CN113559941A

CN113559941A - MOFs material-based metal nanoparticle-loaded catalyst and preparation method and application thereof

Info

Publication number: CN113559941A
Application number: CN202110972250.1A
Authority: CN
Inventors: 肖领平; 孙润仓; 肖文哲; 杨月芹
Original assignee: Dalian Polytechnic University
Current assignee: Dalian Polytechnic University
Priority date: 2021-08-24
Filing date: 2021-08-24
Publication date: 2021-10-29

Abstract

The invention provides a MOFs material-based metal nanoparticle-loaded catalyst, and a preparation method and application thereof. The catalyst comprises carboxylic acids MOFs and metal nanoparticles loaded in the carboxylic acids MOFs; the total weight of the catalyst is 100%, and the loading amount of the metal nanoparticles is 1-3 wt%. The invention has the advantages that the prepared supported catalyst shows excellent catalytic activity by virtue of the stabilization strategy of free amino and the inherent pore limitation of MOFs.

Description

MOFs material-based metal nanoparticle-loaded catalyst and preparation method and application thereof

Technical Field

The invention relates to the field of precious metal nano-system preparation, in particular to a MOFs material-based metal nanoparticle-loaded catalyst, and a preparation method and application thereof.

Background

P-nitrophenol (4-NP) is widely present in industrial wastewater and is difficult to degrade, and even at very low concentrations, it is toxic and carcinogenic to humans. The U.S. has long classified 4-NP as a "priority contaminant" for control. However, the reduction product of 4-NP, 4-aminophenol (4-AP), is an important synthetic intermediate in some fields of pharmacy, chemical industry and the like. The reduction of 4-NP to 4-AP using sodium borohydride as a reducing agent in the presence of a catalyst has become a versatile and effective approach. Nanometals are useful as carriers for electron transport because they can transport electrons from a reducing agent (BH)₄ ^-) Transfer to oxidant (-NO)₂). However, some synthesis methods are complex and difficult to control, so that the catalyst has low activity and poor stability, and the reaction is difficult to smoothly proceed. How to design a simple and high-efficiency catalyst becomes the current problem.

Previous studies neglected the importance of the carrier, and in fact, in addition to their intended role (as an anchor for the active metal center), it also plays a central role in creating the microenvironment around the metal nanoparticles. In this regard, Metal Organic Frameworks (MOFs) have become a promising class of crystalline porous materials due to their high internal surface area, uniform pore size distribution, and tunable structure. Diversified inorganic metal nodes and organic ligands endow MOFs with abundant coordination sites, so that the MOFs become ideal hosts of metal nanoparticles. To date, a number of successful cases have been reported for the production of metal-based nanocomposites at high temperatures using MOFs as supports. Unfortunately, destroyed MOFs after pyrolysis do not exert their inherent advantages, resulting in poor interaction between metal nanoparticles and the support.

Disclosure of Invention

In view of the above, the present invention provides a catalyst based on MOFs material supported metal nanoparticles, and a preparation method and an application thereof, wherein the composite nanomaterial is used for catalyzing p-nitrophenol reduction and degradation reaction of organic dyes, and exhibits very high catalytic activity and stability.

The purpose of the invention and the technical problem to be solved are realized by adopting the following technical scheme. The catalyst based on MOFs material loaded metal nanoparticles comprises carboxylic acids MOFs and metal nanoparticles loaded in the carboxylic acids MOFs; the total weight of the catalyst is 100%, and the loading amount of the metal nanoparticles is 1-3%.

Preferably, the catalyst based on MOFs material loaded with metal nanoparticles is used, wherein the carboxylic acid MOFs are UiO-66 series MOFs, MIL-53 series MOFs or MIL-101 series MOFs.

Preferably, the catalysts based on MOFs materials loaded with metal nanoparticles are used, wherein the specific surface areas of the carboxylic acids MOFs are 1000m²More than/g, and all show a crystalline material with a regular porous structure.

Preferably, the particle size of the carboxylic acid MOFs is 50-300 nm.

Preferably, the aforementioned MOFs material-supported metal nanoparticle-based catalyst, wherein the metal nanoparticle is a silver nanoparticle, a gold nanoparticle, a platinum nanoparticle, an iron nanoparticle or a copper nanoparticle.

Preferably, the MOFs material-supported metal nanoparticle-based catalyst has a particle size of 5-20 nm.

The purpose of the invention and the technical problem to be solved can also be realized by adopting the following technical scheme. The invention provides a preparation method of a MOFs material-based metal nanoparticle-supported catalyst, which comprises the following steps of:

uniformly dispersing carboxylic acid MOFs in a metal precursor solution, and dropwise adding a reducing agent to ensure complete reaction; then continuously washing to remove redundant or incompletely reacted metal ions; and finally, drying under vacuum to obtain the catalyst.

Preferably, in the preparation method of the catalyst based on the metal nanoparticles supported by the MOFs material, the mass ratio of the metal precursor to the MOFs is 1: 20-30; the molar ratio of the metal precursor to the reducing agent is 1: 0.5-1: 2.

preferably, in the preparation method of the catalyst based on the MOFs material supported metal nanoparticles, the reducing agent is sodium borohydride; the reducing agent is slowly added into the mixture by a peristaltic pump drop by drop in a ratio of 10mL to 50 mL/h.

Preferably, in the preparation method of the catalyst based on the MOFs material loaded with the metal nanoparticles, the carboxylic acid MOFs are porous materials, and have high porosity, high crystallinity and complete shape.

Preferably, in the preparation method of the catalyst based on the MOFs material loaded with the metal nanoparticles, the carboxylic MOFs are prepared by the following steps:

dissolving an organic ligand and an inorganic metal salt in a first solvent, and carrying out ultrasonic treatment until the organic ligand and the inorganic metal salt are completely dissolved; then, heating the reaction solution to 120-150 ℃, keeping the temperature for 18-30 hours, taking out, and naturally cooling to room temperature; and after cooling, centrifuging, repeatedly washing with a second solvent to obtain a solid, and drying at the temperature of 50-80 ℃ under a vacuum condition to obtain the carboxylic acids MOFs.

Preferably, in the preparation method of the catalyst based on the metal nanoparticles supported by the MOFs material, the organic ligand is 2-amino terephthalic acid.

Preferably, in the foregoing preparation method of the catalyst based on MOFs material supported metal nanoparticles, the inorganic metal salt is selected from one of aluminum chloride hexahydrate, zirconium chloride and chromium nitrate hydrate.

Preferably, in the preparation method of the catalyst based on the metal nanoparticles supported on the MOFs material, the molar ratio of the organic ligand to the inorganic metal salt is 1: 0.5-1: 2.

preferably, in the preparation method of the catalyst based on the metal nanoparticles supported on the MOFs material, the molar ratio of the first solvent to the inorganic metal is 2: 1-4: 1.

preferably, in the preparation method of the catalyst based on the metal nanoparticles supported by the MOFs material, the metal precursor is silver ammonia solution, chloroauric acid or chloroplatinic acid.

Preferably, in the foregoing preparation method of the catalyst based on MOFs material supported metal nanoparticles, the first solvent is at least one selected from N, N-dimethylformamide, anhydrous acetic acid and deionized water.

Preferably, in the preparation method of the catalyst based on the MOFs material loaded with the metal nanoparticles, the second solvent is N, N-dimethylformamide, ethanol or deionized water.

Preferably, in the foregoing preparation method of the catalyst based on the MOFs material supported metal nanoparticles, the parameters of the vacuum are set as follows: the vacuum degree is-10 Kpa to-30 Kpa; the drying time is 10-18 h; the drying temperature is 50-80 ℃.

The purpose of the invention and the technical problem to be solved can also be realized by adopting the following technical scheme. According to the application of the MOFs material-based metal nanoparticle-loaded catalyst in organic wastewater, the organic wastewater contains at least one of p-nitrophenol and organic dye, and the concentration of the p-nitrophenol and the organic dye is 1.1 g/L-5.6 g/L.

Preferably, the application of the catalyst based on MOFs material loaded metal nanoparticles in organic wastewater treatment, wherein the application comprises the following steps: putting the catalyst and sodium borohydride into organic wastewater for wastewater treatment, wherein the dosage of the catalyst is 16.7-50.0 mg/L, preferably 33.3 mg/L; the input amount of the sodium borohydride is 0.28-1.42 g/L, and preferably 1.14 g/L.

Preferably, the MOFs material loaded metal nanoparticle-based catalyst is applied to the treatment of organic wastewater, wherein the organic wastewater contains at least one of p-nitrophenol and an organic dye, and the concentration of the p-nitrophenol and the organic dye is 0.05 mM-0.2 mM.

Preferably, the application of the catalyst based on MOFs material loaded metal nanoparticles in organic wastewater treatment is carried out, wherein the p-nitrophenol is reduced, the catalytic time is 90s, and the conversion frequency (TOF) is 3.24 x 10⁴h^-1The reaction rate (k) was 0.069s^-1(ii) a The organic dye is degraded: the reaction time is 30 s-6 min, and the reaction rate is 0.0078s^-1～0.2251s^-1。

Preferably, the MOFs material-supported metal nanoparticle-based catalyst is applied to organic wastewater treatment, wherein the organic dye is selected from at least one of rhodamine B, rhodamine 6G, methylene blue, Congo red and methyl orange.

The invention utilizes inorganic metal and organic ligand to prepare and form the functionalized metal organic framework material by solvothermal self-assembly. The metal nano-particles are prepared by reducing sodium borohydride, and are applied to catalytic degradation reaction of organic pollutants. In addition, the supported catalyst which shows ultrahigh catalytic activity, excellent dispersibility and stronger stability also has practical application value. The supported catalyst realizes the high-dispersity loading of metal nanoparticles on various MOFs. In the degradation of reducing p-nitrophenol and 5 organic dyes in an aqueous solution system, the rapid catalytic conversion can be realized. In the catalytic reduction of a p-nitrophenol solution with a certain concentration, the reaction conversion rate of nearly 100 percent can still be ensured after the p-nitrophenol solution is repeatedly used for 10 times.

By means of the technical scheme, the catalyst based on MOFs material loaded metal nanoparticles and the preparation method and application thereof at least have the following advantages:

the preparation method of the catalyst provided by the invention is simple. Firstly, a metal organic framework is synthesized by adopting a solvothermal method, and then a high-efficiency catalyst with high dispersibility is synthesized by adopting an immersion method and taking a metal solution as a precursor and sodium borohydride as a reducing agent. The synthesized catalyst still keeps a relatively complete MOFs structure, and the metal particles are dispersed very uniformly.

The catalytic reduction of p-nitrophenol of the invention has higher catalytic activity, such as Ag/UiO-66-NH₂In the catalytic reduction process of p-nitrophenol, the reaction rate (k) is 0.069s^-1Conversion frequency (TOF) of 3.24 × 10⁴h^-1And still maintain near 100% conversion after 10 cycles. This result demonstrates that the catalyst obtained by the present invention has good catalytic activity and recyclability.

The invention shows ultrahigh activity in the degradation of different organic dyes, and the reaction rate is 0.0078s^-1～0.2251s^-1The results show that the supported catalyst has obvious effect on 5 organic dyes including methylene blue. This further shows that the invention has stronger degradation and reduction capability to organic dyes.

In the invention, the catalytic effect of the catalyst on the reaction substrate at different flow rates is discussed through the designed fixed bed reactor in the simulation of the actual industrial production environment. The p-nitrophenol reduction still remained within 35 hours at a flow rate of 0.5mL/min, also indicating a higher stability of the catalyst, which indicates that a favourable micro-environment regulation can improve the electron transfer process and regulate the intrinsic activity of the catalytic sites. The method can provide a new way for developing a high-efficiency catalyst capable of continuously treating water pollutants.

The catalyst of the invention can effectively stabilize transition metal precursors (provide an empty d orbital) by taking uncoordinated amine groups positioned on a connector as Lewis bases (provide lone pair electrons) in amine functionalized MOFs; in addition, various functional groups pendant to the linker can further prevent the aggregation of metal nanoparticles by modulating the chemical environment of the MOFs pore walls, resulting in enhanced catalysis. Therefore, the catalyst has metal active sites which are more accessible, is beneficial to microenvironment regulation and can improve the stability of liquid phase catalytic reaction.

The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.

Drawings

Fig. 1 is an SEM image of the catalyst prepared in example 1 of the present invention.

FIG. 2 is a TEM image of the catalyst prepared in example 1 of the present invention.

Fig. 3 is an XRD spectrum of the catalyst prepared in example 1 of the present invention.

FIG. 4 is a FT-IR spectrum of the catalyst prepared in example 1 of the present invention.

FIG. 5 is a high resolution XPS Ag3d spectrum of the catalyst prepared in example 1 of the present invention.

Fig. 6 is a TEM image of the catalyst prepared in comparative example 1.

FIG. 7 is a UV-visible absorption spectrum representation of the catalytic reduction of p-nitrophenol by the catalyst prepared in example 1 of the present invention.

FIG. 8 is a graph of catalytic reduction cycle number for the catalyst prepared in example 1 of the present invention.

FIG. 9 shows the product obtained after catalytic reduction of p-nitrophenol by the catalyst prepared in example 1 of the present invention¹³C NMR spectrum.

FIG. 10 shows the product obtained after catalytic reduction of p-nitrophenol by the catalyst prepared in example 1 of the present invention¹H NMR spectrum.

FIG. 11 is a UV-VIS spectrum of p-nitrophenol in the catalytic reduction of the catalyst prepared in comparative example 1.

FIG. 12 is a UV-VIS spectrum characterization diagram of the catalyst-catalyzed reduced rhodamine B dye prepared in example 1 of the present invention.

FIG. 13 is a characterization diagram of the ultraviolet-visible absorption spectrum of the rhodamine 6G dye catalyzed and reduced by the catalyst prepared in example 2 of the invention.

FIG. 14 is a UV-VIS spectrum of a catalyst prepared in example 2 of the present invention.

FIG. 15 is a graph of UV-VIS spectrum characterization of Congo red dye catalyzed and reduced by the catalyst prepared in example 3.

FIG. 16 is a UV-VIS spectrum of a catalyst prepared in example 3 of the present invention.

FIG. 17 is a schematic view showing the structural connection of the catalyst prepared in example 1 of the present invention to a fixed bed reactor.

FIG. 18 is a graph of data for a reaction of a catalyst prepared in example 1 of the present invention on a fixed bed reactor;

FIG. 19 is a TEM image of the catalyst prepared in example 1 of the present invention after reaction on a fixed bed reactor.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be made in conjunction with the preferred embodiments of a catalyst based on MOFs material supported metal nanoparticles, its preparation method, and its embodiments, features and properties. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.

The invention provides a MOFs material-based metal nanoparticle-loaded catalyst, which comprises carboxylic acids MOFs and metal nanoparticles loaded in the carboxylic acids MOFs; the total weight of the catalyst is 100%, the loading amount of the metal nanoparticles is 1-3 wt%, and if the loading amount is less than 1 wt%, the catalytic effect is poor due to fewer catalytic centers; if it is more than 3 wt%, the cost is increased and the catalytic effect is difficult to be further increased due to the aggregation of the catalytic active centers, and the loading amount of the metal nanoparticles is preferably 2 wt% in view of better catalytic effect.

In some embodiments, the said carboxylic MOFs are UiO-66 series MOFs, MIL-53 series MOFs or MIL-101 series MOFs, each with a specific surface area of 1000m²Crystalline materials above/g and all exhibiting a regular porous structure, see fig. 1; as can be seen, the said carboxylic acid MOFs are porous materials,high porosity, high crystallinity and complete shape. The particle size of the carboxylic acid MOFs is 50-300 nm, and if the particle size is less than 50nm, metal aggregation distribution is caused; if it is larger than 300nm, it will cause the metal distribution to be non-uniform, preferably 200nm, and it is preferable to disperse the catalytic center more uniformly in the MOFs.

In other embodiments, the metal nanoparticles are silver nanoparticles, gold nanoparticles, platinum nanoparticles, iron nanoparticles or copper nanoparticles, the particle size is 5-20 nm, and the silver nanoparticles, the gold nanoparticles or the platinum nanoparticles are preferred, and are all noble metals, so that the catalytic activity is high.

The invention also provides a preparation method of the catalyst based on MOFs material loaded metal nanoparticles, which comprises the following steps:

In some embodiments, the mass ratio of the metal precursor to the MOFs is 1: 20-30, and more preferably 1: 25, ensuring that the optimal catalytic effect is achieved under the condition of the lowest consumption of the metal precursor. If less than 1: 30, the catalytic effect is poor due to less catalytic centers; or more than 1: 20, the cost is increased, and the catalytic effect is difficult to further increase due to the aggregation of the catalytic active centers, so that the better catalytic effect is considered; the molar ratio of the metal precursor to the reducing agent is 1: 0.5-1: 2, preferably 1: 1, preferably, the metal can be completely reduced by using the minimum amount of reducing agent; if less than 1: 2 or more than 1: 0.5, incomplete reduction of the metal results.

In some embodiments, the reducing agent is sodium borohydride, which can uniformly disperse the metal nanoparticles into the MOFs. The reducing agent is slowly added into the mixture by a peristaltic pump drop by drop in a ratio of 10mL to 50mL/h, preferably 20mL/h, so that the synthesized metal nanoparticles are uniformly dispersed in particle size; the solution turned black and after 1 hour no further change in color until the reducing agent was added at the rate described above. If the amount is less than 10mL/h or more than 50mL/h, the particle diameter of the reduced metal is too large or the distribution is not uniform, so that the catalytic activity is greatly reduced.

In specific implementation, the carboxylic acid MOFs can be prepared by the following steps:

dissolving an organic ligand and an inorganic metal salt in a first solvent, and carrying out ultrasonic treatment until the organic ligand and the inorganic metal salt are completely dissolved; then, heating the reaction solution to 120-150 ℃ (synthesis temperature), keeping the temperature for 18-30 hours (preferably, after 24 hours, the particle size of the prepared MOFs is more uniform), taking out, and naturally cooling to room temperature; and after cooling, centrifuging, repeatedly washing with a second solvent to obtain a solid, and drying at the temperature of 50-80 ℃ under a vacuum condition to obtain the carboxylic acids MOFs. For UiO-66-NH₂The synthesis temperature is preferably 120 ℃ for MIL-53-NH₂The synthesis temperature is preferably 150 ℃ for MIL101-NH₂In terms of the synthesis temperature, it is preferably 130 ℃. The preferred temperature makes the synthesized MOFs more regular in shape and more uniform in particle size.

In other embodiments, the organic ligand is a 2-amino terephthalic acid organic ligand as a backbone in MOFs for coordinate attachment to an inorganic metal. 2-amino terephthalic acid is selected to lead the skeleton of the produced MOFs to have-NH₂。

In other embodiments, the inorganic metal salt is selected from one of aluminum chloride hexahydrate, zirconium chloride and chromium nitrate hydrate, and the inorganic metal is coordinated and connected with the organic ligand as a metal node to form the MOFs. And the three inorganic metal salts of aluminum chloride hexahydrate, zirconium chloride and chromium nitrate hydrate represent inorganic metal nodes of three different MOFs.

In other embodiments, the molar ratio of organic ligand to inorganic metal salt is 1: 0.5-1: 2; the preferred ratio is 1: 1, the MOFs obtained after optimization has higher crystallinity and more regular shape; if the molar ratio of the organic ligand to the inorganic metal salt is less than 1: 2 or more than 1: 0.5, the MOFs are difficult to mold.

The molar ratio of the first solvent to the inorganic metal is 2: 1-4: 1; preferably 3: 1, the preferred MOFs have higher crystallinity, more uniform pore distribution and more regular shape; if the molar ratio of the first solvent to the inorganic metal is less than 2: 1 or more than 4: 1, the above MOFs cannot be synthesized.

The metal precursor is silver ammonia solution, chloroauric acid or chloroplatinic acid, preferably silver ammonia solution, so that silver particles are smaller, and finally the prepared catalyst has stronger activity.

The first solvent is at least one selected from the group consisting of N, N-dimethylformamide, anhydrous acetic acid and deionized water. For example, for UiO-66-NH₂The first solvent is composed of N, N-dimethylformamide and anhydrous acetic acid, and the volume ratio of the N, N-dimethylformamide to the anhydrous acetic acid is 5: 1-10: 1, preferably 7: 1, the MOFs obtained after optimization has higher crystallinity and more regular shape; if the volume ratio of the N, N-dimethylformamide to the anhydrous acetic acid is less than 5: 1 or greater than 10: 1, the above MOFs cannot be synthesized. For MIL-53-NH₂The first solvent is N, N-dimethylformamide and water, and the volume ratio of the N, N-dimethylformamide to the water is 5: 1-10: 1, preferably 7: 1, the MOFs obtained after optimization has higher crystallinity and more regular shape; if the volume ratio of the N, N, N-dimethylformamide to the water is less than 5: 1 or greater than 10: 1, the above MOFs cannot be synthesized. For MIL-101-NH₂In one aspect, the first solvent is water.

The second solvent is N, N-dimethylformamide, ethanol or deionized water, preferably N, N-dimethylformamide, so that unreacted metal precursors or impurities can be efficiently removed after preference.

The parameters of the vacuum are set as follows: the vacuum degree is-10 Kpa to-30 Kpa, preferably-25 Kpa; the drying time is 10-18 h, and preferably 12 h; the drying temperature is 50-80 ℃, preferably 60 ℃, the drying efficiency of the catalyst can be improved under the conditions of preferred vacuum degree, time and temperature, the durability of the catalyst is improved, and the catalyst is easier to store. If the vacuum setting parameter is not within the above range, it is difficult to improve the drying efficiency of the obtained material.

The invention also provides an application of the MOFs material-based metal nanoparticle-loaded catalyst in organic wastewater, wherein the organic wastewater contains at least one of p-nitrophenol and organic dye, and the concentration of the organic wastewater is 1.1-5.6 g/L, preferably 1.4 g/L; if less than 1.1g/L or more than 5.6g/L, the catalyzed substrate is difficult to be reacted completely.

Specifically, the application comprises the following steps: putting the catalyst and sodium borohydride into organic wastewater for wastewater treatment, wherein the dosage of the catalyst is 16.7-50.0 mg/L, preferably 33.3 mg/L; the input amount of the sodium borohydride is 0.28-1.42 g/L, and preferably 1.14 g/L. Under the conditions of optimal catalyst input amount (33.3mg/L) and optimal sodium borohydride input amount (37.8g/L), the effect is best in a system with a reaction solution of 30mL, and the catalysis time is 90 s.

The organic wastewater contains at least one of p-nitrophenol and organic dye, the concentration of the p-nitrophenol and the organic dye is 0.05 mM-0.2 mM, preferably 0.1mM, the post-catalysis effect is better, and the catalysis can be completed in a short time. In the presence of a catalyst, the p-nitrophenol can be reduced into the p-aminophenol, specifically, the color is faded, the ultraviolet characteristic peak of the p-nitrophenol is weakened to disappear, and the ultraviolet characteristic peak of the p-aminophenol is enhanced. In the presence of a catalyst, different organic dyes can be catalytically degraded, specifically, the color is faded, and the ultraviolet characteristic peak of each organic dye is gradually weakened to disappear.

The p-nitrophenol is reduced with a catalytic time of 90s and a conversion frequency (TOF) of 3.24X 10⁴h^-1The reaction rate (k) was 0.069s^-1(ii) a The organic dye is degraded: the reaction time is 30 s-6 min, and the reaction rate is 0.0078s^-1～0.2251s^-1。

The organic dye is selected from at least one of rhodamine B, rhodamine 6G, methylene blue, Congo red and methyl orange.

The methods in the following examples are conventional methods unless otherwise specified; the materials and reagents used in the following examples are all commercially available unless otherwise specified.

The present invention is further illustrated by the following specific examples, which are not to be construed as limiting the invention thereto. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

Example 1

Typical Ag/UiO-66-NH₂The synthesis method comprises the following steps:

40mg of 2-aminoterephthalic acid and 52mg of zirconium chloride were accurately weighed and dissolved in 44mL of N, N-Dimethylformamide (DMF), 6mL of anhydrous acetic acid was added as a conditioning agent, and sonication was carried out for 30min until complete dissolution. And then, transferring the reaction solution into a hydrothermal reaction kettle, sealing the hydrothermal reaction kettle, placing the hydrothermal reaction kettle in an electrothermal blowing dry box, and heating to 120 ℃. And keeping the temperature for 24 hours, taking out the mixture, and naturally cooling the mixture to room temperature. Cooling, centrifuging, washing with DMF repeatedly to obtain solid, and drying at 60 deg.C under vacuum to obtain UiO-66-NH₂.5mL of silver nitrate solution (4mM) was added dropwise to 2 wt% aqueous ammonia to obtain a silver-ammonia solution. 85mg of UiO-66-NH were added₂Placing the solution in the obtained silver ammonia solution, stirring the solution at normal temperature until the solution is dispersed, slowly dropwise adding sodium borohydride into the solution by using a peristaltic pump (the dropwise adding rate is 20mL/h), continuously stirring the solution, filtering the mixed solution, repeatedly washing the mixed solution by using deionized water, and drying the mixed solution under the vacuum condition at 60 ℃ to obtain Ag/UiO-66-NH₂。

FIG. 1 shows Ag/UiO-66-NH₂The SEM image of (1) shows that the prepared metal organic framework is regular octahedron and has a regular and complete structure; and after Ag is loaded, complete UiO-66-NH is reserved₂And (4) morphology.

FIG. 2 shows Ag/UiO-66-NH₂From the TEM image of (1), it can be seen in FIG. 2 that Ag on the prepared catalyst is uniformly and highly dispersed in UiO-66-NH₂(ii) a The obtained metal was Ag and the exposed crystal planes were (200) and (111) as found by measurement of the lattice spacing.

FIG. 3 shows Ag/UiO-66-NH₂The XRD spectrum of (A) shows from FIG. 3 that the diffraction peak is not strong due to the very uniform and small dispersion of the metal particles obtained, and UiO-66-NH can be observed₂Characteristic diffraction peak of (1).

FIG. 4 shows Ag/UiO-66-NH₂The FT-IR spectrum of (1) is 1258cm as can be seen from FIG. 4^-1And 1665cm^-1At two peaks are respectivelyFrom UiO-66-NH₂Of (5) -NH₂Characteristic signals of the radicals and residual DMF. 1055cm^-1Changes in peak intensity and position shift indicate Ag species with-NH₂There is an interaction between the groups.

FIG. 5 shows Ag/UiO-66-NH₂From the spectrum of high resolution XPS Ag3d, it can be seen from FIG. 5 that by deconvoluting the XPS peak of silver element, the XPS Ag3d spectrum can be divided into 2 peaks, which are Ag3d respectively_5/2(368.2eV) and Ag3d_3/2(374.2eV), silver can be judged to be elemental by the bimodal spacing and peak position, which is consistent with the results observed with the TEM of fig. 2.

Comparative example 1

A typical Ag/UiO-66 synthesis method comprises the following steps:

for comparison, the synthesis was carried out using amino-free UiO-66 as a support. 36mg of terephthalic acid and 52mg of zirconium chloride were accurately weighed and dissolved in 44mL of N, N-Dimethylformamide (DMF), 6mL of acetic acid was added as a conditioning agent, and sonication was carried out for 30min until complete dissolution. And then, transferring the reaction solution into a hydrothermal reaction kettle, sealing the hydrothermal reaction kettle, placing the hydrothermal reaction kettle in an electrothermal blowing dry box, and heating to 120 ℃. And keeping the temperature for 24 hours, taking out the mixture, and naturally cooling the mixture to room temperature. Cooling, centrifuging, washing with DMF repeatedly to obtain solid, and drying at 60 deg.C under vacuum to obtain UiO-66-NH₂.5mL of silver nitrate solution (4mM) was added dropwise to 2 wt% aqueous ammonia to obtain a silver-ammonia solution. And putting 85mg of UiO-66 into the obtained silver ammonia solution, stirring at normal temperature until dispersion is achieved, slowly dropwise adding sodium borohydride (the dropping rate is 20mL/h) by using a peristaltic pump, continuing stirring, carrying out suction filtration on the mixed solution, repeatedly washing by using deionized water, and drying under the vacuum condition of 60 ℃ to obtain Ag/UiO-66.

FIG. 6 is a TEM image of Ag/UiO-66, from which FIG. 6 it can be seen that there is no-NH₂The Ag particles are significantly aggregated resulting in larger particles.

Example 2

Typical Au/MIL-53-NH₂The synthesis method comprises the following steps:

56mg of 2-aminoterephthalic acid and 76mg of aluminum chloride hexahydrate are accurately weighed and dissolved in 8.5mL respectively for separationSublike and 21.5mL DMF, sonicate for 30min to completely dissolve. And then, transferring the reaction solution into a hydrothermal reaction kettle, sealing the hydrothermal reaction kettle, placing the hydrothermal reaction kettle in an electrothermal blowing dry box, and heating to 150 ℃. And keeping the temperature for 24 hours, taking out the mixture, and naturally cooling the mixture to room temperature. Cooling, centrifuging, activating in boiling N, N-dimethylformamide for 5 hr, repeatedly centrifuging, repeatedly washing with DMF to obtain solid, and drying at 60 deg.C under vacuum to obtain MIL-53-NH₂.5mL of chloroauric acid solution (4mM) and 85mg of MIL-53-NH were taken₂Mixing and stirring at normal temperature until dispersion, slowly dropwise adding sodium borohydride (the dropping rate is 20mL/h) by using a peristaltic pump, continuously stirring, carrying out suction filtration on the mixed solution, repeatedly washing by using deionized water, and drying at 60 ℃ under a vacuum condition to obtain Au/MIL-53-NH₂。

Example 3

Typical Pt/MIL-101-NH₂The synthesis method comprises the following steps:

230mg of 2-aminoterephthalic acid and 500mg of chromium nitrate hydrate are accurately weighed and dissolved in 7mL of deionized water, and ultrasonic treatment is carried out for 30min until the solutions are completely dissolved. Then, the reaction solution is transferred to a hydrothermal reaction kettle, sealed and placed in an electrothermal blowing dry box, and the temperature is raised to 130 ℃. And keeping the temperature for 24 hours, taking out the mixture, and naturally cooling the mixture to room temperature. Cooling, centrifuging, washing with anhydrous ethanol, and drying at 60 deg.C under vacuum to obtain MIL-101-NH₂.5mL of chloroplatinic acid solution (4mM) and 85mg of MIL-101-NH were taken₂Mixing and stirring at normal temperature until dispersion, slowly dropwise adding sodium borohydride (the dropping rate is 20mL/h) by using a peristaltic pump, continuously stirring, carrying out suction filtration on the mixed solution, repeatedly washing by using deionized water, and drying at 60 ℃ under a vacuum condition to obtain Pt/MIL-101-NH₂。

Example 4

Weighing quantitative Ag/UiO-66-NH₂(500. mu.L, 2g/L) and sonicated for 10min to give a homogeneous aqueous dispersion. 15mL of 4-NP solution (10mM) was taken with 15mL of freshly prepared NaBH₄The solutions (2.0M) were mixed. The aqueous dispersion was added to the mixture, and the mixture was stirred at room temperature. During which a yellow solution was observed that gradually lightened in color and finally became colorless. During the whole reaction, the reaction solution is passed through the reactor at regular intervals (30s) of 0.2100 mu L of reaction solution is sampled by a membrane filter with the diameter of 2 mu m, diluted by deionized water and subjected to ultraviolet detection, and the UV-vis absorption spectrum within the wavelength range of 200-800nm is recorded. The remaining 4-NP concentration and conversion in the real-time reaction can be calculated from the standard curve. In this example, 4-NP was completely reduced to 4-AP within 1.5min, and the reaction conversion rate was calculated to exceed 99%.

FIG. 7 shows Ag/UiO-66-NH₂Ultraviolet-visible absorption spectrum characterization of catalytic reduction of p-nitrophenol, it can be seen from fig. 7 that p-nitrophenol has been completely converted to the product p-aminophenol within 90 s.

FIG. 8 shows Ag/UiO-66-NH₂Cycle number of catalytic p-nitrophenol, it can be seen from FIG. 8 that Ag/UiO-66-NH is present after 10 repeated uses₂Still exhibit greater than 98% conversion.

FIG. 9 shows Ag/UiO-66-NH₂Of products obtained after catalytic reduction of p-nitrophenol¹³C NMR spectrum. FIG. 10 shows Ag/UiO-66-NH₂Of products obtained after catalytic reduction of p-nitrophenol¹H NMR spectrum. From the peak positions of C and H in fig. 9 and 10, it can be known that the product is p-aminophenol.

Example 5

A quantitative amount of Ag/UiO-66 (500. mu.L, 2g/L) was weighed and sonicated for 10min to obtain a homogeneous aqueous dispersion. 15mL of 4-NP solution (10mM) was taken with 15mL of freshly prepared NaBH₄The solutions (2.0M) were mixed. The aqueous dispersion was added to the mixture, and the mixture was stirred at room temperature. During which a yellow solution was observed that gradually lightened in color and finally became colorless. During the whole reaction process, 100 μ L of the reaction solution was sampled at regular intervals (30s) through a 0.22 μm membrane filter, diluted with deionized water and subjected to UV detection, and UV-vis absorption spectra in the wavelength range of 200-. The remaining 4-NP concentration and conversion in the real-time reaction can be calculated from the standard curve. In this example, 4-NP was completely reduced to 4-AP within 3.5min, and the reaction conversion rate was calculated to exceed 99%.

FIG. 11 is a UV-VIS spectrum characterization of Ag/UiO-66 catalytically reduced p-nitrophenol, from which it can be found in FIG. 11 that within 210s, the p-nitrophenol has been completely converted to the product p-aminophenol.

Example 6

Weighing quantitative Ag/UiO-66-NH₂(200. mu.L, 0.5g/L) and sonicated for 10min to give a homogeneous aqueous dispersion. 2mL of rhodamine B solution (0.1mM) and 1mL of freshly prepared NaBH were taken₄The solutions (80mM) were mixed. The aqueous dispersion was added to the mixture, and the mixture was stirred at room temperature. During which a pink solution was observed that gradually lightened in color and finally became colorless. The UV-vis absorption spectra in the wavelength range of 400-700nm were recorded in real time throughout the reaction. And (4) calculating the concentration and conversion rate of the remaining rhodamine B in the real-time reaction according to the standard curve. In this embodiment, rhodamine B can be completely degraded within 30 seconds.

FIG. 12 shows Ag/UiO-66-NH₂The ultraviolet-visible absorption spectrum characterization diagram of the catalytic reduction rhodamine B dye can be found from FIG. 12 that the characteristic peak of rhodamine B completely disappears within 30 s.

Example 7

Weighing quantitative Au/MIL-53-NH₂(200. mu.L, 0.5g/L) and sonicated for 10min to give a homogeneous aqueous dispersion. 2mL of rhodamine 6G solution (0.11mM) and 1mL of freshly prepared NaBH were taken₄The solutions (80mM) were mixed. The aqueous dispersion was added to the mixture, and the mixture was stirred at room temperature. During which time an orange solution was observed that gradually lightened in color and eventually became colorless. The UV-vis absorption spectra in the wavelength range of 200-700nm were recorded in real time throughout the reaction. And (4) calculating the concentration and conversion rate of the remaining rhodamine 6G in the real-time reaction according to the standard curve. In the embodiment, rhodamine 6G can be completely degraded within 1 min.

FIG. 13 shows Au/MIL-53-NH₂The ultraviolet-visible absorption spectrum characterization diagram of the catalytic reduction rhodamine 6G dye can be found from FIG. 13 that the characteristic peak of rhodamine 6G completely disappears within 1 min.

Example 8

Weighing quantitative Au/MIL-53-NH₂(200. mu.L, 0.5g/L) and sonicated for 10min to give a homogeneous aqueous dispersion. 2mL of methylene blue solution (0.1mM) was taken with 1mL of freshly prepared NaBH₄The solutions (80mM) were mixed. Adding the aqueous dispersion into the mixed solutionAnd stirring at room temperature. During which a gradual lightening of the colour of the sky-blue solution and finally a colourless colour was observed. The UV-vis absorption spectra in the wavelength range of 400-800nm were recorded in real time throughout the reaction. And calculating the concentration and conversion rate of the residual methylene blue in the real-time reaction according to the standard curve. In this example, methylene blue was completely degraded within 6 min.

FIG. 14 shows Au/MIL-53-NH₂The characterization chart of the catalytic reduction methylene blue dye ultraviolet-visible absorption spectrum can show that the characteristic peak of the methylene blue completely disappears within 6min from FIG. 14.

Example 9

Weighing quantitative Pt/MIL-101-NH₂(200. mu.L, 0.5g/L) and sonicated for 10min to give a homogeneous aqueous dispersion. 2mL of Congo Red solution (0.1mM) and 1mL of freshly prepared NaBH were taken₄The solutions (80mM) were mixed. The aqueous dispersion was added to the mixture, and the mixture was stirred at room temperature. During which time an orange solution was observed that gradually lightened in color and eventually became colorless. The UV-vis absorption spectra in the wavelength range of 200-700nm were recorded in real time throughout the reaction. And calculating the concentration and conversion rate of the Congo red remained in the real-time reaction according to the standard curve. In this example, congo red can be completely degraded within 1 min.

FIG. 15 shows Pt/MIL-101-NH₂The ultraviolet-visible absorption spectrum characterization diagram of the catalytic reduction congo red dye can be found from fig. 15 that the characteristic peak of congo red completely disappears within 1 min.

Example 10

Weighing quantitative Pt/MIL-101-NH₂(200. mu.L, 0.5g/L) and sonicated for 10min to give a homogeneous aqueous dispersion. 2mL of methyl orange solution (0.1mM) was taken with 1mL of freshly prepared NaBH₄The solutions (80mM) were mixed. The aqueous dispersion was added to the mixture, and the mixture was stirred at room temperature. During which a yellow solution was observed that gradually lightened in color and finally became colorless. The UV-vis absorption spectra in the wavelength range of 200-700nm were recorded in real time throughout the reaction. And calculating the concentration and conversion rate of the residual methyl orange in the real-time reaction according to the standard curve. In this example, methyl orange was completely degraded within 1 min.

FIG. 16 shows Pt/MIL-101-NH₂The characterization chart of the catalytic reduction methyl orange dye ultraviolet-visible absorption spectrum can show that the characteristic peak of the methyl orange completely disappears within 1min from the graph shown in FIG. 16.

Example 11

Weighing 30mgAg/UiO-66-NH₂Placing in a fixed bed reactor as shown in FIG. 17, 4-NP was reacted with NaBH₄The concentrations of (A) and (B) were 50mg/L and 200mg/L, respectively, and the two solutions were pumped into the cylindrical barrel 1 by the first peristaltic pump 2 and the second peristaltic pump 3, respectively, so that the reaction solution was in complete contact with 30mg of the catalyst of example 1. The reaction rates are respectively 0.5mL/min, 1.0mL/min and 1.5mL/min, and the stability of the catalyst is further determined by discussing the relationship between the catalytic activity and the change of the flow rate through different flow rates. Wherein, the catalyst can be recycled for 35 hours under the condition of flow rate of 0.5 mL/min. The fixed bed reactor comprises a hollow cylindrical barrel 1, wherein 30mg of the catalyst in the embodiment 1 is contained in the cylindrical barrel 1, two ends of the cylindrical barrel 1 are connected with two rubber pipes, one of the rubber pipes is connected with a first peristaltic pump 5 and a second peristaltic pump 6, and the first peristaltic pump 5 and the second peristaltic pump 6 are respectively connected with a 4-NP storage bottle 2 and NaBH₄Storage bottle 3 to store 50 mg/L4-NP and 200mg/L NaBH, respectively₄The accurate pump is gone into cylindrical barrel 1 and is reacted, and another rubber tube connects liquid storage bottle 4 to be used for storing the liquid after the reaction, just the both ends of cylindrical barrel 1 still are equipped with the quartz wool, in order to plug up cylindrical barrel and prevent that the catalyst from losing.

FIG. 18 shows Ag/UiO-66-NH₂Data plotted on the fixed bed reactor, it can be seen from FIG. 18 that the conversion stabilized at 100% over 3 hours when 4-NP was reduced to 4-AP at room temperature at a flow rate of 0.5mL/min (contact time of 8 s). Subsequently, Ag/UiO-66-NH₂The activity of (2) gradually decreased, and at 35h, the conversion rate finally decreased to 10%. At a flow rate of 1.5ml/min, a significant reduction in conversion was observed after 2 hours, whereas after 26 hours of reaction the conversion had dropped to 13%. Ag/UiO-66-NH at a flow rate of 2.5mL/min₂Almost lost after 18 hours. Thus, the fast flow resulted in Ag/UIO-66-NH₂Is inactivated.

FIG. 19 shows Ag/UiO-66-NH₂From the TEM image after 35 hours at a flow rate of 0.5mL/min, it can be seen from FIG. 19 that the particle size of Ag is significantly increased and the distribution is no longer uniform after a long reaction time.

The reaction performance of 200. mu.L, 0.5g/L of the catalyst and 1mL, 80mM of sodium borohydride in examples 1-3 and comparative example 1 in various organic sewages is shown in Table 1, and it can be seen from Table 1 that the method is suitable for use in examples 1-3 of various metals (Au, Ag, Pt), various supports (UiO-66-NH)₂、MIL-53-NH₂、MIL-101-NH₂) And different organic pollutants (p-nitrophenol and 5 dyes), the catalytic effect is more prominent. When used for degrading p-nitrophenol, Ag/UiO-66-NH of example 1 is compared with Ag/UiO-66 of comparative example 1₂The enhancement of catalytic activity further verifies-NH₂Effective immobilization of the group and the metal cation by-NH₂Strong coordination between the lone pair on the Ag and the empty d orbital on the Ag.

Table 1: reactivity of different catalysts to organic contaminants

Sample (I)	Metal	Carrier	Degradation object	Catalytic reaction activity
					Example 1	Ag	UiO-66-NH₂	P-nitrophenol	0.0690s^-1
Example 1	Ag	UiO-66-NH₂	Rhodamine B	0.2251s^-1
					Example 2	Pt	MIL-53-NH₂	Rhodamine 6G	0.1001s^-1
Example 2	Pt	MIL-53-NH₂	Methylene blue	0.0078s^-1
					Example 3	Au	MIL-101-NH₂	Congo red	0.0625s^-1
Example 3	Au	MIL-101-NH₂	Methyl orange	0.0567s^-1
					Comparative example 1	Ag	UiO-66	P-nitrophenol	0.0220s^-1

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiment according to the technical spirit of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A catalyst based on MOFs material loaded with metal nanoparticles is characterized by comprising carboxylic acids MOFs and metal nanoparticles loaded in the carboxylic acids MOFs; the total weight of the catalyst is 100%, and the loading amount of the metal nanoparticles is 1-3 wt%.

2. The MOFs material supported metal nanoparticle catalyst according to claim 1, wherein said carboxylic acid type MOFs are UiO-66 series MOFs, MIL-53 series MOFs or MIL-101 series MOFs; the metal nanoparticles are silver nanoparticles, gold nanoparticles, platinum nanoparticles, iron nanoparticles or copper nanoparticles, and the particle size is 5-20 nm.

3. As claimed in claim 2The catalyst based on MOFs material loaded with metal nanoparticles is characterized in that the specific surface area of the carboxylic acids MOFs is 1000m²More than g, and the particle diameter is 50 to 300 nm.

4. A method for preparing a catalyst based on MOFs material supported metal nanoparticles according to any one of claims 1 to 3, characterized in that it comprises the following steps:

5. The method for preparing a catalyst based on MOFs material supported metal nanoparticles according to claim 4, wherein said metal precursor is silver ammonia solution, chloroauric acid or chloroplatinic acid; the mass ratio of the metal precursor to the MOFs is 1: 20-30; the molar ratio of the metal precursor to the reducing agent is 1: 1; the reducing agent is sodium borohydride; the carboxylic acid MOFs are prepared by the following steps: dissolving an organic ligand and an inorganic metal salt in a first solvent, and carrying out ultrasonic treatment until the organic ligand and the inorganic metal salt are completely dissolved; then, heating the reaction solution to 120-150 ℃, keeping the temperature for 24 hours, taking out, and naturally cooling to room temperature; and after cooling, centrifuging, repeatedly washing with a second solvent to obtain a solid, and drying at 60 ℃ under a vacuum condition to obtain the carboxylic acids MOFs.

6. The method of claim 5, wherein the organic ligand is 2-amino terephthalic acid; the inorganic metal salt is selected from one of aluminum chloride hexahydrate, zirconium chloride and chromium nitrate hydrate; the first solvent is at least one selected from N, N-dimethylformamide, anhydrous acetic acid and deionized water; the second solvent is N, N-dimethylformamide, ethanol or deionized water.

7. Use of a catalyst based on MOFs carrying metal nanoparticles according to any one of claims 1 to 3 in organic waste water.

8. Use of a catalyst based on MOFs materials loaded with metal nanoparticles according to claim 7 in organic wastewater treatment, characterized in that said use comprises the following steps: putting the catalyst and sodium borohydride into organic wastewater for wastewater treatment, wherein the input amount of the catalyst is 16.7-50.0 mg/L; the input amount of the sodium borohydride is 18.6-94.6 g/L.

9. The application of the MOFs material supported metal nanoparticle-based catalyst in organic wastewater treatment according to claim 8, wherein the organic wastewater contains at least one of p-nitrophenol and an organic dye, and the concentration of the at least one of p-nitrophenol and the organic dye is 1.1g/L to 5.6 g/L; the organic dye is selected from at least one of rhodamine B, rhodamine 6G, methylene blue, Congo red and methyl orange.

10. Use of a catalyst based on MOFs materials loaded with metal nanoparticles in organic wastewater treatment according to claim 9, wherein said p-nitrophenol is reduced with a catalytic time of 90s and a transition frequency (TOF) of 3.24 x 10⁴h^-1The reaction rate (k) was 0.069s^-1(ii) a The organic dye is degraded: the reaction time is 30 s-6 min, and the reaction rate is 0.0078s^-1～0.2251s^-1。