CN114471724B - Au-Pd NPs@NMOF-Ni ultrathin nano sheet composite material and preparation method and application thereof - Google Patents

Au-Pd NPs@NMOF-Ni ultrathin nano sheet composite material and preparation method and application thereof Download PDF

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CN114471724B
CN114471724B CN202210050198.9A CN202210050198A CN114471724B CN 114471724 B CN114471724 B CN 114471724B CN 202210050198 A CN202210050198 A CN 202210050198A CN 114471724 B CN114471724 B CN 114471724B
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CN114471724A (en
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温丽丽
郭套连
莫凯丽
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Central China Normal University
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    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/1691—Coordination polymers, e.g. metal-organic frameworks [MOF]
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    • C07C45/37—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups
    • C07C45/38—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups being a primary hydroxyl group
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Abstract

The invention provides an Au-Pd NPs@NMOF-Ni ultrathin nanosheet composite material, and a preparation method and application thereof, belonging to the technical field of organic catalysis, and comprising the following steps: s1, 5,4-PMIA, TPOM, PVP and Ni (CH) 3 COO) 2 ·4H 2 Adding O into a solvent, heating, cooling, washing and drying to obtain NMOF-Ni; s2, dispersing NMOF-Ni in water, and adding HAuCl 4 ·6H 2 O and PdCl 2 Stirring, centrifuging, washing, redispersing in water, adding NaBH 4 Stirring, centrifuging, washing, and drying to obtain Au x Pd y An NMOF-Ni ultrathin nanosheet composite material. Au prepared by the invention x Pd y The @ NMOF-Ni composite material is used for catalyzing benzyl alcohol oxidation reaction, and can realize high-efficiency and high-selectivity conversion into benzaldehyde under the conditions of no alkali and normal pressure.

Description

Au-Pd NPs@NMOF-Ni ultrathin nano sheet composite material and preparation method and application thereof
Technical Field
The invention relates to the technical field of organic catalysis, in particular to an Au-Pd NPs@NMOF-Ni ultrathin nanosheet composite material, and a preparation method and application thereof.
Background
Selective oxidation of alcohols to aldehydes or ketones is an important class of organic synthesis reactions. In recent years, metal nanoparticles (Metal Nanoparticles, MNPs) exhibit high catalytic activity in catalyzing benzyl alcohol oxidation reactions, and have attracted attention. However, MNPs are very susceptible to agglomeration during catalysis, resulting in reduced activity and difficult recovery, which does not meet the requirements for sustainable development of green chemistry. The MNPs are loaded in the porous material, so that the catalytic activity and the recycling property can be effectively improved. The Au and Pd nano-particles, especially Au-Pd bimetallic nano-particle composite material, have excellent catalytic performance in the process of catalyzing benzyl alcohol oxidation reaction. However, most catalytic reactions generally require the performance under conditions of high amounts of base and high pressure, and are accompanied by the formation of benzoic acid and methyl benzoate as by-products. Therefore, it is a research objective of researchers to develop heterogeneous catalysts that can efficiently catalyze the oxidation of alcohols to aldehydes under alkali-free, mild reaction conditions.
Disclosure of Invention
The invention aims at providing an Au-Pd NPs@NMOF-Ni ultrathin nanosheet composite material, a preparation method and application thereof, and prepared Au x Pd y The @ NMOF-Ni composite material is applied to catalyzing benzyl alcohol oxidation reaction, and can realize high-efficiency and high-selectivity conversion into benzaldehyde under the conditions of no alkali and normal pressure.
The technical scheme of the invention is realized as follows:
the invention provides a preparation method of an Au-Pd NPs@NMOF-Ni ultrathin nanosheet composite material, which comprises the following steps:
s1, preparation of NMOF-Ni:
5,4-PMIA, TPOM, PVP and Ni (CH) 3 COO) 2 ·4H 2 Adding O into a solvent, stirring at room temperature for 5-15min, heating to 140-160 ℃, continuously reacting for 20-40min, cooling to room temperature, washing, and drying to obtain NMOF-Ni;
S2.Au x Pd y preparation of @ NMOF-Ni:
dispersing NMOF-Ni in water uniformly, adding HAuCl under stirring 4 ·6H 2 O and PdCl 2 Stirring at room temperature for 20-40min, centrifuging, washing, redispersing in water, adding NaBH to the above dispersion 4 Stirring the aqueous solution for 20-40min, centrifuging, washing, and drying to obtain Au x Pd y An NMOF-Ni ultrathin nanosheet composite material.
As a further improvement of the present invention, the 5,4-PMIA, TPOM, polyvinylpyrrolidone and Ni (CH) described in step S1 3 COO) 2 ·4H 2 The mass ratio of O is 1: (0.5-1.5): (3-7): (0.5-1.5).
As a further improvement of the present invention, the solvent in step S1 is selected from at least one of N, N-dimethylformamide, XX.
As bookFurther improvements of the invention, the HAuCl in step S2 4 ·6H 2 O and PdCl 2 The ratio of the amounts of the substances is (1-3): (1-2).
As a further improvement of the present invention, the HAuCl in step S2 4 ·6H 2 O and PdCl 2 The ratio of the amounts of the substances was 2:1.
As a further improvement of the present invention, the NMOF-Ni, HAuCl, is described in step S2 4 ·6H 2 O and PdCl 2 Total mass of (2), naBH 4 The mass ratio of (2) is 15: (0.5-1): (1-2).
The invention further protects the Au-Pd NPs@NMOF-Ni ultrathin nano sheet composite material prepared by the preparation method.
As a further improvement of the invention, the Au content in the material is 1-4wt% and the Pd content is 0.5-2wt%.
As a further improvement of the present invention, the ratio of the amounts of substances of Au and Pd in the material is (10-27): (10-27).
The invention further protects application of the Au-Pd NPs@NMOF-Ni ultrathin nanosheet composite material in catalyzing organic reactions.
The invention has the following beneficial effects: the invention prepares Au x Pd y The @ NMOF-Ni composite material can be used for catalyzing benzyl alcohol oxidation reaction, and can realize high-efficiency and high-selectivity conversion into benzaldehyde under the conditions of no alkali and normal pressure. Under the same reaction conditions, compared with Au@NMOF-Ni and Pd@NMOF-Ni loaded with single metal nanoparticles, the AuxPdy@NMOF-Ni loaded with the bimetallic nanoparticles has obviously enhanced catalytic performance. When the mole ratio of Au to Pd is 2: in the 1 st step, the catalysis performance of the composite material (Au2Pd1@NMOF-Ni) is optimal, and after recycling for 5 times, the catalysis performance is not obviously changed. Furthermore, the present invention found that Au 2 Pd 1 NMOF-Ni in @ NMOF-Ni may affect Au 2 Pd 1 Electronic properties of NPs surface, forming Au 2 Pd 1 Anionic species of NPs; the synergistic effect between Au and Pd is more effective in converting O 2 Activating to become a peroxidized species, thereby promoting the conversion of benzyl alcohol to benzaldehyde.
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In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.
FIG. 1 shows NMOF-Ni, au@NMOF-Ni, pd@NMOF-Ni and Au x Pd y PXRD pattern of @ NMOF-Ni;
FIG. 2 is NMOF-Ni and Au 2 Pd 1 SEM image of @ NMOF-Ni and Au 2 Pd 1 SEM-EDS element distribution map of @ NMOF-Ni;
FIG. 3 is Au 2 Pd 1 TEM image and HAADF-STEM image of @ NMOF-Ni and Au 2 Pd 1 NPs particle size distribution profile;
FIG. 4 is NMOF-Ni and Au 2 Pd 1 Nitrogen adsorption isotherm and pore size distribution diagram of @ NMOF-Ni at 77K;
FIG. 5 is Au 2 Pd 1 XPS spectrum of @ NMOF-Ni;
FIG. 6 is Au x Pd y Comparative graph of the performance of catalyzing benzyl alcohol oxidation by NMOF-Ni;
FIG. 7 is Au 2 Pd 1 @ NMOF-Ni and Au in bulk phase 2 Pd 1 Comparative experiment of catalytic benzyl alcohol oxidation cycle of @ MOF-Ni and Au 2 Pd 1 PXRD graphs before and after the @ NMOF-Ni cycle;
FIG. 8 is Au 2 Pd 1 TEM image after @ NMOF-Ni cycle and Au after cycle 2 Pd 1 Particle size distribution profile of NPs;
FIG. 9 is Au 2 Pd 1 Schematic of possible reaction mechanism for NMOF-Ni catalyzed benzyl alcohol oxidation.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Chloroauric acid (HAuCl) 4 ·3H 2 O,98%, aletin), palladium chloride (PdCl) 2 98%, leyan), benzyl alcohol (98%, chinese medicine), 4-methyl benzyl alcohol (98%, bi-get), 4-methoxy benzyl alcohol (98%, bi-get), 4-fluoro benzyl alcohol (97%, bi-get), 4-chlorobenzyl alcohol (99.54%, bi-get), the above medicines are directly used after being purchased, and other experimental medicines are the same as in the previous section.
TG 16-II type high-speed centrifuge, magnetic stirrer, USB2000+ ultraviolet-visible absorption spectrometer, ultra 55 scanning electron microscope, NTEGRA/NT-MDT atomic mechanics microscope, quantachrome IQ 2 Specific surface area analyzer, FEI Tecnai G2F 20 transmission electron microscope, samdri-PVT-3D supercritical carbon dioxide dryer, siemens D5005X-ray powder diffractometer (Cu/Ka), K-Alpha X-ray photoelectron spectroscopy, thermo-TRACE-1300 gas chromatograph (FID detector).
Example 1
The embodiment provides a preparation method of an Au-Pd NPs@NMOF-Ni ultrathin nano sheet composite material, which comprises the following steps:
s1. Preparation of NMOF-Ni
5,4-PMIA (0.1 g,0.37 mmol), TPOM (0.1 g,0.22 mmol), PVP (0.5 g) and Ni (CH) 3 COO) 2 ·4H 2 O (0.1 g,0.4 mmol) was added to 10mL DMF and stirred at room temperature for 10min and then heated to 150℃for 30min. Finally, cooling to room temperature, centrifuging, washing with ethanol for three times, and drying at 60 ℃ to obtain NMOF-Ni;
S2.Au 1 Pd 1 preparation of @ NMOF-Ni:
0.15g NMOF-Ni was uniformly dispersed in 20mL deionized water and 300. Mu.L HAuCl was added with stirring 4 ·6H 2 O (0.047M) in water and 300. Mu.L PdCl 2 (0.047M) in water, stirring was continued for 30min at room temperature, and redispersed in 20mL of deionized water by 3 washes with deionized water. Subsequently, 3mL of NaBH was added to the above dispersion 4 (0.1M) WaterThe solution was stirred for a further 30min. Finally centrifuging, washing with deionized water for three times, and vacuum drying to obtain Au 1 Pd 1 @NMOF-Ni。
Example 2
In comparison with example 1, 400. Mu.L of HAuCl is added in step S2 4 ·6H 2 O (0.047M) in water and 200. Mu.L PdCl 2 (0.047M), other conditions were not changed, and Au was obtained 2 Pd 1 @NMOF-Ni。
Example 3
In comparison with example 1, 450. Mu.L of HAuCl is added in step S2 4 ·6H 2 O (0.047M) in water and 150. Mu.L PdCl 2 (0.047M), other conditions were not changed, and Au was obtained 3 Pd 1 @NMOF-Ni。
Example 4
In comparison with example 1, 200. Mu.L of HAuCl was added in step S2 4 ·6H 2 O (0.047M) in water and 300. Mu.L PdCl 2 (0.047M), other conditions were not changed, and Au was obtained 1 Pd 2 @NMOF-Ni。
Comparative example 1
In comparison with example 1, 600. Mu.L of HAuCl is added in step S2 4 ·6H 2 O (0.047M) and other conditions are not changed, and Au@NMOF-Ni is obtained.
Comparative example 2
In comparison with example 1, 600. Mu.L of PdCl is added in step S2 2 (0.047M) and other conditions were unchanged to give Pd@NMOF-Ni.
Comparative example 3
Compared with example 1, NMOF-Ni in step S1 was replaced by MOF-Ni, and the other conditions were not changed to obtain Au 2 Pd 1 @MOF-Ni。
In 5,4-PMIA (6.9 mg,0.025 mmol), TPOM (11.1 mg,0.025 mmol) and Ni (NO 3 ) 2 ·6H 2 To a mixture of O (7.3 mg,0.025 mmol) was added 1 drop of HCl (2M), 2mL of DMA and 1mL of H2O, and the mixture was stirred well. Then transferring the mixture into a 25mL reaction kettle, standing the mixture for 72h at 140 ℃, naturally cooling the mixture to room temperature, washing the mixture, and drying the mixture to obtain the MOF-Ni.
Test example 1
The material powders prepared in examples 1 to 4 and comparative examples 1 to 2 were subjected to X-ray diffraction (PXRD), and the results are shown in FIG. 1. From the graph, the crystal structure of NMOF-Ni is not changed obviously after NPs are loaded. Furthermore, no Au NPs, pd NPs and Au were observed in the PXRD spectra x Pd y The characteristic diffraction peak of NPs is probably due to the low content of MNPs and the too small particle size.
Test example 2
The material powders prepared in examples 1 to 4 and comparative examples 1 to 2 were measured for the content of Au and Pd elements in the composite material by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the results are shown in Table 1.
TABLE 1
Figure BDA0003473612140000071
As can be seen from the above table, the total molar content of (Au+Pd) in all samples was very similar, i.e. the content of MNPs was around 0.017mmol per 100mg of composite material (Table 1). In addition, composite material Au 3 Pd 1 @NMOF-Ni、Au 2 Pd 1 @NMOF-Ni、Au 1 Pd 1 @NMOF-Ni and Au 1 Pd 2 The mol ratio of Au element to Pd element contained in the @ NMOF-Ni is 26: 11. 17: 10. 49:50 and 11:25, very close to the molar ratios of 3:1, 2:1, 1:1 and 1:2 of Au and Pd we initially added.
Test example 3
The material powders obtained in examples 1 to 4 and comparative examples 1 to 2 were subjected to Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) analyses, and the results are shown in FIGS. 2 and 3.
FIG. 2, wherein (a) is an SEM image of NMOF-Ni; (b) Is Au 2 Pd 1 SEM image of @ NMOF-Ni; (c) Is Au 2 Pd 1 SEM-EDS elemental profile of @ NMOF-Ni. NMOF-Ni and Au 2 Pd 1 Characterization of Scanning Electron Microscope (SEM) at NMOF-Ni showed a load of Au 2 Pd 1 Au after nanoparticles 2 Pd 1 Both @ NMOF-Ni and unsupported NMOF-Ni exhibit nanoflower-like compositions of similar nanoplateletsThe structure (fig. 2a and 2 b) shows that the original microstructure is not destroyed after the material is compounded. Au (gold) and method for producing the same 2 Pd 1 SEM-EDS element distribution diagram of @ NMOF-Ni shows that both Au and Pd elements exhibit a uniform spatial distribution (FIG. 2 c), indicating Au 2 Pd 1 The NPs are uniformly dispersed throughout the composite matrix.
As shown in FIG. 3, wherein (a) and (b) are Au 2 Pd 1 TEM image of @ NMOF-Ni, (c) HAADF-STEM image, (d) Au 2 Pd 1 Au in @ NMOF-Ni 2 Pd 1 NPs particle size distribution profile. Au (gold) and method for producing the same 2 Pd 1 Characterization results of Transmission Electron Microscope (TEM) at NMOF-Ni (FIGS. 3a and 3 b) and high angle annular dark field scanning transmission electron microscope (HAADF-STEM) (FIG. 3 c) show Au 2 Pd 1 NPs were highly homogeneously dispersed throughout the NMOF-Ni nanoplatelets with an average particle size of 1.17nm (FIG. 3 d).
Test example 4
The material powders obtained in examples 1 to 4 and comparative examples 1 to 2 were mixed in N 2 Physical adsorption testing was performed at 77K and the results are shown in fig. 4.
As shown in FIG. 4, wherein (a) is NMOF-Ni and Au 2 Pd 1 Nitrogen adsorption isotherms at 77K for @ NMOF-Ni; (b) Is NMOF-Ni and Au 2 Pd 1 Pore size distribution plot of NMOF-Ni. NMOF-Ni and Au 2 Pd 1 Both @ NMOF-Ni exhibit type I curves of typical microporous structure. Au (gold) and method for producing the same 2 Pd 1 The specific surface area and pore volume of the @ NMOF-Ni are determined by 762m of NMOF-Ni 2 g -1 And 0.631cm 3 g -1 Respectively reduced to 328.8m 2 g -1 And 0.455cm 3 g -1 . The significant decrease in specific surface area and pore volume may be due to Au 2 Pd 1 NPs are distributed inside NMOF-Ni and occupy part of the pore canal. In addition, as can be seen from the pore size distribution, in Au 2 Pd 1 In @ NMOF-Ni, the microporous structure still occupies the main part, indicating that Au is supported 2 Pd 1 After NPs, au 2 Pd 1 The @ NMOF-Ni structure remains unchanged.
Test example 5
The material powders obtained in examples 1 to 4 and comparative examples 1 to 2 were subjected to X-ray photoelectron spectroscopy (XPS) analysis, and the results are shown in FIG. 5.
As shown in FIG. 5, au is shown in FIG. 5a 2 Pd 1 Peaks of C1 s, N1 s, O1 s, ni 2p, pd 3d, and Au 4f appear in the @ NMOF-Ni sample. In XPS spectra of Ni 2p, peaks at 855.4 and 873.0eV are Ni 2+ 2p of (2) 3/2 And 2p 1/2 And a peak indicating that the valence state of Ni element is unchanged before and after the composition. In the XPS spectrum of Au 4f, there are two distinct peaks at 83.2 and 86.9 eV, respectively belonging to the metal Au 0 4f of (2) 7/2 And 4f 5/2 (FIG. 5 c). With Au in Au@NMOF-Ni 0 Binding energy of 4f (Au 0 4f 7/2 :83.8eV；Au 0 4f 5/2 87.5 eV) Au 2 Pd 1 Au in @ NMOF-Ni 0 The peak of 4f shifts toward the low binding energy. In the XPS spectrum of Pd 3d, two peaks at 340.6 and 335.0 eV are ascribed to metallic Pd 0 3d of (2) 3/2 And 3d 5/2 (FIG. 5 d). Similarly, compared to Pd in Pd@NMOF-Ni 0 Binding energy of 3d (Pd) 0 3d 3/2 :341.1eV；Pd 0 3d 5/2 :335.7 eV)，Au 2 Pd 1 Pd in @ NMOF-Ni 0 The peak of 3d shifts toward the low binding energy. Bimetallic Au 2 Pd 1 Au in NPs 0 4f and Pd 0 Shift of binding energy of 3d, indicating Au 2 Pd 1 There is a synergistic effect between Au and Pd in NMOF-Ni. Notably, the two peaks at 342.9 eV and 337.5 eV in the XPS spectrum of Pd 3d are assigned to Pd 2+ 3d of (2) 3/2 And 3d 5/2 Indicating Au 2 Pd 1 In NPs, the surface of Pd is partially oxidized, pd 2+ The proportion of (2) is 7.8%. Compared with Pd in Pd@NMOF-Ni 2+ Ratio (33%) of Au 2 Pd 1 Pd in @ NMOF-Ni 0 The degree of oxidation of (c) is greatly reduced. This is probably because of Au 2 Pd 1 Au and Pd atoms in the @ NMOF-Ni are arranged at intervals, so that Au can be effectively prevented 2 Pd 1 Pd atoms in NPs undergo oxidation.
Test example 6 catalytic Performance test
Benzyl alcohol oxidation reaction process: 0.5mmol of benzyl alcohol, 2mL of toluene and 10mg of the powdery catalyst materials prepared in examples 1-4 and comparative examples 1-2 were added to a 10mL reaction flask, and the mixture was uniformly dispersed by ultrasound. The reaction flask was connected to a reflux condenser, and after 5min of vacuum, an oxygen balloon was inserted for 0.5h of pre-adsorption, and then reacted at 120℃for 9h with ice water reflux. After the reaction, chlorobenzene (30. Mu.L) was added as an internal standard for gas chromatography, and the supernatant was collected after centrifugal filtration and subjected to gas chromatography to determine the conversion.
The results are shown in FIG. 6.
As shown in FIG. 6, under the same reaction conditions, au loaded with bimetallic nanoparticles was compared with Au@NMOF-Ni and Pd@NMOF-Ni loaded with single metal nanoparticles x Pd y The catalytic performance of @ NMOF-Ni is obviously enhanced. The results show that the molar ratio of Au to Pd is 2:1, which is the optimal ratio, au 2 Pd 1 The @ NMOF-Ni has the highest catalytic activity, the reaction is carried out for 9 hours, the conversion rate is 99%, and the TOF reaches 30.7 hours -1 。
Au prepared in example 2 of the present invention 2 Pd 1 The catalyst @ NMOF-Ni was replaced with other catalysts, and the catalytic efficiency under different reaction conditions is shown in Table 2.
TABLE 2
Figure BDA0003473612140000101
Figure BDA0003473612140000111
As is clear from the above table, au produced in example 2 of the present invention 2 Pd 1 The catalytic performance of the @ NMOF-Ni catalyst is higher than that of most of the reported MNPs/MOFs composite materials. The above results indicate that there is a clear synergistic effect between Au and Pd.
Immobilization of the powdery catalyst of Material to Au prepared in example 2 2 Pd 1 At NMOF-Ni, benzyl alcohol was replaced with a different starting material, and the conversion results are shown in Table 3.
TABLE 3 Table 3
Figure BDA0003473612140000112
Considering the experimental results, we consider Au with optimal catalytic performance 2 Pd 1 The @ NMOF-Ni composite material was used as a research target, and benzyl alcohol derivative substrates containing different substituents were developed, and the results are shown in Table 3. When the substituent of benzyl alcohol is electron donating group (such as 4-methoxy benzyl alcohol and 4-methyl benzyl alcohol), the conversion rate is high, and the conversion rate reaches 99%. When the substituents are electron withdrawing groups (4-fluorobenzyl alcohol and 4-chlorobenzyl alcohol), the conversion is relatively low, 34.6% and 15.9%, respectively. This is probably because the electron cloud density of the benzene ring increases with an increase in the electron donating ability of the substituent, so that the aromatic alcohol is more easily oxidized into aromatic aldehyde. It is notable that in all benzyl alcohol derivatives oxidation reactions, the product is the corresponding benzaldehyde derivative, exhibiting excellent selectivity. This result shows that the catalytic system has good substrate applicability.
Test example 7 catalytic cycle test
Au prepared in example 2 2 Pd 1 N-NMOF-Ni and Au prepared in comparative example 3 2 Pd 1 Catalytic cycle experimental tests were carried out on @ MOF-Ni and the results are shown in FIGS. 7 and 8.
As shown in FIG. 7, (a) is Au 2 Pd 1 @ NMOF-Ni and Au in bulk phase 2 Pd 1 Comparison of catalytic benzyl alcohol oxidation cycle experiment of @ MOF-Ni; (b) Is Au 2 Pd 1 PXRD graphs before and after the @ NMOF-Ni cycle; compared with Au 2 Pd 1 Nano composite material @ NMOF-Ni, bulk Au 2 Pd 1 The catalytic activity of @ MOF-Ni was relatively low and the benzyl alcohol conversion was 83.2% under the same reaction conditions. We are specific to Au 2 Pd 1 Catalytic cycle experiments were performed on NMOF-Ni and found that after 5 cycles there was no significant decrease in catalytic performance (fig. 7 a). And bulk Au 2 Pd 1 The circularity of @ MOF-Ni was relatively poor. As shown in FIG. 8, (a) is Au 2 Pd 1 TEM image after @ NMOF-Ni cycling; (b) Is Au after circulation 2 Pd 1 Granules of NPsRadial distribution diagram, au after circulation 2 Pd 1 TEM image and particle size distribution plot of @ NMOF-Ni show Au 2 Pd 1 NPs still exhibit a uniform distribution. The results show that the MOFs ultrathin nanosheets can better disperse MNPs, so that the catalytic activity and stability of the catalyst are further improved.
Based on the above results, for Au 2 Pd 1 The reaction mechanism possible is proposed by the catalytic oxidation of benzyl alcohol to benzaldehyde by NMOF-Ni, as shown in fig. 9.Au (gold) and method for producing the same 2 Pd 1 NMOF-Ni in the @ NMOF-Ni composite may affect Au 2 Pd 1 Electronic properties of NPs surface, forming Au with anion form 2 Pd 1 NPs, which more readily activate O 2 . Thus, O 2 Possibly adsorbed on its surface in the form of peroxygen (Step 1). Subsequently, benzyl alcohol is adsorbed on O 2 δ- Nearby Au 2 Pd 1 NPs (Step 2). Finally benzyl alcohol undergoes elimination of beta-H to form the corresponding benzaldehyde, accompanied by O 2 And H 2 O is generated (Step 3). And the catalyst is restored to the original metal state.
The invention prepares Au@NMOF-Ni and Pd@NMOF-Ni loaded with single metal nano particles and Au containing bimetallic nano particles with different Au and Pd molar ratios x Pd y The @ NMOF-Ni composite material is applied to catalyzing benzyl alcohol selective oxidation reaction. Under the reaction condition of no alkali and normal pressure, compared with Au@NMOF-Ni and Pd@NMOF-Ni, au is prepared x Pd y The @ NMOF-Ni shows higher catalytic activity and product selectivity. Wherein Au is 2 Pd 1 The @ NMOF-Ni has the best catalytic activity (TOF of 30.7h -1 ) And excellent recyclability, and has good applicability to expanding substrates. The possible mechanisms are: (1) Au (gold) and method for producing the same 2 Pd 1 NMOF-Ni in @ NMOF-Ni may affect Au 2 Pd 1 Electronic properties of NPs surface, forming Au 2 Pd 1 Anionic species of NPs; (2) The synergistic effect between Au and Pd enables more effective activation of O 2 Becomes a peroxidized species. Therefore, au is contained under normal pressure without alkali 2 Pd 1 The @ NMOF-Ni shows excellent propertiesCatalytic oxidation properties of benzyl alcohol. This work points to a new direction for the design of efficient, mild benzyl alcohol oxidation catalysts.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims (6)

1. The preparation method of the Au-Pd NPs@NMOF-Ni ultrathin nano sheet composite material is characterized by comprising the following steps of:
s1, preparation of NMOF-Ni:
5,4-PMIA, TPOM, PVP and Ni (CH) 3 COO) 2 ·4H 2 Adding O into a solvent, stirring at room temperature for 5-15min, heating to 140-110 ℃, continuously reacting for 20-40min, cooling to room temperature, washing, and drying to obtain NMOF-Ni;
S2.Au x Pd y preparation of @ NMOF-Ni:
dispersing NMOF-Ni in water uniformly, adding HAuCl under stirring 4 ·1H 2 O and PdCl 2 Stirring at room temperature for 20-40min, centrifuging, washing, redispersing in water, adding NaBH to the above dispersion 4 Stirring the aqueous solution for 20-40min, centrifuging, washing, and drying to obtain Au x Pd y An NMOF-Ni ultrathin nanosheet composite material;
the HAuCl 4 ·1H 2 O and PdCl 2 The ratio of the amounts of the substances was 2:1.
2. The method according to claim 1, wherein the 5,4-PMIA, TPOM, polyvinylpyrrolidone and Ni (CH 3 COO) 2 ·4H 2 The mass ratio of O is 1: (0.5-1.5): (3-7): (0.5-1.5).
3. The method according to claim 1, wherein the solvent in step S1 is N, N-dimethylformamide.
4. The method according to claim 1, wherein the NMOF-Ni, HAuCl is prepared in step S2 4 ·1H 2 O and PdCl 2 Total mass of (2), naBH 4 The mass ratio of (2) is 15: (0.5-1): (1-2).
5. An Au-Pd nps@nmof-Ni ultrathin nanosheet composite material prepared by the preparation method as claimed in any one of claims 1-4.
6. Use of the Au-Pd nps@nmof-Ni ultrathin nanosheet composite material according to claim 5 in catalyzing organic reactions.
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WO2017218065A1 (en) * 2016-06-17 2017-12-21 Battelle Memorial Institute System and process for continuous and controlled production of metal-organic frameworks and metal-organic framework composites
CN107497488A (en) * 2017-09-11 2017-12-22 大连理工大学 A kind of preparation method and application of the monatomic alloy catalysts of high hydrogenation selectivity Au Pd
CN111359670A (en) * 2020-03-10 2020-07-03 浙江工业大学 Au-Pd/NH2-MIL-101(Cr) catalyst and preparation and application thereof

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Publication number Priority date Publication date Assignee Title
WO2014046107A1 (en) * 2012-09-20 2014-03-27 国立大学法人京都大学 Metal nanoparticle complex and method for producing same
WO2017218065A1 (en) * 2016-06-17 2017-12-21 Battelle Memorial Institute System and process for continuous and controlled production of metal-organic frameworks and metal-organic framework composites
CN107497488A (en) * 2017-09-11 2017-12-22 大连理工大学 A kind of preparation method and application of the monatomic alloy catalysts of high hydrogenation selectivity Au Pd
CN111359670A (en) * 2020-03-10 2020-07-03 浙江工业大学 Au-Pd/NH2-MIL-101(Cr) catalyst and preparation and application thereof

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