Metal-organic framework containing electron-withdrawing group, preparation method and application thereof

Abstract

This application proposes a metal organic framework containing an electron-withdrawing group, a preparation method thereof, and an application thereof. The method for preparing the metal organic framework containing an electron-withdrawing group comprises: (1) mixing a metal salt, a regulator, and a first organic solvent to obtain a first solution; (2) heating the first solution for a first time, cooling it, and adding a mixed ligand to form a second solution, wherein the mixed ligand comprises an organic ligand containing an electron-withdrawing group and an organic ligand not containing an electron-withdrawing group, wherein the electron-withdrawing group comprises at least one of a nitro group, a cyano group, a fluorine atom, a chlorine atom, and a trifluoromethyl group; and (3) heating the second solution, cooling it, centrifuging it, and drying it to obtain the metal organic framework containing an electron-withdrawing group. In this way, the light absorption capacity of the metal organic framework is improved, the separation and transfer of photogenerated carriers of the metal organic framework are promoted, and the rate of hydrogen production by catalyzing water decomposition as a photocatalyst is increased.

Description

Technical Field

[0001] The present application relates to the field of porous materials, and in particular to a metal organic framework containing an electron-withdrawing group, a preparation method thereof, and an application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are porous materials assembled from inorganic metal nodes and organic ligands. They possess the advantages of high specific surface area, high porosity, and abundant active sites. Their structure and chemical properties can be controlled and regulated through modification of the metal nodes and organic ligands, as well as through the assembly of various metal nodes and organic ligands. Researchers have exploited the structural tunability of MOFs to develop a range of modification strategies, resulting in a diverse range of MOFs and expanding their applications in numerous fields.

[0003] In the field of photocatalysis, functionalization of organic ligands is a common modification strategy to improve the photocatalytic efficiency of metal-organic frameworks (MOFs). Typically, electron-donating amino groups are introduced into the organic ligands of MOFs, positively impacting their photocatalytic performance. However, the effects of electron-withdrawing groups on the photocatalytic performance of MOFs have not been systematically investigated. Furthermore, the inductive effect and steric hindrance of electron-withdrawing groups can reduce the coordination capacity of organic ligands in large conjugated systems, making the synthesis of MOFs difficult. Summary of the Invention

[0004] This application aims to solve at least one of the technical problems existing in the prior art.

[0005] In the first aspect of the present application, a method for preparing a metal organic framework containing an electron-withdrawing group is proposed, comprising: (1) mixing a metal salt, a regulator, and a first organic solvent to obtain a first solution; (2) heating the first solution for a first time, cooling it, and adding a mixed ligand to form a second solution, wherein the mixed ligand includes an organic ligand containing an electron-withdrawing group and an organic ligand not containing an electron-withdrawing group, wherein the electron-withdrawing group includes at least one of a nitro group, a cyano group, a fluorine atom, a chlorine atom, and a trifluoromethyl group; (3) heating the second solution for a second time, cooling it, centrifuging it, and drying it to obtain the metal organic framework containing an electron-withdrawing group. In this way, the light absorption capacity of the metal organic framework is improved, the separation and transfer of photogenerated carriers of the metal organic framework are promoted, and the rate of hydrogen production by catalyzing water decomposition as a photocatalyst is increased.

[0006] The method proposed in this application also has the following additional technical features:

[0007] According to some embodiments of the present application, the organic ligand containing an electron-withdrawing group and the organic ligand without an electron-withdrawing group have the same skeleton, and the skeleton includes terephthalic acid, 1,3,5-tricarboxyphenylbenzene, 4,4',4'',4'''-(perylene-2,5,8,11-tetrayl)tetrabenzoic acid, meso-tetra(4-carboxyphenyl)porphine, 4,4',4'',4'''-(dibenzo[g, at least one of: tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene, 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid, and 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid).

[0008] According to some embodiments of the present application, the electron-withdrawing group replaces the hydrogen atom at the ortho or meta position of the carboxyl group.

[0009] According to some embodiments of the present application, the mixed ligand includes a pyrenyl ligand containing a nitro group and a pyrenyl ligand not containing a nitro group.

[0010] According to some embodiments of the present application, the molar ratio of the nitro-containing pyrenyl ligand to the nitro-free pyrenyl ligand is (1-10): (1-10).

[0011] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the nitro-containing pyrenyl ligand includes 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid, 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid) At least one, the nitro group replaces the hydrogen atom at the ortho or meta position of the carboxyl group; the pyrene-based ligand not containing a nitro group includes at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid and 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid).

[0012] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the metal salt includes at least one of metal chloride, metal nitrate, metal acetate, and metal sulfate; the regulator includes at least one of benzoic acid, acetic acid, trifluoroacetic acid, formic acid, and hydrochloric acid.

[0013] According to some embodiments of the present application, the method satisfies at least one of the following conditions: the temperature of the first heating is 40°C-150°C, and the time of the first heating is 0.5h-2h; the temperature of the second heating is 80°C-200°C, and the time of the second heating is 8h-72h; the metal in the metal salt includes at least one of zirconium, hafnium, cerium, titanium, iron, cobalt, and nickel.

[0014] The second aspect of the present application proposes a metal organic framework containing an electron-withdrawing group, which is prepared using the method proposed in the first aspect of the present application.

[0015] The third aspect of the present application proposes the application of the electron-withdrawing metal organic framework prepared by the method proposed in the first aspect of the present application or the electron-withdrawing metal organic framework proposed in the second aspect of the present application in the field of photocatalysis.

[0016] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 It is a schematic flow chart of a preparation method according to an embodiment of the present application.

[0019] Figure 2 Schematic diagram of the structure of a metal organic framework according to an embodiment of the present application.

[0020] Figure 3 These are the powder X-ray diffraction patterns and theoretical simulation diagrams of the metal organic frameworks prepared in Example 1, Example 2, Example 3, Example 4, and Comparative Example 1 of the present application.

[0021] Figure 4 This is the powder X-ray diffraction pattern of the metal organic framework prepared in Example 5 and Example 6 of the present application.

[0022] Figure 5 This is the Fourier transform infrared absorption spectrum of the metal organic framework powder prepared in Example 1 and Comparative Example 1 of the present application.

[0023] Figure 6 This is the Fourier transform infrared absorption spectrum of the metal organic framework powder prepared in Example 4 and Comparative Example 1 of the present application.

[0024] Figure 7 This is the Fourier transform infrared absorption spectrum of the metal organic framework powder prepared in Example 5 of the present application.

[0025] Figure 8 This is the Fourier transform infrared absorption spectrum of the metal organic framework powder prepared in Example 6 of the present application.

[0026] Figure 9 This is an SEM image of the metal organic framework prepared in Comparative Example 1 of the present application.

[0027] Figure 10 This is an SEM image of the metal organic framework prepared in Example 1 of the present application.

[0028] Figure 11 These are the thermogravimetric curves of the two metal organic frameworks prepared in Example 1 and Comparative Example 1 of the present application.

[0029] Figure 12 These are the UV-visible diffuse reflectance spectra of the two metal organic frameworks prepared in Example 1 and Comparative Example 1 of the present application.

[0030] Figure 13 These are the band gap analysis curves of the two metal organic frameworks prepared in Example 1 and Comparative Example 1 of the present application.

[0031] Figure 14 These are the photoluminescence spectra of the two metal organic frameworks prepared in Example 1 and Comparative Example 1 of the present application.

[0032] Figure 15 This is the Mott-Schottky curve of the metal organic framework prepared in Comparative Example 1 of the present application.

[0033] Figure 16 This is the Mott-Schottky curve of the metal organic framework prepared in Example 1 of the present application.

[0034] Figure 17 This is an analysis curve of the hydrogen production in 5 hours of the two metal organic frameworks prepared in Example 1 and Comparative Example 1 of the present application.

[0035] Figure 18 These are the analysis curves of the photocatalytic hydrogen production rates of the two metal organic frameworks prepared in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0036] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0037] In the first aspect of the present application, a method for preparing a metal organic framework containing an electron-withdrawing group is proposed, the method comprising: (1) mixing a metal salt, a regulator, and a first organic solvent to obtain a first solution; (2) heating the first solution, cooling it, and adding a mixed ligand to form a second solution, wherein the mixed ligand comprises an organic ligand containing an electron-withdrawing group and an organic ligand not containing an electron-withdrawing group, wherein the electron-withdrawing group comprises at least one of a nitro group, a cyano group, a fluorine atom, a chlorine atom, and a trifluoromethyl group; and (3) heating the second solution for a second time, cooling it, centrifuging it, and drying it to obtain the metal organic framework containing an electron-withdrawing group. In this way, a metal organic framework containing an electron-withdrawing group can be prepared, the light absorption capacity of the metal organic framework can be improved, the separation and transfer of photogenerated carriers of the metal organic framework can be promoted, and the rate of hydrogen production by catalyzing water decomposition as a photocatalyst can be increased.

[0038] The following is a detailed description of the principle by which this application can achieve the above beneficial effects:

[0039] The method for preparing a metal-organic framework proposed in this application uses a mixed ligand in the preparation process. The mixed ligand includes an organic ligand containing an electron-withdrawing group and an organic ligand without an electron-withdrawing group. By adding an organic ligand without an electron-withdrawing group, on the one hand, the density of the electron-withdrawing group in the second solution can be reduced, the spatial blockage caused by the presence of a large number of electron-withdrawing groups in the local space of the metal-organic framework can be reduced, and the space effect of the electron-withdrawing group on crystal synthesis can be weakened; on the other hand, the organic ligand without an electron-withdrawing group is conducive to coordination with the metal node, and can form a template framework to induce the organic ligand containing the electron-withdrawing group to coordinate with the metal node, and finally form a metal-organic framework containing an electron-withdrawing group. By introducing electron-withdrawing groups into the metal-organic framework, the position of the lowest unoccupied molecular orbital of the metal-organic framework can be moved in a direction that is conducive to photocatalytic hydrogen production, and its optical band gap can be reduced, the light absorption capacity can be improved, and the separation and transfer rate of photogenerated carriers can be increased, thereby increasing the rate of photocatalytic hydrogen production.

[0040] The following is a detailed description of each step of the method proposed in this application, with reference to Figure 1 , the method comprising:

[0041] S10: mixing a metal salt, a regulator, and a first organic solvent to obtain a first solution;

[0042] According to some embodiments of the present application, the metal salt, the regulator, and the first organic solvent are placed in a pressure-resistant tube and ultrasonically dissolved to obtain the first solution.

[0043] According to some embodiments of the present application, the molar ratio of the metal salt to the modifier is 1:(0.1-500), for example, it can be 1:0.1, 1:1, 1:10, 1:50, 1:100, 1:200, 1:300, 1:400 or 1:500, or it can be a range composed of any of the above values. Thus, the modifier competes with the organic ligand for the coordination sites of the metal node, thereby slowing down the kinetics of the crystallization process and avoiding the formation of amorphous material in the early stage of the reaction. According to some specific embodiments of the present application, the molar ratio of the metal salt to the modifier is 1:(10-50).

[0044] According to some embodiments of the present application, the metal salt includes at least one of metal chloride, metal nitrate, metal acetate, and metal sulfate.

[0045] According to some embodiments of the present application, the metal in the metal salt includes at least one of zirconium, hafnium, cerium, titanium, iron, cobalt, and nickel.

[0046] According to some embodiments of the present application, the regulator includes at least one of benzoic acid, acetic acid, trifluoroacetic acid, formic acid, and hydrochloric acid.

[0047] According to some embodiments of the present application, the organic solvent includes at least one of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N,N-diethylformamide (DEF).

[0048] S20: heating the first solution for the first time, cooling it, and adding a mixed ligand;

[0049] According to some embodiments of the present application, the first solution is placed in an oven for a first heating, and after the heating is completed, it is cooled to room temperature, and the mixed ligand is added and ultrasonically dissolved to obtain a second solution.

[0050] According to some embodiments of the present application, the organic ligand containing an electron-withdrawing group and the organic ligand without an electron-withdrawing group have the same skeleton, and the skeleton includes terephthalic acid, 1,3,5-tricarboxyphenylbenzene, 4,4',4'',4'''-(perylene-2,5,8,11-tetrayl)tetrabenzoic acid, meso-tetra(4-carboxyphenyl)porphine, 4,4',4'',4'''-(dibenzo[g, at least one of: tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene, 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid, and 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid). Therefore, by adding an organic ligand without electron-withdrawing groups, on the one hand, the density of electron-withdrawing groups in the second solution can be reduced, reducing the spatial blockage caused by the presence of a large number of electron-withdrawing groups in the local space of the metal-organic framework, and weakening the steric effect of electron-withdrawing groups that is unfavorable to crystal synthesis. On the other hand, the organic ligand without electron-withdrawing groups is conducive to coordination with the metal node, forming a template framework, inducing the organic ligand containing electron-withdrawing groups to coordinate with the metal node, and ultimately forming a metal-organic framework containing electron-withdrawing groups. By introducing electron-withdrawing groups into the metal-organic framework, the position of the lowest unoccupied molecular orbital of the metal-organic framework can be shifted in a direction that is conducive to photocatalytic hydrogen production, and its optical band gap can be reduced, its light absorption capacity can be improved, and the separation and transfer rate of photogenerated carriers can be increased, thereby increasing the rate of photocatalytic hydrogen production.

[0051] According to some embodiments of the present application, the electron-withdrawing group replaces the hydrogen atom at the ortho or meta position of the carboxyl group.

[0052] According to some embodiments of the present application, the mixed ligand includes a nitro-containing pyrene-based ligand and a nitro-free pyrene-based ligand. Thus, by adding an organic ligand that does not contain a nitro group, on the one hand, the density of the nitro group in the second solution can be reduced, the presence of a large number of nitro groups in the local space of the metal-organic framework can be reduced to cause spatial blockage, and the spatial effect of the nitro group on crystal synthesis that is unfavorable can be weakened; on the other hand, the organic ligand that does not contain a nitro group is conducive to coordination with the metal node, and can form a template framework, inducing the nitro-containing organic ligand to coordinate with the metal node, and finally forming a nitro-containing metal-organic framework. By introducing a nitro group into the metal-organic framework, the position of the lowest unoccupied molecular orbital of the metal-organic framework can be moved in a direction that is conducive to photocatalytic hydrogen production, and its optical band gap can be reduced, the light absorption capacity can be improved, and the separation and transfer rate of photogenerated carriers can be increased, thereby increasing the rate of photocatalytic hydrogen production.

[0053] According to some embodiments of the present application, the molar ratio of the nitro-containing pyrenyl ligand to the nitro-free pyrenyl ligand is (1-10):(1-10). For example, it can be 7:1, 3:1, 2:1, 1:1, 1:3, 1:5, 1:7, etc. Thus, by adjusting the molar ratio of the nitro-containing pyrenyl ligand to the nitro-free pyrenyl ligand within the above range, the density of nitro groups and the steric blocking effect in the mixed ligand can be reduced, thereby improving the efficiency of preparing the metal-organic framework. According to some embodiments of the present application, the molar ratio of the nitro-containing pyrenyl ligand to the nitro-free pyrenyl ligand is (1-3):(1-3).

[0054] According to some embodiments of the present application, the nitro-containing pyrene-based ligand includes at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid, and 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid), and the nitro group replaces the hydrogen atom at the ortho or meta position of the carboxyl group.

[0055] According to some embodiments of the present application, the nitro-containing pyrenyl ligand includes a compound represented by Formula 2: Formula 2.

[0056] According to some embodiments of the present application, the nitro-free pyrene-based ligand includes at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid, 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid), and pyrene-1,3,6,8-tetracarboxylic acid.

[0057] According to some embodiments of the present application, the pyrenyl ligand not containing a nitro group includes a compound represented by Formula 3:

[0058] Formula 3.

[0059] According to some embodiments of the present application, the temperature of the first heating is 40° C.-150° C., and the time of the first heating is 0.5 h-2 h. Thus, by setting the temperature and time of the first heating within the above ranges, the reaction rate is increased while avoiding uneven structure of the resulting metal clusters.

[0060] As an example, the temperature of the first heating may be 40° C., 60° C., 80° C., 100° C., or 120° C., or may be within a range consisting of any of the above values.

[0061] As an example, the first heating time may be 0.5 h, 1 h, 1.5 h or 2 h, or may be within a range consisting of any of the above values.

[0062] S30: heating the second solution for a second time, cooling, centrifuging, and drying to obtain the metal-organic framework;

[0063] According to some embodiments of the present application, the second solution is placed in an oven for a second heating. After the reaction is completed, the solution is cooled to room temperature, centrifuged, and dried to obtain the metal-organic framework.

[0064] According to some embodiments of the present application, the second heating temperature can be 80° C.-200° C., and the second heating time can be 8 hours-72 hours. Thus, by setting the second heating temperature within the above range, the reaction rate can be increased while preventing an increase in metal-organic framework defects.

[0065] As an example, the temperature of the second heating may be 80°C, 90°C, 100°C, 110°C, 120°C, 150°C, 200°C, etc., or may be a range consisting of any of the above values.

[0066] As an example, the second heating time may be 8 h, 10 h, 20 h, 30 h, 40 h, 50 h, 60 h, 70 h or 72 h, etc., or may be a range consisting of any of the above values.

[0067] According to some embodiments of the present application, the method further comprises washing the metal-organic framework. Specifically, washing can be performed using a second organic solvent. The second organic solvent comprises at least one of methanol, ethanol, acetone, and DMF.

[0068] The second aspect of the present application proposes a metal organic framework containing an electron-withdrawing group, which is prepared using the method proposed in the first aspect of the present application.

[0069] According to some embodiments of the present application, the metal organic framework containing electron-withdrawing groups is as shown in the attached Figure 2 shown.

[0070] The third aspect of the present application proposes the application of the electron-withdrawing metal organic framework prepared by the method proposed in the first aspect of the present application or the electron-withdrawing metal organic framework proposed in the second aspect of the present application in the field of photocatalysis.

[0071] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0072] Example 1

[0073] ZrOCl2·8H2O (97 mg, 0.3 mmol) and benzoic acid (0.7 g, 5.7 mmol) were placed in a pressure tube, 8 mL of DMF was added, and the mixture was sonicated for 30 minutes. The mixture was then reacted in a forced-air drying oven at 80°C for 60 minutes. After cooling to room temperature, H4TBAPy (20 mg, 0.029 mmol) (Formula 3) and H4TBAPy-NO2 (78 mg, 0.088 mmol) (Formula 2) were added to the reaction solution, and the mixture was sonicated for 30 minutes. The reaction was continued in a forced-air drying oven at 100°C for 24 hours. After cooling to room temperature, the resulting product was transferred to a 50 mL centrifuge tube and centrifuged at 11,000 rpm for 5 minutes. The product was then washed with DMF until the supernatant became colorless and transparent. The product was then washed three times with ethanol to replace the DMF solution. The isolated solid was dried in vacuum at 60°C for 18 hours to obtain the nitro-containing metal-organic framework.

[0074] Example 2

[0075] The preparation method of the metal organic framework was the same as that in Example 1, except that H4TBAPy (27 mg, 0.039 mmol) and H4TBAPy-NO2 (67 mg, 0.078 mmol) were added to the reaction solution.

[0076] Example 3

[0077] The preparation method of the metal organic framework was the same as that in Example 1, except that H4TBAPy (40 mg, 0.058 mmol) and H4TBAPy-NO2 (50 mg, 0.058 mmol) were added to the reaction solution.

[0078] Example 4

[0079] The preparation method of the metal-organic framework was the same as that of Example 1, except that HfCl4 (96 mg, 0.3 mmol) was placed in a pressure tube, and H4TBAPy (60 mg, 0.088 mmol) and H4TBAPy-NO2 (25 mg, 0.029 mmol) were added to the reaction solution.

[0080] Example 5

[0081] ZrCl₄ (214 mg, 0.918 mmol) and acetic acid (3.6 ml, 61.7 mmol) were placed in a reaction vessel, and 45 mL of DMF was added. The mixture was sonicated for 10 minutes and allowed to react in a forced-air drying oven at 40°C for 30 minutes. After cooling to room temperature, terephthalic acid (76 mg, 0.46 mmol) and tetrafluoroterephthalic acid (109 mg, 0.46 mmol) were added to the reaction solution. The mixture was sonicated for 30 minutes and allowed to react in a forced-air drying oven at 120°C for 16 hours. After cooling to room temperature, the resulting product was transferred to a 50 mL centrifuge tube and centrifuged at 11,000 rpm for 5 minutes. The product was then washed with DMF until the supernatant became colorless and transparent. The product was then washed three times with methanol to replace the DMF solution. The isolated solid was dried in vacuo at 80°C for 12 hours.

[0082] Example 6

[0083] ZrCl₄ (214 mg, 0.918 mmol) and acetic acid (3.6 ml, 61.7 mmol) were placed in a reactor, and 45 mL of DMF was added. The mixture was sonicated for 10 minutes and allowed to react in a forced-air drying oven at 40°C for 30 minutes. After cooling to room temperature, terephthalic acid (76 mg, 0.46 mmol) and tetrachloroterephthalic acid (140 mg, 0.46 mmol) were added to the reaction solution. The mixture was sonicated for 30 minutes and allowed to react in a forced-air drying oven at 120°C for 16 hours. After cooling to room temperature, the resulting product was transferred to a 50 mL centrifuge tube and centrifuged at 11,000 rpm for 5 minutes. The product was then washed with DMF until the supernatant became colorless and transparent. The product was then washed three times with methanol to replace the DMF solution. The isolated solid was dried in vacuo at 80°C for 12 hours.

[0084] Comparative Example 1

[0085] ZrOCl2·8H2O (97 mg, 0.3 mmol) and benzoic acid (0.7 g, 5.7 mmol) were placed in a 15 mL pressure tube and 8 mL of DMF was added. The reaction solution was sonicated for 30 minutes and then reacted at 80°C in a forced air drying oven for 60 minutes. After cooling to room temperature, H4TBAPy (80 mg, 0.117 mmol) was added to the reaction solution and sonicated for 30 minutes. The reaction was then allowed to react at 100°C in a forced air drying oven for 24 hours. After cooling to room temperature, the synthesized NU-901 product was transferred to a 50 mL centrifuge tube and centrifuged at 11,000 rpm for 5 minutes. The supernatant containing unliganded ligand was poured into a waste container, and NU-901 was washed with fresh DMF until the supernatant became colorless and transparent. The solution was then washed three times with ethanol to replace the DMF solution. Finally, the isolated NU-901 was dried in a vacuum at 60°C for 18 hours.

[0086] Performance Testing

[0087] Powder X-ray diffraction (PXRD) was performed under the following test conditions: a Cu-Ka radiation source, a voltage of 40 kV, a current of 20 mA, a step size of 0.05°, and a scanning speed of 8° / min over a range of 2θ = 2-50°. The photocatalysts were ground into powder using an agate mortar for testing.

[0088] Fourier transform infrared absorption spectroscopy (FT-IR): The FT-IR measurements of the embodiment were recorded on a Bruker INVENIO S using a KBr disk in the range of 1250 cm -1 -1450cm -1 .

[0089] Scanning electron microscope (SEM): SEM testing is conducted on a JEOL 7900F field emission scanning electron microscope. The sample droplets need to be dispersed and sprayed with gold on a silicon wafer before testing.

[0090] Thermogravimetric analysis (TGA) was performed on a Rigaku STA8122 series thermogravimetric analyzer. The samples were heated from room temperature to 700°C at a rate of 10°C / min in a nitrogen atmosphere.

[0091] Ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS): carried out on a Lambda 850+ series UV-visible spectrophotometer from PerkinElmer, USA, using BaSO4 as a control, and the test range was 250nm-800nm.

[0092] Band gap calculation (Eg): Calculated based on UV-Vis DRS data using the Tauc Plot formula.

[0093] Photoluminescence spectroscopy (PL) was performed on a FLS980 series steady-state / transient fluorescence spectrometer (Edinburgh, UK) with an excitation wavelength of 405 nm.

[0094] Mott-Schottky tests were conducted on a CHI 760E electrochemical workstation using a standard three-electrode system. A 1cm*1cm Pt sheet was used as the counter electrode, an Ag / AgCl reference electrode was used, and a 3mm diameter Pt-carbon electrode was used as the working electrode. The electrolyte was a 0.5M Na₂SO₄ aqueous solution. The test range was -1V to 1V, and the test frequencies were 200Hz, 500Hz, and 1000Hz.

[0095] Photocatalytic hydrogen production (HER) performance was tested using a Perfil all-glass automated online trace gas analysis system (LabSolar 6A) coupled with a Furley gas chromatograph (GC9790II). The specific process was as follows: 7.5 mg of the metal-organic framework (MOF) photocatalyst and 3.52 g of ascorbic acid (sacrificial agent) were added to 100 ml of deionized water and dispersed uniformly by ultrasonication for 10 minutes. Then, 20 μl of a 4 mg / ml chloroplatinic acid solution was added to deposit 0.50 wt% Pt onto the photocatalyst via photodeposition. The LabSolar 6A was used as the reaction system. After thorough evacuation, 20 ml of argon was added as the carrier gas. The catalytic test system temperature was maintained at 4°C, a xenon lamp was used as the simulated light source, and photocatalytic gas emissions were detected by gas chromatograph.

[0096] Depend on Figure 3 It can be seen that the pyrene-based metal-organic frameworks prepared in Examples 1, 2, 3 and 4 of the present application have the same crystal structure.

[0097] Depend on Figure 4 It can be seen that the crystal structures of the metal organic frameworks prepared in Example 5 and Example 6 of the present application are the same.

[0098] Depend on Figure 5 It can be seen that Example 1 of the present application introduces a nitro group (having a nitro characteristic peak) into the pyrene-based metal-organic framework.

[0099] Depend on Figure 6 It can be seen that Example 4 of the present application introduces a nitro group (with a nitro characteristic peak) into the pyrene-based metal-organic framework.

[0100] Depend on Figure 7 It can be seen that Example 5 of the present application introduces an electron-withdrawing group F atom (having a characteristic peak of an F-containing ligand) into the metal organic framework.

[0101] Depend on Figure 8 It can be seen that Example 6 of the present application introduces an electron-withdrawing group Cl atom (having a characteristic peak of a Cl-containing ligand) into the metal organic framework.

[0102] Depend on Figure 9 It can be seen that the morphology of the metal organic framework prepared in Comparative Example 1 of the present application is formed by the agglomeration of ultrasmall nanoparticles.

[0103] Depend on Figure 10 It can be seen that in Example 1 of the present application, by introducing nitro groups into the metal organic framework, the metal organic framework prepared has the morphology of ellipsoidal particles.

[0104] Depend on Figure 11It can be seen that the introduction of nitro groups does not destroy the thermal stability of the original metal-organic framework, and both materials can maintain good thermal stability below 500°C.

[0105] Depend on Figure 12 It can be seen that the introduction of nitro groups improves the light absorption ability of the pyrene-based metal-organic framework.

[0106] Depend on Figure 13 It can be seen that the introduction of nitro groups reduces the optical band gap of the pyrene-based metal-organic framework.

[0107] Depend on Figure 14 It can be seen that the strong electron-withdrawing ability of the nitro group causes the photogenerated electrons generated by light excitation to transfer toward the nitro group, reducing the recombination rate of photogenerated electrons and holes, which is manifested as a significant quenching of emission in the photoluminescence spectrum.

[0108] Depend on Figure 15 and Figure 16 It can be seen that the calculated flat band potential of the nitrated pyrene-based metal-organic framework in Example 1 is more negative than that in Comparative Example 1, indicating that the introduction of the nitro group causes the lowest unoccupied molecular orbital of the pyrene-based metal-organic framework to move in a direction that is conducive to hydrogen production.

[0109] Depend on Figure 17 and Figure 18 It can be seen that the amount of hydrogen produced by the nitrated pyrene-based metal-organic framework prepared in Example 1 as a photocatalyst within 5 hours is significantly higher than that in Comparative Example 1, and the hydrogen production rate is also significantly higher than that in Comparative Example 1, indicating that the present application can indeed improve its catalytic effect by introducing a nitro group on the pyrene-based metal-organic framework as a photocatalyst for hydrolysis and hydrogen production.

[0110] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and intent of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for preparing a metal organic framework containing an electron-withdrawing group, characterized in that: include: (1) mixing a metal salt, a regulator, and a first organic solvent to obtain a first solution; (2) The first solution is heated for the first time, cooled, and a mixed ligand is added to form a second solution, wherein the mixed ligand includes an organic ligand containing an electron-withdrawing group and an organic ligand not containing an electron-withdrawing group, and the organic ligand containing an electron-withdrawing group and the organic ligand not containing an electron-withdrawing group have the same skeleton, and the skeleton includes terephthalic acid, 1,3,5-tricarboxyphenylbenzene, 4,4',4'',4'''-(perylene-2,5,8,11-tetrayl)tetrabenzoic acid, meso-tetra(4-carboxyphenyl)porphine, 4,4',4'',4'''-(dibenzo[g, At least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrakis(2-naphthoic acid); the electron-withdrawing group comprises at least one of a nitro group, a cyano group, a fluorine atom, a chlorine atom, and a trifluoromethyl group; (3) The second solution is heated for a second time, cooled, centrifuged, and dried to obtain the metal-organic framework.

2. The method according to claim 1, characterized in that The electron-withdrawing group replaces the hydrogen atom at the ortho or meta position of the carboxyl group.

3. The method according to claim 2, characterized in that The mixed ligand comprises a pyrenyl ligand containing a nitro group and a pyrenyl ligand not containing a nitro group.

4. The method according to claim 3, characterized in that The molar ratio of the nitro-containing pyrenyl ligand to the nitro-free pyrenyl ligand is (1-10): (1-10).

5. The method according to claim 4, characterized in that At least one of the following conditions is met: The nitro-containing pyrenyl ligand includes at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid, and 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid), wherein the nitro group replaces the hydrogen atom at the ortho or meta position of the carboxyl group; The nitro-free pyrene-based ligand includes at least one of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, 1,3,6,8-tetrakis(3-carboxyphenyl)pyrene, 4,4',4'',4''-(1,3,6,8-pyrenetetraalkyl-2,1-ethynyl)-tetrabenzoic acid, and 6,6',6'',6'''-(pyrene-1,3,6,8-tetramethylphenyl)tetrakis(2-naphthoic acid).

6. The method according to any one of claims 1 to 5, characterized in that Meet at least one of the following conditions: The metal salt includes at least one of metal chloride, metal nitrate, metal acetate, and metal sulfate; The regulator includes at least one of benzoic acid, acetic acid, trifluoroacetic acid, formic acid, and hydrochloric acid.

7. The method according to any one of claims 1 to 5, characterized in that Meet at least one of the following conditions: The temperature of the first heating is 40°C-150°C, and the time of the first heating is 0.5h-2h; The second heating temperature is 80°C-200°C, and the second heating time is 8h-72h; The metal in the metal salt includes at least one of zirconium, hafnium, cerium, titanium, iron, cobalt, and nickel.

8. A metal organic framework containing an electron-withdrawing group, characterized in that The method is prepared by any one of claims 1 to 7.

9. Use of the metal-organic framework containing electron-withdrawing groups prepared by the method according to any one of claims 1 to 7 or the metal-organic framework containing electron-withdrawing groups according to claim 8 in the field of photocatalysis.

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