CN110064435A - A kind of method of one-step synthesis method MOF package metals catalysis material - Google Patents

Abstract

The present invention relates to a kind of methods of one-step synthesis method MOF package metals catalysis material, belong to the preparation and application field of catalysis material.Metal ion presoma is added in the reaction kettle of synthesis MOF by the present invention using solvent-thermal method, directly prepares the M@MOF catalysis material with elemental.The metal ion intervened in preparation process of the present invention can be reduced directly to metal simple-substance state, without further reduction.The skeleton structure of MOF is not influenced after addition metal ion of the present invention, and there is good thermal stability.

Description

A method for one-step synthesis of MOF-encapsulated metal catalytic materials

technical field

The invention relates to a one-step method for synthesizing MOF-encapsulated metal catalytic materials, and belongs to the field of preparation and application of catalytic materials.

Background technique

Metal-organic frameworks (MOFs) have attracted extensive attention due to their special surface area and porosity, and controllable structure and function. MOFs are a series of porous crystalline materials self-assembled by metal ions and organic ligands through coordination bonds. Due to their different coordination metals and organic ligands, a variety of topological crystalline materials with functional groups can be formed. These unique structures give them unique properties that conventional materials do not have, and are mainly used in the fields of gas storage and separation, drug delivery, chemical sensing, and catalysis. Mihet[MihetM,Blanita G,Dan M,et al.Pt/UiO-66Nanocompositesas Catalysts for CO2Methanation Process,JournalOfNanoscienceAndNanotechnology,2019,19:3187-3196] et al. used simple wet impregnation followed by hydrogen thermal reduction and wet impregnation of NaBH, respectively. Pt/Zr-MOF catalysts were prepared by three methods: ₄ reduction and two-solvent NaBH ₄ reduction, and the three catalysts were studied for the activity test of carbon dioxide methanation.

Compared with the impregnation method to support metals on MOFs, more research work is to encapsulate active metal nanoparticles into the framework structure of MOFs, so as to control the size distribution of metal nanoparticles and prepare catalytically active metal NPs. @MOF. Li[JiangD, FangG, TongY, et al., MultifunctionalPd@UiO-66CatalystsforContinuous CatalyticUpgrading of Ethanolton-Butanol,Acs Catalysis,2018,8(12):11973-11978] et al. added a certain amount of palladium acetylacetonate to the previously synthesized Zr- In MOF, the small pore structure of Zr-MOF can limit the growth of metal nanoparticles by slow stirring and evaporation at a temperature of 383K. The prepared Pd nanocatalyst Pd@Zr-MOF with a particle size of 2.2 nm is used to prepare n-butanol from ethanol. efficient catalyst. Dong[DongW,Feng C,ZhangL,et al.,Pd@UiO-66:An Efficient Catalyst for Suzuki-Miyaura Coupling Reactionat Mild Condition,Catalysis Letters,2016,146(1):117-125] adopts in-situ encapsulation method The Pd nanoparticles were encapsulated in the Zr-MOF framework structure, and the Pd nanoparticles were reduced and activated by microwave assisted in the presence of the reducing agent NaBH4, and the Zr _- MOF was activated. good catalytic activity. Wu[WuTB, ZhangP, MaJ, et al., Catalytic activity of immobilized Ru nanoparticles inaporous metal-organic framework using supercritical fluid, Chinese Journal of Catalysis, 2013, 34(1): 167-175] et al. synthesized Zr-MOF with microporous structure materials, and prepared Ru@Zr-MOF catalysts in supercritical CO ₂ and methanol solutions. The prepared catalysts had smaller Ru nanoparticle size and uniform dispersion compared with Ru/Zr-MOF prepared by impregnation method. , and the Ru@Zr-MOF catalyst has both microporous and mesoporous structures, better diffusion coefficient, and good conversion activity in the hydrogenation of benzene to cyclohexane. Therefore, the use of the porous skeleton structure of MOFs material as the carrier of metal catalysts can limit the growth of metal nanoparticles, and the reduced metal has a small particle size and a high degree of dispersion. Metal catalytic materials.

From the existing reports, the common method for preparing encapsulated metal catalytic materials is to first prepare MOF materials, and then load metal ions on the MOF by impregnation or encapsulation, and then use a reducing agent for further reduction. There is no report on the one-step synthesis of MOF-encapsulated metal catalytic materials.

SUMMARY OF THE INVENTION

The invention provides a one-step method for synthesizing MOF encapsulated metal catalyst materials, which can directly reduce the added active metal ions into elemental state, and solves the above problems.

The invention provides a one-step method for synthesizing MOF-encapsulated metal catalytic materials. The method adopts a solvothermal method to add metal ion precursors into a reactor for synthesizing MOF, and directly prepares an M@MOF catalytic material with an elemental state.

The preparation process of the present invention includes:

Step a): at room temperature, weigh the organic ligands and coordination metal salts for synthesizing MOF respectively, dissolve them in an organic solvent, add a certain amount of precious metal or transition metal salts, and finally add 0.5-1 ml of concentrated hydrochloric acid (37wt%) ), ultrasonic for 10-30 minutes, dissolving and then moving to the autoclave, heating at a certain temperature for a certain period of time, and then cooling to room temperature overnight with the furnace;

Step b): pour the solution in the autoclave after cooling into the beaker, wash 3-5 times with the same organic solvent as in step a, the centrifugal speed is 6000-10000 rev/min, and centrifuge each time for 10-30 minutes; After cleaning with solvent, it is washed three times with anhydrous methanol, and the solid is separated by suction filtration after each cleaning; after washing with anhydrous methanol, it is placed in a vacuum drying box and dried at 80-120°C for 3-5 hours to finally obtain a white powder.

The organic ligand is preferably terephthalic acid, 2-aminoterephthalic acid or 4,4-biphenyl dicarboxylic acid.

The complex metal salt is preferably zirconium tetrachloride or chromium tetrachloride.

The organic solvent is preferably N,N-dimethylformamide, N,N-dimethylacetamide or tetrahydrofuran.

The noble metal is preferably a ruthenium salt, a rhodium salt, a gold salt or a palladium salt. More preferably H ₂ PdCl ₄ or RuCl ₃

The transition metal salt is preferably a cobalt salt or a nickel salt.

In the step a, the ratio of the added amount of the noble metal or transition metal salt to the amount of the coordinating metal salt is between 0.1-0.4.

In the step b, the heating temperature is 80-200° C., and the heating time is 12-36 h.

The beneficial effects of the present invention are:

① The metal ions involved in the preparation process of the present invention can be directly reduced to a metal elemental state without further reduction;

② The addition of metal ions in the present invention has no effect on the skeleton structure of the MOF, and can effectively increase its thermal stability in a low temperature environment.

Description of drawings

There are 5 accompanying drawings of the present invention.

Fig. 1 is the XRD pattern of embodiment 1, embodiment 2 and embodiment 3

Fig. 2 is the XPS spectrogram of Ru@MOF prepared in Example 1;

Fig. 3 is the SEM spectrogram of Ru@MOF prepared in Example 1;

Fig. 4 is the FT-IR spectrum of Ru@MOF prepared in Example 1;

5 is the TG spectrum of Ru@MOF prepared in Example 1.

Detailed ways

The following non-limiting examples may enable those of ordinary skill in the art to more fully understand the present invention, but do not limit the present invention in any way.

Example 1

Preparation method of Ru@UiO-66 material: Dissolve 0.816g zirconium chloride (ZrCl ₄ ), 0.831g terephthalic acid (C ₈ H ₆ O ₄ ) and 0.415g ruthenium trichloride (RuCl ₃ ) in 30 mL DMF solution and 0.8ml of concentrated HCl solution, ultrasonically stirred for 20 minutes to dissipate heat, and then moved to a homogeneous reaction kettle. Then, the reaction kettle was placed in a constant temperature drying oven at 120 °C for 24 hours and then cooled to room temperature naturally. Filtration, DMF washing, anhydrous methanol washing, drying in a drying oven at 100 °C for 3 h to obtain Ru@UiO-66 metal organic framework material.

Example 2

Preparation method of Pd@UiO-66 material: Dissolve 0.816g zirconium chloride (ZrCl ₄ ), 0.831g terephthalic acid (C ₈ H ₆ O ₄ ) and 0.532g H ₂ PdCl ₄ in 30mL DMF solution and 0.8ml concentrated In the HCl solution, ultrasonically stirred for 20 minutes to dissipate heat, and then moved to a homogeneous reaction kettle. Then, the reaction kettle was placed in a constant temperature drying oven at 120 °C for 24 hours, and then cooled to room temperature naturally. Filtration, DMF washing, anhydrous methanol washing, drying in a drying oven at 100 °C for 3 h to obtain Pd@UiO-66 metal organic framework material.

Example 3

Preparation method of Ni@UiO-66 material: Dissolve 0.816g zirconium chloride (ZrCl ₄ ), 0.831g terephthalic acid (C ₈ H ₆ O ₄ ) and 0.52g Ni(NO ₃ ) ₂ ·6H ₂ O in 30 mL DMF The solution and 0.8ml of concentrated HCl solution, ultrasonically stirred for 20 minutes and dissipated, and then moved to a homogeneous reaction kettle. Then, the reaction kettle was placed in a constant temperature drying box at 120 °C for 24 hours, and then cooled to room temperature naturally. Filtration, washing with DMF, washing with anhydrous methanol, drying in a drying oven at 100 °C for 3 h, and obtaining the Ni@UiO-66 metal-organic framework material.

The metal-organic framework materials prepared in Examples 1-3 were tested, and the test results were shown in Figures 1-5. It can be seen from Figure 1-2 that the materials obtained in Examples 1-3 can detect Ru, Pd, Ni metal elemental states respectively, which proves that the active component metal ions of the metal catalytic materials are directly reduced to elemental metals during the MOF synthesis process. It can be clearly seen from FIG. 3 that the particle size distribution of the material obtained by the method provided by the present invention is uniform and has a relatively high specific surface area. It can be seen from Fig. 5 that the material prepared by the present invention exhibits good thermal stability.

The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or modification of the created technical solution and its inventive concept shall be included within the protection scope of the present invention.

Claims (10)

1. a method for synthesizing MOF encapsulated metal catalytic material by one-step method, is characterized in that, adopt solvothermal method to encapsulate active component metal ion in MOF and react in autoclave, obtain the M@MOF catalytic material with elemental state ; M is Ru, Rh, Au, Pb, Co, Ni. 2. method according to claim 1, is characterized in that, specifically comprises the steps: Step a): at room temperature, weigh the organic ligands and coordination metal salts for synthesizing MOF respectively, dissolve them in an organic solvent, add a certain amount of precious metal or transition metal salts, and finally add 0.5-1 ml of 37wt% concentrated hydrochloric acid. , ultrasonic for 10-30 minutes, dissolved and then moved to the autoclave, heated at a certain temperature for a certain period of time, and then cooled to room temperature overnight with the furnace; Step b): pour the solution in the autoclave after cooling into the beaker, wash with organic solvent for 3-5 times, the centrifugal speed is 6000-10000 rpm, and centrifuge for 10-30 minutes each time; Wash with anhydrous methanol for three times, and separate the solid by suction filtration after each washing; after washing with anhydrous methanol, place it in a vacuum drying box to dry at 80-120°C for 3-5 hours, and finally obtain a white powder. 3. The method according to claim 1, wherein the organic ligand is terephthalic acid, 2-aminoterephthalic acid or 4,4-biphenyl dicarboxylic acid. 4. The method according to claim 1, wherein the coordination metal salt is zirconium tetrachloride or chromium tetrachloride. 5. The method according to claim 1, wherein the organic solvent is N,N-dimethylformamide, N,N-dimethylacetamide or tetrahydrofuran. 6. The method according to claim 1, wherein the precious metal salt is a ruthenium salt, a rhodium salt, a gold salt or a palladium salt. 7. The method according to claim ₆ , wherein the noble metal salt is _H2PdCl4 or _RuCl3 . 8. The method of claim 1, wherein the transition metal salt precursor is a cobalt salt or a nickel salt. 9 . The method according to claim 1 , wherein the substance amount ratio of the noble metal salt or transition metal salt to the coordination metal salt is between 0.1 and 0.4. 10 . The method according to claim 1, characterized in that, in the step b, the heating temperature is 80-200°C, and the heating time is 12-36h.