Indium-based metal organic framework heterojunction catalyst with core-shell structure and preparation method of indium-based metal organic framework heterojunction catalyst

Abstract

The invention discloses a preparation method of an indium-based metal organic framework heterojunction catalyst with a core-shell structure, which comprises the following steps: simultaneously adding a carboxylic acid ligand and a tetra (4-carboxyphenyl) porphyrin ligand into an organic solvent, and then ultrasonically mixing with a metal indium salt solution uniformly to obtain a purple mixed solution of the metal indium salt and the ligand; the purple mixed solution is subjected to a solvothermal reaction for 4-8 h at the temperature of 100-150 DEG C, then a red wet solid is separated out, and after washing and drying, the obtained red powder is the indium-based metal organic framework material of the core-shell structure, namely the NH2-MIL-68 (In)-In-TCPP heterostructure. The NH2-MIL-68 (In) (at) In-TCPP heterostructure with a core-shell structure is constructed by taking a shared indium metal node as an interface, and meanwhile, the excellent electron transmission performance and relatively high CO2 adsorption and wide spectrum response capability of the tetra (4-carboxyphenyl) porphyrin unit are combined, so that the utilization rate of sunlight and the CO2 photocatalytic conversion efficiency are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal catalysis, and specifically relates to an indium-based metal organic framework heterojunction catalyst with a core-shell structure, and a preparation method and application thereof. Background Art

[0002] Metal-organic framework (MOFs) materials have attracted much attention in the fields of gas separation, catalysis, environmental purification, etc. due to their wide monomer sources, adjustable structural units, excellent specific surface area and pore structure. However, most single MOFs materials have weak conductivity, low electron transfer efficiency, weak light absorption ability, and poor stability due to the mismatch between metal orbitals and ligand orbitals, which greatly limits their application in the fields of catalytic conversion such as light, electricity, and heat.

[0003] Compared with single MOFs materials, constructing multi-component MOFs heterostructures can improve the efficiency of photogenerated charge transfer and enhance interfacial interactions to improve stability. The current methods for preparing MOFs heterojunctions are mainly through heteroepitaxial growth, surfactant template assistance, metal ion exchange and other methods. However, the above strategies have high requirements for the adaptation between metal and ligand units, and different metal and ligand units need to be screened, making the steps complicated and the success rate low. In addition, the mismatch of the band structures of different MOFs materials and metal orbitals is not conducive to the stability of heterostructures, light absorption capacity, carrier separation efficiency and other properties. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a core-shell structure indium-based metal organic framework heterojunction catalyst and a preparation method thereof in view of the deficiencies in the above-mentioned prior art, so as to improve the problems of weak conductivity, low electron transfer efficiency, weak light absorption ability and poor stability in the existing MOFs-based catalysts.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is:

[0006] A core-shell structured indium-based metal organic framework heterojunction catalyst, which uses two-dimensional layered indium tetracarboxylphenylporphyrin (In-TCPP) nanosheets as a shell layer and a spindle-structured metal organic framework NH2-MIL-68 (In) as a core, and the shell layer wraps the inner core of the spindle structure to form a core-shell structure; wherein the length of the spindle is in the range of 1 to 2.0 μm.

[0007] The method for preparing the above-mentioned indium-based metal-organic framework heterojunction catalyst with a core-shell structure comprises the following steps:

[0008] (1) adding 2-aminoterephthalic acid and tetrakis(4-carboxyphenyl)porphyrin as ligands into an organic solvent and mixing them evenly to obtain a ligand solution; dissolving a metal indium salt into the organic solvent to obtain a metal indium salt solution;

[0009] (2) uniformly mixing the ligand solution obtained in step (1) with the metal indium salt solution to obtain a purple solution of a mixture of the metal indium salt and the ligand;

[0010] (3) The purple solution in step (2) is subjected to a solvothermal reaction at 100 to 150° C. for 4 to 8 hours, and then a red wet solid is separated. After washing and drying, the resulting red powder is an indium-based metal organic framework heterojunction catalyst with a core-shell structure, that is, an NH2-MIL-68(In)@In-TCPP heterostructure with a core-shell structure.

[0011] According to the above scheme, in step (1), in the ligand solution, the concentration of 2-aminoterephthalic acid is in the range of 10 to 100 mmol / L, the concentration of tetrakis(4-carboxyphenyl)porphyrin is in the range of 1 to 10 mmol / L, and the molar ratio of 2-aminoterephthalic acid to tetrakis(4-carboxyphenyl)porphyrin is (4 to 20): 1. Preferably, in the ligand solution, the concentration of 2-aminoterephthalic acid is in the range of 10 to 30 mmol / L, the concentration of tetrakis(4-carboxyphenyl)porphyrin is in the range of 1 to 4 mmol / L, and the molar ratio of 2-aminoterephthalic acid to tetrakis(4-carboxyphenyl)porphyrin is (7.5 to 15): 1.

[0012] According to the above scheme, in step (1), the metal indium salt solution In 3+ The theoretical concentration (based on In in indium salt) 3+ (calculated based on complete ionization) is in the range of 0.05 to 0.25 mol / L.

[0013] According to the above scheme, in step (1), the organic solvent is a mixture of one or more of N-N-dimethylformamide, methanol, etc.; the metal indium salt is a mixture of one or more of indium nitrate, indium chloride, etc.

[0014] According to the above scheme, in step (1), 2-aminoterephthalic acid can also be replaced by one or more carboxylic acid ligands such as terephthalic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid, and 1,3,5-benzenetricarboxylic acid.

[0015] According to the above scheme, in step (2), when the ligand solution is mixed with the metal indium salt solution, tetrakis(4-carboxyphenyl)porphyrin and In 3+ The molar ratio is in the range of (0.01~0.05):1.

[0016] According to the above scheme, the mixing in step (1) and step (2) is carried out by ultrasonic treatment, and the ultrasonic time does not exceed 0.5h.

[0017] According to the above scheme, in step (3), the temperature of the solvothermal reaction is 100-150°C, and the time of the solvothermal reaction is 4-8 hours. Preferably, the temperature of the solvothermal reaction is 120-140°C, and the time of the solvothermal reaction is 4.5-6 hours.

[0018] The indium-based metal organic framework heterojunction catalyst with a core-shell structure described in the present invention can be used for the CO2 reduction reaction coupled with water oxidation to prepare formic acid and H2O2.

[0019] The technical concept of the present invention is as follows:

[0020] The present invention adopts a one-pot method for the first time to control the nucleation kinetics of two indium-based MOFs materials to construct a NH2-MIL-68(In)@In-TCPP heterostructure with a core-shell structure, so that it has both a stable heterogeneous interface and efficient carrier separation efficiency. The present invention first adjusts the nucleation kinetics of the two MOFs materials to form a metal indium-based node with defect sites under the action of competitive coordination, and then forms an efficient and stable heterogeneous interface through a shared metal indium-based node. Among them, due to the rapid reaction nucleation of 2-aminoterephthalic acid and indium salt, NH2-MIL-68(In) forms an inner core platform, and the indium metal sites developed on the surface will coordinate with the porphyrin ligands with slower nucleation kinetics to form In-TCPP nanosheets on the surface, thereby obtaining a NH2-MIL-68(In)@In-TCPP heterostructure with a stable core-shell structure.

[0021] Taking the photocatalytic CO2 reduction coupled with H2O oxidation reaction as an example, it is proved that the NH2-MIL-68(In)@In-TCPP heterostructure with core-shell structure of the present invention has excellent sunlight utilization, carrier migration efficiency and CO2 reduction reaction coupled with water oxidation conversion efficiency. Among them, the In-O bond in the metal indium node of the inner core NH2-MIL-68(In) is a water oxidation site, and the In-N site in In-TCPP is a CO2 RR site. The defective indium metal node formed can further optimize the electron transfer between interfaces and enhance the activity of the catalyst. Moreover, the spindle-shaped NH2-MIL-68(In) is completely wrapped by the two-dimensional In-TCPP nanosheets. This heterogeneous structure not only ensures the separation of the redox sites of CO2 and H2O, but also avoids the recombination of photogenerated carriers, further enhances the absorption capacity of sunlight, and realizes the effective separation of photogenerated electrons and holes. At the same time, it combines the excellent electron transport performance of the porphyrin unit and the high CO2 adsorption and wide spectrum response capabilities, thereby significantly improving the utilization of solar energy and the CO2 photocatalytic conversion efficiency.

[0022] The preparation method provided by the present invention can construct a variety of MOFs heterojunction catalysts with core-shell structures, such as replacing metal In with transition metals such as Fe and Al to form MOF cores of NH2-MIL-68 (Al) and MIL-88B (Fe), and in situ growing MOFs materials such as Fe-TCPP and Al-TCPP to synthesize different MOFs-based heterojunction metal catalysts. According to the characteristics of each metal, it can be applied to different types of catalytic reactions, greatly improving the catalytic activity.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] First, the present invention successfully synthesized a core-shell structured NH2-MIL-68(In)@In-TCPP heterojunction through a unique synthesis strategy, forming a novel metal-organic framework material composite material. This structure not only provides a stable heterojunction for the transmission of interface electrons and holes, but also effectively inhibits the recombination of photogenerated electrons and holes, accelerates the transfer of carriers, thereby improving its light absorption capacity and showing excellent catalytic activity and stability.

[0025] Second, compared with the traditional bottom-up synthesis method of dual MOF heterojunction catalysts, the present invention is the first to use a one-pot method to regulate the reaction kinetics to form a core-shell structured heterojunction without adding any template agent, thereby reducing the cumbersome steps of the heterojunction catalyst and greatly reducing the preparation cost. The preparation method is green and simple, and does not produce polluting gases, which helps to promote the large-scale and widespread application of heterojunction catalysts in the fields of light, electricity, and thermal catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the metal indium frame material NH2-MIL-68 (In) prepared in Comparative Example 1.

[0027] Figure 2 This is a scanning electron microscope image of the metal indium frame material In-TCPP prepared in Comparative Example 2.

[0028] Figure 3 This is a scanning electron microscope image of the core-shell structured indium-based metal organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) prepared in Example 1.

[0029] Figure 4 These are transmission electron microscope images of the core-shell structured indium-based metal organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) prepared in Example 1 at different growth times (i.e., the solvent thermal time in step (3) of Example 1 is 0.5h, 1h, 3h, and 5h, respectively).

[0030] Figure 5 a is the X-ray diffraction spectrum of the final product prepared in Comparative Example 1, Comparative Example 2 and Example 1; Figure 5 b is the X-ray diffraction spectrum of the product when the solvent thermal time in step (3) of Example 1 is 0.5h, 1h, 3h and 5h respectively.

[0031] Figure 6 This is the activity diagram of the indium-based metal organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) with a core-shell structure prepared in Example 1 driven by CO2 reduction and H2O oxidation under sunlight conditions. Note: Figure 6 The vertical axis is the total output for 4 hours.

[0032] Figure 7 It is a performance diagram of the catalysts prepared in Example 1, the blank control and Comparative Examples 1 to 3 for photocatalytic CO2 reduction and H2O oxidation.

[0033] Figure 8 This is a stability test chart of CO2 reduction and H2O oxidation of the core-shell structured indium-based metal organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) prepared in Example 1.

[0034] Fig. 9 This is a cyclic performance diagram of the core-shell indium-based metal organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) prepared in Example 1 for CO2 reduction and H2O oxidation.

[0035] M68N in the accompanying drawings represents NH2-MIL-68(In), and M68N@In-TCPP represents NH2-MIL-68(In)@In-TCPP. DETAILED DESCRIPTION

[0036] In order to better understand the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments.

[0037] Example 1

[0038] A method for preparing a core-shell structured indium-based metal organic framework heterojunction catalyst, the specific steps are as follows

[0039] (1) Weigh 0.09 mmol 2-aminoterephthalic acid and 0.01 mmol tetrakis(4-carboxyphenyl)porphyrin into a round-bottom flask, then add 5 mL NN dimethylformamide, and sonicate for 0.5 h to obtain a ligand solution (wherein the concentration of 2-aminoterephthalic acid is within the range of 18 mmol / L, and the concentration of tetrakis(4-carboxyphenyl)porphyrin is 2 mmol / L); add indium nitrate salt into NN dimethylformamide to prepare a 0.1 mol / L indium nitrate solution. 3+ The theoretical concentration is 0.1 mol / L;

[0040] (2) The ligand solution described in step (1) and indium nitrate are mixed uniformly in a volume ratio of 1:1 to obtain a purple mixed solution; wherein tetrakis(4-carboxyphenyl)porphyrin and In 3+ The molar ratio is 0.02:1;

[0041] (3) The purple mixed solution was transferred to a sealed reactor and reacted at 130°C for 5 h. After the reaction was completed, it was washed and centrifuged with N-N-dimethylformamide solution, dried and ground into powder. The resulting red powder was a core-shell indium-based metal organic framework heterojunction catalyst, i.e., NH2-MIL-68(In)@In-TCPP heterojunction with a core-shell structure.

[0042] The scanning electron microscopy of the core-shell indium-based metal organic framework heterojunction catalyst prepared in Example 1 is as follows: Figure 3 As shown, it can be seen that the morphology and structure of NH2-MIL-68(In)@In-TCPP are uniform, the surface is rough, and the overall structure is a spindle. The length is mainly concentrated between 1 and 1.5 μm, and the outer layer of the spindle structure is wrapped with two-dimensional layered nanosheets. This is because the nucleation kinetics of tetrakis(4-carboxyphenyl)porphyrin and indium salt are slow, and they will compete with 2-aminoterephthalic acid ligands for coordination at the same time, thereby acting as a capping agent to inhibit the growth of NH2-MIL-68(In) and shorten the length.

[0043] The transmission electron microscopy images of the core-shell indium-based metal organic framework heterojunction catalyst prepared in Example 1 at different growth time periods are as follows: Figure 4 As shown in the figure, the inner core spindle NH2-MIL-68 (In) was synthesized within 0.5 h. As time went by, a two-dimensional lamellar structure gradually formed on the surface, which became thicker as the reaction time progressed. It was preliminarily inferred that this was due to the growth and wrapping of In-TCPP on the surface.

[0044] The X-ray diffraction of the core-shell indium-based metal organic framework heterojunction catalyst prepared in Example 1 (the final product after 5 hours of solvent thermal reaction) is as follows: Figure 5As shown in a, 4.9° and 9.8° are the characteristic peaks of spindle NH2-MIL-68 (In), corresponding to the (110) and (220) crystal planes, respectively; 7.5° belongs to the characteristic peak of In-TCPP (021) crystal plane. Figure 5 b is the X-ray diffraction spectrum of the product when the solvent thermal time in step (3) of Example 1 is 0.5h, 1h, 3h and 5h respectively, showing that the characteristic peak of spindle NH2-MIL-68(In) appears within 10min of the reaction, proving that NH2-MIL-68(In)@In-TCPP heterostructure is based on NH2-MIL-68(In) as the core. As the reaction time proceeds, the characteristic peak at 7.5° belonging to the In-TCPP(021) crystal plane gradually increases, proving that the In-TCPP framework material is wrapped on the surface in the form of two-dimensional nanosheets.

[0045] Comparative Example 1

[0046] The difference between Comparative Example 1 and Example 1 is that tetrakis(4-carboxyphenyl)porphyrin is not added, and the final product is the metal indium framework material NH2-MIL-68(In).

[0047] The scanning electron microscopy of the single NH2-MIL-68 (In) prepared in Comparative Example 1 is as follows: Figure 1 As shown, it is a rod-like structure similar to a spindle, with a relatively uniform size, and the rod length is mainly between 7 and 10 μm.

[0048] Comparative Example 2

[0049] The difference between Comparative Example 2 and Example 1 is that 2-aminoterephthalic acid is not added, and the final product is a metal indium frame material In-TCPP. Figure 2 As shown, it is a bulk amorphous structure.

[0050] Comparative Example 3

[0051] The products of Comparative Example 1 and Comparative Example 2 were mixed at a mass ratio of 10:1, i.e., a physical mixture of metal indium framework materials (NH2-MIL-68(In)+In-TCPP).

[0052] Application Examples

[0053] The catalysts prepared in Example 1 and Comparative Examples 1 to 3 were used for the CO2 reduction reaction coupled with water oxidation to produce formic acid and H2O2. Outdoor tests and tests under laboratory conditions were conducted respectively.

[0054] The specific process of outdoor testing is as follows: 5 mg of each catalyst is added to 10 mL of pure water to prepare a catalyst solution with a concentration of 0.5 mg / mL, and then sunlight (with a light intensity of 1.0 to 1.3 W / cm 2) is directly used to drive the photocatalytic reaction, and the intensity of the concentrated sunlight is 1.0-1.33W / cm 2 After the reaction, the CO2 conversion products are mainly HCOOH and CO, and the H2O oxidation product is mainly H2O2, and no additional sacrificial agent and photosensitizer are required. Continuous illumination and timely collection and detection of gas and liquid products.

[0055] like Figure 6 As shown in Figure 1, the NH2-MIL-68(In)@In-TCPP catalyst prepared in Example 1 has a HCOOH yield of up to 397.5 μmol g -1 h -1 The CO yield was 61.2 μmol g -1 h -1 Meanwhile, the activity of water oxidation product H2O2 was 312 μmol g -1 h -1 The calculated solar energy conversion efficiency (STC) is 0.04%. This result proves that the synthesized NH2-MIL-68(In)@In-TCPP heterojunction catalyst has very good practical application potential and can achieve efficient CO2 reduction to produce HCOOH and H2O oxidation to produce H2O2 under sunlight conditions.

[0056] Different from the outdoor test, the test process under laboratory conditions is as follows: 5 mg of each catalyst is added to 10 mL of pure water to prepare a catalyst solution with a concentration of 0.5 mg / mL. A 300 W xenon lamp is used as the light source, a 400 nm visible light cutoff filter is configured, and the light source intensity is adjusted to 0.3 W / cm 2 . Continuous illumination and timely collection and detection of gas and liquid products. The stability test is to continuously illuminate the reaction for 25 hours, and the gas and liquid products are tested every 5 hours. The cyclic test is to conduct a 5-hour cyclic test on the above catalyst. After each 5-hour test, the catalyst is centrifuged and washed with pure water and dried. The test is repeated 5 times, and the catalyst activity is recorded each time. The results are as follows Figures 7 to 9 shown.

[0057] like Figure 7 As shown in the figure, the HCOOH activity of the core-shell indium-based metal organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) prepared in Example 1 is 121.1 μmol g -1 h -1 The yield of H2O2 was 119.3 μmol g -1 h -1 In Comparative Example 1, the HCOOH yield of NH2-MIL-68(In) as the catalyst was 16.7 μmol g -1 h-1 The yield of H2O2 was 21.3 μmol g -1 h -1 In comparative example 2, the HCOOH activity of In-TCPP as a catalyst was 15.8 μmol g -1 h -1 No H2O2 was produced, O2 was the main product, and the yield was 4.3 μmol g -1 h -1 In Comparative Example 3, the catalytic activity of NH2-MIL-68(In)+In-TCPP as a catalyst was 12.4 μmol g -1 h -1 The yield of H2O2 was 22.5 μmol g -1 h -1 It can be seen that compared with NH2-MIL-68(In) and In-TCPP prepared in Comparative Examples 1 and 2, the activity of the NH2-MIL-68(In)@In-TCPP catalyst prepared in the present invention is significantly improved, and is 10 times that of Comparative Example 3. This result proves that the heterogeneous interface in the NH2-MIL-68(In)@In-TCPP catalyst significantly promotes the migration of photogenerated carriers, so that the separated electrons and holes participate in CO2 reduction and H2O oxidation reactions, respectively.

[0058] like Figure 8 and Fig. 9 As shown, after 5 cycles and a total of 25 hours of photocatalytic experiments, the chemical skeleton and crystal structure of the core-shell structure indium-based metal-organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) prepared in Example 1 are also very stable, and the activity can be maintained at more than 91%.

[0059] It can be seen that the core-shell structured indium-based metal-organic framework heterojunction catalyst of the present invention is superior to conventional inorganic semiconductor catalysts in the prior art in terms of key indicators such as absorption energy of sunlight, catalytic activity and stability in the solar-driven photocatalytic CO2 reduction and H2O oxidation reactions. In particular, in the long-term stability test, the NH2-MIL-68(In)@In-TCPP catalyst exhibited excellent chemical skeleton and crystal structure stability.

[0060] Example 2

[0061] A method for preparing a core-shell structured indium-based metal organic framework heterojunction catalyst, the specific steps are as follows

[0062] (1) Weigh 0.12 mmol of 2-aminoterephthalic acid and 0.01 mmol of tetrakis(4-carboxyphenyl)porphyrin into a round-bottom flask, then add 5 mL of NN dimethylformamide, and sonicate for 0.5 h to obtain a ligand solution (wherein the concentration of 2-aminoterephthalic acid is within the range of 25 mmol / L, and the concentration of tetrakis(4-carboxyphenyl)porphyrin is 2 mmol / L); add indium nitrate salt into NN dimethylformamide to prepare a 0.1 mol / L indium nitrate solution. 3+ The theoretical concentration is 0.1 mol / L;

[0063] (2) The ligand solution described in step (1) and indium nitrate are mixed uniformly in a volume ratio of 1:1 to obtain a purple mixed solution; wherein tetrakis(4-carboxyphenyl)porphyrin and In 3+ The molar ratio is 0.02:1;

[0064] (3) The purple mixed solution was transferred to a sealed reactor and reacted at 130°C for 5 h. After the reaction was completed, it was washed with N-N-dimethylformamide solution and centrifuged. After drying, it was ground into powder. The resulting red powder was a core-shell indium-based metal organic framework heterojunction catalyst, i.e., NH2-MIL-68(In)@In-TCPP heterostructure with a core-shell structure.

[0065] The test was carried out under the same laboratory conditions as in Example 1. The HCOOH yield of the NH2-MIL-68(In)@In-TCPP catalyst obtained in Example 2 was 42.4 μmol g -1 h -1 The yield of H2O2 was 50.6 μmol g -1 h -1 .

[0066] Example 3

[0067] A method for preparing a core-shell structured indium-based metal organic framework heterojunction catalyst, the specific steps are as follows

[0068] (1) Weigh 0.075 mmol of 2-aminoterephthalic acid and 0.01 mmol of tetrakis(4-carboxyphenyl)porphyrin into a round-bottom flask, then add 5 mL of NN dimethylformamide, and sonicate for 0.5 h to obtain a ligand solution (wherein the concentration of 2-aminoterephthalic acid is within the range of 15 mmol / L, and the concentration of tetrakis(4-carboxyphenyl)porphyrin is 2 mmol / L); add indium nitrate salt into NN dimethylformamide to prepare a 0.1 mol / L indium nitrate solution. 3+ The theoretical concentration is 0.1 mol / L;

[0069] (2) The ligand solution described in step (1) and indium nitrate are mixed uniformly in a volume ratio of 1:1 to obtain a purple mixed solution; wherein tetrakis(4-carboxyphenyl)porphyrin and In 3+ The molar ratio is 0.02:1;

[0070] (3) The purple mixed solution was transferred to a sealed reactor and reacted at 130°C for 5 h. After the reaction was completed, it was washed with N-N-dimethylformamide solution and centrifuged. After drying, it was ground into powder. The resulting red powder was a core-shell indium-based metal organic framework heterojunction catalyst, i.e., NH2-MIL-68(In)@In-TCPP heterostructure with a core-shell structure.

[0071] The test was carried out under the same laboratory conditions as in Example 1. The HCOOH yield of the NH2-MIL-68(In)@In-TCPP catalyst obtained in Example 3 was 45.4 μmol g -1 h -1 The yield of H2O2 was 53.2 μmol g -1 h -1 .

[0072] In summary, compared with traditional catalysts, the core-shell structure indium-based metal organic framework heterojunction catalyst (NH2-MIL-68(In)@In-TCPP) provided by the present invention exhibits excellent catalytic activity and stability in the technology of solar-driven CO2 reduction to prepare formic acid coupled with H2O oxidation to prepare H2O2, with low cost and wide application range.

[0073] The above is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and changes without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. An indium-based metal-organic framework heterojunction catalyst with a core-shell structure, characterized in that: The steps include: (1) adding a carboxylic acid ligand and a tetrakis(4-carboxyphenyl)porphyrin ligand into an organic solvent and mixing them evenly to obtain a ligand solution; dissolving a metal indium salt into the organic solvent to obtain a metal indium salt solution; (2) uniformly mixing the ligand solution obtained in step (1) with the metal indium salt solution to obtain a purple solution of a mixture of the metal indium salt and the ligand; (3) The purple solution in step (2) is subjected to a solvothermal reaction, and then a red wet solid is separated. After washing and drying, the resulting red powder is an indium-based metal-organic framework heterojunction catalyst with a core-shell structure.

2. The method for preparing the core-shell indium-based metal-organic framework heterojunction catalyst according to claim 1, characterized in that: In step (1), the concentration of 2-aminoterephthalic acid in the ligand solution is in the range of 10 to 100 mmol / L, the concentration of tetrakis(4-carboxyphenyl)porphyrin is 1 to 10 mmol / L, and the molar ratio of 2-aminoterephthalic acid to tetrakis(4-carboxyphenyl)porphyrin is (4 to 20):

1.

3. The method for preparing the core-shell indium-based metal-organic framework heterojunction catalyst according to claim 1, characterized in that: In step (1), the metal indium salt solution In 3+ The theoretical concentration is in the range of 0.05 to 0.25 mol / L.

4. The method for preparing the core-shell indium-based metal-organic framework heterojunction catalyst according to claim 1, characterized in that: The organic solvent in step (1) includes one or both of N-N-dimethylformamide and methanol; the metal indium salt is one or both of indium nitrate and indium chloride; and the carboxylic acid ligand is one of 2-aminoterephthalic acid, terephthalic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid and 1,3,5-benzenetricarboxylic acid.

5. The method for preparing the core-shell indium-based metal-organic framework heterojunction catalyst according to claim 1, characterized in that: In step (2), when the ligand solution is mixed with the metal indium salt solution, tetrakis(4-carboxyphenyl)porphyrin and In 3+ The molar ratio is (0.01~0.05):

1.

6. The method for preparing the core-shell indium-based metal-organic framework heterojunction catalyst according to claim 1, characterized in that: In step (3), the temperature of the solvent thermal reaction is 100 to 150° C., and the time of the solvent thermal reaction is 4 to 8 hours.

7. The method for preparing the core-shell indium-based metal-organic framework heterojunction catalyst according to claim 6, characterized in that: In step (3), the temperature of the solvent thermal reaction is 120 to 140° C., and the time of the solvent thermal reaction is 4.5 to 6 hours.

8. An indium-based metal-organic framework heterojunction catalyst with a core-shell structure, characterized in that: It uses two-dimensional layered tetracarboxylphenylporphyrin indium nanosheets as the shell layer and a spindle-structured metal organic framework NH2-MIL-68 (In) as the core. The shell layer wraps the inner core of the spindle structure to form a core-shell structure; wherein the length of the spindle is in the range of 1 to 2.0 μm.

9. Use of the indium-based metal organic framework heterojunction photocatalyst with a core-shell structure as described in claim 8 in the preparation of formic acid and H2O2 by coupling CO2 reduction reaction with water oxidation.

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