxygen electrode in water electrolysis or secondary zinc-air battery, compared with TM-CAT or MIL-xx(Fe) alone, MIL-xx@TM-CAT makes up The problem of high cost of TM-CAT is solved, the problem of poor conductivity of MIL-xx is solved, and the electrocatalytic activity can be regulated according to the interaction of metals in TM-CAT and MIL-xx; at the same time, the preparation process is simple, The raw materials are easy to obtain, so the application prospect is broad.

A composite metal-organic framework with MIL-xx as the core and TM-CAT grown on the surface. The metal in the MIL-xx is Fe, and the mole percentage of Fe in the composite metal-organic framework to the total metal content is 30-90%, preferably 70-90%. The ligand in TM-CAT is 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP), which has excellent electrical conductivity; the metal (TM) is one or both of Mn, Co, and Ni. more than one species.

Its preparation method comprises the following steps:

(1) Synthesis of MIL-xx: prepare a mixed solution of Fe metal salt and polycarboxylate organic ligand, carry out solvothermal reaction of the mixed solution at high temperature, and separate the product to obtain Fe-based metal organic framework;

(2) Preparation of composite metal organic framework: ultrasonically disperse the mixed solvent of metal organic framework water and DMF obtained in step (1), add transition metal (TM) salt and 2, 3, 6, 7, 10, 11 -Hexahydroxytriphenyl (HHTP), and carry out solvothermal reaction at high temperature, and separate the product to obtain composite metal organic framework;

The Fe metal salt described in the step (1) is one or both of ferric nitrate and ferric chloride; the organic ligand is one or both of terephthalic acid, trimesic acid, and fumaric acid. More than two kinds; The solvent is one or more mixtures of DMF, methanol or water; The amount ratio of Fe ions and the substance with ligands in the mixed solution described in the step (1) is 2:1-1:2 .

The solvothermal reaction temperature in step (1) is 60-120° C., and the duration is 8-48 hours.

The volume ratio of water and DMF described in the step (2) is 2:1-1:2; the transition metal (TM) salt is one of Mn, Co, Ni nitrate, chloride, acetate or More than two kinds; the molar ratio of transition metal (TM) salt and 2,3,6,7,10,11-hexahydroxytriphenyl is 1:1.

In step (2), the temperature of the solvothermal reaction is 60-90° C., and the duration is longer than 1 hour.

Compared with the prior art, the present invention has the following advantages: the electrical conductivity of the material can be improved by modifying a small amount of TM-CAT on the surface of MIL-xx, and the catalytic activity can be regulated by the interaction between MIL-xx and TM-CAT, thereby greatly improving Electrocatalytic properties of materials. At the same time, the preparation process is simple and the raw materials are easily obtained. In addition, the high oxygen evolution performance and good stability make it have broad application prospects in the oxygen electrode of water electrolysis and secondary metal-air batteries.

Description of drawings

Figure 1 Example 1 X-ray fluorescence spectrum (XRF) diagram.

Fig. 2 Test diagram of electrochemical performance of oxygen evolution in Example 1. The curves were tested using a three-electrode system in an oxygen-saturated 1M KOH electrolyte. The catalyst was coated on a rotating disk electrode as the working electrode with a loading of 100 mg cm ^-2 . A graphite rod was used as the counter electrode, and saturated calomel with an external salt bridge was used. The electrode is the reference electrode, and the potential in the figure has been corrected to that of the reversible hydrogen electrode.

Detailed ways

Comparative Example 1

Weigh 2.03g ferric chloride hexahydrate in a beaker, add 25ml DMF, stir to form a solution, weigh 0.618g terephthalic acid in a beaker, add 25ml DMF, stir to form a solution, slowly pour the ferric chloride solution Put it into the terephthalic acid solution, continue stirring for 30 minutes, then transfer it to the reaction kettle and heat it to 110 °C for 8 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product is obtained by centrifugation, and washed with ethanol three times to remove the residual solvent in the air. , which was characterized by XRD as MIL-101(Fe).

MIL-101(Fe) has poor conductivity and low performance of single metal catalysts.

Comparative Example 2

Weigh 20mg of nickel acetate tetrahydrate and 13mg of 2,3,6,7,10,11-hexahydroxytriphenyl in 2ml of water and N,N-dimethylformamide mixed solvent (volume ratio 1:1) for ultrasonic dispersion, It was placed in an oven at 80 °C for 8 h, centrifuged, washed three times with water and methanol, and characterized as Ni-CAT by XRD.

The price of 2,3,6,7,10,11-hexahydroxytriphenyl is about 1200 yuan/g, and the price of pure Ni-CAT is higher.

Example 1

Weigh 2.03g ferric chloride hexahydrate in a beaker, add 25ml DMF, stir to form a solution, weigh 0.618g terephthalic acid in a beaker, add 25ml DMF, stir to form a solution, slowly pour the ferric chloride solution Put it into the terephthalic acid solution, continue stirring for 30 minutes, then transfer it to the reaction kettle and heat it to 110 °C for 8 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product is obtained by centrifugation, and washed with ethanol three times to remove the residual solvent in the air. , thereby obtaining MIL-101(Fe).

Take 100mg MIL-101(Fe) and disperse it in 8mL water and N,N-dimethylformamide mixed solvent (volume ratio 1:1) for ultrasonic dispersion, add 10mg nickel acetate tetrahydrate and 6.5mg 2,3,6,7 ,10,11-hexahydroxytriphenyl was placed in an oven at 80°C for 8h, centrifuged, washed three times with water and methanol, respectively, to obtain MIL-101/Ni-CAT. XPS test shows that the mole percentage of Fe in the composite metal organic framework is 87.4% of the total metal, and the mole percentage of Ni in the total metal is 12.6%.

Example 2

Weigh 2.03g ferric chloride hexahydrate in a beaker, add 25ml DMF, stir to form a solution, weigh 0.618g terephthalic acid in a beaker, add 25ml DMF, stir to form a solution, slowly pour the ferric chloride solution Put it into the terephthalic acid solution, continue stirring for 30 minutes, then transfer it to the reaction kettle and heat it to 110 °C for 8 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product is obtained by centrifugation, and washed with ethanol three times to remove the residual solvent in the air. , thereby obtaining MIL-101(Fe).

Disperse 100mg MIL-101(Fe) in 8mL water and N,N-dimethylformamide mixed solvent (volume ratio 1:1) for ultrasonic dispersion, add 10mg cobalt acetate tetrahydrate and 6.5mg2,3,6,7, 10,11-hexahydroxytriphenyl was placed in an oven at 80 °C for 8 h, centrifuged, washed three times with water and methanol, respectively, to obtain MIL-101/Co-CAT.

The XPS test showed that the molar percentage of Fe in the composite metal-organic framework was 90%.

XPS test showed that the mole percentage of Fe in the composite metal-organic framework was 88.3% of the total metals, and the mole percentage of Co in the total metals was 11.7%.

Example 3

Weigh 2.03g ferric chloride hexahydrate in a beaker, add 25ml DMF, stir to form a solution, weigh 0.618g terephthalic acid in a beaker, add 25ml DMF, stir to form a solution, slowly pour the ferric chloride solution Put it into the terephthalic acid solution, continue stirring for 30 minutes, then transfer it to the reaction kettle and heat it to 110°C for 8 hours. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product is obtained by centrifugation, and washed with ethanol three times to remove the residual solvent in the air. , thereby obtaining MIL-101(Fe).

Disperse 100mg MIL-101(Fe) in 8mL water and N,N-dimethylformamide mixed solvent (volume ratio 1:1) for ultrasonic dispersion, add 10mg manganese acetate and 6.5mg2,3,6,7,10, 11-hexahydroxytriphenyl was placed in an oven at 80 °C for 8 h, centrifuged, washed three times with water and methanol, respectively, to obtain MIL-101/Mn-CAT.

XPS test showed that the mole percentage of Fe to the total metals in the composite metal-organic framework was 85.6%, and the mole percentage of Co to the total metals was 14.4%.

Example 4

Weigh 0.674g ferric chloride hexahydrate in a beaker, add 25ml DMF, stir to form a solution, weigh 0.415g terephthalic acid in a beaker, add 25ml DMF, stir to form a solution, slowly pour the ferric chloride solution Put it into the terephthalic acid solution, continue stirring for 30min, then transfer it to the reaction kettle and heat it to 150°C for 15h. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product is obtained by centrifugation, and washed with ethanol alcohol three times to remove airborne residues. solvent to obtain MIL-53(Fe). Weigh 100mg of MIL-53(Fe) and disperse it in 8mL of water and N,N-dimethylformamide mixed solvent (volume ratio 1:1) for ultrasonic dispersion, add 20mg of nickel acetate tetrahydrate and 13mg of 2,3,6, 7,10,11-hexahydroxytriphenyl was placed in an oven at 80°C for 8 h, centrifuged, washed three times with water and methanol, respectively, to obtain MIL-53/Ni-CAT.

XPS test showed that the mole percentage of Fe in the composite metal-organic framework was 73.7% of the total metals, and the mole percentage of Ni in the total metals was 26.3%.

Example 5

Weigh 2.70g ferric chloride hexahydrate in a beaker, add 25ml DMF, stir to form a solution, weigh 1.66g terephthalic acid in a beaker, add 25ml DMF, stir to form a solution, slowly pour the ferric chloride solution into the terephthalic acid solution, then add 4ml of 2M NaOH, continue to stir for 30min, then transfer to the reaction kettle and heat to 100°C for 12h. After the reaction is completed, the reaction kettle is cooled to room temperature, and the product is obtained by centrifugation. The solvent remaining in the air was removed by washing three times, thereby obtaining MIL-88B(Fe). Weigh 100mg of MIL-88B(Fe) and disperse it in 8mL of water and N,N-dimethylformamide mixed solvent (volume ratio 1:1) for ultrasonic dispersion, add 40mg of nickel acetate tetrahydrate and 26mg of 2,3,6, 7,10,11-hexahydroxytriphenyl was placed in an oven at 80°C for 8 h, centrifuged, washed three times with water and methanol, respectively, to obtain MIL-88B/Ni-CAT.

XPS test showed that the mole percentage of Fe in the composite metal-organic framework was 63.4% of the total metals, and the mole percentage of Ni in the total metals was 36.6%.

Claims (9)

1. a composite metal-organic framework, is characterized in that: take iron-based metal-organic framework MIL-xx as a core, and its surface grows TM-CAT; Comprise the following steps: (1) Synthesis of MIL-xx: prepare a mixed solution of Fe metal salt and polycarboxyl organic ligand, carry out solvothermal reaction of the mixed solution, and separate the product to obtain Fe-based metal organic framework; (2) Preparation of composite metal-organic framework: The metal-organic framework obtained in step (1) was ultrasonically dispersed in a mixed solvent of water and DMF, and added with transition metal TM salt and 2,3,6,7,10,11- Hexahydroxytriphenyl (HHTP), and subjected to a solvothermal reaction to separate the product to obtain a composite metal-organic framework; the metal in MIL-xx is Fe, and the mole percentage of Fe in the composite metal-organic framework to the total metal content of Fe and TM is 30 %-90%; metal TM is one or more of Mn, Co, and Ni. 2. The composite metal-organic framework of claim 1, wherein the metal in the MIL-xx is Fe, and the mole percentage of Fe in the composite metal-organic framework of the total metal content of Fe and TM is 70%-90%. 3. The composite metal-organic framework according to claim 1 or 2, wherein the ligand in TM-CAT is 2,3,6,7,10,11-hexahydroxytriphenyl (HHTP), which has excellent Conductivity. 4. a preparation method of the arbitrary described composite metal organic framework of claim 1-3, is characterized in that: comprise the following steps: (1) Synthesis of MIL-xx: prepare a mixed solution of Fe metal salt and polycarboxyl organic ligand, carry out solvothermal reaction of the mixed solution, and separate the product to obtain Fe-based metal organic framework; (2) Preparation of composite metal-organic framework: The metal-organic framework obtained in step (1) was ultrasonically dispersed in a mixed solvent of water and DMF, and added with transition metal TM salt and 2,3,6,7,10,11- Hexahydroxytriphenyl (HHTP), and a solvothermal reaction is carried out to separate the product to obtain a composite metal organic framework. 5. the preparation method of composite metal organic framework as claimed in claim 4, is characterized in that: Fe metal salt described in step (1) is one or both in ferric nitrate, ferric chloride; Organic ligand is to One or more of phthalic acid, trimesic acid and fumaric acid; the solvent is a mixture of one or more of DMF, methanol or water; the mixed solution described in step (1) The ratio of Fe ions to ligand-containing substances is 2:1-1:2. 6 . The preparation method of the composite metal organic framework according to claim 4 , wherein the solvothermal reaction temperature in the step (1) is 60-120 °C, and the duration is 8-48 hours. 7 . 7. the preparation method of composite metal organic framework as claimed in claim 4 is characterized in that: the volume ratio of water and DMF described in step (2) is 2:1-1:2; Transition metal TM salt is Mn, Co , one or more of Ni, one or more of chloride, acetate; transition metal TM salt and 2,3,6,7,10,11-hexahydroxytri- The molar ratio of benzene is 1:1. 8 . The preparation method of the composite metal organic framework according to claim 4 , wherein the solvothermal reaction temperature in step (2) is 60-90°C, and the duration is longer than 1 hour. 9 . 9. An application of the composite metal-organic framework according to any one of claims 1-3, characterized in that: the composite metal-organic framework is used as an electrocatalyst for electrolysis of water or oxygen evolution of an oxygen electrode of a secondary zinc-air battery.

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