CN114950562A - Titanium-based three-dimensional nano organic complex with adjustable defect density and preparation method and application thereof - Google Patents

Abstract

The invention discloses a titanium-based three-dimensional nano organic complex with adjustable defect density, a preparation method and application thereof. The titanium-based three-dimensional nano organic complex with the metal cluster deletion defect has the advantages of simple and efficient preparation method and low cost. Meanwhile, the defect content of the titanium-based three-dimensional nano organic complex with the metal cluster deletion defect can be regulated and controlled by regulating the proportion of the organic ligand terephthalic acid and the 2-amino terephthalic acid, so that the photocatalytic activity of the titanium-based three-dimensional nano organic complex is regulated and controlled.

Description

A titanium-based three-dimensional nano-organic complex with tunable defect density and its preparation method and application

technical field

The invention belongs to the field of material preparation, in particular to a titanium-based three-dimensional nano-organic complex with adjustable defect density, a preparation method and application thereof.

Background technique

Three-dimensional nano-metal-organic complexes show outstanding performance in adsorption and catalysis studies due to their high porosity, large specific surface area, unsaturated metal coordination sites, and diverse structures and functions. Three-dimensional nano-organic metal complexes are a class of porous crystalline materials with periodic structures composed of metal centers composed of metal ions or metal clusters and organic ligands connected by self-assembly. However, it is difficult to synthesize real Flawless 3D nanoscale metal-organic complexes, because any small change in reaction conditions can cause vacancies or deletions in the material, resulting in material defects. Defects in three-dimensional nanometal-organic complexes can be vacancies in metal centers, absence of organic ligands, or doped defects or functionalized ligands.

In some specific cases, defects in 3D nanometal-organic complexes can enhance their performance in certain aspects by changing the external surface properties, internal pore structure or generating new active metal sites of 3D nano-metal-organic complexes, such as Adsorption, catalysis, etc. Therefore, researchers in the environmental field began to artificially introduce defects to obtain defective three-dimensional nano-metal-organic complex materials with enhanced adsorption and catalysis properties for pollution control. In the prior art, defects are usually introduced into three-dimensional nano-metal organic complexes by adding monocarboxylic acids such as formic acid and acetic acid as regulators, but the present invention does not require acid intervention, and is clean and environmentally friendly. Therefore, it is crucial to prepare defective three-dimensional nanoscale metal-organic complexes by a safe and environmentally friendly method.

SUMMARY OF THE INVENTION

In view of the above technical problems existing in the prior art, the purpose of the present invention is to provide a titanium-based three-dimensional nano-organic complex with adjustable defect density and a preparation method and application thereof. In the method of the invention, after the titanium-based three-dimensional nano-organic complex is synthesized by a simple solvothermal method, the titanium-based three-dimensional nano-organic complex with metal cluster deficiency defects is formed by calcination, and the titanium-based three-dimensional nano-organic complex with metal cluster deficiency defects is formed. The complexes are highly active in solar photocatalytic water splitting for hydrogen production.

In order to synthesize titanium-based three-dimensional nano-organic complexes with metal cluster deletion defects, the present invention adopts a new idea: the melting point of terephthalic acid is about 427°C, and the melting point of 2-aminoterephthalic acid is about At 324 °C, two different ligands, terephthalic acid and 2-aminoterephthalic acid, were mixed, uniformly dispersed in the solvent, and then titanium tetraisopropoxide was added as the metal center, and the mixed ligand was synthesized by solvothermal method. Titanium-based three-dimensional nano-organic complexes; the obtained titanium-based three-dimensional nano-organic complexes with mixed ligands are calcined in a tube furnace to remove 2-aminoterephthalic acid ligands, and titanium-based three-dimensional titanium-based three-dimensional organic complexes with metal cluster deletion defects are obtained. Nano-organic complexes.

The method for preparing a titanium-based three-dimensional nano-organic complex with adjustable defect density specifically includes the following steps:

1) The terephthalic acid and 2-aminoterephthalic acid are uniformly dispersed in the solvent, then titanium tetraisopropoxide is added, ultrasonicated and stirred to make the dissolution uniform, and then the obtained solution is transferred into a polytetrafluoroethylene-lined In the reaction kettle, it is then heated in an oven at 125-175 ° C for 12-18 h, cooled to room temperature and then centrifuged. The obtained solid is washed, dried and ground to obtain a yellow powder, which is a titanium-based three-dimensional nano-organic compound with mixed ligands. complex;

2) The yellow powder obtained in step 1) is placed in a tube furnace, and calcined in a nitrogen or air atmosphere. The calcination temperature is greater than the melting point of 2-aminoterephthalic acid and less than the melting point of terephthalic acid. - After the aminoterephthalic acid ligand, grinding to obtain a pale white sample powder, that is, a titanium-based three-dimensional nano-organic complex with metal cluster deletion defects.

Further, in step 1), in the mixture of terephthalic acid and 2-amino terephthalic acid, the mass percentage ratio of 2-amino terephthalic acid is 1~20%, preferably 5~12%. %.

Further, in step 1), the ratio of the mass of terephthalic acid to the volume of titanium tetraisopropoxide is (1.9-2.5) g: 1.3 mL.

Further, in step 1), the solvent is composed of N,N-dimethylformamide and methanol in a volume ratio of 5 to 15:1, and the volume ratio of N,N-dimethylformamide and methanol is preferably 9:1.

Further, in step 1), the heating temperature in the oven is 140-160°C, preferably 150°C, and the heating time is 14-16 h, preferably 15 h.

Further, in step 2), the calcination temperature of the tube furnace is 325-425°C, preferably 360-390°C, more preferably 375°C, and the calcination time is 60-210 min, preferably 150 min.

The application of the titanium-based three-dimensional nano-organic complex with adjustable defect density in photocatalytic water splitting for hydrogen production, the application method is: adding the titanium-based three-dimensional nano-organic complex into the sacrificial agent aqueous solution, and bubbling argon. Chloroplatinic acid solution is added after the gas, and the obtained mixed solution is irradiated under a high pressure mercury lamp to carry platinum for 0.5-1 h, and the metal halide lamp is turned on for photocatalytic hydrogen production.

Further, the sacrificial agent aqueous solution is methanol aqueous solution, and its volume concentration is 10%～70%, preferably 30%; the ratio of the mass of the titanium-based three-dimensional nano-organic complex to the sacrificial agent aqueous solution volume is (15～30 ) mg: 100 mL; the mass ratio of the platinum element in the chloroplatinic acid solution to the titanium-based three-dimensional nano-organic complex is 0.2 to 0.5:25.

Compared with the prior art, the present invention has achieved the following technical effects:

1) The present invention provides a method for preparing a titanium-based three-dimensional nano-organic complex with adjustable defect density, so that the titanium-based three-dimensional nano-organic complex has metal cluster deletion defects to enhance its photocatalytic activity. The titanium-based three-dimensional nano-organic complex with metal cluster deficiency defect of the invention has a simple and efficient preparation method and low cost. At the same time, by adjusting the ratio of organic ligands terephthalic acid and 2-aminoterephthalic acid, the defect content of titanium-based three-dimensional nano-organic complexes with metal cluster deletion defects can be regulated, thereby regulating their photocatalytic activity.

2) The titanium-based three-dimensional nano-organic complex with metal cluster deletion defect synthesized by the present invention has ultra-high catalytic performance for photocatalytic water splitting. In the preparation method of the material of the present invention, the 2-aminoterephthalic acid ligand with a lower melting point is removed by calcination, and the defect of metal cluster deficiency is introduced without destroying the topological structure of the titanium-based three-dimensional nano-organic complex, so that the catalyst structure is improved. At the same time, it has good photocatalytic activity and stability.

Description of drawings

Fig. 1 is the transmission electron microscope scanning image of the titanium-based three-dimensional nano-organic complex with metal cluster deletion defect prepared in Example 1;

Fig. 2 is the transmission electron microscope scanning image of the titanium-based three-dimensional nano-organic complex with metal cluster deletion defect prepared in Example 4;

FIG. 3 is a transmission electron microscope scanning image of the titanium-based three-dimensional nano-organic complex with metal cluster deletion defect prepared in Example 6. FIG.

Detailed ways

The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

Example 1

In this embodiment, the specific steps for preparing the synthesized titanium-based three-dimensional nano-organic complex with metal cluster deficiency defects are as follows:

(1) Disperse 2492.0 mg of terephthalic acid in 45 mL of N,N-dimethylformamide and 5 mL of methanol, stir for 30 min, then add 1.3 mL of titanium tetraisopropoxide, and sonicate briefly for 30 minutes. After s, stir for 30 min to make the dispersion uniform.

(2) Put the dispersion liquid in step (1) into a reaction kettle with 100 mL of polytetrafluoroethylene lining, and then transfer it into an electric heating blast drying oven at 150 ° C for 15 h, and after cooling to room temperature, use N, After washing with N-dimethylformamide and methanol three times, the solvent was removed under vacuum at 60 °C and activated for 24 h, and triturated to obtain a white powder.

(3) The powder obtained in step (2) was placed in a tube furnace, and calcined at a temperature of 375° C. for 150 min in an air atmosphere, and ground to obtain an off-white sample powder.

Example 2

(1) 2467.0 mg of terephthalic acid and 27.2 mg of 2-aminoterephthalic acid were uniformly dispersed in 45 mL of N,N-dimethylformamide and 5 mL of methanol, briefly sonicated for 30 s and then stirred for 30 min After that, 1.3 mL of titanium tetraisopropoxide was added, ultrasonicated and stirred for 30 min to make the dispersion uniform.

(2) Put the dispersion liquid in step (1) into a reaction kettle with 100 mL of polytetrafluoroethylene lining, and then transfer it into an electric heating blast drying oven at 150 ° C for 15 h, and after cooling to room temperature, use N, After washing with N-dimethylformamide and methanol three times, the solvent was removed under vacuum at 60 °C and activated for 24 h, and triturated to obtain a pale yellow powder.

(3) The powder obtained in step (2) was placed in a tube furnace, and kept at a temperature of 375° C. for 150 min in an air atmosphere, and ground to obtain an off-white sample powder.

Example 3

(1) 2442.1 mg of terephthalic acid and 54.3 mg of 2-aminoterephthalic acid were uniformly dispersed in 45 mL of N,N-dimethylformamide and 5 mL of methanol, briefly sonicated for 30 s and then stirred for 30 min After that, 1.3 mL of titanium tetraisopropoxide was added, ultrasonicated and stirred for 30 min to make the dispersion uniform.

(2) Put the dispersion liquid in step (1) into a reaction kettle with 100 mL of polytetrafluoroethylene lining, and then transfer it into an electric heating blast drying oven at 150 ° C for 15 h, and after cooling to room temperature, use N, After washing with N-dimethylformamide and methanol three times, the solvent was removed under vacuum at 60 °C and activated for 24 h, and triturated to obtain a pale yellow powder.

(3) The powder obtained in step (2) was placed in a tube furnace, and kept at a temperature of 375° C. for 150 min in an air atmosphere, and ground to obtain an off-white sample powder.

Example 4

(1) 2367.4 mg of terephthalic acid and 136.0 mg of 2-aminoterephthalic acid were uniformly dispersed in 45 mL of N,N-dimethylformamide and 5 mL of methanol, briefly sonicated for 30 s and then stirred for 30 min After that, 1.3 mL of titanium tetraisopropoxide was added, ultrasonicated and stirred for 30 min to make the dispersion uniform.

(2) Put the dispersion liquid in step (1) into a reaction kettle with 100 mL of polytetrafluoroethylene lining, and then transfer it into an electric heating blast drying oven at 150 ° C for 15 h, and after cooling to room temperature, use N, After washing with N-dimethylformamide and methanol three times, the solvent was removed under vacuum at 60 °C and activated for 24 h, and triturated to obtain a yellow powder.

(3) The powder obtained in step (2) was placed in a tube furnace, and kept at a temperature of 375° C. for 150 min in an air atmosphere, and ground to obtain an off-white sample powder.

Example 5

(1) 2242.8 mg of terephthalic acid and 271.7 mg of 2-aminoterephthalic acid were uniformly dispersed in 45 mL of N,N-dimethylformamide and 5 mL of methanol, briefly sonicated for 30 s and then stirred for 30 min After that, 1.3 mL of titanium tetraisopropoxide was added, ultrasonicated and stirred for 30 min to make the dispersion uniform.

(2) Put the dispersion liquid in step (1) into a reaction kettle with 100 mL of polytetrafluoroethylene lining, and then transfer it into an electric heating blast drying oven at 150 ° C for 15 h, and after cooling to room temperature, use N, After washing with N-dimethylformamide and methanol three times, the solvent was removed under vacuum at 60 °C and activated for 24 h, and triturated to obtain a yellow powder.

(3) The powder obtained in step (2) was placed in a tube furnace, and kept at a temperature of 375° C. for 150 min in an air atmosphere, and ground to obtain an off-white sample powder.

Example 6

(1) 1933.6 mg of terephthalic acid and 543.4 mg of 2-aminoterephthalic acid were uniformly dispersed in 45 mL of N,N-dimethylformamide and 5 mL of methanol, briefly sonicated for 30 s and then stirred for 30 min After that, 1.3 mL of titanium tetraisopropoxide was added, ultrasonicated and stirred for 30 min to make the dispersion uniform.

(2) Put the dispersion liquid in step (1) into a reaction kettle with 100 mL of polytetrafluoroethylene lining, and then transfer it into an electric heating blast drying oven at 150 ° C for 15 h, and after cooling to room temperature, use N, After washing with N-dimethylformamide and methanol three times, the solvent was removed under vacuum at 60 °C and activated for 24 h, and triturated to obtain a yellow powder.

(3) The powder obtained in step (2) was placed in a tube furnace, and kept at a temperature of 375° C. for 150 min in an air atmosphere, and ground to obtain an off-white sample powder.

The titanium-based three-dimensional nano-organic complexes obtained in Examples 1, 4, and 6 were scanned by transmission electron microscopy, and the results are shown in Figure 1, Figure 2, and Figure 3, respectively.

Application Example 1:

Using the titanium-based three-dimensional nano-organic complexes obtained in Examples 1-6, the photo-splitting water test was carried out under the condition of sunlight irradiation.

The test conditions are: weigh 25 mg of the titanium-based three-dimensional nano-organic complexes obtained in Examples 1-6, 30 mL of methanol and 70 mL of water in a beaker, and the solution is subjected to argon aeration treatment for 30 min. 200 μL of chloroplatinic acid solution containing platinum with a concentration of 1.883 g/L was added to the solution, and the solution was slowly stirred for 30 min under the irradiation of a 300 W high-pressure mercury lamp. Transfer the beaker into the photoreactor, pass argon gas for 30 min to fill the reactor with argon atmosphere, cover it with AM 1.5 filter, and carry out photo-splitting water reaction under the irradiation of metal halide lamp. The gas concentration in the reactor was detected by gas chromatography, and the results are shown in Table 1.

It can be seen from Table 1 that the titanium-based three-dimensional nano-organic complex with adjustable defect density synthesized by the present invention has good catalytic activity for splitting water under sunlight. Examples 1-6 When preparing titanium-based three-dimensional nano-organic complexes, the addition amount of the ligand 2-aminoterephthalic acid gradually increased, while the hydrogen production rate of water splitting under sunlight increased first and then decreased.

Using the sample obtained in Example 4, the cycle test was carried out under the same test conditions as above. After 12 hours of circulation, the photo-splitting water hydrogen production rate of the sample obtained in Example 4 was 13278.8 μmol/g/h, which remained at a very high level. , it can be seen that the catalyst has good stability.

Compared with the titanium-based three-dimensional nano-organic complex in Figure 1, the structure is relatively uniform. When 2-aminoterephthalic acid is not added during the preparation process, the titanium-based three-dimensional nano-organic complex does not form an obvious metal cluster deletion defect structure. , the organic ligands and metal centers in the titanium-based three-dimensional nano-organic complexes do not overlap, and electron transport is difficult, resulting in poor photocatalytic activity of the material and no good photocatalytic water splitting efficiency for hydrogen production.

Contrast that with the structure of titanium-based three-dimensional nano-organic complexes with tunable defect density in Fig. 2, an obvious metal cluster deletion defect structure is formed (the part inside the circle in the control figure), with the increase of 2-aminoterephthalic acid during the material preparation process. increased, 2-aminoterephthalic acid was involved in the construction of titanium-based three-dimensional nano-organic complexes, which were then removed by tube furnace calcination, forming a metal cluster missing defect structure, and the formed metal cluster missing defect structure resulted in titanium-based Structural asymmetry emerges in 3D nano-organic complexes, which affects the electronic structure in titanium-based 3-D nano-organic complexes, leading to photocatalytic splitting of titanium-based 3-D nano-organic complexes with metal cluster deletion defects for water production. to raise efficiency. This also shows that the removal of 2-aminoterephthalic acid can introduce a metal cluster deletion defect structure into the titanium-based three-dimensional nano-organic complex structure. Precise regulation of metal cluster deletion defects.

Compared with the structure of titanium-based three-dimensional nano-organic complexes with tunable defect density in Fig. 3, a larger range of metal cluster-deficient defect structures appeared (the part in the circle in the control figure). The further increase of the amount of metal clusters in the structure of titanium-based three-dimensional nano-organic complexes increases the number of defects in metal clusters, and even damages the structure of titanium-based three-dimensional nano-organic complexes to a certain extent, hindering the normal transmission of electrons in the structure, making it have Titanium-based three-dimensional nano-organic complexes lacking defects in metal clusters have decreased activity for photocatalytic water splitting for hydrogen production.

It can be seen that the photocatalytic water splitting of this titanium-based three-dimensional nano-organic complex with tunable defect density is very efficient, and the photocatalytic water splitting hydrogen production efficiency can be adjusted by adjusting the amount of 2-aminoterephthalic acid. After several rounds of cycling experiments, the titanium-based three-dimensional nano-organic complexes with tunable defect density still exhibit high catalytic activity.

The above-mentioned embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. For example, although in the above example, the solvothermal solvent in the preparation process is 45 mL of N,N-dimethylformamide and 5 mL of methanol, it does not mean that the solvent must be dimethylformamide and methanol Or this ratio, as long as the solvent can ensure that the organic ligand can be effectively dissolved, and the solvent ratio can ensure that the organic ligand and the metal center can form a complex, the effect of the present invention can be achieved. For another example, terephthalic acid and 2-amino terephthalic acid are added in the preparation process, but it does not mean that terephthalic acid and 2-amino terephthalic acid must be added, as long as two kinds with different melting points are selected. Similar organic ligands can jointly participate in the formation of titanium-based three-dimensional nano-organic complexes and then be removed by calcination treatment, that is, the effects of the present invention can be achieved.

The content described in this specification is only an enumeration of the realization forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms stated in the embodiments.

Claims (10)

1. a preparation method of a titanium-based three-dimensional nano-organic complex whose defect density can be regulated, is characterized in that by mixing two different ligands terephthalic acid and 2-amino terephthalic acid, uniformly dispersed in a solvent , and then add titanium tetraisopropoxide as the metal center, synthesize titanium-based three-dimensional nano-organic complexes with mixed ligands by solvothermal method, and then remove the titanium-based three-dimensional nano-organic complexes with mixed ligands by calcination The 2-aminoterephthalic acid ligand is obtained, namely, the titanium-based three-dimensional nano-organic complex with metal cluster deletion defect is obtained. 2. the preparation method of a kind of titanium-based three-dimensional nano-organic complex with adjustable defect density as claimed in claim 1, is characterized in that specifically comprising the following steps: 1) The terephthalic acid and 2-aminoterephthalic acid are uniformly dispersed in the solvent, then titanium tetraisopropoxide is added, ultrasonicated and stirred to make the dissolution uniform, and then the obtained solution is transferred into a polytetrafluoroethylene-lined In the reaction kettle, it is then heated in an oven at 125-175 ° C for 12-18 h, cooled to room temperature and centrifuged. The obtained solid is washed, dried and ground to obtain a white or yellow powder, which is a titanium-based three-dimensional complex with mixed ligands. Nano organic complexes; 2) The yellow powder obtained in step 1) is placed in a tube furnace, and calcined in a nitrogen or air atmosphere. The calcination temperature is greater than the melting point of 2-aminoterephthalic acid and less than the melting point of terephthalic acid. -After the amino terephthalic acid ligand, grinding to obtain a gray-white sample powder, that is, a titanium-based three-dimensional nano-organic complex with metal cluster deletion defects. 3. The method for preparing a titanium-based three-dimensional nano-organic complex with adjustable defect density as claimed in claim 2, characterized in that in step 1), a mixture of terephthalic acid and 2-aminoterephthalic acid In, the mass percentage ratio of 2-amino terephthalic acid is 1~20%, preferably 5~12%; in step 1), the ratio of the mass of terephthalic acid to the volume of titanium tetraisopropoxide For (1.9~2.5) g: 1.3mL. 4. The preparation method of a titanium-based three-dimensional nano-organic complex with adjustable defect density as claimed in claim 2, characterized in that in step 1), the solvent is composed of N in a volume ratio of 5 to 15:1, It is composed of N-dimethylformamide and methanol, and the volume ratio of N,N-dimethylformamide and methanol is preferably 9:1. 5. The method for preparing a titanium-based three-dimensional nano-organic complex with adjustable defect density according to claim 2, wherein in step 1), the heating temperature in an oven is 140-160°C, preferably 150°C , the heating time is 14-16 h, preferably 15 h. 6. The method for preparing a titanium-based three-dimensional nano-organic complex with adjustable defect density according to claim 2, wherein in step 2), the calcination temperature of the tube furnace is 325-425°C, preferably 375°C ℃, the calcination time is 60-210 min, preferably 150 min. 7. The titanium-based three-dimensional nano-organic complex with adjustable defect density prepared by the method according to any one of claims 1 to 6. 8. The application of the titanium-based three-dimensional nano-organic complex with adjustable defect density as claimed in claim 7 in photocatalytic splitting of water for hydrogen production. 9. The application according to claim 8, characterized in that adding the titanium-based three-dimensional nano-organic complex to the sacrificial agent aqueous solution, adding a chloroplatinic acid solution after bubbling argon, and the resulting mixed solution is placed under a high-pressure mercury lamp. Irradiate the platinum carrier for 0.5-1 h, and turn on the metal halide lamp for photocatalytic hydrogen production. 10. application as claimed in claim 9 is characterized in that described sacrificial agent aqueous solution is methanol aqueous solution, and its volume concentration is 10%～70%, preferably 30%; The volume ratio of the sacrificial agent aqueous solution is (15-30) mg:100 mL; the mass ratio of platinum element in the chloroplatinic acid solution to the titanium-based three-dimensional nano-organic complex is 0.2-0.5:25.

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