A method for preparing a MOF-based Cu(I) monatomic catalytic material

Abstract

The application discloses a preparation method of MOF-based Cu(I) single-atom catalytic material and belongs to the field of MOF-based single-atom catalytic hydrogenation for preparing high-quality aviation fuel. In a mixed solution of soluble cerium salt and organic ligand, a monocarboxylic acid regulator is added, a Ce-based MOFs carrier with high crystallinity and adjustable size is synthesized through a solvothermal method, the Ce-based MOFs carrier is uniformly dispersed in a solution, a solution containing a metal salt is added under stirring, and then 2-valence metal ions are reduced to 1-valence metal ions and anchored to metal nodes through ethanol soaking and vacuum high-temperature activation treatment, so that a Ce-based MOFs anchored metal single-atom catalyst is prepared. The MOF-based single-atom catalytic material prepared by the application has Cu(I) capable of in-situ reduction and single-atom dispersion, the raw materials used are cheap and easy to obtain, the single-atom metal electron and geometric structure anchored on the metal Ce6 node are adjustable, and the active site microenvironment is controllable.

Description

Technical Field

[0001] This invention belongs to the field of MOF-based single-atom catalytic hydrogenation for the preparation of high-quality aviation fuel, specifically involving a method for preparing a non-noble metal single-atom Cu(I) catalytic material anchored on Ce-MOF-88 with atomic dispersion. Background Technology

[0002] Emerging single-atom catalysts (SACs), also known as atomically dispersed catalysts, have attracted widespread attention due to their well-defined active sites, maximum atom utilization, and tunable electronic and geometric structures. This has not only made it possible to design and construct catalysts with high activity, selectivity, and stability, but has also deepened our understanding of structure-activity relationships and catalytic reaction mechanisms. To prevent the easy migration and sintering of single-atom catalysts at high temperatures due to their high surface energy, loading SACs onto high-surface-area supports with strong channel transport capabilities is an effective strategy to stabilize single-atom active sites and maintain catalytic performance under harsh reaction conditions. Therefore, the rational design of a porous support structure that can precisely coordinate with the support and precisely control its electronic and microenvironment is of great significance for improving catalytic performance.

[0003] Metal-organic frameworks (MOFs) are renowned for their ultra-high specific surface area, finely tunable structures, designable functions, and pore sizes. Therefore, research on MOF-supported SACs (SACs-MOFs) has garnered significant attention. Atomically dispersed noble metals, such as Pt, Rh, Pa, Ir, Ru, and Au, have become key catalysts for numerous important chemical reactions in the energy and environmental fields due to their high activity, selectivity, and stability. However, the high cost of these noble metals presents a challenge that needs to be addressed. Through post-processing synthesis, single atoms of noble metals (Co) on MOF clusters can be synthesized. 2+ Ni 2+ Zn 2+ Al 3+ Ti 4+ Mo 6+ Rare earth MOFs (RE-MOFs) exhibit excellent catalytic performance in cycloaddition reactions, alkane oxidation, and CO oxidation. RE-MOFs are a subclass of MOFs that showcase the unique characteristics of MOF chemistry and the complex inherent properties of rare earth elements. Single-atom anchoring in RE-MOF combinations provides an ideal platform for the fabrication of single-atom catalysts. The transition metal Cu is low-cost and can promote heterolytic cleavage of H2 in hydrogenation reactions. Therefore, effectively anchoring Cu single atoms and precisely controlling their microenvironment using multifunctional RE-MOFs to improve catalytic hydrogenation performance has been a persistent and challenging synthetic technique. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a method for preparing single-atom Cu(I) anchored in Ce-MOF-88 catalytic materials with tunable electronic and geometric structures, controllable microenvironment of active sites, low cost, and high atom utilization.

[0005] This invention provides a method for preparing MOF-based Cu(I) single-atom catalytic material, comprising the following steps:

[0006] 1) A certain amount of monocarboxylic acid regulator was added to a mixed solution of soluble cerium salt and organic ligand, and Ce-based MOFs support with high crystallinity and adjustable size was synthesized by solvothermal method;

[0007] 2) At a certain temperature, Ce-based MOFs support is uniformly dispersed in a solution, and a solution containing metal salt is added under stirring conditions. Then, divalent metal ions are reduced to monovalent metal ions and anchored to the metal nodes by ethanol soaking and vacuum high-temperature activation treatment, thus obtaining Ce-based MOFs anchored metal single-atom catalyst.

[0008] The specific preparation steps are as follows:

[0009] 1) Synthesis of Ce-MOF-808

[0010] Add N,N-dimethylformamide (DMF) and formic acid to a round-bottom flask, then add trimesic acid (H3BTC) and cerium(IV) ammonium nitrate aqueous solution (NH4)2Ce(NO3)6. The molar ratio of each component is (NH4)2Ce(NO3)6:H3BTC:formic acid:DMF:H2O = 1~3:1:100~0:155:1~10. Seal the round-bottom flask and heat it vigorously in an oil bath at 100 °C for 10~30 min. After cooling to room temperature, centrifuge the white precipitate in the mother liquor, wash it, and dry it to obtain Ce-MOF-808.

[0011] 2) Synthesis of Ce-MOF-808-xCu-y

[0012] A soluble anchoring metal salt, copper acetate monohydrate, was dissolved in DMF, and then Ce-MOF-808 was added to form a suspension. The suspension was then placed in a reaction vessel of a PTFE-lined stainless steel reactor for post-modification reaction. The reaction was carried out in an oven at 100-120°C for 24-36 h. After cooling to room temperature, the mother liquor was poured off and washed with DMF until the DMF was colorless. The resulting solid material was soaked in DMF, then soaked in acetone to exchange solvents with acetone, followed by ethanol or vacuum activation, or ethanol and vacuum activation, to obtain Ce-MOF-808-xCu-y, where x = 20, 25, or 30 wt%.

[0013] Furthermore, the formic acid concentration in step 1) is 99%.

[0014] Further, in step 1), the white precipitate is centrifuged, washed, and dried in the mother liquor by centrifuging the white precipitate twice in DMF to remove DMF, then the solid is washed with acetone and centrifuged four times, and the resulting white solid is dried in a vacuum at 60 °C.

[0015] Furthermore, the preferred mass percentage of copper acetate monohydrate added in step 2) is 25 wt%.

[0016] Furthermore, the DMF washing cycle in step 2) is 3 times.

[0017] Further, in step 2), the soaking in DMF is for 36 hours, during which the DMF is replaced every 10 to 12 hours; and the soaking in acetone is for 30 to 40 hours, during which the acetone is replaced every 10 to 12 hours.

[0018] Further, step 2) specifically refers to the ethanol or vacuum activation or ethanol and vacuum activation treatment:

[0019] (1) Ethanol treatment involves placing the solid in an ethanol solution at 60-80 ℃ for 4-7 h and then drying it to obtain Ce-MOF-808-xCu-E (y=E indicates ethanol treatment).

[0020] (2) Vacuum activation treatment is a process of exchanging solvent with acetone and then drying, followed by vacuum activation treatment at 80 ~ 150 ℃ for 1 ~ 5 h to obtain Ce-MOF-808-xCu-A (y=A indicates vacuum activation treatment).

[0021] (3) Ethanol and vacuum activation treatment is to exchange solvent with acetone, then treat with ethanol, place the solid in ethanol solution at 60~80℃ for 4~7 h and dry it, and then activate it in vacuum at 80~150℃ for 1~5 h to obtain Ce-MOF-808-xCu-EA (y=EA means ethanol and activation treatment).

[0022] Further, the synthesis reaction described in step 2) yields Ce-MOF-808-xCu-y, preferably y=EA, and preferably the ethanol treatment time is 6 h, and the activation treatment is performed at a temperature of 100 ℃ for 5 h.

[0023] Furthermore, the vacuum activation or ethanol and vacuum activation drying treatment is performed by vacuum drying at 80 °C for 24 h.

[0024] Features of this invention:

[0025] This invention selects Ce-MOF-808 with a 6-coordination framework to anchor Cu, which not only significantly promotes the accessibility of abundant coordination of unsaturated centers as active sites, but also enables the MOF structure to have mesoporous properties through the regulation of regulators. A series of atomically dispersed single-atom Cu(II) anchored on the Ce6 node of the Ce-MOF-8088 framework with strong metal-loaded interaction (SMSI) effect were designed and synthesized, resulting in a series of Ce-MOF-808-xCu-y. Through ethanol treatment and subsequent thermal activation, the Cu(II) active sites were reduced in situ to Cu(I) sites. This invention is based on a systematic study of the hydrogenation reaction pathway of DCPD on different metal active centers and the revelation of the low-energy route of single-atom Cu anchoring on MOF-808 through density functional theory (DFT) calculations. In addition, the Cu(I) site, as a dual active site for H2 activation, generates a pair of protons and hydrides (*H) in the form of heterolytic cleavage. δ+ -H δ- This invention effectively lowers the energy barrier for catalytic hydrogenation. It provides a valuable synthetic method for further utilizing (enhancing) the catalytic activity of non-noble metal Cu(I) site MOFs, demonstrates the excellent hydrogenation performance of the catalyst, and offers a rational design for multi-active-site synergistic catalysts. It provides a new approach for developing novel, highly efficient, and highly selective DCPD hydrogenation catalysts.

[0026] In summary, the advantages of this invention are: (1) developing a novel MOFs-based single-atom catalytic material; (2) the prepared MOFs-based single-atom catalytic material has Cu(I) that can be reduced in situ and is a single-atom dispersion; (3) the raw materials provided by this invention are inexpensive and readily available, the single-atom metal electrons anchored on the metal Ce6 node are tunable and the microenvironment of the active site is controllable. Attached Figure Description

[0027] Figure 1 The XRD patterns of Ce-MOF-808 prepared with different amounts of formic acid added, as shown in Example 1 of this invention.

[0028] Figure 2 The N2 adsorption-desorption curves of Ce-MOF-808 prepared with different amounts of formic acid obtained in Example 1 of this invention are shown.

[0029] Figure 3 The X-ray diffraction comparison analysis diagrams of Ce-MOF-88 and Ce-MOF-808-25Cu-EA obtained in Implementation Example 1 of the present invention and standard MOF-808 are shown.

[0030] Figure 4The images are TEM and EDS images of Ce-MOF-88 and Ce-MOF-808-25Cu-EA obtained in Implementation Example 1 of this invention.

[0031] Figure 5 XPS images of Cu in Ce-MOF-88 and Ce-MOF-808-25Cu obtained under different treatment conditions in Implementation Example 3 of this invention.

[0032] Figure 6 The figure shows a performance comparison analysis of Ce-MOF-88 and Ce-MOF-808-25Cu under different treatment conditions obtained in Implementation Example 3 of the present invention.

[0033] Figure 7 This is a comparative analysis chart of the hydrogenation performance of Ce-MOF-808-xCu-EA obtained after different amounts of Cu metal salt were added, as shown in Embodiment 4 of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0035] Example 1

[0036] In a round-bottom flask, DMF (12 mL) and formic acid (0, 1.6, 2.4, 3.2, 4.0 mL, 99%) were added, followed by H3BTC (224 mg, 1.06 mmol). An aqueous solution of (NH4)2Ce(NO3)6 (6 mL, 0.533 M) was then added. The flask was sealed and heated vigorously in an oil bath at 100 °C for 15 min with stirring. After cooling to room temperature, the white precipitate was centrifuged in the mother liquor, washed, and centrifuged twice in DMF (20 mL). To remove DMF from the product, the solid was subsequently washed and centrifuged four times with acetone (20 mL). The resulting white solid was dried under vacuum at 60 °C. 1 mmol Cu(OAc)2·H2O (25 wt%, 200 mg) was dissolved in 60 mL of DMF, followed by the addition of 200 mg Ce-MOF-808. The suspension was placed in a 100 mL polytetrafluoroethylene-lined stainless steel reactor and reacted in an oven at 100 °C for 24 h. After cooling to room temperature, the mother liquor was poured off and washed three times with DMF (3 × 50 mL) until the DMF was colorless. The resulting solid material was soaked in DMF (50 mL) for 36 h, with the DMF being replaced every 12 h during this period. The DMF-soaked material was then soaked in acetone (50 mL) for 36 h, with the acetone being replaced every 12 h during this period. After exchanging the solvent with acetone, the solid was placed in an ethanol solution at 70 °C for 6 h, dried under vacuum at 80 °C for 24 h, and activated under vacuum at 100 °C for 5 h before the reaction was carried out. Ce-MOF-808-25Cu-EA was synthesized by anchoring atomically dispersed Cu(II) sites to the Ce6 nodes of the Ce-MOF-808 framework. The added Cu(II) was reduced to Cu(I) in situ through ethanol treatment and subsequent thermal activation.

[0037] DCPD hydrogenation was carried out in a 50 ml stainless steel sealed autoclave. 200 μL of DCPD, 5 ml of cyclohexane (solvent), and 20 mg of active catalyst were loaded into the autoclave. N2 was introduced into a sealed autoclave and then released, repeated 2-3 times to remove air from the reactor. Then H2 was introduced, and the pressure was increased to 2 MPa. The mixture was stirred and heated to 100 °C at a speed of 600 r / min. After the reaction was complete, the product was analyzed by gas chromatography-mass spectrometry. Cyclic stability test: After cycling, the reactants and catalyst were added to an ethanol solution, centrifuged, and dried under vacuum at 60 °C overnight before the next round of reaction.

[0038] After the reaction was complete, the product was removed and the sample was centrifuged. 50 μL of the supernatant was pipetted into a gas chromatography vial (ANW 2ml injection vial with blue cap and pad, ANW 2ml transparent injection vial), and cyclohexane was added to a final volume of 1.5 mL. The mixture was thoroughly mixed. Gas chromatography (Agilent 6820) was performed using an FID detector and a DB-5 capillary column (30 m × 0.32 mm × 0.25 μm).

[0039] The prepared single-atom Cu(I) catalyst exhibits excellent catalytic performance for the hydrogenation reaction of DCPD under the conditions of 100 °C, 2 MPa, and 15 h, with a DCPD conversion rate of 100% and a selectivity of 100% for dihydrodicyclopentadiene (DHDCPD).

[0040] like Figure 1 XRD patterns of Ce-MOF-808 prepared with different amounts of formic acid. It can be seen that the addition of formic acid increases the crystallinity of MOFs.

[0041] like Figure 2 N2 adsorption-desorption curves of Ce-MOF-808 prepared with different amounts of formic acid are shown. It can be seen that the formic acid at 80 eq has a larger pore structure.

[0042] like Figure 3 X-ray diffraction patterns of Ce-MOF-88 and Ce-MOF-808-25Cu-EA are shown. It can be seen that the MOFs maintain their intact crystal structure.

[0043] like Figure 4 The images show the TEM and EDS spectra of Ce-MOF-88 and Ce-MOF-808-25Cu-EA. It can be seen that Cu is uniformly distributed and exists in the form of single atoms.

[0044] Example 2

[0045] In a round-bottom flask, DMF (12 mL) and formic acid (4.0 mL, 99%) were added, followed by H3BTC (224 mg, 1.06 mmol). An aqueous solution of (NH4)2Ce(NO3)6 (6 mL, 0.533 M) was then added. The flask was sealed and heated vigorously in an oil bath at 100 °C for 15 min with stirring. After cooling to room temperature, the white precipitate was centrifuged in the mother liquor, washed, and centrifuged twice in DMF (20 mL). To remove DMF from the product, the solid was subsequently washed and centrifuged four times with acetone (20 mL). The resulting white solid was dried under vacuum at 60 °C. 1 mmol Cu(OAc)2·H2O was dissolved in 60 mL of DMF, followed by the addition of 200 mg Ce-MOF-808. The suspension was placed in a 100 mL polytetrafluoroethylene-lined stainless steel reactor and reacted in an oven at 100 °C for 24 h. After cooling to room temperature, the mother liquor was poured off and washed three times with DMF (3 × 50 mL) until the DMF was colorless. The resulting solid material was then soaked in 50 mL of DMF for 36 h, with the DMF replaced every 12 h. The DMF-soaked material was then soaked in 50 mL of acetone for 36 h, with the acetone replaced every 12 h. After vacuum drying at 80 °C for 24 h and vacuum activation at 100 °C for 5 h, Ce-MOF-808-25Cu-A was obtained.

[0046] Example 3

[0047] In a round-bottom flask, DMF (12 mL) and formic acid (4.0 mL, 99%) were added, followed by H3BTC (224 mg, 1.06 mmol). An aqueous solution of (NH4)2Ce(NO3)6 (6 mL, 0.533 M) was then added. The flask was sealed and heated vigorously in an oil bath at 100 °C for 15 min with stirring. After cooling to room temperature, the white precipitate was centrifuged in the mother liquor, washed, and centrifuged twice in DMF (20 mL). To remove DMF from the product, the solid was subsequently washed and centrifuged four times with acetone (20 mL). The resulting white solid was dried under vacuum at 60 °C. 1 mmol Cu(OAc)2·H2O was dissolved in 60 mL of DMF, followed by the addition of 200 mg Ce-MOF-808. The suspension was placed in a 100 mL polytetrafluoroethylene-lined stainless steel reactor and reacted in an oven at 100 °C for 24 h. After cooling to room temperature, the mother liquor was poured off and washed three times with DMF (3 × 50 mL) until the DMF was colorless. The resulting solid material was soaked in DMF (50 mL) for 36 h, with the DMF replaced every 12 h during this period. The DMF-soaked material was then soaked in acetone (50 mL) for 36 h, with the acetone replaced every 12 h during this period. After exchanging the solvent with acetone, the solid was placed in an ethanol solution at 70 °C for 6 h and then vacuum dried at 80 °C for 24 h. In the obtained Ce-MOF-808-25Cu-E single-atom catalyst, the active Cu sites were predominantly located in Cu(II).

[0048] like Figure 5 XPS plots of Cu in Ce-MOF-88 and Ce-MOF-808-25Cu under different treatment conditions are shown to analyze the changes in valence states. It can be seen that more Cu appears after ethanol and activation treatment. + .

[0049] like Figure 6 The chart shows a performance comparison between Ce-MOF-88 and Ce-MOF-808-25Cu, with a reaction time of 10 h. It can be seen that ethanol and the activation treatment resulting in uniformly distributed single-atom Cu(I) in Ce-MOF-808 are beneficial for improving catalytic performance.

[0050] Example 4

[0051] In a round-bottom flask, DMF (12 mL) and formic acid (4.0 mL, 99%) were added, followed by H3BTC (224 mg, 1.06 mmol). An aqueous solution of (NH4)2Ce(NO3)6 (6 mL, 0.533 M) was then added. The flask was sealed and heated vigorously in an oil bath at 100 °C for 15 min with stirring. After cooling to room temperature, the white precipitate was centrifuged in the mother liquor, washed, and centrifuged twice in DMF (20 mL). To remove DMF from the product, the solid was subsequently washed and centrifuged four times with acetone (20 mL). The resulting white solid was dried under vacuum at 60 °C. Cu(OAc)2·H2O (20 wt%: 157 mg; 25 wt%: 200 mg, 1 mmol; 30 wt%: 269 mg) was dissolved in 60 mL of DMF, followed by the addition of 200 mg Ce-MOF-808. The suspension was placed in a 100 mL polytetrafluoroethylene-lined stainless steel reactor and reacted in an oven at 100 °C for 24 h. After cooling to room temperature, the mother liquor was poured off and washed three times with DMF (3 × 50 mL) until the DMF was colorless. The resulting solid material was then immersed in 50 mL of DMF for 36 h, with the DMF being replaced every 12 h. The DMF-immersed material was then immersed in 50 mL of acetone for 36 h, with the acetone being replaced every 12 h. After exchanging the solvent with acetone, the solid was placed in an ethanol solution at 70 °C for 6 h, vacuum dried at 80 °C for 24 h, and vacuum activated at 100 °C for 5 h before the reaction was carried out. Ce-MOF-808 catalysts with different Cu doping amounts were obtained. Figure 7 It can be seen that, with a test reaction time of 15 h, Ce-MOF-808-20Cu-EA, Ce-MOF-808-25Cu-EA, and Ce-MOF-808-30Cu-EA all exhibit good catalytic hydrogenation DCPD performance.

[0052] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for preparing MOF-based Cu(I) single-atom catalytic material for dicyclopentadiene (DCPD) hydrogenation reaction, characterized in that, The specific preparation steps are as follows: 1) Synthesis of Ce-MOF-808 In a round-bottom flask, N,N-dimethylformamide DMF, formic acid, and then trimesic acid H3BTC and cerium (IV) ammonium nitrate aqueous solution (NH4)2Ce(NO3)6 were added, and the molar ratio of each component was (NH4)2Ce(NO3)6:H3BTC:formic acid:DMF:H2O = 1-3:1:100-0:155:1-10, wherein the formic acid content was not 0, the round-bottom flask was sealed, and was heated with vigorous stirring in an oil bath at 100 ℃ for 10-30 min, and after cooling to room temperature, the white precipitate was centrifuged in the mother liquor, washed, and dried to obtain Ce-MOF-808; 2) Synthesis of Ce-MOF-808-xCu-y The soluble anchor metal salt copper acetate monohydrate was dissolved in DMF, and then Ce-MOF-808 was added to form a suspension, and the suspension was placed in the reaction kettle of a polytetrafluoroethylene-lined stainless steel reactor for post-modification reaction, and was reacted in an oven at 100-120 ℃ for 24-36 h, and after cooling to room temperature, the mother liquor was poured out and washed with DMF until the DMF was colorless, and the obtained solid material was soaked in DMF and then in acetone, and the solvent was exchanged with acetone, and then ethanol and vacuum activation treatment were performed to obtain Ce-MOF-808-xCu-y, wherein x = 20, 25, 30 wt%; The ethanol and vacuum activation treatment in step 2) is after the solvent exchange with acetone, ethanol treatment is performed, the solid is placed in an ethanol solution at 60-80 ℃ for 4-7 h, and then dried, and then vacuum activation treatment is performed at 80-150 ℃ for 1-5 h to obtain Ce-MOF-808-xCu-y, y = EA, indicating ethanol and vacuum activation treatment.

2. The production method according to claim 1, wherein The formic acid concentration in step 1) is 99%.

3. The production method according to claim 1, wherein The white precipitate in step 1) is centrifuged in the mother liquor, washed, and dried, which is centrifuged twice in DMF to remove DMF, and then the solid is washed with acetone and centrifuged four times, and the obtained white solid is dried in a vacuum at 60 ℃.

4. The production method according to claim 1, wherein The number of times of DMF washing in step 2) is 3 times.

5. The production method according to claim 1, wherein The soaking in DMF in step 2) is for 36 h, and during this period, the DMF is replaced every 10-12 h; the soaking in acetone is for 30-40 h, and during this period, the acetone is replaced every 10-12 h.

6. The production method according to claim 1, wherein In the ethanol and vacuum activation treatment in step 2), the ethanol treatment time is 6 h, and the vacuum activation treatment at 100 ℃ is 5 h.

7. The production method according to claim 1, wherein The drying treatment in the ethanol and vacuum activation treatment is vacuum drying at 80 ℃ for 24 h.

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