A Specific Gas Enrichment Method Based on Laser Stealth Processing Technology

Abstract

The present invention discloses a specific gas enrichment method based on laser stealth machining technology, comprising the following steps: S1: Synthesize MOFs single crystal materials with a characteristic size of more than 30 μm; S2: Use a laser to perform stealth machining inside the MOFs single crystal materials in step S1 to form secondary pores; S3: Place the materials in step S2 in a mixed gas for gas screening and enrichment. This method uses laser stealth machining technology to invisibly machine secondary pores inside the framework material without damaging the surface body of the material, and at the same time realizes the screening of specific gases and the enrichment of the screened single gas inside the material, thereby improving the detection limit and detection sensitivity.

Description

Technical Field

[0001] The present invention belongs to the field of laser processing, and particularly relates to a specific gas enrichment method based on laser stealth processing technology. Background Art

[0002] The screening of specific gases is of great significance to human environmental health and the sustainable utilization of energy. For example, screening methane, ethane, etc. from natural gas mixtures plays an important role in improving combustion efficiency. Another example is that screening carbon monoxide, carbon dioxide, etc. from harmful gases and converting them into combustible fuels such as methanol and ethanol also has important value for energy conversion. For another example, screening harmful gases such as formaldehyde from the air is also of great significance to human environmental health. At the same time, enriching and detecting the purity and gas components of the screened gases also has a very important strategic position in reducing detection costs and improving detection efficiency.

[0003] Since the microscopic topological structure of metal-organic framework materials (i.e., MOFs materials) is adapted to the structure of highly symmetric molecules, MOFs materials are good materials for screening specific gas molecules. As Figure 1 shown, the prior art uses the ordered nanopores of MOFs materials and screens these gas molecule mixtures according to the size and shape of the pores.

[0004] CN202310277401.0 discloses a scheme for separating TMS and isopentane based on a copper-based MOF constructed with an adamantane tetracarboxylic acid ligand. The metal-organic framework material therein is Cu2(ATC)(2H2O)·5H2O, and ATC is the acid radical ion of 1,3,5,7-adamantane tetracarboxylic acid after removing four hydrogens; this technical solution utilizes the adjustable characteristics of MOF pores, can accurately synthesize MOFs suitable for the separation and purification of TMS, and is thus used for the separation of the TMS and isopentane mixture generated in industrial production, filling the gap in the separation application of MOFs. At the same time, separating with ATC-Cu can obtain extremely high-purity TMS, which has a better separation effect than zeolite molecular sieves and is more energy-efficient than the distillation method.

[0005] However, the pore size of metal-organic framework materials is relatively small, mostly concentrated in the nanometer level. The screening method remains at the replacement type, that is, the flow screening of one molecule after another. Since there is no in-situ enrichment of the screened molecules in a relay container, the subsequent detection sensitivity of such single molecules is low and the detection limit is poor. Summary of the Invention

[0006] The object of the present invention is to provide a specific gas enrichment method based on laser stealth machining technology. This method uses laser stealth machining technology to invisibly machine secondary pores inside a metal-organic framework material without damaging the surface body of the material, and at the same time realizes the screening of specific gases and the internal enrichment of the single gas after screening in the material, thereby improving the detection limit and detection sensitivity.

[0007] Another object of the present invention is the use of the above-mentioned specific gas enrichment method based on laser stealth machining technology for screening and enriching specific gases.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A specific gas enrichment method based on laser stealth machining technology, comprising the following steps:

[0010] S1: Synthesize MOFs single crystal materials with a characteristic size of more than 30 μm;

[0011] S2: Use a laser to perform stealth machining inside the MOFs single crystal material in step S1 to form secondary pores;

[0012] S3: Place the material in step S2 in a mixed gas for gas screening and enrichment.

[0013] Further, the pore diameter of the MOFs single crystal material in step S1 is 2 nm or less.

[0014] Further, the MOFs single crystal material in step S1 includes but is not limited to HKUST-1, MOF-5 or ZIF-8.

[0015] Further, step S1 adopts a general solvothermal synthesis method, the synthesis temperature is 70°C - 120°C, and the synthesis time is 10 h - 48 h.

[0016] Further, in step S2, a pulsed laser with a wavelength of 532 nm - 1064 nm is used, the laser power is 2 W - 3W, and the laser spot diameter is 5 μm - 10 μm.

[0017] Further, in step S2, the machining is performed at a depth of 10 μm - 20 μm from the surface inside the MOFs single crystal material.

[0018] Further, in step S2, the laser machining time is 10 s - 30 s.

[0019] Further, in step S2, the diameter of the secondary pores is 20 μm - 30 μm and is located at the center of the MOFs single crystal material.

[0020] Further, in step S3, the types of the mixed gas include, but are not limited to, methanol / carbon monoxide mixed gas and methane / ethane mixed gas.

[0021] The present invention has the following beneficial effects:

[0022] Compared with the previously simply synthesized metal-organic framework materials, the present invention first synthesizes metal-organic framework material crystals with specific nanopore shapes and specific chemical groups modifying the nanopores according to the chemical and physical properties of specific gases to screen the mixed gas; then, under the action of laser invisible processing in the center of the material, a relatively large secondary pore is formed inside the material. Therefore, while realizing the screening of small-size gases, the enrichment of the screened gas is directly realized in situ, avoiding the problem of low detection efficiency caused by molecular diffusion after screening.

[0023] Based on the method of the present invention, the enrichment degree of small-size gases is high, the enrichment time is shorter, and the enrichment efficiency is higher. Description of the Drawings

[0024] Figure 1 is the gas screening technology of the prior art;

[0025] Figure 2 is the schematic diagram of the method of the present invention;

[0026] Figure 3 is the TEM image of the HKUST-1 single crystal material with secondary pores in Example 1. Detailed Embodiments

[0027] The present invention will be described in detail below with reference to the drawings and embodiments:

[0028] As used herein, the term "laser invisible processing technology" refers to a technology in which the focus of a laser is focused inside a material for processing without causing processing damage to the surface of the material.

[0029] As used herein, the term "metal-organic framework material" refers to a long-range ordered crystal material having pores with an orderly arrangement of less than 10 nm inside the material.

[0030] As used herein, the term "characteristic size" refers to the length between the two farthest points on the surface of a single crystal particle. For example, when it is described that the characteristic size of a MOFs single crystal material is 30 μm or more, it means that the length between the two farthest points on the surface of the MOFs single crystal material is greater than or equal to 30 μm.

[0031] As used herein, unless otherwise specified, numerical ranges include the starting and ending values of the range. For example, when describing the wavelength of a laser as "532 nm - 1064 nm", this means that both 532 nm and 1064 nm are valid values for the wavelength.

[0032] As used herein, unless otherwise specified, the materials, reagents, devices, etc. used in the present invention are all commercially available products.

[0033] As Figures 2 to 3 shown, the specific gas enrichment method based on laser stealth processing technology of the present invention includes the following steps:

[0034] S1: Synthesize MOFs single crystal materials with a characteristic size of more than 30 μm;

[0035] S2: Use a laser to perform stealth processing inside the MOFs single crystal material in step S1 to form secondary pores;

[0036] S3: Place the material in step S2 in a mixed gas for gas screening and enrichment.

[0037] In step S1, there is no particular limitation on the method for synthesizing MOFs single crystal materials, and conventional methods known to those skilled in the art can be used for synthesis.

[0038] In one embodiment of the present invention, a general solvothermal synthesis method is used to synthesize MOFs single crystal materials. Specifically, step S1 includes: dissolving the selected metal salt and organic ligand in a mixed solution of DMF, water, and ethanol with a volume ratio of 1:1:1, and then standing at a temperature of 70°C - 120°C for 10 h - 48 h to generate MOFs single crystal materials.

[0039] After synthesizing MOFs single crystal materials of appropriate size, a series of post-treatments are also required to obtain the final MOFs single crystal sample. Specifically, step S1 also includes: replacing the generated MOFs single crystal materials into 15 mL - 35 mL of pure ethanol liquid for soaking, then filtering the crystals, and then drying in a vacuum drying oven for 20 h - 28 h to obtain dry MOFs crystals.

[0040] In the present invention, the soaking time in ethanol liquid is generally at least two days, and during the soaking period, the ethanol liquid needs to be replaced every 8 hours to ensure the soaking effect.

[0041] As known to those skilled in the art, the pore shapes and sizes of different types of MOFs materials are different, which can be controlled by selecting different types of reaction raw materials. For example, in one embodiment of the present invention, the metal ions in the metal salt are metal ions with specific orientations, including but not limited to Cu 2+ 、Zn 2+ The organic ligand is generally selected to be an organic ligand with good rigidity and strong directionality, including but not limited to terephthalic acid and trimesic acid. Based on the selected metal salt and organic ligand, the MOFs single crystal material in step S1 includes but is not limited to HKUST-1, MOF-5 and ZIF-8.

[0042] In the present invention, the MOFs single crystal material synthesized in step S1 has nanoscale pores. The nanoscale pores inside the MOFs single crystal material itself should be compatible with the gas with smaller molecular size in the mixed gas, generally about 2 nm or less, to ensure that the smaller molecules in the mixed gas can pass through the nanoscale pores inside the MOFs crystal, while the larger molecules cannot pass through the nanoscale pores, thereby achieving screening of the two. In addition, the size of the MOFs single crystal material should be large enough to ensure that the size of the single crystal particles is larger than the size of the laser spot, avoiding ablation of the outer surface of the single crystal, so as to achieve processing inside without damaging its surface morphology. Therefore, the synthesized MOFs single crystal material should be a MOFs single crystal material with a characteristic size of more than 30 μm to ensure the smooth progress of laser stealth processing.

[0043] In the present invention, the laser processing device used in step S2 is a conventional device and will not be described in detail here.

[0044] During the laser stealth processing, the thermal effect of the laser is used to ablate secondary holes inside the MOFs single crystal. Since the general MOFs crystal has low absorbance to lasers with a wavelength of 532 nm-1064 nm, it can be ensured that the laser spot within this wavelength range can be focused inside the MOFs crystal body. Therefore, the laser used in the present invention is a pulsed laser with a wavelength of 532 nm-1064 nm. At the same time, the laser spot diameter must be smaller than the size of the MOFs single crystal material to ensure that it will not affect the outer surface of the single crystal. Therefore, the laser spot diameter is preferably 5 μm-10 μm. In addition, in conjunction with the laser spot size, the laser power used is 2 W-3 W. If the laser power is too large, it may penetrate the MOFs crystal or ablate the MOFs crystal, resulting in the inability to form suitable secondary holes inside it.

[0045] In addition, an appropriate laser processing time should be selected. If the processing time is too short, it is impossible to ensure the generation of secondary pores of appropriate size; while if the processing time is too long, excessive ablation may occur. Therefore, in the present invention, the laser processing time is 10 s - 30 s.

[0046] In addition, in order to avoid damage to the surface of the MOFs crystal caused by the laser thermal effect, during the laser stealth processing, under appropriate laser processing parameter conditions, the laser is selected to be focused at a depth of 10 μm - 20 μm from the surface inside the MOFs single crystal material for processing, so as to create secondary pores inside the MOFs single crystal material. At the same time, during the processing, the imaging system in the laser processing device is used to observe the processing position in real time, so as to ensure that the secondary pores are located at the center position of the MOFs single crystal material through the movement of the motion platform.

[0047] In the present invention, the size of the secondary pores is adapted to the size of the single crystal material and the size of the gas molecules to be accommodated. For example, secondary pores with a diameter of more than 20 μm can be formed to accommodate the sieved gas molecules, so as to achieve the enrichment effect on the mixed gas.

[0048] The MOFs single crystal material with secondary pores inside according to the present invention can realize the sieving and enrichment of specific mixed gases under the cooperation of the nano-scale pores and micro-scale secondary pores of the material itself. Generally, the specific mixed gas to be sieved and enriched is selected according to the pore diameter of the MOFs material. For the present invention, the pore diameter below 2 nm can be used to sieve small-sized gases such as methane and carbon monoxide. Therefore, for example, the types of the specific mixed gases of the present invention include but are not limited to methanol / carbon monoxide mixed gas, methane / ethane mixed gas.

[0049] The working principle of the present invention is as follows:

[0050] The present invention forms a MOFs single crystal material with an internal pore size of about 2 nm or less by selecting an organic ligand with good rigidity and strong directionality and metal ions with a specific orientation. Since the sizes of the two gas molecules in the mixed gas are different, the smaller-sized molecules are adapted to the nano-scale pore size of the MOFs crystal, and the larger-sized molecules cannot pass through the nano-scale pores. Based on this, the sieving of the two can be realized. At the same time, the laser stealth processing technology is used to create larger secondary pores with a diameter between 10 μm - 20 μm inside the MOFs single crystal material to accommodate the sieved gas molecules, so as to achieve the sieving and enrichment effects on the mixed gas, and improve the detection limit and detection sensitivity.

[0051] The present invention is further illustrated by the following examples. Examples

[0052] S1: Place 200 mg of benzene-1,3,5-tricarboxylic acid and 400 mg of copper(II) nitrate trihydrate in a 23 mL sealed vial. Then add 12 mL of a mixed solution of DMF, water, and ethanol with a volume ratio of 1:1:1 to it and dissolve it thoroughly. Let it stand at 85 °C for 12 h to synthesize HKUST-1 single crystal material with a characteristic size of 50 μm. Subsequently, transfer the generated HKUST-1 single crystal material to 25 mL of pure ethanol liquid for soaking, and change the ethanol liquid every 8 hours for three days. Then filter the crystals and dry them in a vacuum drying oven for 24 h to obtain dry HKUST-1 crystals.

[0053] S2: Select a nanosecond laser with a wavelength of 1064 nm, keep the laser power at 2 W, the processing distance focus at 2 cm, the spot diameter at 10 μm, and focus at a depth of 20 μm from the surface inside the HKUST-1 single crystal material, and the processing duration is 10 s. After ablation, a secondary hole with a diameter of 22 μm is obtained at the center position inside the HKUST-1 single crystal particle.

[0054] S3: Place 100 mg of the laser-processed HKUST-1 single crystal particles and the untreated HKUST-1 single crystals in spherical glass tubes with a volume of 1 cm 3 respectively, which are filled with a methane / ethane (volume ratio of 1:1) mixed gas. The open end of the glass tube is connected to a gas sorption instrument, which can respond to the pressure change inside the tube. Then let it stand at 77 K for 1 h and measure the pressure reduction amount respectively. According to the ideal gas equation: pV = nRT, under the condition of constant volume and temperature, the reduced amount of methane gas in the glass tube is converted, which is the amount of methane adsorbed by the single crystal.

[0055] As Figure 3 shown, after step S2, a secondary hole with a diameter of 22 μm is obtained at the center position inside the HKUST-1 single crystal particle, and the secondary hole is basically circular.

[0056] By comparing the results after step S3, it can be seen that the specific adsorption amount of methane by the HKUST-1 single crystal particles of the present invention, that is, the laser-processed HKUST-1 single crystal particles, is about 2667.9 cm 3 / g, while the specific adsorption amount of methane by the untreated HKUST-1 single crystal particles is only 532.6 cm 3 / g. Example

[0057] S1: Place 150 mg of terephthalic acid and 300 mg of copper sulfate pentahydrate in a 25 mL sealed vial. Then add 12 mL of a mixed solution of DMF, water, and ethanol with a volume ratio of 1:1:1 to it, and dissolve it thoroughly. Let it stand at 100 °C for 24 h to synthesize MOF-5 single crystal materials with a characteristic size of 60 μm. Subsequently, transfer the generated MOF-5 single crystal materials to 30 mL of pure ethanol liquid for soaking, and change the ethanol liquid every 8 hours for three days. Then filter the crystals and dry them in a vacuum drying oven for 25 h to obtain dry MOF-5 crystals.

[0058] S2: Select a picosecond laser with a wavelength of 532 nm, keep the laser power at 3 W, and the processing distance focus at 2 cm, with a spot diameter of 5 μm. Focus it at a depth of 20 μm from the surface inside the MOF-5 single crystal particles, and the processing duration is 20 s. After ablation, a secondary hole with a diameter of 25 μm is obtained at the center position inside the MOF-5 single crystal particles.

[0059] S3: Place 100 mg of laser-processed MOF-5 single crystal particles and untreated MOF-5 single crystals in a spherical glass tube with a volume of 1 cm 3 respectively. The inside is filled with a methanol / carbon monoxide (volume ratio of 1:1) mixed gas. The open end of the glass tube is connected to a gas adsorption instrument, which can respond to the pressure change inside the tube. Then let it stand at 77 K for 1 h and measure the pressure reduction amount respectively. According to the ideal gas equation: pV = nRT, under the condition of constant volume and temperature, convert to obtain the reduced amount of carbon monoxide gas in the glass tube, which is the amount of carbon monoxide adsorbed by the single crystal.

[0060] By comparing the results after step S3, it can be seen that for the MOF-5 single crystal particles of the present invention, that is, the laser-processed MOF-5 single crystal particles, the specific adsorption amount of carbon monoxide is about 1877.8 cm 3 / g, while the specific adsorption amount of carbon monoxide for untreated MOF-5 single crystal particles is only 268.7 cm 3 / g.

[0061] In summary, according to the method of the present invention, pulsed laser ablation is used inside the MOFs single crystal with nanoscale pores that can screen small-sized gas molecules to obtain micron-scale secondary pores. These micron-scale secondary pores can accommodate a large number of specific molecules after screening. This size combination of nanoscale pores and micron-scale secondary pores can simultaneously achieve the screening and enrichment of small-sized molecules, thereby improving the detection limit and detection sensitivity of the single gas after screening.

[0062] The specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art shall fall within the protection scope determined by the claims.

Claims

1. A specific gas enrichment method based on laser stealth processing technology, characterized in that: It includes the following steps: S1: Synthesize MOFs single crystal materials with a characteristic size of more than 30 μm; S2: Use a laser to perform invisible processing inside the MOFs single crystal materials in step S1 to form secondary pores; S3: Place the materials in step S2 in a mixed gas for gas screening and enrichment; Among them, the pore diameter of the MOFs single crystal materials in step S1 is below 2 nm; In step S2, a pulsed laser with a wavelength of 532 nm - 1064 nm is used, the laser power is 2 W - 3 W, the laser spot diameter is 5 μm - 10 μm, and the processing is carried out at a depth of 10 μm - 20 μm from the surface inside the MOFs single crystal materials, and the laser processing time is 10 s - 30 s; In step S2, the diameter of the secondary pores is 20 μm - 30 μm and is located at the center of the MOFs single crystal materials.

2. The specific gas enrichment method based on laser stealth processing technology according to claim 1, wherein: In step S3, the types of the mixed gas include methanol / carbon monoxide mixed gas, methane / ethane mixed gas.

3. The specific gas enrichment method based on laser stealth processing technology according to claim 1, characterized in that: Step S1 adopts a solvothermal synthesis method, the synthesis temperature is 70°C - 120°C, and the synthesis time is 10 h - 48 h.

4. Use of the specific gas enrichment method based on the laser invisible processing technology according to any one of claims 1 to 3 for screening and enriching specific gases.

5. The use according to claim 4, characterized in that: The types of the specific gases include methanol / carbon monoxide mixed gas, methane / ethane mixed gas.

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