Method for improving performance of In2O3 in catalyzing CO2 hydrogenation reduction reaction and application thereof

Abstract

The invention discloses a preparation method of an In2O3 catalyst with an epitaxial growth structure by growing an indium-based metal organic framework B on the surface of a metal organic framework precursor A serving as a substrate through an MOF-on-MOF heteroepitaxial growth strategy and application of the In2O3 catalyst in a carbon dioxide reduction reaction. The preparation process comprises the following steps: reacting soluble metal salt and terephthalic acid in a solvent DMF to obtain a metal organic framework precursor A; dispersing the precursor A, soluble indium salt, polyvinylpyrrolidone and terephthalic acid in DMF (Dimethyl Formamide) for reaction to obtain an In-based metal organic framework B growing on the metal organic framework precursor A; and then roasting in an inert atmosphere of a tubular furnace to obtain the In2O3 composite catalyst which is rich in oxygen vacancies and has enhanced interface action. The catalyst obtained by the invention not only retains the inherent characteristics of high specific surface area and multiple pore channels of the MOFs material, but also enables heterogeneous metal components and the indium-based metal organic framework to form high-grade doping with higher interfacial activity and space mutual embedding relationship. From the aspect of catalytic effect, the In2O3 catalyst with the epitaxial growth structure prepared by the invention realizes synergistic coupling of a loading effect and a doping effect.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a method for improving the performance of In2O3 in the catalytic reduction of CO2 and its application. Background Technology

[0002] With the advancement of global carbon neutrality goals, the catalytic conversion of CO2 into high-value-added chemicals has become an important way to alleviate environmental pressure and the energy crisis. In the CO2 hydrogenation reduction reaction, methanol and CO are common products. Due to their stable chemical properties and wide applications, they are often used as key chemical intermediates and are also important clean fuels.

[0003] Indium oxide (In₂O₃), as an n-type semiconductor catalyst, has shown great potential in this reaction. Its surface, rich in oxygen vacancies and numerous hydroxyl groups, effectively modulates electrons and generates adsorption sites, giving it excellent CO₂ adsorption activation capacity and methanol selectivity. However, pure-phase In₂O₃ has significant drawbacks, such as low catalytic activity and high recombination rate of photogenerated electron-hole pairs. To optimize the catalytic performance of In₂O₃, existing technologies often employ strategies such as support loading and elemental or composite oxide doping modification. For example, In₂O₃ is loaded onto supports such as ZnO and ZrO₂ to improve its dispersibility and promote oxygen vacancy formation, thereby optimizing catalytic performance; or In₂O₃ is doped with elements such as N, Ga, Ni, and Pd. This method can adjust the electronic band structure, expand the photoresponse range, and promote electron-hole pair separation, thereby improving the photocatalytic CO₂ reduction efficiency. Simultaneously, the introduction of metal elements can also enhance the adsorption and dissociation of H₂. However, from the perspective of catalytic efficiency and stability, there is still considerable room for improvement in performance even with the simple application of these two optimization methods of loading and doping.

[0004] The MOF-on-MOF strategy, as a novel method for constructing heterostructures, achieves the directional composite of two MOFs through stepwise epitaxial growth, enabling the creation of ordered heterostructures with controllable structures. However, there are currently no reports on applying this strategy to the preparation of In2O3-based catalysts to improve CO2 hydrogenation performance. Therefore, there is an urgent need to develop a method for preparing In2O3 catalysts based on MOF-on-MOF technology to address the challenges of interface control and poor dispersion of active sites in existing technologies. Summary of the Invention

[0005] The purpose of this invention is to overcome the performance defects of existing In2O3 catalysts in the CO2 hydrogenation reaction and to provide a method for preparing an In2O3-based composite catalyst with abundant heterostructures based on a MOF-on-MOF heteroepitaxial growth strategy. This method uses a metal-organic framework precursor A as a substrate, directionally grows an indium-based metal-organic framework B on its surface, and then calcines it to obtain the catalyst. The method also applies the catalyst to CO2 reduction. By precisely constructing the heterostructure, the oxygen vacancy concentration and charge separation efficiency of the catalyst are improved, thereby enhancing the activity, selectivity, and stability of the CO2 hydrogenation reduction reaction.

[0006] The technical solution provided by this invention is as follows:

[0007] A method for improving the performance of In2O3 in the catalytic CO2 hydrogenation reduction reaction and its application are disclosed. The method involves a MOF-on-MOF heteroepitaxial growth strategy, using a metal-organic framework precursor A as a substrate, and directionally growing an indium-based metal-organic framework B on its surface to form a hybrid material with abundant heterostructure interfaces. The hybrid material is then calcined under an inert atmosphere to obtain an In2O3-based composite catalyst rich in oxygen vacancies and with enhanced interfacial interactions.

[0008] Preferably, the method for improving the performance of In2O3 in the catalytic CO2 hydrogenation reduction reaction includes:

[0009] Step 1: Dissolve a certain mass of soluble metal salt and terephthalic acid BDC in N,N-dimethylformamide DMF solution. Transfer the mixed solution to a polytetrafluoroethylene reactor liner and react for several hours. Centrifuge to collect the precipitate, wash with DMF and ethanol several times, and dry to obtain metal-organic framework precursor A.

[0010] Step 2: Take a certain mass of soluble indium salt, polyvinylpyrrolidone (PVP), and the metal-organic framework precursor A prepared in Step 1, disperse them in DMF solution, add a certain mass of DMF solution containing BDC, stir thoroughly, transfer the resulting suspension to a hydrothermal reactor and react for several hours, centrifuge to collect the precipitate, wash with DMF and ethanol several times, and dry to obtain indium-based metal-organic framework B grown on metal-organic framework precursor A;

[0011] Step 3: The In-based metal-organic framework B epitaxially grown on metal-organic framework A is calcined in a tube furnace.

[0012] Preferably, the metal center of the metal-organic framework precursor A is a heterometallic metal with indium, and is not Ce or Al.

[0013] Preferably, the metal center of the metal-organic framework A is Zn, Ga, Cu, or Mg; more preferably, the metal center of the metal-organic framework A is Zn or Cu.

[0014] Preferably, the soluble metal salt and soluble indium salt are Zn(NO3)2·6H2O, Ga(NO3)3·4H2O, Cu(NO3)2·3H2O, Mg(NO3)2·6H2O, and In(NO3)3·4H2O.

[0015] Preferably, the polyvinylpyrrolidone (PVP) has a relative molecular mass of 58,000.

[0016] Preferably, the synthesis temperature range of the metal-organic framework A and the In2O3 catalyst with epitaxial growth structure is 100-140℃, and the reaction time is 6-48h.

[0017] Preferably, the roasting temperature of the roasting treatment is 400-600℃, the roasting time is 1-6h, and the inert atmosphere gas is N2 or Ar.

[0018] Preferably, in step one, 1 mmol of a soluble metal salt is dissolved in 15 mL of DMF, and then 15 mL of DMF solution containing 0.166 g BDC is added. After stirring for 30 min to ensure thorough mixing, the mixed solution is transferred to a 100 mL polytetrafluoroethylene reactor liner and reacted in an oven at 120 °C for 24 h. The precipitate is collected by centrifugation, washed multiple times with DMF and ethanol, and dried to obtain metal-organic framework precursor A.

[0019] Preferably, in step two, 1.492g In(NO3)3·4H2O, 0.58g PVP, and a certain mass of metal-organic framework precursor A are then dispersed in 30mL DMF solution. 30mL of DMF solution containing 0.664g BDC is added, and after thorough stirring, the resulting suspension is transferred to a 100mL polytetrafluoroethylene reactor liner and reacted in an oven at 120℃ for 12h. The precipitate is collected by centrifugation, washed multiple times with DMF and ethanol, and dried to obtain an indium-based metal-organic framework B epitaxially grown on metal-organic framework A.

[0020] Preferably, the mass fraction of metal in the In2O3 catalyst with epitaxial growth structure is 5-50%, and the mass of the added metal-organic framework precursor A is 0.1-2.5g.

[0021] Preferably, the roasting process in step three is roasting in a tube furnace at 500°C for 2 hours under an Ar atmosphere.

[0022] Preferably, the In2O3 catalyst with an epitaxial growth structure, or the In2O3 catalyst with an epitaxial growth structure prepared by the preparation method of the In2O3 catalyst with an epitaxial growth structure, is used in CO2 heating catalytic reduction reaction, CO2 photocatalytic reduction reaction, or CO2 electrocatalytic reduction reaction.

[0023] More preferably, it is used in the CO2 hydrogenation reduction reaction to prepare methanol or CO. 0.15g of catalyst and 0.15g of quartz sand are placed in a quartz reaction tube of a fixed-bed reactor, and N2 is introduced into it. Activation is carried out for 1 hour at atmospheric pressure and 200℃. The temperature is then increased to the reaction temperature of 260℃, irradiated with a 300W xenon lamp, and a mixed gas of CO2, H2, and N2 (feed ratio 1:3:1) is introduced. The pressure is increased to 3MPa, and the reaction is carried out continuously for several hours at a space velocity (GHSV) of 12000mL / (g·h). The gas effluent from the reactor is analyzed online using a gas chromatograph (GC-7920) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID).

[0024] The beneficial effects of this invention are as follows:

[0025] To address the issue of low efficiency and yield in methanol production via CO2 hydrogenation reduction, this invention effectively improves the In2O3 catalyst. The resulting In2O3 catalyst with a MOF epitaxial growth structure uses a pre-synthesized metal MOF as a substrate. Indium sources and ligands are introduced into the reaction system, and by controlling the reaction conditions, the indium-based metal-organic framework is directionally coordinated and grown on the surface and interface of the substrate MOF, forming a heterostructure with a well-defined crystal structure. This eliminates the need for subsequent additional loading steps, simplifying the preparation process and improving loading stability. This invention, based on a rational preparation process of "epitaxy growth" and "calcination," enhances the oxygen vacancy activity of the metal phase without causing the organic ligands to be consumed and leading to MOF structure collapse. The heterostructure metal MOF epitaxial growth structure retains the inherent characteristics of MOF materials—high specific surface area and porous structure—while also forming a more advanced doping with enhanced interfacial activity and spatial interlocking relationships. Furthermore, this invention employs a metal-organic framework precursor with a specific metal center to achieve interfacial synergy of heterogeneous metal oxides, resulting in a multiple improvement in both CO2 conversion rate and methanol selectivity compared to pure In2O3 catalysts. Detailed Implementation

[0026] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0027] Example 1: Preparation of In2O3-based catalyst with epitaxial growth structure of Zn MOF@In MOF:

[0028] 1 mmol of Zn(NO3)2·6H2O was dissolved in 15 mL of DMF, and then 15 mL of DMF solution containing 0.166 g BDC was added. The mixture was stirred for 30 min to ensure thorough mixing. The mixture was then transferred to a 100 mL polytetrafluoroethylene reactor liner and reacted in an oven at 120 °C for 24 h. The precipitate was collected by centrifugation, washed several times with DMF and ethanol, and dried to obtain the precursor Zn-MOF. Subsequently, 1.492 g of In(NO3)3·4H2O, 0.58 g of PVP, and 0.54 g of Zn-MOF were dispersed in 30 mL of DMF solution. 30 mL of DMF solution containing 0.664 g of BDC was added, and the mixture was stirred thoroughly. The resulting suspension was transferred to a 100 mL polytetrafluoroethylene (PTFE) reactor liner and reacted in an oven at 120 °C for 12 h. The precipitate was collected by centrifugation, washed multiple times with DMF and ethanol, dried in an oven at 80 °C, and then calcined in a tube furnace at 500 °C under an argon inert atmosphere for 2 h. The product was designated ZnO / In2O3.

[0029] Example 2: Preparation of In2O3-based catalysts with epitaxially grown structures from Ga MOF@In MOF:

[0030] First, 1 mmol of Ga(NO3)3·4H2O was dissolved in 15 mL of LDM to prepare Ga MOF; then 1.492 g of In(NO3)3·4H2O, 0.58 g of PVP and 0.52 g of GaMOF were added, and the other steps were the same as in Example 1.

[0031] Example 3: Preparation of Cu MOF@In MOF In2O3 catalyst with epitaxial growth structure

[0032] First, 1 mmol of Cu(NO3)2·3H2O was dissolved in 15 mL of DMF, and 0.216 g of trimesic acid (BTC) was added to prepare Cu MOF; then 1.492 g of In(NO3)3·4H2O, 0.58 g of PVP and 0.51 g of Cu MOF were added, and the other steps were the same as in Example 1.

[0033] Example 4: Preparation of In2O3-based catalysts with epitaxial growth structures in Mg MOF@In MOF:

[0034] First, 1 mmol of Mg(NO3)3·6H2O was dissolved in 15 mL of DMF to prepare Mg MOF; then 1.492 g of In(NO3)3·4H2O, 0.58 g of PVP and 1.28 g of Mg MOF were added, and the other steps were the same as in Example 1.

[0035] Comparative Example 1: Preparation of In2O3 from Urea via Hydrothermal Method

[0036] Procedure: Dissolve 0.5595 g In(NO3)3·4H2O and 1 g urea in 90 mL of water. After stirring for 30 min, transfer the mixture to a 150 mL PTFE-lined stainless steel autoclave and maintain it in a 120 °C oven for 24 h. Centrifuge to collect the white precipitate, wash it three times with water, and dry it overnight in an 80 °C oven. Finally, calcine it in a muffle furnace at 500 °C for 2 h to obtain pure phase In2O3, denoted as h-InO.

[0037] Comparative Example 2: Preparation of In2O3 by MOF calcination derivatization

[0038] Steps: Dissolve 0.373g In(NO3)3·4H2O in 15mL DMF solution, add 15mL DMF solution containing 0.166g BDC, stir thoroughly, transfer the resulting mixed solution to a hydrothermal reactor and react at 120℃ for 12h, centrifuge to collect the precipitate, wash several times with DMF and ethanol, dry overnight, and then calcine the product in a tube furnace at 500℃ for 2h to obtain In2O3 derived from MOF, denoted as m-InO.

[0039] Comparative Example 3: Preparation of In2O3-based catalysts with epitaxially grown Ce MOF@In MOF

[0040] First, 1 mmol of Ce(NO3)2·6H2O was dissolved in 15 mL of LDMF to prepare Ce MOF; then 1.492 g of In(NO3)3·4H2O, 0.58 g of PVP and 0.48 g of Ce MOF were added, and the other steps were the same as in Example 1.

[0041] Comparative Example 4: Preparation of In2O3-based catalysts with epitaxial growth structure from Al MOF@In MOF

[0042] First, 1 mmol of Al(NO3)3·9H2O was dissolved in 15 mL of LDMF to prepare Al MOF; then 1.492 g of In(NO3)3·4H2O, 0.58 g of PVP and 0.35 g of Al MOF were added, and the other steps were the same as in Example 1.

[0043] In the examples 2-4 and 3-4, the In2O3-based composite catalysts are abbreviated as MO / InO (MO stands for the corresponding metal oxide).

[0044] 0.15g of calcined catalyst and 0.15g of quartz sand were placed in the quartz reaction tube of a fixed-bed reactor, and N2 was introduced into it. Activation was carried out for 1 hour at atmospheric pressure and 200℃. The temperature was then increased to the reaction temperature of 260℃, and irradiated with a 300W xenon lamp. A mixed gas of CO2, H2, and N2 (feed ratio of 1:3:1) was introduced and pressurized to 3MPa. The reaction was carried out continuously for several hours at a space velocity GHSV = 12000mL / (g·h). The gas outlet gas of the reactor was analyzed online using a gas chromatograph (GC-7920) equipped with a thermal conductivity detector (TCD) and a flame ionization detector (FID). Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 FTIR characterization of the In2O3-based catalyst with epitaxial growth structure prepared by the present invention (Zn MOF@In MOF: In2O3 catalyst with epitaxial growth structure; Zn MOF: zinc-based metal-organic framework precursor A; In MOF: In2O3 prepared by MOF calcination derivatization).

[0047] Figure 2 The N2 adsorption-desorption isotherm and specific surface area radar plot of the In2O3-based catalyst with epitaxial growth structure of Zn MOF@In MOF prepared in this invention.

[0048] Figure 3 A comparison of the performance of In2O3-based composite catalysts in catalyzing CO2 reduction—CO2 conversion rate and methanol selectivity

[0049] Figure 4 A comparison of the performance of In2O3-based composite catalysts in catalyzing CO2 reduction—the space-time yield of methanol.

Claims

1. A method for improving the performance of In₂O₃ in the catalytic CO₂ hydrogenation reduction reaction and its application, comprising the following steps: using a MOF-on-MOF heteroepitaxial growth strategy, an indium-based metal-organic framework (IMO) B is directionally grown on the surface of a metal-organic framework precursor A, followed by calcination under an inert atmosphere. Step 1: Dissolve a certain mass of soluble metal salt and terephthalic acid BDC in N,N-dimethylformamide (DMF) solution. Transfer the mixed solution to a polytetrafluoroethylene (PTFE) reactor liner and react for several hours. Centrifuge to collect the precipitate, wash several times with DMF and ethanol, and dry to obtain metal-organic framework precursor A. Step 2: Take a certain mass of soluble indium salt, polyvinylpyrrolidone (PVP), and the metal-organic framework precursor A prepared in Step 1, disperse them in DMF solution, add a certain mass of DMF solution containing BDC, stir thoroughly, transfer the resulting suspension to a hydrothermal reactor and react for several hours, centrifuge to collect the precipitate, wash with DMF and ethanol several times, and dry to obtain indium-based metal-organic framework B grown on metal-organic framework precursor A. Step 3: The In-based metal-organic framework B grown on metal-organic framework A is calcined in a tube furnace.

2. The method for improving the performance of In2O3 catalyzing the hydrogenation reduction reaction of CO2 according to claim 1, characterized in that, The metal center of metal-organic framework precursor A is a heterometallic metal with indium, and is not Ce or Al.

3. The method for improving the performance of In2O3 in the catalytic reduction of CO2 hydrogenation reaction according to claim 1, characterized in that, The metal-organic framework A has a metal center of Zn, Ga, Cu, or Mg.

4. The method for improving the performance of In2O3 catalyzing the hydrogenation reduction reaction of CO2 according to claim 3, characterized in that, A more preferred metal center is Zn or Cu.

5. The method for improving the performance of In2O3 catalyzing the hydrogenation reduction reaction of CO2 according to claims 1-4, characterized in that, The soluble metal salt and soluble indium salt are Zn(NO3)2·6H2O, Ga(NO3)3·4H2O, Cu(NO3)2·3H2O, Mg(NO3)2·6H2O, Ce(NO3)4·6H2O, Al(NO3)3·9H2O, and In(NO3)3·4H2O.

6. The method for improving the performance of In2O3 catalyzing the hydrogenation reduction reaction of CO2 according to claim 1, characterized in that, The relative molecular mass of the polyvinylpyrrolidone (PVP) is 58,000.

7. The method for improving the performance of In2O3 catalyzing the hydrogenation reduction reaction of CO2 according to claim 1, characterized in that, The synthesis temperature range of the metal-organic framework A and the In2O3 catalyst with epitaxial growth structure is 100-140℃, and the reaction time is 6-48h.

8. The method for improving the performance of In₂O₃ in the catalytic hydrogenation reduction reaction of CO₂ according to claim 1, characterized in that, The mass fraction of metal in the In2O3 catalyst with epitaxial growth structure is 5-50%, and the mass of metal-organic framework precursor A added is 0.1-2.5g.

9. The method for improving the performance of In2O3 catalyzing the hydrogenation reduction reaction of CO2 according to claim 1, characterized in that, The roasting temperature for the roasting process is 400-600℃, the roasting time is 1-6h, and the inert atmosphere gas is N2 or Ar.

10. The method for improving the performance of In2O3 catalyzing the hydrogenation reduction reaction of CO2 according to claims 1-9, characterized in that, The In2O3 catalyst with an epitaxial growth structure prepared according to the method described above, or the method for preparing an In2O3 catalyst with an epitaxial growth structure, is used in CO2 heating catalytic reduction reaction, CO2 photothermal catalytic reduction reaction, or CO2 electrocatalytic reduction reaction.

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