Metal-loaded mesoporous cerium-based MOFs, and preparation method and application thereof

Abstract

The application discloses a metal-loaded mesoporous cerium-based MOF as well as a preparation method and application thereof. A soft template is used as a template agent, and mesoporous cerium-based MOFs are prepared after constant-temperature warm water bath stirring, and ball milling is performed using a metal for loading. The metal-loaded mesoporous cerium-based MOFs prepared by the application have excellent photocatalytic carbon dioxide reduction to carbon monoxide performance. In an acetonitrile system, using triethylamine as a sacrificial agent and chlorotris(2,2'-bipyridine)ruthenium(II) as a photosensitizer, the metal-loaded mesoporous cerium-based MOFs can convert carbon dioxide into carbon monoxide, and the highest catalytic conversion rate can reach 313.4 mu mol.g ‑1 ·h ‑1 .

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalytic materials and nanomaterials, and particularly relates to a metal-loaded mesoporous cerium-based MOF as well as a preparation method and application thereof. BACKGROUND

[0002] Carbon dioxide is a greenhouse gas, and its emission is a byproduct of human activities, including energy production, transportation, industrial production, etc. These emissions released into the atmosphere will block the heat from the earth's surface from being dissipated outward, resulting in rising temperatures.

[0003] Metal organic framework materials or metal organic framework materials (Metal Organic Frameworks, abbreviated as MOFs) are an important classification of new materials in metal organic materials (MOM), and MOFs are composed of one-dimensional, two-dimensional or three-dimensional structures of metal atoms or atomic clusters coordinated by organic coordination bonds. MOFs are widely used, such as hydrogen storage, material separation, selective catalysis, carbon dioxide capture catalysis, etc. Although MOFs can be synthesized in various pore sizes, most MOFs have small pores in the micropore range (<2nm), but small pore size limits the entry of substrates and mass transfer in the framework. Therefore, it is very important to develop metal organic framework materials with larger pores.

[0004] Cerium is a silver-white, lustrous metal with high photoelectrochemical reactivity. Cerium is widely used in various fields, and almost all rare earth application fields contain cerium. The carbon dioxide catalytic reduction performance of cerium has been widely studied, and EeTeng Kho team uses light radiation to initiate a heating effect in a catalyst bed loaded with nickel to promote the conversion of CO2, and studies the influence of cerium oxide-titanium oxide composite oxides with different compositions on the photo-thermal catalytic conversion of CO2.

[0005] In recent years, metal organic framework (MOFs) as a carrier, and then through metal loading to form a high-efficiency synergistic catalyst has become an effective method. The high porosity and uniform doping characteristics of mesoporous MOFs can be well inherited in the synergistic catalyst, thereby showing excellent catalytic performance. Therefore, how to combine MOFs and metals to prepare a material with high catalytic performance is a technical problem that those skilled in the art need to solve. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a metal-loaded mesoporous cerium-based MOF and a preparation method thereof.

[0007] The specific technical solutions are as follows:

[0008] A preparation method of a metal-loaded mesoporous cerium-based MOF, comprising the following steps:

[0009] 1) adding a soft template agent into water to stir and dissolve, then adding acetic acid and sodium perchlorate to obtain a mixed solution;

[0010] 2) adding cerium ammonium nitrate and terephthalic acid into the mixed solution of step 1) and stirring to react under the condition of a constant-temperature water bath, then centrifuging, washing, soaking in ethanol, centrifuging and drying the obtained reaction product to obtain mesoporous cerium-based MOFs;

[0011] 3) putting the mesoporous cerium-based MOFs obtained in step 2) and a metal compound into a ball mill to obtain metal-loaded mesoporous cerium-based MOFs by ball milling.

[0012] Further, the soft template agent in step 1) is polyoxyethylene-polyoxypropylene ether copolymer or polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer.

[0013] Further, the mass ratio of the soft template agent, acetic acid, water, sodium perchlorate, cerium ammonium nitrate and terephthalic acid is 100-800:1:20-50:1000-3500:1000-3500:400-1400.

[0014] Further, the stirring temperature in step 2) is 50-80℃, the stirring time is 15-40min and the stirring speed is 500-1000rpm.

[0015] Further, the soaking in step 2) is soaking under stirring, the temperature is 50-70℃, the time is 24-48h and the stirring speed is 500-1000rpm.

[0016] Further, the metal compound in step 3) is cobalt chloride hexahydrate, iron chloride hexahydrate, nickel chloride hexahydrate or copper chloride dihydrate, preferably cobalt chloride hexahydrate.

[0017] Further, the loading mass fraction of the metal in the metal compound on the mesoporous cerium-based MOFs is 0.25%-1.5%, the ball milling speed is 500-1000rpm and the time is 4-8h.

[0018] A metal-loaded mesoporous cerium-based MOFs prepared by the above preparation method, the specific surface area of which is 90-150m 2 / g, the pore volume is 0.1-0.2cc / g and the pore size is 2-10nm.

[0019] The application of a metal-loaded mesoporous cerium-based MOFs in photocatalytic reduction of carbon dioxide.

[0020] The application has the following beneficial effects:

[0021] The metal-loaded mesoporous cerium-based MOFs prepared by the application have excellent photocatalytic performance in reducing carbon dioxide into carbon monoxide, and the catalytic conversion rate can reach 313.4 μmol·g -1 ·h -1 . BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A scanning electron microscope (SEM) image of the metal-loaded mesoporous cerium-based MOFs prepared in Example 1;

[0023] Figure 2 A BET graph of the metal-loaded mesoporous cerium-based MOFs prepared in Example 1. DETAILED DESCRIPTION

[0024] The application will be further described below in conjunction with the accompanying drawings and examples, but the scope of protection of the application is not limited thereto.

[0025] Example 1

[0026] (1) 100 mg of polyoxyethylene-polyoxypropylene ether copolymer was added to 10 mg of deionized water and stirred to dissolve, then 0.3 mg of acetic acid and 500 mg of sodium perchlorate were added and stirred uniformly to obtain a mixed solution;

[0027] (2) 500 mg of cerium ammonium nitrate and 200 mg of terephthalic acid were added to the above mixed solution, and the reaction was carried out under the condition of a constant temperature water bath at 60°C with stirring at 500 rpm for 30 min. The obtained product was centrifuged and washed with DMF for 3 times, then was immersed in ethanol at a speed of 500 rpm and a temperature of 60°C for 24 h. After centrifugation, the product was dried in a vacuum drying oven at a temperature of 60°C for 24 h to obtain mesoporous cerium-based MOFs;

[0028] (3) 10 mg of cobalt chloride hexahydrate and 1000 mg of mesoporous MOFs were put into a ball mill and ball-milled at a speed of 800 rpm for 4 h to obtain cobalt metal-loaded mesoporous cerium-based MOFs, and the metal loading amount was 0.25%.

[0029] As can be seen from Figure 1 , the cerium-based MOFs exhibit a specific regular crystal shape, and there are many interpenetrating pores on the surface. As can be seen from Figure 2 , there is a clear mesoporous hysteresis ring, which confirms that it is a mesoporous material. The specific surface area is 115 m 2 / g, the pore volume is 0.15 cc / g, and the average pore size is 4 nm.

[0030] Example 2

[0031] The experimental operation process is the same as that of Example 1, except that the metal compound added in step 3) is iron chloride hexahydrate, and the loading amount is 0.25%.

[0032] Example 3

[0033] The experimental operation process is the same as that of Example 1, except that the metal compound added in step 3) is nickel chloride hexahydrate, and the loading amount is 0.25%.

[0034] Example 4

[0035] The experimental operation process is the same as that of Example 1, except that the metal compound added in step 3) is copper chloride dihydrate, and the loading amount is 0.25%.

[0036] Example 5

[0037] The experimental operation process is the same as that of Example 1, except that the metal compound added in step 3) is cobalt chloride hexahydrate, and the loading amount is 0.125%.

[0038] Example 6

[0039] The experimental operation process is the same as that of Example 1, except that the metal compound added in step 3) is cobalt chloride hexahydrate, and the loading amount is 0.5%.

[0040] Example 7

[0041] The metal-loaded mesoporous cerium-based MOFs prepared in Examples 1-6 were respectively added to a photocatalytic reaction device, 10 ml of acetonitrile was added as a solvent, 3 mg of tris(2,2'-bipyridine)ruthenium(II) chloride was added as a photosensitizer, and 1 ml of triethanolamine was added as a sacrificial agent. Carbon dioxide was continuously introduced for 10 min, and then the solution was allowed to stand for 30 min to reach saturation of carbon dioxide concentration. Finally, the photocatalytic reaction device was placed under a xenon lamp for irradiation for 2 hours. Then, 1 ml of gas in the photocatalytic reaction device was extracted using a needle tube for gas chromatography detection. The conversion rate of carbon dioxide to carbon monoxide is shown in Table 1.

[0042] Table 1 Performance summary table of metal-loaded mesoporous cerium-based MOFs prepared in Examples 1-6

[0043]

[0044] From Table 1, it can be seen that the four metal-loaded cerium-based MOFs all exhibit certain CO2 catalytic reduction performance, among which the catalytic conversion rate of cobalt-loaded material is significantly better than that of the other three metals. In addition, the different loading amounts of cobalt also lead to differences in performance, and the cobalt loading amount of 0.25% exhibits the best performance.

Claims

1. A method for preparing metal-supported mesoporous cerium-based MOFs, characterized in that, Includes the following steps: 1) Add the soft template agent to water and stir to dissolve, then add acetic acid and sodium perchlorate to obtain a mixed solution; 2) Add cerium ammonium nitrate and terephthalic acid to the mixed solution in step 1), and stir the reaction under constant temperature water bath conditions. After centrifugation and washing, the reaction product is soaked in ethanol, centrifuged and dried to obtain mesoporous cerium-based MOFs. 3) The mesoporous cerium-based MOFs and metal compounds obtained in step 2) are placed in a ball mill and ball milled to obtain metal-loaded mesoporous cerium-based MOFs; The metal compounds are cobalt chloride hexahydrate, ferric chloride hexahydrate, nickel chloride hexahydrate, or copper chloride dihydrate; The mass fraction of metal in the metal compound loaded on mesoporous cerium-based MOFs is 0.25%-1.5%, and the ball milling speed is 500-1000 rpm for 4-8 hours.

2. The preparation method according to claim 1, characterized in that, The soft template agent mentioned in step 1) is a polyoxyethylene-polyoxypropylene ether copolymer or a polyoxyethylene-polyoxypropylene-polyoxyethylene triblock polymer.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the soft template agent, acetic acid, water, sodium perchlorate, cerium ammonium nitrate and terephthalic acid is 100-800:1:20-50:1000-3500:1000-3500:400-1400.

4. The preparation method according to claim 1, characterized in that, The stirring reaction in step 2) is carried out at a temperature of 50-80℃ for 15-40 minutes and at a stirring speed of 500-1000 rpm.

5. The preparation method according to claim 1, characterized in that, Step 2) The soaking is carried out under stirring, at a temperature of 50-70℃, for a time of 24-48 hours, and at a stirring speed of 500-1000 rpm.

6. A metal-supported mesoporous cerium-based MOF prepared by the preparation method described in claim 1, characterized in that, Its specific surface area is 90-150 m². 2 / g, pore volume is 0.1-0.2cc / g, pore size is 2-10nm.

7. The application of the metal-supported mesoporous cerium-based MOFs as described in claim 6 in the photocatalytic reduction of carbon dioxide.

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