A method for preparing a metal-organic framework-coated Cs 3 Bi 2 Br 9 nanocrystal

Abstract

The present invention discloses a preparation method and application of a metal-organic framework encapsulated all-inorganic perovskite. The preparation method includes the following steps: First, UiO-66 material is prepared by a simple solvothermal method, and then the prepared UiO-66 is mixed with oleic acid, oleylamine, octadecene, and BiBr 3 powder, and a Cs 3 Bi 2 Br 9 nanocrystal composite material encapsulated with UiO-66 is prepared by a thermal injection method. The present invention utilizes the stability and porosity of the UiO-66 material to nucleate and crystallize perovskite quantum dots in its pores, which not only improves the environmental stability of Cs 3 Bi 2 Br 9 nanocrystals, but also enriches the pore structure of the UiO-66 material. The prepared composite material is used for visible light water splitting application, and the results show that its H 2 generation rate is as high as 1054.2 μmol·g ‑1 ·h ‑1 , showing high catalytic activity. This invention is expected to be applied in the field of photocatalytic water splitting for hydrogen production.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite material preparation, and particularly relates to a preparation method of a metal-organic framework encapsulated organic-inorganic perovskite composite material. Background Art

[0002] Metal halide perovskites, such as CsPbX 3 (X = Cl, Br, I), have been widely studied in optoelectronic fields such as solar cells, light-emitting diodes, and photodetectors due to their advantages such as tunable bandgap, long carrier lifetime, large absorption coefficient, and high mobility. Considering these advantages, metal halide perovskites have developed into a new type of photocatalytic material in recent years and achieved remarkable results. Unfortunately, the inherent toxicity of lead elements and the sensitivity of these perovskite materials to light, heat, and humidity have hindered the large-scale production and commercialization of such materials. All-inorganic bismuth-based halide perovskites (Cs 3 Bi 2 X 9 , X = Cl, Br, I,) have become a remarkable class of semiconductor materials to replace lead-based halide perovskites due to their low toxicity. Bi 3+ has an electronic structure similar to that of Pb 2+ (6s 2 6p 0 ), and Bi 3+ has a more stable valence state compared to Sn 2+ , Ge 2+ . However, as a perovskite quantum dot material, long-term physicochemical stability is also a fatal problem, further restricting its further application in optoelectronics and photocatalysis. To improve the stability of perovskite quantum dots, many encapsulation methods have been proposed. For example, polymers and silica are used for coating to prevent the intrusion of moisture and polar solvents, thereby improving stability. However, this strategy not only leads to a decrease in the carrier transport efficiency of the host material but also inhibits the contact between the reactants and the material.

[0003] Metal-organic framework (MOF) materials, also known as porous coordination polymers, are three-dimensional porous materials with a periodic network structure, which are formed by connecting metal ions (or metal clusters) and organic ligands through coordination bonds. MOF materials have advantages such as large specific surface area, orderly adjustable porous structure, high porosity, and surface functional groups that can be modified, making them widely used in gas adsorption and separation, optoelectronics, catalysis, and other fields. Therefore, MOFs can be used as a good template for encapsulating perovskite nanocrystals, which can improve the stability of perovskite nanocrystals while avoiding the aggregation of nanoparticles. However, this also poses requirements for the MOF materials themselves, such as their stability not being affected by factors such as moisture, temperature, and environmental humidity.

[0004] In summary, the research dedicated to achieving the encapsulation of perovskite nanocrystals with metal-organic framework materials is required by the current situation of materials research and is also for realizing potential applications in the catalytic field. Summary of the Invention

[0005] To solve the problems existing in the prior art, we have invented a method for preparing metal-organic framework-coated Cs 3 Bi 2 Br 9 nanocrystals, which ensures green and non-toxic materials while also improving the stability of perovskite nanocrystals. The present invention realizes the encapsulation of perovskite nanocrystals in two steps, specifically including the following steps:

[0006] (1) Preparation of metal-organic framework UiO-66: Dissolve 0.2330 g of zirconium chloride and terephthalic acid in 50 mL of DMF, 6 mL of acetic acid, and 0.5 mL of deionized water, heat and stir under sealed conditions, and then cool to room temperature. Centrifuge and wash the solution three times with a mixed solution of DMF and methanol, and finally dry and collect the powder.

[0007] (2) Preparation of cesium oleate precursor: Load 1.628 g of Cs 2 CO 3 , 5 mL of OA, and 20 mL of ODE into a 100 mL three-necked flask, dry under 120 °C and N 2 atmosphere for 60 minutes, and then continue to heat up to 150 °C until all Cs 2 CO 3 reacts fully.

[0008] (3) Preparation of Cs 3 Bi 2 Br 9 @UiO-66 composite material: Load 0.1687 g of BiBr 3 , 1 mL of OA, 1 mL of OLA, 10 mL of ODE, 0.05 mL of HBr, and 0.25 g of UiO-66 into a 100 mL three-necked flask, dry under vacuum at 120 °C for 60 minutes, and then continue to heat up to 200 °C. At this time, quickly inject 0.8 mL of Cs-OA under vigorous stirring, and after 5 seconds, quickly cool the reaction mixture to below 50 °C by means of an ice-water bath. Obtain the precipitate by centrifugal washing, and finally dry it in an oven to obtain Cs 3 Bi 2 Br 9 @UiO-66 powder.

[0009] Furthermore, in step (1), the heating temperature is 120 °C and the time is 3 h. The ratio of the mixed solution of DMF and methanol is 1:1.

[0010] Furthermore, in step (1), the centrifugation conditions are a speed of 10,000 r / min and a centrifugation time of 5 min. The drying time is 12 h and the drying temperature is 60 °C.

[0011] Furthermore, in step (2), Cs 2 CO 3 The phenomenon of sufficient reaction is that the solution is transparent and golden yellow.

[0012] Furthermore, in step (3), the washing organic solvent used is n-hexane and the number of washing times is three. The centrifugation conditions are a speed of 7,000 r / min and a centrifugation time of 5 min. The drying time is 12 h and the drying temperature is 60 °C.

[0013] Compared with the existing technology, the present invention has the following beneficial effects:

[0014] To solve the toxicity and stability problems of metal halide perovskite nanocrystals, the present invention synthesizes lead-free Cs 3 Bi 2 Br 9 nanocrystals, which have the characteristics of simple preparation process and low cost. The present invention also uses the porous crystal material UiO-66 with good stability as a template to encapsulate Cs 3 Bi 2 Br 9 nanocrystals. By virtue of the specific surface area and porosity of the UiO-66 material, Cs 3 Bi 2 Br 9 nanocrystals are nucleated and crystallized inside it. This not only ensures the stability of the nanocrystals but also avoids problems such as low photogenerated carrier transport efficiency caused by aggregation. Finally, the composite material is used for photocatalytic carbon dioxide reduction, realizing the preparation and production of high-value-added organic substances, and having broad application prospects in the field of photocatalysis. Description of the Drawings

[0015] Figure 1 is the XRD pattern of the UiO-66 material prepared in Example 1.

[0016] Figure 2 is the XRD pattern of the Cs 3 Bi 2 Br 9 @UiO-66 composite material prepared in Example 2.

[0017] Figure 3is Cs prepared in Example 2 3 Bi 2 Br 9 TEM spectrum of the @UiO-66 composite material.

[0018] Figure 4 are the UiO-66 materials and Cs prepared in Example 1 and Example 2 3 Bi 2 Br 9 Absorption spectrum of the @UiO-66 composite material.

[0019] Figure 5 is a comparison chart of the photocatalytic hydrogen production rates of the materials prepared in Example 1 and Example 2 under visible light irradiation. Detailed implementation manners

[0020] The present invention will be further described in detail below in conjunction with the specific implementation manners, but the protection scope of the present invention

[0021] is not limited to the above content.

[0022] Example 1: A preparation method of metal-organic framework-coated Cs 3 Bi 2 Br 9 nanocrystals, the specific steps are as follows:

[0023] Dissolve 0.2330 g of zirconium chloride and terephthalic acid in 50 mL of DMF, 6 mL of acetic acid, and 0.5 mL of deionized water. Heat and stir at 120 °C for 3 h under sealed conditions, and then cool to room temperature. The obtained solution was centrifugally washed three times with a mixed solution of DMF and methanol (the ratio of the two is 1:1) at a centrifugal speed of 1000 rpm for 5 min. Finally, it was placed in an oven at 60 °C and dried for 12 h to collect the powder.

[0024] Example 2: A preparation method of metal-organic framework-coated Cs 3 Bi 2 Br 9 nanocrystals, the specific steps are as follows:

[0025] (1) Prepare the cesium oleate precursor: Put 1.628 g of Cs 2 CO 3 , 5 mL of OA and 20 mL of ODE into a 100 mL three-necked flask, dry at 120 °C and N 2 atmosphere for 60 minutes, and then continue to heat up to 150 °C until all Cs 2 CO 3 fully reacts, and the solution is transparent and golden yellow at this time.

[0026] (2)Cs 3 Bi 2 Br 9 @UiO-66 composite material preparation: Load 0.1687 g of BiBr 3 , 1 mL of OA, 1 mL of OLA, 10 mL of ODE, 0.05 mL of HBr, and 0.25 g of UiO-66 into a 100 mL three-necked flask, dry it under vacuum at 120 °C for 60 minutes, and then continue to heat up to 200 °C. At this time, quickly inject 0.8 mL of Cs-OA under vigorous stirring. After timing for 5 seconds, quickly cool the reaction mixture solution to below 50 °C through an ice-water bath. Wash the precipitate collected by centrifugation three times with n-hexane (centrifugation speed: 7000 r / min, time: 5 min), and finally place it in an oven to dry at 60 °C for 12 h to obtain Cs 3 Bi 2 Br 9 @UiO-66 powder.

[0027] Figure 1 is the XRD pattern of the pure-phase UiO-66 material synthesized in Example 1. It can be seen from the figure that UiO-66 has good crystallinity, strong diffraction intensity, and complete correspondence with the simulated diffraction peaks, indicating that the UiO-66 material has been successfully synthesized.

[0028] Figure 2 is the XRD pattern of the Cs 3 Bi 2 Br 9 @UiO-66 composite material synthesized in Example 2. It can be seen that the diffraction peaks of the composite material match well with the XRD spectra of the simulated UiO-66 and Cs 3 Bi 2 Br 9 standard cards, which also indicates that the growth process of Cs 3 Bi 2 Br 9 has not changed the structure of UiO-66.

[0029] Figure 3 is the TEM pattern of the Cs 3 Bi 2 Br 9 @UiO-66 composite material synthesized in Example 2. It can be seen from the figure that the octahedral morphology of UiO-66 is well maintained. The small particles distributed on UiO-66 are Cs 3 Bi 2 Br 9 nanocrystals, proving Cs 3 Bi 2 Br 9entered the pores of UiO-66.

[0030] Figure 4 is Cs prepared in Example 2 3 Bi 2 Br 9 @UiO-66 composite material. As can be seen from the figure, after introducing Cs 3 Bi 2 Br 9 the absorption edge in the visible light region redshifts from 300 nm to 550 nm. The redshift indicates that the synthesized composite material has excellent light absorption ability.

[0031] Figure 5 is a comparison chart of the photocatalytic hydrogen production rates of the materials prepared in Example 1 and Example 2 under visible light irradiation. It can be seen that the hydrogen production rate of Cs 3 Bi 2 Br 9 is 827.6 μmol g -1 h -1 , while after encapsulating it, the hydrogen production rate of Cs 3 Bi 2 Br 9 @UiO-66 composite material is 1054.2 μmol g -1 h -1 , indicating that the introduction of UiO-66 improves the stability of Cs 3 Bi 2 Br 9 and thus enhances the hydrogen production performance.

[0032] Finally, it should be noted that the above is only the preferred embodiment of the present invention. For those skilled in the art and subsequent applications and production, without departing from the principle of the present invention's patent technology, some improvements and optimizations can be made, which are still regarded as the protection scope of the present invention's patent technology.

Claims

1. Application of a metal-organic framework-coated Cs 3 Bi 2 Br 9 nanocrystalline composite material in hydrogen production by water decomposition under visible light radiation, and the preparation method of the composite material comprises the following steps: (1) Preparation of metal-organic framework UiO-66: Dissolve 0.2330 g of zirconium chloride and terephthalic acid in 50 mL of dimethylformamide (DMF), 6 mL of acetic acid, and 0.5 mL of deionized water. Heat and stir under sealed conditions, then cool to room temperature. Centrifuge and wash the solution three times with a mixed solution of DMF and methanol, and finally dry and collect the powder; (2) Preparation of cesium oleate precursor Cs-OA: 1.628 g of Cs 2 CO 3 , 5 mL of oleic acid and 20 mL of octadecene were loaded into a 100 mL three-necked flask, dried at 120 °C under N 2 atmosphere for 60 minutes, and then the temperature was further raised to 150 °C until all Cs 2 CO 3 reacted fully; (3)Cs 3 Bi 2 Br 9 Preparation of Cs@UiO-66 composite material: 0.1687 g of BiBr 3 , 1 mL of oleic acid, 1 mL of oleylamine, 10 mL of octadecene, 0.05 mL of hydrobromic acid and 0.25 g of UiO-66 were loaded into a 100 mL three-necked flask, dried under vacuum at 120 °C for 60 minutes, and then the temperature was further raised to 200 °C; at this time, 0.8 mL of Cs-OA was rapidly injected under vigorous stirring. After 5 seconds of timing, the reaction mixture solution was quickly cooled to below 50 °C by an ice-water bath; the precipitate was obtained by centrifugal washing and finally dried in an oven to obtain Cs 3 Bi 2 Br 9 @UiO-66 powder.

2. The application according to claim 1, characterized in that: in step (1), the heating temperature is 120 °C and the time is 3 h; the ratio of the DMF and methanol mixed solution is 1:

1.

3. The application according to claim 1, characterized in that: in step (1), the centrifugation conditions are a speed of 10,000 r / min and a centrifugation time of 5 min, the drying time is 12 h, and the drying temperature is 60 °C.

4. The application according to claim 1, characterized in that: in step (3), the washing is carried out with n-hexane, the number of washing times is three, the centrifugation conditions are a speed of 7000 r / min and a centrifugation time of 5 min, the drying time is 12 h, and the drying temperature is 60 °C.

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