1. A preparation method of a Prussian blue analogue nano-framework material is characterized by comprising the following steps: adopting a re-dissolving-recrystallization method, comprising the following steps:

(1) mixing divalent manganese salt, trivalent ferric salt, ethanol, deionized water and PVP (polyvinyl pyrrolidone), and completely dissolving to form a mixed solution A;

(2) adding K into the mixed solution A₃Fe(CN)₆Solution to form mixed solution B;

(3) stirring, centrifuging, washing and drying the mixed solution B to obtain a reaction precursor;

(4) dispersing the reaction precursor in deionized water to form a heterogeneous solution C, adding one of divalent cobalt salt, nickel salt and copper salt, stirring, centrifuging, washing and drying to obtain the Prussian blue analogue nano-framework material.

2. The method of claim 1, wherein: in the step (1), the divalent manganese salt is manganese sulfate MnSO₄·H₂O, ferric iron salt is ferric sulfate Fe₂(SO₄)₃PVP is polyvinylpyrrolidone; the mass ratio of the divalent manganese salt to the trivalent ferric salt is 5:2-20:3, and the mass ratio of the ethanol, the deionized water and the PVP is 0.789:1: 0.03.

3. The method of claim 1, wherein: the mixing in the step (1) is specifically as follows: ultrasonic dispersion and magnetic stirring; the ultrasonic dispersion time is 10-20 min; the stirring speed is 500-1000 rpm, and the stirring time is 10-30 min.

4. The method of claim 1, wherein: k in step (2)₃Fe(CN)₆The amount of the solution added was 100 mL.

5. The method of claim 1, wherein: the steps (3) and (4) are stirring and centrifuging: magnetic stirring is carried out, the stirring speed is 500-; the centrifuge speed is 8000 rpm.

6. The method of claim 1, wherein: the washing in the step (3) is as follows: washing with ethanol for 2 times, and washing with deionized water for 2 times; the washing in the step (4) is as follows: deionized water washing 3 times.

7. The method of claim 1, wherein: the drying in the steps (3) and (4) is as follows: vacuum-53 deg.C freeze-drying for 6-12 h.

8. The method of claim 1, wherein: in the step (4), the mass ratio of the reaction precursor to the deionized water is 1: 500-1: 2000; the divalent cobalt salt, nickel salt and copper salt are respectively cobalt chloride CoCl₂·6H₂O, nickel chloride NiCl₂·6H₂O, copper chloride CuCl₂·2H₂O。

9. A prussian blue analogue nano-framework material prepared by the method of any one of claims 1-8.

10. Use of a prussian blue analogue nano-framework material prepared by the method of any one of claims 1 to 8, characterized in that: the Prussian blue analogue nano-framework material is used for photocatalytic reduction of carbon dioxide into carbon monoxide under mild conditions.

Background

In recent years, Metal Organic Frameworks (MOFs) have been widely studied for their advantages of many kinds, many pores, good catalytic performance, and controllable structure. In addition, the photocatalyst has a huge application potential in a photocatalytic system due to the open three-dimensional structure. A re-dissolution-recrystallization-based method opens up a new method and idea for preparing a novel functionalized Metal Organic Framework (MOF).

Few previous studies have focused on the use of MOFs to construct a nano-framework, mainly because it is difficult to find suitable MOFs templates that selectively remove the MOF side. While prussian blue is used as a template, a novel functional nano material with a hollow or porous structure can be developed under acidic, alkaline or sulfur-rich environments, but because PBA is poor in stability under the environments, an oxide or sulfide nano-framework is generally generated instead of the PBA-based nano-framework.

At present, because PBA belongs to MOFs materials, and has the advantages of multiple types, multiple pores, good catalytic performance, adjustable structure, unique three-dimensional open structure and the like, a great deal of research is devoted to the application of PBA nanoparticles, nanotubes and composite materials thereof in photocatalysis. Although open three-dimensional structures have unlimited promise in this regard, the synthesis of PBA nanostmods, combination with specific metals, and manipulation of unique internal structures remain a significant challenge. In order to solve the difficulty, a simple process is designed, and the preparation of the nano-framework type Prussian blue analogue nano-material is of great significance.

Disclosure of Invention

The invention aims to provide a method for reducing CO with high activity aiming at the defects of the prior art₂The preparation method of the Prussian blue analogue nano-framework material is a green synthesis method of the Prussian blue analogue nano-framework material with simple process, strong universality and applicability, and the prepared Prussian blue nano-framework material is used for photocatalytic reduction of CO₂In order to ensure that the CO has high activity,low cost, simple method, good economic benefit and environmental benefit, and can be produced and applied in large scale.

In order to achieve the purpose, the invention adopts the following technical scheme:

high-activity reduction CO₂The Prussian blue analogue nano-framework material comprises the following raw materials: manganese sulfate monohydrate (MnSO)₄·H₂O), iron (Fe) sulfate₂(SO₄)₃) Potassium ferricyanide (K)₃Fe(CN)₆) Ethanol (C)₂H₅OH), polyvinylpyrrolidone (PVP), cobalt chloride hexahydrate (CoCl)₂·6H₂O), nickel chloride hexahydrate (NiCl)₂·6H₂O), copper chloride dihydrate (CuCl)₂·2H₂O）。

The preparation method of the cobalt-iron Prussian blue nano-framework material comprises the following steps: adding manganese sulfate monohydrate and ferric sulfate into a mixed solution of ethanol, deionized water and polyvinylpyrrolidone, fully mixing to form a uniform solution, then adding a potassium ferricyanide solution into the uniform solution, and stirring, centrifuging, washing and drying to obtain a reaction precursor. Dispersing the reaction precursor in water, and performing ultrasonic treatment to form a heterogeneous solution. And adding the cobalt chloride solution into the solution, and performing magnetic stirring, centrifugation, washing and drying to obtain the Prussian blue analogue nano-framework material.

The method specifically comprises the following steps:

(1) adding divalent manganese salt and trivalent ferric salt into a mixed solution of alcohol, deionized water and polyvinylpyrrolidone, and fully mixing and dissolving to prepare a uniformly dispersed reaction precursor solution;

(2) adding a potassium ferricyanide solution into the reaction precursor solution, and stirring, centrifuging, washing and drying to obtain a reaction precursor;

(3) dispersing a reaction precursor in water to form a heterogeneous solution;

(4) and adding the divalent cobalt salt solution into the heterogeneous solution, and stirring, centrifuging, washing and freeze-drying to obtain the Prussian blue analogue nano-framework material.

Further, step (a)1) The ferric iron salt is ferric sulfate Fe₂(SO₄)₃(ii) a The divalent manganese salt is manganese sulfate monohydrate MnSO₄·H₂O; the alcohol is ethanol C₂H₅OH。

Further, in the step (1), the mass ratio of the ferric iron salt to the divalent manganese salt is 5:2-20:3, the using amount of the alcohol is 100 mL, the using amount of the deionized water is 100 mL, and the using amount of the PVP is 1.5 g.

Further, the mixing and dissolving in the step (1) specifically comprises: magnetic stirring; the stirring speed is 500-1000 rpm; the stirring time is 10-30 min.

Further, the amount of the potassium ferricyanide solution used in step (2) was 100 mL.

Further, the stirring in the step (2) is specifically as follows: magnetic stirring; the stirring speed is 500-1000 rpm; the stirring time is 60-120 min.

Further, the centrifugation in the step (2) is specifically as follows: centrifuging with a centrifuge at 8000rpm for 3-5 min.

Further, the washing in the step (2) is specifically as follows: alternate washes with ethanol and deionized water were performed 2 times.

Further, the drying in the step (2) is specifically as follows: the drying method is vacuum-53 deg.C freeze drying; the drying time is 6-12 h.

Further, the precursor in the step (3) is specifically Mn/Fe PBAs.

Further, the dosage of the precursor in the step (3) is 20 mg.

Further, the mixing and dissolving in the step (3) specifically comprises: dissolving by ultrasonic oscillation; the ultrasonic treatment time is 5-15 min.

Further, the divalent cobalt salt solution in the step (4) is cobalt chloride hexahydrate CoCl₂·6H₂And (4) O solution.

Further, the dosage of the divalent cobalt salt solution in the step (4) is 5 mL.

Further, the stirring in the step (4) is specifically as follows: magnetic stirring; the stirring speed is 300-1000 rpm; the stirring time is 60-120 min.

Further, the centrifugation in the step (4) is specifically as follows: the centrifugation speed is 8000 rpm; the centrifugation time is 3-5 min.

Further, the washing in the step (4) is specifically as follows: washed 3 times with deionized water.

Further, the drying in the step (4) is specifically as follows: the drying method is vacuum-53 deg.C freeze drying; the drying time is 6-12 h.

The prepared Prussian blue analogue nano-framework material is used for photocatalytic reduction of carbon dioxide into carbon monoxide under mild conditions.

The technical principle of the invention is as follows: the method is characterized in that ferromanganese Prussian blue analogues (Mn/Fe PBAs) are used as precursors, different metal ions are exchanged to the ferromanganese Prussian blue analogues through the difference of precipitation equilibrium constants among different substances, and therefore the PBA nano-framework structure is synthesized. Firstly, Mn/Fe-PBA is slowly dissociated in water to generate manganese ions, iron cyanide and iron ions. Furthermore, cations such as cobalt ions, copper ions and nickel ions are added to be complexed with the ferricyanide, so that the dissociation of the PBA is continuously promoted, and meanwhile, the nano-framework materials such as Co/Fe-PBA, Cu/Fe-PBA and Ni/Fe-PBA are formed.

The invention has the beneficial effects that:

(1) the invention adopts a re-dissolving-recrystallization method, realizes the preparation of the Prussian blue analogue nano-framework material, provides a new synthetic method of the Prussian blue nano-framework material, and provides a new idea for constructing the nano-framework type double-metal Prussian blue analogue composite material.

(2) The Prussian blue analogue nano-framework material prepared by the invention can form a nano shell, can effectively construct a nano framework and form a hollow structure.

(3) The Prussian blue analogue nano-framework material prepared by the invention has high photocatalytic activity due to the Co, so that Mn is replaced by Co, and high-efficiency high-activity photocatalytic reduction of CO is realized₂。

(4) The preparation method has the advantages of simple and easily-obtained raw materials and equipment, simple process, easy operation and safety, relatively low cost and large-scale industrial production; can be combined with other different transition metal ions, has high selectivity and photocatalytic efficiency compared with other MOF-based catalysts and homogeneous phase cobalt-based catalysts, is an environment-friendly new material, and has good popularization and application values and application prospects.

Drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of a Co/Fe PBAs nano-framework material prepared in example 1, a Mn/Fe PBAs nano-composite material prepared in comparative example 1, and a commercially available Mn-PBA solid material;

FIG. 2 is a set of Co/Fe PBAs nano-framework material prepared in example 1, Mn/Fe PBAs nano-composite material prepared in comparative example 1, commercially available Mn-PBA solid material and commercially available Co-PBA solid material, CO and H₂Schematic graph of yield as a function of reaction time;

FIG. 3 shows CO and H in the photocatalytic cycle reaction of the Co/Fe PBAs nano-framework material prepared in example 1₂A schematic of the yield;

FIG. 4 is a Scanning Electron Microscope (SEM) image of the Co/Fe PBAs nano-framework material prepared in example 1;

FIG. 5 is a Transmission Electron Microscope (TEM) image of the Co/Fe PBAs nano-framework material prepared in example 1;

FIG. 6 is an energy dispersive X-ray Spectroscopy (EDX) plot of the Co/Fe PBAs nano-framework material prepared in example 1;

FIG. 7 is an SEM image of the Ni/Fe PBAs nano-framework material prepared in example 2;

FIG. 8 is a TEM image of the Ni/Fe PBAs nano-framework material prepared in example 2;

FIG. 9 is an EDX plot of the Ni/Fe PBAs nano-framework material made in example 2;

FIG. 10 is an SEM image of Cu/Fe PBAs nano-framework material prepared in example 3;

FIG. 11 is a TEM image of Cu/Fe PBAs nano-framework material prepared in example 3

FIG. 12 is an EDX plot of Cu/Fe PBAs nano-framework material made in example 3;

FIG. 13 is an SEM image of a Mn/Fe PBAs nanocomposite prepared in comparative example 1;

FIG. 14 is a TEM image of the Mn/Fe PBAs nanocomposite obtained in comparative example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings, which are examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features mentioned in the embodiments of the present invention described below may be combined as long as they do not conflict with each other.

Example 1

Preparation of Co/Fe PBAs nano-framework material:

(1) 0.106 g of ferric sulfate Fe is weighed by an electronic balance₂(SO4)₃And 0.270 g MnSO manganese sulfate monohydrate₄·H₂O, 1.5 g of polyvinylpyrrolidone PVP, measuring 100 ml of ethanol and 100 ml of deionized water by using a measuring cylinder, and mixing the three;

(2) then stirring the mixed solution for 10 min under magnetic stirring, and carrying out ultrasonic treatment for 5min to obtain a uniformly mixed solution A;

(3) 6.585 g of potassium ferricyanide K are weighed by an electronic balance₃Fe(CN)₆Measuring 100 ml of deionized water by using a measuring cylinder, and mixing to form a uniform mixed solution B;

(4) and adding the mixed solution B into the mixed solution A, magnetically stirring for 30min, performing centrifugal separation to obtain a precipitate, washing with ethanol for 2 times, washing with deionized water for 2 times, and freeze-drying for 6 h to obtain the Mn/Fe PBAs nanocomposite.

(5) Weighing 20 mg of Mn/Fe PBAs nano composite material by using an electronic balance, weighing 20 ml of deionized water by using a measuring cylinder, mixing the Mn/Fe PBAs nano composite material and the deionized water, and carrying out ultrasonic treatment for 5min to obtain a heterogeneous solution C;

(6) 0.05 mmol of cobalt chloride hexahydrate CoCl was weighed out by an electronic balance₂·6H₂O, measuring 5ml of deionized water by using a measuring cylinder, mixing the deionized water and the deionized water, and carrying out ultrasonic treatment for 20min to obtain a uniformly mixed solution D;

(7) and adding the mixed solution D into the heterogeneous solution C, magnetically stirring for 60 min, performing centrifugal separation to obtain a precipitate, washing with deionized water for 3 times, and freeze-drying for 6 h to obtain the Co/Fe PBAs nano-framework material.

Example 2

Preparation of Ni/Fe PBAs nano-framework material:

(1) 0.106 g of ferric sulfate Fe is weighed by an electronic balance₂(SO4)₃And 0.270 g MnSO manganese sulfate monohydrate₄·H₂O, 1.5 g of polyvinylpyrrolidone PVP, measuring 100 ml of ethanol and 100 ml of deionized water by using a measuring cylinder, and mixing the three;

(2) then stirring the mixed solution for 10 min under magnetic stirring, and carrying out ultrasonic treatment for 5min to obtain a uniformly mixed solution A;

(3) 6.585 g of potassium ferricyanide K are weighed by an electronic balance₃Fe(CN)₆Measuring 100 ml of deionized water by using a measuring cylinder, and mixing to form a uniform mixed solution B;

(4) and adding the mixed solution B into the mixed solution A, magnetically stirring for 30min, performing centrifugal separation to obtain a precipitate, washing with ethanol for 2 times, washing with deionized water for 2 times, and freeze-drying for 6 h to obtain the Mn/Fe PBAs nanocomposite.

(5) Weighing 20 mg of Mn/Fe PBAs nano composite material by using an electronic balance, weighing 20 ml of deionized water by using a measuring cylinder, mixing the Mn/Fe PBAs nano composite material and the deionized water, and carrying out ultrasonic treatment for 5min to obtain a heterogeneous solution C;

(6) 0.05 mmol of NiCl hexahydrate is weighed by an electronic balance₂·6H₂O, measuring 5ml of deionized water by using a measuring cylinder, mixing the deionized water and the deionized water, and carrying out ultrasonic treatment for 20min to obtain a uniformly mixed solution D;

(7) and adding the mixed solution D into the heterogeneous solution C, magnetically stirring for 60 min, performing centrifugal separation to obtain a precipitate, washing with deionized water for 3 times, and freeze-drying for 6 h to obtain the Ni/Fe PBAs nano-framework material.

Example 3

Preparing a Cu/Fe PBAs nano-framework material:

(1) 0.106 g of ferric sulfate Fe is weighed by an electronic balance₂(SO4)₃And 0.270 g MnSO manganese sulfate monohydrate₄·1H₂O, 1.5 g of polyvinylpyrrolidone PVP, measuring 100 ml of ethanol and 100 ml of deionized water by using a measuring cylinder, and mixing the three;

(2) then stirring the mixed solution for 10 min under magnetic stirring, and carrying out ultrasonic treatment for 5min to obtain a uniformly mixed solution A;

(3) 6.585 g of potassium ferricyanide K are weighed by an electronic balance₃Fe(CN)₆Measuring 100 ml of deionized water by using a measuring cylinder, and mixing to form a uniform mixed solution B;

(4) and adding the mixed solution B into the mixed solution A, magnetically stirring for 30min, performing centrifugal separation to obtain a precipitate, washing with ethanol for 2 times, washing with deionized water for 2 times, and freeze-drying for 6 h to obtain the Mn/Fe PBAs nanocomposite.

(5) Weighing 20 mg of Mn/Fe PBAs nano composite material by using an electronic balance, weighing 20 ml of deionized water by using a measuring cylinder, mixing the Mn/Fe PBAs nano composite material and the deionized water, and carrying out ultrasonic treatment for 5min to obtain a heterogeneous solution C;

(6) 0.05 mmol of copper chloride dihydrate CuCl is weighed by an electronic balance₂·2H₂O, measuring 5ml of deionized water by using a measuring cylinder, mixing the deionized water and the deionized water, and carrying out ultrasonic treatment for 20min to obtain a uniformly mixed solution D;

(7) and adding the mixed solution D into the heterogeneous solution C, magnetically stirring for 60 min, performing centrifugal separation to obtain a precipitate, washing with deionized water for 3 times, and freeze-drying for 6 h to obtain the Cu/Fe PBAs nano-framework material.

Comparative example 1

Preparation of Mn/Fe PBAs nanocomposite:

(1) 0.106 g of ferric sulfate Fe is weighed by an electronic balance₂(SO4)₃And 0.270 g MnSO manganese sulfate monohydrate₄·H₂O, 1.5 g of polyvinylpyrrolidone PVP, measuring 100 ml of ethanol and 100 ml of deionized water by using a measuring cylinder, and mixing the three;

(2) then stirring the mixed solution for 10 min under magnetic stirring, and carrying out ultrasonic treatment for 5min to obtain a uniformly mixed solution A;

(3) 6.585 g of potassium ferricyanide K are weighed by an electronic balance₃Fe(CN)₆Measuring 100 ml of deionized water by using a measuring cylinder, and mixing to form a uniform mixed solution B;

(4) and adding the mixed solution B into the mixed solution A, magnetically stirring for 30min, performing centrifugal separation to obtain a precipitate, washing with ethanol for 2 times, washing with deionized water for 2 times, and freeze-drying for 6 h to obtain the Mn/Fe PBAs nanocomposite.

Carbon dioxide reduction experiment under visible light irradiation

Application example 1

The Co/Fe PBAs nano-framework material obtained in the example 1 is used for carbon dioxide reduction, and the specific steps are as follows:

(1) 1 mg of Co/Fe PBAs catalyst and 6.5 mg of ruthenium terpyridyl chloride hexahydrate are added into a 25mL reactor containing 2 mL of deionized water, 3 mL of acetonitrile and 1 mL of triethanolamine mixed solution;

(2) at 1 atm, high purity CO₂Filling into a reactor;

(3) placing the quartz reactor under a 300W xenon lamp for irradiation at 25 ℃;

(4) stirring the whole system by a magnetic stirrer;

(5) after a certain period of time, 0.5 mL of the generated gas was taken for gas chromatography.

Application example 2

The Ni/Fe PBAs nano-framework material obtained in the example 2 is used for carbon dioxide reduction, and the specific steps are as follows:

(1) 1 mg of Ni/Fe PBAs catalyst and 6.5 mg of ruthenium terpyridyl chloride hexahydrate are added into a 25mL reactor containing 2 mL of deionized water, 3 mL of acetonitrile and 1 mL of triethanolamine mixed solution;

(2) at 1 atm, high purity CO₂Filling into a reactor;

(3) placing the quartz reactor under a 300W xenon lamp for irradiation at 25 ℃;

(4) stirring the whole system by a magnetic stirrer;

(5) after a certain period of time, 0.5 mL of the generated gas was taken for gas chromatography.

Application example 3

The nano Cu/Fe PBAs nano-framework material obtained in the example 3 is used for carbon dioxide reduction, and the specific steps are as follows:

(1) adding 1 mg of Cu/Fe PBAs catalyst and 6.5 mg of terpyridine chloride hexahydrate ruthenium chloride into a 25mL reactor containing 2 mL of deionized water, 3 mL of acetonitrile and 1 mL of triethanolamine mixed solution;

(2) at 1 atm, high purity CO₂Filling into a reactor;

(3) placing the quartz reactor under a 300W xenon lamp for irradiation at 25 ℃;

(4) stirring the whole system by a magnetic stirrer;

(5) after a certain period of time, 0.5 mL of the generated gas was taken for gas chromatography.

Application example 4

The Mn/Fe PBAs nanocomposite obtained in the comparative example 1 is used for carbon dioxide reduction, and the specific steps are as follows:

(1) adding 1 mg of Mn/Fe PBAs catalyst and 6.5 mg of terpyridine chloride hexahydrate ruthenium chloride into a 25mL reactor containing 2 mL of deionized water, 3 mL of acetonitrile and 1 mL of triethanolamine mixed solution;

(2) at 1 atm, high purity CO₂Filling into a reactor;

(3) placing the quartz reactor under a 300W xenon lamp for irradiation at 25 ℃;

(4) stirring the whole system by a magnetic stirrer;

(5) after a certain period of time, 0.5 mL of the generated gas was taken for gas chromatography.

FIG. 2 is a schematic diagram showing the change of CO yield of the Co-PBA nano-framework structure material, the Mn-PBA solid structure material, the Mn-PBA nano-composite material and the Co-PBA solid structure material prepared in example 1 with reaction time, and it can be seen that the Co-PBA nano-framework structure material has the best photocatalytic activity, and the CO yield is up to 12411 [ mu ] mol.h⁻¹·g⁻¹The material is 2.4 times of Mn-PBA nano composite material and 18 times of Mn-PBA solid structure material. In order to further prove that the nano-framework structure is favorable for the catalytic performance of the nano-framework structure, a Co-PBA solid structure material is used as a control group, and the CO yield of the Co-PBA solid structure material is found to be 6416 mu mol.h⁻¹·g⁻¹Therefore, the performance of the Co-PBA nano framework structure material is higher than that of the Co-PBA solid material. FIG. 3 is a schematic diagram of CO yield when the Co-PBA nano-framework structure material prepared in example 1 of the present invention is subjected to a cyclic reaction, and after 4 cycles, the Co-PBA nano-framework structure material is subjected to a cyclic reactionThe loss of performance of the frame structure is substantially negligible. FIG. 4 is an SEM image of the Co-PBA nanoscaffold material from which it can be seen that the nanoscaffold structure remained unchanged. The results show that the Co-PBA nano framework structure is used for photocatalytic reduction of CO₂So as to realize good activity of the cocatalyst of the high-efficiency synthesis gas.

It will be understood by those skilled in the art that the foregoing is merely a preferred embodiment of the invention, and is not intended to limit the invention, and that any modification, equivalent replacement or improvement made within the spirit and principle of the invention should be included within the scope of protection of the invention.