A TiO2 / Cu-Yb MOF composite photocatalyst, its preparation method and application

Abstract

This invention relates to a TiO2 / Cu-Yb MOF composite photocatalyst, its preparation method, and its application. The preparation method includes the following steps: S1, introducing copper salt and ytterbium salt into TCPP in a sequential manner through heating reaction to obtain Cu-Yb MOF powder; S2, preparing Cu-Yb MOF powder into Cu-Yb MOF dispersion, adding a heat-treated ethanol solution of tetrabutyl titanate to the Cu-Yb MOF dispersion, stirring and heating, cooling, washing, and centrifuging to obtain an intermediate; S3, preparing the intermediate into an intermediate dispersion, and solvothermal composite to obtain the TiO2 / Cu-Yb MOF photocatalyst, completing the reaction. Compared with the prior art, the TiO2 / Cu-Yb MOF composite photocatalyst prepared by this invention has higher photodynamic and photocatalytic activity, and can effectively solve the problem of easy electron-hole recombination.

Description

Technical Field

[0001] This invention relates to the field of photocatalytic hydrogen production technology, and in particular to a TiO2 / Cu-Yb MOF composite photocatalyst, its preparation method, and its application. Background Technology

[0002] Solar energy, with its advantages of being environmentally friendly and inexpensive, has become a recognized renewable energy source with broad application prospects. Currently, it is widely believed that using solar energy to decompose water into hydrogen is one of the effective ways to solve the energy crisis.

[0003] In 1972, Fujishima et al. experimentally demonstrated that titanium dioxide (TiO2) semiconductors could act as photocatalysts to decompose water and produce hydrogen under ultraviolet light irradiation, a study that greatly interested researchers. Since then, hydrogen evolution technology using semiconductors as photocatalysts has received widespread attention, and many materials, including metal oxides, metal-organic frameworks (MOFs), and carbon nitride, have been applied to photocatalysis. However, traditional photocatalysts face problems such as poor light absorption, low chemical stability, and particularly poor electron-hole separation capabilities, leading to a demand for next-generation photocatalysts.

[0004] Patent publication number CN109482241A discloses a TiO2 / MOF-5 photocatalyst and its preparation method. The preparation method of the TiO2 / MOF-5 photocatalyst includes the following steps: providing MOF-5 material; preparing a mixed solution of ethanol and water, and adjusting the pH to 2-4 to obtain a first solution; mixing tetrabutyl titanate, glacial acetic acid, and ethanol to form a second solution; adding MOF-5 material to the second solution to obtain a third solution; adding the first solution to the third solution and stirring evenly; filtering; aging the obtained filtrate, drying, and calcining to obtain the TiO2 / MOF-5 photocatalyst. However, in this method, the TiO2 / MOF-5 photocatalyst obtained by calcination is prone to agglomeration due to excessively high local TiO2 concentration, resulting in uneven TiO2 distribution and low photocatalytic activity. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing a TiO2 / Cu-YbMOF composite photocatalyst, its preparation method, and its application. The prepared TiO2 / Cu-Yb MOF composite photocatalyst has higher photodynamic and photocatalytic activity, and can effectively solve the problem of easy electron-hole recombination.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of this invention is to provide a method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst, comprising the following steps:

[0008] S1. Copper salt and ytterbium salt are introduced into tetra(4-carboxyphenyl)porphyrin (TCPP) in sequence by heating reaction to obtain Cu-Yb MOF powder;

[0009] S2. Cu-Yb MOF powder was prepared into Cu-Yb MOF dispersion. After heat treatment of the ethanol solution of tetrabutyl titanate, it was added to the Cu-Yb MOF dispersion, stirred and heated, cooled, washed and centrifuged to obtain the intermediate.

[0010] S3. The intermediate is prepared into an intermediate dispersion, and then solvothermal composite is used to obtain the TiO2 / Cu-Yb MOF photocatalyst. The reaction is complete.

[0011] Further, in step S1, the preparation process of the Cu-Yb MOF powder specifically involves: dissolving TCPP in an organic solvent, heating to 100–150°C, stirring and heating, adding an organic solvent containing copper salt, refluxing at 100–150°C, adding an organic solvent containing ytterbium salt, continuing refluxing at 110–160°C, cooling to room temperature, washing, centrifuging, and drying to obtain Cu-Yb MOF. Ytterbium metal ions form the MOF network structure with metal nodes.

[0012] Furthermore, the mass ratio of the copper salt, ytterbium salt, and TCPP is 6–10:6–10:3;

[0013] The mass-to-volume ratio of the copper salt to the organic solvent is 7.5–12.5 mg / ml;

[0014] The copper salt is copper chloride (CuCl2);

[0015] The ytterbium salt is ytterbium nitrate (Yb(NO3)3);

[0016] The organic solvent is N,N-dimethylformamide (DMF).

[0017] Furthermore, TCPP was ultrasonically dissolved in an organic solvent, heated to 100–150°C, stirred and heated, and an organic solvent containing copper salt was added dropwise. The mixture was kept at 100–150°C under reflux for 10–60 min. Then, an organic solvent containing ytterbium salt was added dropwise. The mixture was kept at 110–160°C under reflux for 4–10 h. After cooling to room temperature, the mixture was washed 1–5 times with ethanol, centrifuged at 5500–6500 rpm for 2–10 min, and dried at 40–80°C for 1–5 h to obtain Cu-Yb MOF.

[0018] Further, in step S2, the mass-to-volume ratio of Cu-Yb MOF to tetrabutyl titanate in the Cu-Yb MOF dispersion is 4:25–100 mg / μL. The optimal ratio of Cu-Yb MOF to TiO2 is explored by varying the amount of tetrabutyl titanate added, in order to achieve the best hydrogen production efficiency and hydrogen production cycle stability.

[0019] Further, in step S2, the mass-to-volume ratio of Cu-Yb MOF to dispersion medium in the Cu-Yb MOF dispersion is 0.5–0.8 mg / mL;

[0020] The volume ratio of tetrabutyl titanate to ethanol in the ethanol solution is (2.5–10) × 10⁻⁶. -3 :1.

[0021] Furthermore, the dispersion medium in the Cu-Yb MOF dispersion includes water and ethanol, with a volume ratio of water to ethanol of (1-5):1, preferably 2:1.

[0022] Further, in step S2, the temperature of the ethanol solution of tetrabutyl titanate is 80-90°C and the time is 1-2 hours; the temperature of the stirring and heating is 80-90°C and the time is 4-6 hours.

[0023] Further, in step S3, the dispersion medium in the intermediate dispersion includes water and DMF, with a volume ratio of 30 to 40:1;

[0024] The mass-to-volume ratio of the intermediate to the dispersion medium is 2.3–6.9 mg / ml.

[0025] Furthermore, in step S3, the temperature of solvothermal composite is 100-150°C, and the time is 10-15 hours, and the solvothermal composite is carried out in a reaction vessel.

[0026] The second technical solution of the present invention is to provide a TiO2 / Cu-Yb MOF composite photocatalyst, which is prepared by the preparation method described above.

[0027] Furthermore, in the TiO2 / Cu-Yb MOF composite photocatalyst, TiO2 nanoparticles are uniformly covered on the surface of Cu-YbMOF nanosheets, with almost no irregular aggregation of TiO2 particles.

[0028] The third technical solution of the present invention is to provide an application of TiO2 / Cu-Yb MOF composite photocatalyst in the field of photocatalysis, wherein the TiO2 / Cu-Yb MOF composite photocatalyst is used as a photocatalyst for hydrogen production by water electrolysis.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) This invention utilizes the characteristic that ytterbium ions readily coordinate with oxygen. First, copper and ytterbium metal ions are introduced into TCPP via heating to form a Cu-Yb MOF network structure. Then, TiO2 nanoparticles are uniformly loaded onto the surface of Cu-Yb MOF nanosheets using an in-situ growth method. Compared to TiO2 and Cu-Yb MOF alone, the TiO2 / Cu-Yb MOF composite photocatalyst allows electrons generated by TiO2 to be transferred to the MOF in a timely manner, thereby separating electrons and holes and solving the problem of easy electron-hole recombination, further improving the photocatalytic hydrogen production performance.

[0031] (2) Even with the method of hydrolyzing the MOF aqueous solution directly by adding tetrabutyl titanate under stirring (in-situ growth method), aggregation is still inevitable due to the excessively high concentration of TiO2 generated by local hydrolysis. After the introduction of ytterbium ions, the strong interaction between ytterbium ions and oxygen in TiO2 allows TiO2 to fully combine with oxygen in the MOF, resulting in a dense and uniform distribution of TiO2. This leads to a larger contact interface between TiO2 and MOF and more active sites. At the same time, the combination of in-situ growth method and oven heating greatly enhances the interaction between TiO2 and MOF, resulting in improved chemical stability of the composite synthesized by this method.

[0032] (3) In this invention, TCPP is the monomer for MOF synthesis, and ytterbium ions are uniformly distributed in the synthesized MOF nanosheets. At the same time, due to the effective energy and electron transfer between TCPP and ytterbium ions, the constructed 2D Yb-MOF nanosheets have higher photodynamic activity than other synthesized 2D MOFs, thereby greatly improving photocatalytic activity by enhancing light absorption.

[0033] (4) This invention explores the optimal composite for hydrogen production efficiency and hydrogen production cycle stability by adjusting the amount of tetrabutyl titanate and the TiO2 loading ratio. The hydrogen production efficiency of the TiO2 / Cu-Yb MOF composite photocatalyst is increased to 5424 μmol / g / h.

[0034] (5) Due to their large specific surface area and rich pore structure, MOF materials are often used to design materials with filtration and adsorption functions. The TiO2 / Cu-Yb MOF composite material provided by this invention not only has the advantages of traditional MOF materials, but also has excellent photoelectrochemical properties. It can be applied to the field of photocatalytic hydrogen production, which has high novelty and broad application prospects. This invention provides a new method and approach for exploring the application of MOF materials. Attached Figure Description

[0035] Figure 1The image shows a SEM image of the TiO2 / Cu-Yb MOF photocatalyst powder shown in Example 1.

[0036] Figure 2 The photocatalytic hydrogen production performance of TiO2 / Cu-Yb MOF photocatalysts shown in Examples 1-4 and TiO2 / Cu-Zn MOF, TiO2@Cu-Yb MOF, and Cu-Yb MOF shown in Comparative Examples 1-3 is compared. (a) Examples 1-4, (b) Examples 1 and Comparative Examples 1-3.

[0037] Figure 3 Transient photocurrent response diagrams of TiO2 / Cu-Yb MOF photocatalysts shown in Examples 1-4 and TiO2 / Cu-Zn MOF, TiO2@Cu-Yb MOF, and Cu-Yb MOF shown in Comparative Examples 1-3 are shown, (a) Examples 1-4, (b) Examples 1 and Comparative Examples 1-3. Detailed Implementation

[0038] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. All other embodiments obtained by those skilled in the art based on the given embodiments without creative effort are within the scope of protection of this application.

[0039] Unless otherwise specified, the reagents, methods, instruments and equipment used in this invention are conventional reagents, methods, instruments and equipment in the art.

[0040] All the following chemicals were used as received without further purification. TCPP, CAS number 14609-54-2, brand: Frontier Scientific, purchased from Anolun (Beijing) Biotechnology Co., Ltd.; DMF, CAS number 68-12-2, brand: Adamas, purchased from Shanghai Titan Technology Co., Ltd.; tetrabutyl titanate, CAS number 5593-70-4, brand: Greatent, purchased from Shanghai Titan Technology Co., Ltd.; TiO2 used in Comparative Example 2, CAS number 13463-67-7, 20nm (P25), brand: Ron, purchased from Shanghai E-En Chemical Technology Co., Ltd.

[0041] Example 1

[0042] A TiO2 / Cu-Yb MOF composite photocatalyst is prepared by the following steps:

[0043] (I) Synthesis of Cu-Yb MOF

[0044] 30 mg TCPP was dissolved in 2 ml DMF by sonication, then transferred to a 10 ml round-bottom flask in an oil bath. The mixture was heated to 120 °C with stirring, and 2 ml of DMF solution containing 70 mg CuCl2 was added dropwise. The mixture was then refluxed at 120 °C for 20 min. Next, 4 ml of DMF solution containing 70 mg Yb(NO3)3 was added dropwise, and the mixture was refluxed at 120 °C for 5 h 10 min. The mixture was then allowed to cool to room temperature, washed three times with ethanol, centrifuged at 6500 rpm for 5 min, and then vacuum dried at 60 °C for 3 h to obtain Cu-Yb MOF powder.

[0045] (II) In-situ growth of TiO2 nanoparticles on Cu-Yb MOF surface

[0046] 150 μl of tetrabutyl titanate was added dropwise to 20 ml of ethanol, transferred to a 50 ml three-necked flask A in an oil bath, and heated to 85 °C with stirring for 1 h. During this period, 8 ml of deionized water and 4 ml of anhydrous ethanol were mixed, and 8 mg of Cu-YbMOF powder synthesized in the first step was added. The mixture was sonicated for 30 min to disperse the powder evenly. This dispersion was then transferred to a 50 ml three-necked flask B. The solution in the three-necked flask A was then added dropwise to the three-necked flask B while still hot. The mixture was heated to 85 °C with stirring for 4 h. After naturally cooling to room temperature, the mixture was washed twice with ethanol and centrifuged at 6000 rpm for 5 min to obtain the intermediate. 43.5 mg of the intermediate was added to 8 ml of deionized water and 250 μl of DMF, and the mixture was shaken to obtain an intermediate dispersion. This dispersion was transferred to a 10 ml reaction vessel and heated to 120 °C in an oven for a solvothermal composite reaction for 12 h. After naturally cooling to room temperature, the powder was washed three times with ethanol, centrifuged at 5500 rpm for 5 min, and then vacuum dried at 60℃ for 3 h to obtain TiO2 / Cu-Yb MOF photocatalyst powder.

[0047] (III) Photocatalytic hydrogen production conditions

[0048] 10 mg of TiO2 / Cu-Yb MOF photocatalyst powder was dissolved in 10 ml of deionized water and sonicated for 10 min. The solution was then transferred to a photocatalytic reactor, and 40 ml of deionized water was added while stirring. A mixed sacrificial reagent of methanol and triethanolamine (methanol:triethanolamine = 7:1) was prepared. 10 ml of this mixed sacrificial reagent was added to the photocatalytic reactor. After purging with nitrogen for 10 min, the reactor was irradiated under a mercury lamp. The hydrogen content was measured hourly for a total of 6 hours.

[0049] Example 2

[0050] A TiO2 / Cu-Yb MOF composite photocatalyst is prepared by the following steps:

[0051] (I) Synthesis of Cu-Yb MOF

[0052] 30 mg TCPP was dissolved in 2 ml DMF by sonication, then transferred to a 10 ml round-bottom flask in an oil bath. The mixture was heated to 100 °C with stirring, and 2 ml of DMF solution containing 60 mg CuCl2 was added dropwise. The mixture was then refluxed at 100 °C for 30 min. Next, 4 ml of DMF solution containing 60 mg Yb(NO3)3 was added dropwise, and the mixture was refluxed at 110 °C for 6 h. After cooling naturally to room temperature, the mixture was washed three times with ethanol, centrifuged at 6000 rpm for 5 min, and then vacuum dried at 60 °C for 3 h to obtain Cu-Yb MOF powder.

[0053] (II) In-situ growth of TiO2 nanoparticles on Cu-Yb MOF surface

[0054] 100 μl of tetrabutyl titanate was added dropwise to 20 mL of ethanol, transferred to a 50 mL three-necked flask A in an oil bath, and heated to 80 °C with stirring for 1 h. During this time, 6.6 mL of deionized water and 3.4 mL of anhydrous ethanol were mixed, and 8 mg of Cu-Yb MOF powder synthesized in the first step was added. The mixture was sonicated for 30 min to disperse the powder evenly. This dispersion was then transferred to a 50 mL three-necked flask B. The solution in the three-necked flask A was then added dropwise to the three-necked flask B while still hot. The mixture was heated to 80 °C with stirring for 6 h. After naturally cooling to room temperature, the mixture was washed twice with ethanol and centrifuged at 6000 rpm for 5 min to obtain the intermediate. 31.7 mg of the intermediate was added to 8 mL of deionized water and 200 μl of DMF, and the mixture was shaken to obtain an intermediate dispersion. This dispersion was transferred to a 10 mL reaction vessel and heated to 100 °C in an oven for a solvothermal recombination reaction for 12 h. After naturally cooling to room temperature, the powder was washed three times with ethanol, centrifuged at 6000 rpm for 5 min, and then vacuum dried at 60℃ for 3 h to obtain TiO2 / Cu-Yb MOF photocatalyst powder.

[0055] (III) Photocatalytic hydrogen production conditions

[0056] 10 mg of TiO2 / Cu-Yb MOF photocatalyst powder was dissolved in 10 ml of deionized water and sonicated for 10 min. The solution was then transferred to a photocatalytic reactor, and 40 ml of deionized water was added while stirring. A mixed sacrificial reagent of methanol and triethanolamine (methanol:triethanolamine = 7:1) was prepared. 10 ml of this mixed sacrificial reagent was added to the photocatalytic reactor. After purging with nitrogen for 10 min, the reactor was irradiated under a mercury lamp. The hydrogen content was measured hourly for a total of 6 hours.

[0057] Example 3

[0058] A TiO2 / Cu-Yb MOF composite photocatalyst is prepared by the following steps:

[0059] (I) Synthesis of Cu-Yb MOF

[0060] 30 mg TCPP was dissolved in 2 ml DMF by sonication, then transferred to a 10 ml round-bottom flask in an oil bath. The mixture was heated to 150 °C with stirring, and 2 ml of DMF solution containing 100 mg CuCl2 was added dropwise. The mixture was then refluxed at 150 °C for 25 min. Next, 4 ml of DMF solution containing 100 mg Yb(NO3)3 was added dropwise, and the mixture was refluxed at 160 °C for 5 h 30 min. The mixture was then allowed to cool to room temperature, washed three times with ethanol, centrifuged at 6500 rpm for 5 min, and then vacuum dried at 60 °C for 3 h to obtain Cu-Yb MOF powder.

[0061] (II) In-situ growth of TiO2 nanoparticles on Cu-Yb MOF surface

[0062] 50 μl of tetrabutyl titanate was added dropwise to 20 ml of ethanol, transferred to a 50 ml three-necked flask A in an oil bath, and heated to 90 °C with stirring for 1 h. During this time, 10.7 ml of deionized water and 5.3 ml of anhydrous ethanol were mixed, and 8 mg of Cu-YbMOF powder synthesized in the first step was added. The mixture was sonicated for 30 min to disperse the powder evenly. This dispersion was then transferred to a 50 ml three-necked flask B. The solution in the three-necked flask A was then added dropwise to the three-necked flask B while still hot. The mixture was heated to 90 °C with stirring for 5 h. After naturally cooling to room temperature, the mixture was washed twice with ethanol and centrifuged at 6000 rpm for 5 min to obtain the intermediate. 19.8 mg of the intermediate was added to 8 ml of deionized water and 267 μl of DMF, and the mixture was shaken to obtain an intermediate dispersion. This dispersion was transferred to a 10 ml reaction vessel and heated to 150 °C in an oven for a solvothermal recombination reaction for 12 h. After naturally cooling to room temperature, the sample was washed three times with ethanol, centrifuged at 6500 rpm for 5 min, and then vacuum dried at 60℃ for 3 h to obtain TiO2 / Cu-Yb MOF photocatalyst powder.

[0063] (III) Photocatalytic hydrogen production conditions

[0064] 10 mg of TiO2 / Cu-Yb MOF photocatalyst powder was dissolved in 10 ml of deionized water and sonicated for 10 min. The solution was then transferred to a photocatalytic reactor, and 40 ml of deionized water was added while stirring. A mixed sacrificial reagent of methanol and triethanolamine (methanol:triethanolamine = 7:1) was prepared. 10 ml of this mixed sacrificial reagent was added to the photocatalytic reactor. After purging with nitrogen for 10 min, the reactor was irradiated under a mercury lamp. The hydrogen content was measured hourly for a total of 6 hours.

[0065] Example 4

[0066] A TiO2 / Cu-Yb MOF composite photocatalyst is prepared by the following steps:

[0067] (I) Synthesis of Cu-Yb MOF

[0068] 30 mg TCPP was dissolved in 2 ml DMF by sonication, then transferred to a 10 ml round-bottom flask in an oil bath. The mixture was heated to 120 °C with stirring, and 2 ml of DMF solution containing 70 mg CuCl2 was added dropwise. The mixture was then refluxed at 120 °C for 20 min. Next, 4 ml of DMF solution containing 70 mg Yb(NO3)3 was added dropwise, and the mixture was refluxed at 120 °C for 5 h 10 min. The mixture was then allowed to cool to room temperature, washed three times with ethanol, centrifuged at 6500 rpm for 5 min, and then vacuum dried at 60 °C for 3 h to obtain Cu-Yb MOF powder.

[0069] (II) In-situ growth of TiO2 nanoparticles on Cu-Yb MOF surface

[0070] 200 μl of tetrabutyl titanate was added dropwise to 20 ml of ethanol, transferred to a 50 ml three-necked flask A in an oil bath, and heated to 85 °C with stirring for 1 h. During this period, 8 ml of deionized water and 4 ml of anhydrous ethanol were mixed, and 8 mg of Cu-YbMOF powder synthesized in the first step was added. The mixture was sonicated for 30 min to disperse the powder evenly. This dispersion was then transferred to a 50 ml three-necked flask B. The solution in the three-necked flask A was then added dropwise to the three-necked flask B while still hot. The mixture was heated to 85 °C with stirring for 4 h. After naturally cooling to room temperature, the mixture was washed twice with ethanol and centrifuged at 6000 rpm for 5 min to obtain the intermediate. 55.3 mg of the intermediate was added to 8 ml of deionized water and 250 μl of DMF, and the mixture was shaken to obtain an intermediate dispersion. This dispersion was transferred to a 10 ml reaction vessel and heated to 120 °C in an oven for a solvothermal composite reaction for 12 h. After naturally cooling to room temperature, the powder was washed three times with ethanol, centrifuged at 5500 rpm for 5 min, and then vacuum dried at 60℃ for 3 h to obtain TiO2 / Cu-Yb MOF photocatalyst powder.

[0071] (III) Photocatalytic hydrogen production conditions

[0072] 10 mg of TiO2 / Cu-Yb MOF photocatalyst powder was dissolved in 10 ml of deionized water and sonicated for 10 min. The solution was then transferred to a photocatalytic reactor, and 40 ml of deionized water was added while stirring. A mixed sacrificial reagent of methanol and triethanolamine (methanol:triethanolamine = 7:1) was prepared. 10 ml of this mixed sacrificial reagent was added to the photocatalytic reactor. After purging with nitrogen for 10 min, the reactor was irradiated under a mercury lamp. The hydrogen content was measured hourly for a total of 6 hours.

[0073] Comparative Example 1

[0074] A TiO2 / Cu-Zn MOF composite photocatalyst, compared to Example 1, with all other conditions unchanged except that Yb(NO3)3 is replaced with Zn(NO3)2.

[0075] Its preparation method is as follows:

[0076] (I) Synthesis of Cu-Zn MOF

[0077] 30 mg TCPP was dissolved in 2 ml DMF by sonication, then transferred to a 10 ml round-bottom flask in an oil bath. The mixture was heated to 120 °C with stirring, and 2 ml of DMF solution containing 70 mg CuCl2 was added dropwise. The mixture was then refluxed at 120 °C for 20 min. Next, 4 ml of DMF solution containing 70 mg Zn(NO3)2 was added dropwise, and the mixture was refluxed at 120 °C for 5 h 10 min. The mixture was then allowed to cool to room temperature, washed three times with ethanol, centrifuged at 5500 rpm for 5 min, and then vacuum dried at 60 °C for 3 h to obtain Cu-Zn MOF powder.

[0078] (II) In-situ growth of TiO2 nanoparticles on Cu-Zn MOF surface

[0079] 150 μl of tetrabutyl titanate was added dropwise to 20 ml of ethanol, transferred to a 50 ml three-necked flask A in an oil bath, and heated to 85 °C with stirring for 1 h. During this period, 8 ml of deionized water and 4 ml of anhydrous ethanol were mixed, and 8 mg of Cu-ZnMOF powder synthesized in the first step was added. The mixture was sonicated for 30 min to disperse the powder evenly. This dispersion was then transferred to a 50 ml three-necked flask B. The solution in the three-necked flask A was then added dropwise to the three-necked flask B while still hot. The mixture was heated to 85 °C with stirring for 4 h. After naturally cooling to room temperature, the mixture was washed twice with ethanol and centrifuged at 6000 rpm for 5 min to obtain the intermediate. 43.5 mg of the intermediate was added to 8 ml of deionized water and 250 μl of DMF, and the mixture was shaken to obtain an intermediate dispersion. This dispersion was transferred to a 10 ml reaction vessel and heated to 120 °C in an oven for a solvothermal composite reaction for 12 h. After naturally cooling to room temperature, the product was washed three times with ethanol, centrifuged at 6000 rpm for 5 min, and then vacuum dried at 60℃ for 3 h to obtain TiO2 / Cu-Zn MOF photocatalyst powder.

[0080] (III) Photocatalytic hydrogen production conditions

[0081] 10 mg of TiO2 / Cu-Zn MOF photocatalyst powder was dissolved in 10 ml of deionized water and sonicated for 10 min. The solution was then transferred to a photocatalytic reactor, and 40 ml of deionized water was added while stirring. A mixed sacrificial reagent of methanol and triethanolamine (methanol:triethanolamine = 7:1) was prepared. 10 ml of this mixed sacrificial reagent was added to the photocatalytic reactor. After purging with nitrogen for 10 min, the reactor was irradiated under a mercury lamp. The hydrogen content was measured hourly for a total of 6 hours.

[0082] Comparative Example 2

[0083] A TiO2@Cu-Yb MOF composite photocatalyst, compared with Example 1, with all other conditions unchanged, but without the in-situ growth method, the TiO2 source is commercially available TiO2, model P25, rather than generated by the hydrolysis of tetrabutyl titanate.

[0084] (I) Synthesis of Cu-Yb MOF

[0085] 30 mg TCPP was dissolved in 2 ml DMF by sonication, then transferred to a 10 ml round-bottom flask in an oil bath. The mixture was heated to 120 °C with stirring, and 2 ml of DMF solution containing 70 mg CuCl2 was added dropwise. The mixture was then refluxed at 120 °C for 20 min. Next, 4 ml of DMF solution containing 70 mg Yb(NO3)3 was added dropwise, and the mixture was refluxed at 120 °C for 5 h 10 min. The mixture was then allowed to cool to room temperature, washed three times with ethanol, centrifuged at 5500 rpm for 5 min, and then vacuum dried at 60 °C for 3 h to obtain Cu-Yb MOF powder.

[0086] (II) In-situ growth of TiO2 nanoparticles on Cu-Yb MOF surface

[0087] 35.5 mg of TiO2 was ground and added to 20 ml of ethanol, then transferred to a 50 ml three-necked flask A in an oil bath. The mixture was heated to 85 °C and stirred for 1 h. During this time, 8 ml of deionized water and 4 ml of anhydrous ethanol were mixed and 8 mg of Cu-YbMOF powder synthesized in the first step was added. The mixture was sonicated for 30 min to disperse the powder evenly. This dispersion was then transferred to a 50 ml three-necked flask B. The dispersion in the three-necked flask A was then added dropwise to the three-necked flask B while still hot. The mixture was heated to 85 °C and stirred for 4 h. After naturally cooling to room temperature, the mixture was washed twice with ethanol and centrifuged at 6000 rpm for 5 min to obtain an intermediate. 43.5 mg of the intermediate was added to 8 ml of deionized water and 250 μl of DMF and mixed evenly by shaking to obtain an intermediate dispersion. This dispersion was transferred to a 10 ml reaction vessel and heated to 120 °C in an oven for a solvothermal composite reaction for 12 h. After naturally cooling to room temperature, the sample was washed three times with ethanol, centrifuged at 6000 rpm for 5 min, and then vacuum dried at 60℃ for 3 h to obtain TiO2@Cu-Yb MOF photocatalyst powder.

[0088] (III) Photocatalytic hydrogen production conditions

[0089] 10 mg of TiO2@Cu-Yb MOF photocatalyst powder was dissolved in 10 ml of deionized water and sonicated for 10 min. The solution was then transferred to a photocatalytic reactor, and 40 ml of deionized water was added while stirring. A mixed sacrificial reagent of methanol and triethanolamine (methanol:triethanolamine = 7:1) was prepared. 10 ml of this mixed sacrificial reagent was added to the photocatalytic reactor. After purging with nitrogen for 10 min, the reactor was irradiated under a mercury lamp. The hydrogen content was measured hourly for a total of 6 hours.

[0090] Comparative Example 3

[0091] A Cu-Yb MOF photocatalyst, with all other conditions unchanged compared to Example 1, except for the removal of the second step of in-situ growth of TiO2 nanoparticles on the Cu-YbMOF surface.

[0092] (I) Synthesis of Cu-Yb MOF

[0093] 30 mg TCPP was dissolved in 2 ml DMF by sonication, then transferred to a 10 ml round-bottom flask in an oil bath. The mixture was heated to 120 °C with stirring, and 2 ml of DMF solution containing 70 mg CuCl2 was added dropwise. The mixture was then refluxed at 120 °C for 20 min. Next, 4 ml of DMF solution containing 70 mg Yb(NO3)3 was added dropwise, and the mixture was refluxed at 120 °C for 5 h 10 min. The mixture was then allowed to cool to room temperature, washed three times with ethanol, centrifuged at 5500 rpm for 5 min, and then vacuum dried at 60 °C for 3 h to obtain Cu-Yb MOF powder.

[0094] (II) Photocatalytic hydrogen production conditions

[0095] 10 mg of Cu-Yb MOF photocatalyst powder was dissolved in 10 ml of deionized water and sonicated for 10 min. The solution was then transferred to a photocatalytic reactor, and 40 ml of deionized water was added while stirring. A mixed sacrificial reagent of methanol and triethanolamine (methanol:triethanolamine = 7:1) was prepared. 10 ml of this mixed sacrificial reagent was added to the photocatalytic reactor. After purging with nitrogen for 10 min, the reactor was irradiated under a mercury lamp. The hydrogen content was measured hourly for a total of 6 hours.

[0096] The present invention analyzes the results using the products prepared in Examples 1-4 and Comparative Examples 1-3 as examples:

[0097] The morphology of the TiO2 / Cu-Yb MOF prepared in Example 1 of this invention is as follows: Figure 1 As shown, TiO2 nanoparticles uniformly and densely cover the surface of Cu-Yb MOF nanosheets, with almost no irregular agglomerations. This is the result of the combined effect of the introduction of ytterbium ions and the use of an in-situ growth method.

[0098] The hydrogen production activity of the TiO2 / Cu-Yb MOF prepared in Examples 1-4 of this invention is as follows: Figure 2 (a) shows that the hydrogen production rate in Example 1 over 6 hours was 32.5 mmol / g. -1 Example 2 (27.9 mmol g) -1 1.16 times that of Example 3 (18.8 mmol g) -1 1.7 times that of Example 4 (24.8 mmol g) and Example 5 (24.8 mmol g) -1 The TiO2 loading ratio was 1.3 times that of Example 1 (81.6%), Example 2 (74.8%), Example 3 (59.8%), and Example 4 (85.6%), respectively. This not only demonstrates that the composites with the TiO2 loading ratios of Examples 1 to 4 all exhibited good photocatalytic performance, but also shows that Example 1 had the best performance.

[0099] The method for calculating the loading ratio of TiO2 is as follows:

[0100]

[0101] Among them, M 钛酸四丁酯 =340,

[0102] The TiO2 / Cu-Yb MOF prepared in Example 1, the TiO2 / Cu-Zn MOF prepared in Comparative Example 1, the TiO2@Cu-Yb MOF prepared in Comparative Example 2, and the Cu-Yb MOF prepared in Comparative Example 3 of this invention are as follows: Figure 2 (b) shows that in Comparative Example 1 (ytterbium ions were replaced with zinc ions), the hydrogen production was only 19 mmol / g. -1 Comparative Example 2 (in situ growth method replaced by classical method) had even less, only 18.1 mmol / g. -1 Comparative Example 3 (without TiO2 loading) produced the least hydrogen, with a yield of 0.6 mmol / g. -1 Comparative Example 3 showed the lowest hydrogen production, demonstrating the necessity of supporting TiO2. Meanwhile, Comparative Examples 1 and 2 produced less than 60% of the hydrogen produced in Example 1, indicating that without the introduction of ytterbium ions or the use of in-situ growth, the photocatalytic activity would decrease significantly.

[0103] The transient photocurrent responses of the TiO2 / Cu-Yb MOFs prepared in Examples 1-4 of this invention are as follows: Figure 3 As shown in (a), the TiO2 / Cu-Yb MOF prepared in Example 1, the TiO2 / Cu-Zn MOF prepared in Comparative Example 1, the TiO2@Cu-Yb MOF prepared in Comparative Example 2, and the Cu-Yb MOF prepared in Comparative Example 3 are as follows: Figure 3 (b) shows: with Figure 2The results of photocatalytic hydrogen production correspond accordingly. Higher transient photocurrents indicate higher electron-hole separation and transfer efficiency in the composite material, resulting in higher photocatalytic hydrogen production activity. This further confirms that the material's high photocatalytic performance is due to its excellent photoelectrochemical properties, rather than accidental factors, thus ensuring the reproducibility of its applications.

[0104] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst, characterized in that, Includes the following steps: S1. Copper salt and ytterbium salt are introduced into TCPP in sequence through heating reaction to obtain Cu-Yb MOF powder. The TCPP is tetra(4-carboxyphenyl)porphyrin. The specific preparation process of the Cu-Yb MOF powder is as follows: TCPP is dissolved in an organic solvent, heated to 100~150℃, stirred and heated, an organic solvent containing copper salt is added, refluxed at 100~150℃, an organic solvent containing ytterbium salt is added, refluxed at 110~160℃ is continued, cooled to room temperature, washed, centrifuged and dried to obtain Cu-Yb MOF. S2. Cu-Yb MOF powder was prepared into Cu-Yb MOF dispersion. After heat treatment of the ethanol solution of tetrabutyl titanate, it was added to the Cu-Yb MOF dispersion, stirred and heated, cooled, washed and centrifuged to obtain the intermediate. S3. The intermediate is prepared into an intermediate dispersion, and then solvothermal composite is used to obtain the TiO2 / Cu-Yb MOF photocatalyst. The reaction is complete.

2. The method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst according to claim 1, characterized in that, The mass ratio of copper salt, ytterbium salt, and TCPP is 6~10:6~10:3; The mass-to-volume ratio of the copper salt to the organic solvent is 7.5~12.5 mg / ml; The copper salt is CuCl2; The ytterbium salt is Yb(NO3)3; The organic solvent is DMF.

3. The method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst according to claim 1, characterized in that, In step S2, the mass-to-volume ratio of Cu-Yb MOF to tetrabutyl titanate in the Cu-Yb MOF dispersion is 4:25~100 mg / μL.

4. The method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst according to claim 1, characterized in that, In step S2, the mass-to-volume ratio of Cu-Yb MOF to dispersion medium in the Cu-Yb MOF dispersion is 0.5~0.8 mg / mL; The volume ratio of tetrabutyl titanate to ethanol in the ethanol solution is (2.5~10)×10. -3 :

1.

5. The method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst according to claim 1, characterized in that, In step S2, the temperature for heat treatment of the tetrabutyl titanate ethanol solution is 80~90℃; the temperature for stirring and heating is 80~90℃.

6. The method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst according to claim 1, characterized in that, In step S3, the dispersion medium in the intermediate dispersion includes water and DMF, with a volume ratio of 30~40:1; The mass-to-volume ratio of the intermediate to the dispersion medium is 2.3~6.9 mg / ml.

7. The method for preparing a TiO2 / Cu-Yb MOF composite photocatalyst according to claim 1, characterized in that, In step S3, the temperature of solvothermal composite is 100~150℃.

8. A TiO2 / Cu-Yb MOF composite photocatalyst, which is prepared by any one of the preparation methods described in claims 1 to 7.

9. The application of the TiO2 / Cu-Yb MOF composite photocatalyst as described in claim 8 in the field of photocatalysis, wherein the TiO2 / Cu-Yb MOF composite photocatalyst is used as a photocatalyst for hydrogen production through water electrolysis.

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