A rare earth-based mixed ligand photocatalyst and its preparation method and application

Abstract

The present invention discloses a rare earth-based mixed ligand photocatalyst, its preparation method and application. The preparation method of the photocatalyst includes the following steps: adding Dy(NO3)3, Co-TCPP, and H4TBAPy into a solvent to obtain a mixed solution, stirring the mixed solution at room temperature, then transferring it to a reactor with a polytetrafluoroethylene lining for heat preservation treatment, then cooling to room temperature, followed by centrifugation treatment. The obtained solid is washed successively with DMF, ethanol, and deionized water, and finally dried to obtain a khaki solid, which is the rare earth-based mixed ligand photocatalyst. The rare earth-based mixed ligand photocatalyst prepared by the present invention has a uniform spherical morphology and has very good catalytic activity and stability in the applications of photocatalytic water splitting for hydrogen production and photocatalytic carbon dioxide for carbon monoxide production. Moreover, the preparation method of the present invention is simple, has good practicability, and has very good application prospects.

Description

Technical Field

[0001] The invention relates to the field of photocatalysts, and in particular to a rare earth-based mixed ligand photocatalyst and a preparation method and application thereof. Background Art

[0002] As the demand for sustainable and efficient energy solutions continues to rise, research in the field of photocatalysis has seen unprecedented intense challenges. Photocatalytic process technologies have shown great promise in addressing various environmental issues and energy-related challenges. MOFs are a class of porous crystalline materials consisting of metal ions or metal clusters connected by organic linkers. They are characterized by high specific surface area, tunable pore size, and tailored functionality, which makes them ideal candidates for a wide range of applications, including gas storage, separation, and catalysis.

[0003] Ln-based metal MOFs have become a promising material in the research field due to their unique properties and multifunctional structures. However, relevant research is still immature, especially the catalytic activity needs to be improved. Therefore, how to find a coordination environment and organic ligand suitable for Ln-based metals to optimize photocatalytic activity and selectivity is the focus of current research. Summary of the invention

[0004] The main purpose of the present invention is to provide a rare earth-based mixed ligand photocatalyst having very good catalytic activity and stability in applications of photolysis of water to produce hydrogen and photocatalytic carbon dioxide reduction, as well as a preparation method and application thereof.

[0005] To achieve the above object, the present invention provides a method for preparing a rare earth-based mixed ligand photocatalyst, comprising the following steps:

[0006] Change Dy(NO 3 ) 3 、Co-TCPP、H 4 TBAPy is added to a solvent to obtain a mixed solution, the mixed solution is stirred at room temperature, and then transferred to a reactor with a tetrafluoroethylene liner for heat preservation, then cooled to room temperature, and then centrifuged. The obtained solid is washed with DMF, ethanol, and deionized water in sequence, and finally dried to obtain a yellowish brown solid, which is the rare earth-based mixed ligand photocatalyst.

[0007] Furthermore, Dy(NO 3 ) 3 、Co-TCPP、H 4 The molar mass ratio of TBAPy is 0.114 mmol:25 mg:10 mg.

[0008] Furthermore, the solvent and H 4The volume-to-mass ratio of TBAPy was 1 mL:1 mg, the solvent was a combination of ethanol and DMF, and the volume ratio of ethanol to DMF was 1:4.

[0009] Furthermore, the heat preservation treatment conditions are 80° C. and 24 h.

[0010] Furthermore, the drying conditions are vacuum, temperature 60° C., and time 12 h.

[0011] The present invention also provides a rare earth-based mixed ligand photocatalyst, which is prepared according to the above preparation method.

[0012] The present invention also provides the use of the rare earth-based mixed ligand photocatalyst in photolysis of water to produce hydrogen or photocatalytic reduction of carbon dioxide.

[0013] The present invention also provides a process for photolysis of water to produce hydrogen, comprising the following steps: adding a hole sacrificial agent, trisodium citrate, the above catalyst and H 2 PtCl 6 The solution was then degassed with a pump and stirred in a light-proof condition. Finally, a xenon lamp was turned on and the reaction was carried out at 6°C.

[0014] Further, water, hole sacrificial agent, trisodium citrate, catalyst and H 2 PtCl 6 The volume mass ratio of the solution is 50mL:400mg:54mg:10mg:15μL.

[0015] Furthermore, the hole sacrificial agent is selected from any one of EDTA-2Na, MeOH, and lactic acid, and the reaction pH value condition is 2-7.

[0016] The beneficial effects of the present invention are embodied in:

[0017] The rare earth-based mixed ligand photocatalyst prepared by the present invention has a uniform spherical morphology and has very good catalytic activity and stability in the applications of photolysis of water to produce hydrogen and photocatalytic carbon dioxide to produce carbon monoxide. The preparation method of the present invention is simple and practical, and has very good application prospects.

[0018] The rare earth-based mixed ligand photocatalyst prepared by the present invention has good catalytic performance under visible light and is suitable for a variety of sacrificial agents and acidic application conditions. The introduction of dual ligands can effectively promote photocatalysis and provide a better idea for the design of photocatalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1SEM and TEM images of Dy-Co TCPP&TBAPy catalyst, where (a)-(c) are SEM images of Dy-Co TCPP&TBAPy at different magnifications; (d) is the TEM image of Dy-Co TCPP&TBAPy.

[0020] Figure 2 This is a comparison chart of hydrogen production activity data of different rare earth-based single-ligand catalysts under visible light.

[0021] Figure 3 This is a comparison chart of hydrogen production activity data of different rare earth-based dual-ligand catalysts under visible light.

[0022] Figure 4 This is the hydrogen production activity diagram of Dy-Co TCPP&TBAPy under visible light with different hole sacrificial agents.

[0023] Figure 5 This is the activity diagram of Dy-Co TCPP&TBAPy for photolysis of water to produce hydrogen under different pH conditions under visible light.

[0024] Figure 6 (a) The photocatalytic activity of Dy-Co TCPP&TBAPy for hydrogen production under light sources of different wavelengths; (b) The cyclic stability experimental results of Dy-Co TCPP&TBAPy under visible light.

[0025] Figure 7 This is a data graph of the photocatalytic carbon dioxide reduction activity of different rare earth-based single-ligand catalysts.

[0026] Figure 8 This is a data graph of the photocatalytic carbon dioxide reduction activity of different rare earth-based dual-ligand catalysts. DETAILED DESCRIPTION

[0027] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0028] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or can be obtained by existing known methods; unless otherwise specified, the methods used in the examples of the present invention are methods known to those skilled in the art.

[0029] Example 1

[0030] Preparation of Co-TCPP

[0031] 8.12 g of methyl p-formylbenzoate and 4.21 g of pyrrole were added to 120 ml of propionic acid solution, refluxed at 130 ° C for 16 hours, the reaction mixture was cooled to room temperature, the precipitate was collected by filtration, and washed with methanol (MeOH), ethyl acetate and tetrahydrofuran (THF) in sequence, and then dried at 70 ° C and vacuum 0.09 MPa for 12 hours to obtain a dark purple solid, which was recorded as TPP-COOMe. Then 1.281 g of TPP-COOMe and 4.65 g of Co(NO 3 ) 2 6H 2 O was added to 100 mL of DMF solution and heated at 120 °C for 12 h. The reaction mixture was cooled to room temperature, 150 mL of deionized water was added, filtered and washed 3 times with deionized water to obtain dark red crystals, which were then dissolved in CHCl 3 After the solvent was removed by suspension evaporation, the remaining powder was dried at 70°C and vacuum degree 0.09 MPa for 12 hours to obtain a dark red powder, namely Co-TCPP.

[0032] Example 2

[0033] Preparation of rare earth-based mixed ligand photocatalysts

[0034] 0.114 mmol Dy(NO 3 ) 3 , 25 mg Co-TCPP, 10 mg H 4 TBAPy (1,3,6,8-tetrakis (p-benzoic acid) pyrene) was added to 8 mL of DMF solution containing 2 mL of ethanol to obtain a mixed solution. The mixed solution was stirred at room temperature (stirring speed 250 r / min) for 1 h, then transferred to a reactor with a tetrafluoroethylene liner and kept at 80°C for 24 h, then cooled to room temperature, and then centrifuged in a centrifuge at 15000 r / min. The obtained solid was washed three times with DMF, ethanol, and deionized water in sequence, and finally dried at a vacuum degree of 0.09 MPa and a temperature of 60°C for 12 h to obtain a khaki solid, which is a rare earth-based mixed ligand photocatalyst, denoted as Dy-Co TCPP&TBAPy.

[0035] Comparative Example 1

[0036] Based on the preparation method of Example 2, Dy(NO 3 ) 3 Eu(NO 3 ) 3 Ho(NO 3 ) 3 、Sm(NO3 ) 3 、Tb(NO 3 ) 3 By replacing the above catalysts, catalysts containing different lanthanide metals were obtained, which were respectively recorded as Eu-Co TCPP&TBAPy, Ho-Co TCPP&TBAPy, Sm-Co TCPP&TBAPy, and Tb-Co TCPP&TBAPy.

[0037] Comparative Example 2

[0038] Based on the preparation method of Example 2, H 4 TBAPy, the catalyst was prepared and recorded as Dy-Co TCPP. Further, H 4 TBAPy, and then Dy(NO 3 ) 3 Eu(NO 3 ) 3 Ho(NO 3 ) 3 、Sm(NO 3 ) 3 、Tb(NO 3 ) 3 The catalysts were prepared by replacement and were recorded as Eu-Co TCPP, Ho-Co TCPP, Sm-Co TCPP and Tb-Co TCPP respectively.

[0039] Structure determination of the catalyst

[0040] like Figure 1 The SEM and TEM analysis of Dy-Co TCPP&TBAPy catalyst is shown. It can be seen that Dy-Co TCPP&TBAPy has a uniform spherical morphology ( Figure 1 ac), and it can be observed that there is a scale-like structure on the surface of the ball. TEM verifies that the catalyst synthesized in the present invention is a solid ball ( Figure 1 d).

[0041] Determination of catalytic performance of catalysts

[0042] 1. Photolysis of water to produce hydrogen

[0043] In the photocatalytic reaction experiment, hole sacrificial agent, 54 mg trisodium citrate, 10 mg photocatalyst and 15 μL H were added to 50 mL water. 2 PtCl 6(0.1ωt%) solution, then degassed with a mechanical pump for 30 minutes, and then stirred (stirring speed 250r / min) for 30 minutes in a dark environment to reach adsorption-desorption equilibrium. After no bubbles were generated on the surface, the xenon lamp was turned on and the test was started. The temperature of the reaction system was controlled at 6°C by a water cooling system. The reaction product H was detected every half an hour by online gas chromatography. 2 , single illumination time is 4h.

[0044] By using different catalysts, different hole sacrificial agents, and adjusting different pH values, we verified the influence of metal elements on the catalytic performance of the material and the influence of hole sacrificial agents, pH and other conditions in the photolysis of water. The results are as follows:

[0045] A: The influence of different metal elements on the catalytic performance of materials

[0046] The wavelength of the light source is 400nm≤λ≤750nm. After replacing different catalysts of the same mass and irradiating for 4 hours, observe the corresponding H 2 The production rate is as follows Figure 2 and Figure 3 shown. Figure 2 The hydrogen production results of MOF materials formed by Ln metals and Co-TCPP are shown in Figure 2. It can be seen that Dy-Co TCPP has the highest hydrogen production activity, reaching 532.63 μmol g under 4 hours of illumination. -1 h -1 The second is Ho-Co TCPP, whose hydrogen production activity reaches 230.01 μmol g -1 h -1 ; Sm-CoTCPP produced 82.74 μmol g hydrogen in 4 hours. -1 h -1 .

[0047] At the same time, under the same test conditions, the mixed ligand catalyst was also tested, and the results were as follows Figure 3 It can be observed that the hydrogen production of Dy-Co TCPP&TBAPy was the highest under the condition of 4 h of illumination, reaching 971.43 μmol g -1 h -1 The second is Ho-Co TCPP&TBAPy, with a hydrogen production of 269.02 μmol g in 4 hours. -1 h -1 The third is Sm-Co TCPP&TBAPy with 115.57 μmol g -1 h -1 Based on the above test results, it can be found that the Dy-Co TCPP&TBAPy prepared in the present invention has the highest hydrogen production activity.

[0048] B: Effects of different sacrificial hole agents on the process of photolysis of water to produce hydrogen

[0049] The wavelength of the light source was 400nm≤λ≤750nm, and Dy-Co TCPP&TBAPy catalyst was used. By changing different hole sacrificial agents (400mg EDTA-2Na, 5ml methanol, 5ml lactic acid, 0.1M Na 2 S&Na 2 SO 3 , 5mlTEOA), and observe the hydrogen production effect. The results are as follows Figure 4 shown.

[0050] Figure 4 The results of hydrogen production of Dy-Co TCPP&TBAPy in different hole sacrificial agents show that Dy-CoTCPP&TBAPy performs well in hydrogen production in EDTA-2Na, MeOH, and lactic acid, with the hydrogen production amounts of 971.73 μmol g -1 h -1 , 896.56 μmol g -1 h -1 , 1163.25 μmol g -1 h -1 , and when TEOA, Na 2 S&Na 2 SO 3 As a hole sacrificial agent, the hydrogen production effect is poor, only 84.68 μmol g -1 h -1 , 60.12 μmol g -1 h -1 . Through the above experimental results, Dy-Co PMOF, Dy-Co TCPP&TBAPy can have a relatively good photocatalytic hydrogen production reaction in the three sacrificial agents of EDTA-2Na, MeOH, and lactic acid, among which lactic acid has the best effect. Because rare earth photocatalysts are most stable under acidic conditions, this can also be seen in the effect of pH on photocatalytic hydrogen production performance below. EDTA-2Na, MeOH, and lactic acid can still play the role of sacrificial agents under acidic conditions, while TEOA and Na 2 S&Na 2 SO 3 It is unstable under acidic conditions and cannot function as a sacrificial agent.

[0051] C: Effect of different pH values ​​on the process of photolysis of water to produce hydrogen

[0052] Lactic acid was used as the hole sacrificial agent, and the pH value of the initial solution (50 mL deionized water + 3 mL lactic acid) was measured by a pH meter to be 2.31. After that, 0.1 M HCL and 0.1 M NaOH were added dropwise to the solution to prepare a pH gradient of 1, 4, 7, 10, and 13, and then the catalyst and other raw materials were added. The wavelength of the light source was 400 nm ≤ λ ≤ 750 nm, and the photocatalytic hydrogen production experiment was carried out under the same conditions. The data results are as follows: Figure 5 shown.

[0053] Figure 5 The results of hydrogen production activity of Dy-Co TCPP&TBAPy under different pH conditions show that the hydrogen production activity of the catalyst is very low under pH = 1, which may be due to the strong acidic environment. The strong acidic environment has a certain inhibitory effect on the hydrogen production performance of the catalyst. With the gradual addition of NaOH, the pH value increases, and the hydrogen production is gradually reduced. For example, when pH = 4, the hydrogen production of Dy-Co TCPP&TBAPy is 674.56 μmol g -1 h -1 When pH = 7, the hydrogen production of Dy-Co TCPP&TBAPy is 503.04 μmol g -1 h -1 . When pH>7, the hydrogen production activity is greatly reduced, which may be due to the fact that Ln-based MOF materials are easily decomposed under alkaline conditions and their structures are easily destroyed. In summary, after comparing the results, the Dy-Co TCPP&TBAPy catalyst has a better effect when pH=2.31, that is, only lactic acid is added as a hole sacrificial agent without additionally changing the pH value.

[0054] D: Effects of different lighting conditions on the process of photolysis of water to produce hydrogen

[0055] like Figure 6 As shown in (a), the catalytic activity of Dy-Co TCPP&TBAPy catalyst under ultraviolet light (200nm≤λ≤750nm) irradiation has increased compared with that under visible light irradiation. The hydrogen generation rate of Dy-Co TCPP&TBAPy in four hours is 1298.95μmol g -1 h -1 However, since the ultraviolet light emitted by the xenon lamp used in the experiment is unstable and the light intensity is not high, the results obtained may be somewhat accidental and cannot be used as a quantitative reference standard. Therefore, a 400nm cut-off filter is finally used to process the light source to ensure that the light source emitted during the illumination process is visible light with a wavelength range of 400nm≤λ≤750nm.

[0056] Figure 6(b) is the cyclic stability experimental test diagram of Dy-Co TCPP&TBAPy catalyst. It can be found that during 16 hours of continuous illumination, the catalytic activity of the catalyst remains stable, thus verifying that the photocatalyst has a certain light stability and will not cause photocorrosion and molecular decomposition under light conditions.

[0057] 2. Photocatalytic carbon dioxide reduction reaction experiment

[0058] In the photocatalytic reaction experiment, 25 mL of H 2 O, 3 mL lactic acid, 10 mg photocatalyst and 15 μL 0.1 M HO 2 PtCl 6 Then use a mechanical pump to degas for 30 minutes, and when no bubbles are generated on the surface, fill with CO 2 The gas was stirred until the pressure reached 0.3 atm. The solution was stirred for 30 min in a dark environment to reach adsorption-desorption equilibrium. The xenon lamp (light source wavelength 400nm≤λ≤750nm) was turned on and the test was started. The temperature of the reaction system was controlled at about 6°C by a water cooling system. 2 During the reduction test, the products (CO, CH 4 ), single illumination time is 4h.

[0059] When other conditions remain unchanged, the type of catalyst is changed, and the reaction results are as follows Figure 7 and Figure 8 shown. Figure 7 The amount of carbon monoxide generated in the carbon dioxide reduction of the MOF material formed by Ln metal and Co-TCPP can be observed that this series of catalysts has a 2 The effect of the reduction reaction was not very ideal. In parallel comparison, the carbon monoxide production rate of Dy-Co TCPP reached 26.61 μmol g in seven hours. -1 h -1 , while the CO production rates of other catalysts were all below 10 μmol g - 1 h -1 The generation rate is too small to be compared.

[0060] Figure 8 The data results of the mixed ligand catalyst for reducing carbon dioxide show that the CO production rate increased significantly. The most active Dy-Co TCPP&TBAPy has a CO production rate of 87.43 μmol g in seven hours. -1 h -1 The carbon monoxide production rate of Eu-Co TCPP&TBAPy reached 23.94 μmol g-1 h -1 .

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a rare earth-based mixed ligand photocatalyst, characterized in that: The following steps are involved: Dy(NO3)3, Co-TCPP and H4TBAPy are added to a solvent to obtain a mixed solution. The mixed solution is stirred at room temperature and then transferred to a reactor with a tetrafluoroethylene lining for heat preservation. The mixture is then cooled to room temperature and centrifuged. The solid is washed with DMF, ethanol and deionized water in sequence and finally dried to obtain a yellowish brown solid, which is the rare earth-based mixed ligand photocatalyst.

2. The method for preparing the rare earth-based mixed ligand photocatalyst according to claim 1, characterized in that: The molar mass ratio of Dy(NO3)3, Co-TCPP, and H4TBAPy is 0.114mmol:25mg:10mg.

3. The method for preparing the rare earth-based mixed ligand photocatalyst according to claim 1, characterized in that: The volume mass ratio of the solvent to H4TBAPy is 1 mL:1 mg, the solvent is a combination of ethanol and DMF, and the volume ratio of ethanol to DMF is 1:

4.

4. The method for preparing the rare earth-based mixed ligand photocatalyst according to claim 1, characterized in that: The conditions for the heat preservation treatment are a temperature of 80°C and a time of 24 hours.

5. The method for preparing the rare earth-based mixed ligand photocatalyst according to claim 1, characterized in that: The drying conditions were vacuum, temperature 60°C, and time 12 h.

6. A rare earth-based mixed ligand photocatalyst, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the rare earth-based mixed ligand photocatalyst as claimed in claim 6 in photocatalytic water splitting to produce hydrogen or photocatalytic carbon dioxide reduction.

8. A process for producing hydrogen by photolysis of water, characterized in that: The following steps are involved: Add a hole sacrificial agent, trisodium citrate, the catalyst as described in claim 6 and H2PtCl6 solution to water, then degas with a pump, stir under light-proof conditions, and finally turn on a xenon lamp to react at 6°C.

9. The process for producing hydrogen by photolysis of water as claimed in claim 8, characterized in that: The volume mass ratio of water, hole sacrificial agent, trisodium citrate, catalyst and H2PtCl6 solution is 50mL:400mg:54mg:10mg:15μL.

10. The process for producing hydrogen by photolysis of water as claimed in claim 8 or 9 is characterized in that the hole sacrificial agent is selected from any one of EDTA-2Na, MeOH and lactic acid, and the reaction pH value condition is 2-7.

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