Preparation method of nano alkenyl gas desorption agent and application of nano alkenyl gas desorption agent in coal mine drainage and mining

Abstract

The invention relates to the technical field of adsorption, and mainly relates to a preparation method of a nano alkenyl gas desorption agent and application of the nano alkenyl gas desorption agent in coal mine drainage and mining, and the preparation method comprises the following steps: mixing a graphene oxide aqueous solution with an ionic liquid, performing ultrasonic treatment, performing liquid nitrogen freezing and freeze drying to obtain three-dimensional graphene aerogel, immersing the three-dimensional graphene aerogel into a zinc nitrate ethanol solution, and performing vacuum infiltration to obtain the nano alkenyl gas desorption agent. The preparation method comprises the following steps: preparing graphene, then transferring the graphene into a 2-methylimidazole aqueous solution, carrying out hydrothermal reaction and plasma treatment to obtain graphene / MOF heterojunction, dispersing the graphene / MOF heterojunction in water to obtain a water phase, introducing the water phase and an oil phase into a microfluidic device to obtain microcapsules, dipping the microcapsules in a calcium chloride solution, carrying out simulated body fluid mineralization treatment, and drying to obtain desorption agent particles. According to the preparation method of the nano alkenyl gas desorption agent, the three-dimensional graphene aerogel is prepared through liquid nitrogen freezing and ionic liquid cross-linking, so that a multi-stage gradient pore channel structure is formed, the gas adsorption capacity is remarkably improved, lamellar cross-linking is enhanced through the ionic liquid, and an aerogel skeleton is stabilized.

Description

Technical Field

[0001] The present application relates to the field of adsorption technology, and particularly to a preparation method of a nano-ene-based gas desorbent and its application in coal mine drainage. Background Art

[0002] Traditional gas desorbents mostly use single porous materials such as activated carbon and molecular sieves, and their adsorption capacity is limited by the single specific surface area and pore size distribution. Research shows that conventional adsorption materials are prone to pore blockage in a high-pressure gas environment, resulting in a significant decrease in desorption efficiency with the increase in the number of uses. In addition, the surface chemical properties of existing materials are single, and it is difficult to simultaneously achieve the synergistic effect of physical adsorption and chemical bonding, especially in a complex gas system containing high-concentration CO 2 For example, the nano-silicon-based self-percolating desorbent disclosed in CN118620599B improves wettability by compounding multi-branched surfactants and organosilicon components, but its mechanism of relying on surfactants to reduce the interfacial tension still shows insufficient selective adsorption of CO 2 Moreover, the long-term binding problem between nano-materials and coal matrix under high pressure has not been solved, resulting in easy migration loss of active components in the dynamic gas flow.

[0003] In the existing preparation process, the mechanical mixing method is difficult to achieve uniform compounding of multi-component materials, often resulting in uneven distribution of active sites. At the same time, the particles prepared by traditional granulation techniques (such as spray drying method) have problems such as wide particle size distribution and poor sphericity, and are prone to migration loss in coal seam fractures, affecting the long-term desorption effect. Summary of the Invention

[0004] The present application provides a preparation method of a nano-ene-based gas desorbent, including the following steps: S10. Mix an aqueous solution of graphene oxide with 1-butyl-3-methylimidazolium hexafluorophosphate and then perform ultrasonic treatment, and obtain a three-dimensional graphene aerogel through liquid nitrogen freezing and freeze-drying, wherein the mass of the 1-butyl-3-methylimidazolium hexafluorophosphate is 15% of the mass of the graphene oxide; S20. Immerse the three-dimensional graphene aerogel in an ethanol solution of Zn(NO 3 ) 2 ·6H 2 O for vacuum infiltration, and then transfer it to an aqueous solution of 2-methylimidazole, and obtain a graphene / MOF heterojunction through hydrothermal reaction and plasma treatment, wherein the Zn(NO 3 ) 2 ·6H 2The molar ratio of O to the 2-methylimidazole is 1: (3.8-4.2); S30, dispersing the graphene / MOF heterojunction in water to obtain an aqueous phase, mixing mineral oil with Span80 to obtain an oil phase, and passing the aqueous phase and the oil phase into a microfluidic device to prepare microcapsules; S40, sequentially passing the microcapsules through CaCl 2 The desorbent particles are obtained by solution impregnation, simulated body fluid mineralization treatment and drying.

[0005] In some embodiments, in S10, the concentration of the graphene oxide aqueous solution is 8 mg / mL.

[0006] In some embodiments, in S10, the freeze-drying conditions are -50°C and 10Pa for 48 hours.

[0007] In some embodiments, in S20, the Zn(NO 3 ) 2 6H 2 The concentration of the ethanol solution is 0.1 mol / L, and the concentration of the 2-methylimidazole aqueous solution is 0.4 mol / L.

[0008] In some embodiments, in S20, the parameters of the plasma treatment are power 200 W, time 90 s, and argon gas flow rate 5 L / min.

[0009] In some embodiments, in S20, the vacuum penetration pressure is -0.1 MPa, and the penetration time is 30 min.

[0010] In some embodiments, in S20, the temperature of the hydrothermal reaction is 80° C., and the time of the hydrothermal reaction is 5-7 hours.

[0011] In some embodiments, in S30, the flow rate of the water phase is 0.2 mL / min, and the flow rate of the oil phase is 0.8-1.0 mL / min.

[0012] In some embodiments, in S40, the mineralization treatment is performed at 37° C. and 100-120 rpm shaking for 24 hours.

[0013] The present application also provides an application of a nano-olefin-based gas desorbent prepared by any of the aforementioned methods in coal mine drainage.

[0014] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art: 1. Three-dimensional graphene aerogel is prepared by rapid freezing with liquid nitrogen and cross-linking with ionic liquid, so as to form a multi-level gradient pore structure, significantly improve the gas adsorption capacity, and enhance the cross-linking of the sheets through ionic liquid to stabilize the aerogel skeleton.

[0015] 2. Graphene / MOF heterojunction is constructed through vacuum infiltration, hydrothermal reaction and plasma treatment, so that MOF crystals grow in situ on the graphene surface, forming a synergistic effect of physical adsorption and chemical bonding, enhancing the CO 2 The selective adsorption capacity of the nanostructured carbon nanotubes was improved, and the plasma treatment enhanced the interface bonding strength.

[0016] 3. The flow rate ratio of the water phase and the oil phase is regulated by microfluidic technology to generate monodisperse microcapsules with uniform particle size, ensuring the effective retention of particles in the coal seam fissures.

[0017] 4. Through CaCl 2 Impregnation and simulated body fluid mineralization treatment form a dense hydroxyapatite protective layer on the surface of the microcapsules, which improves the mechanical strength to resist stratum stress, neutralizes acidic mine water, and prevents the dissolution of metal ions.

[0018] 5. By optimizing the S10 step parameters, a dynamic balance between the pore size distribution and mechanical stability of the aerogel is achieved to avoid pore collapse and maintain a high specific surface area.

[0019] 6. Through the S20 step, Zn(NO 3 ) 2 6H 2 The molar ratio of O to 2-methylimidazole and the hydrothermal reaction conditions ensure the directional growth of ZIF-8 MOF crystals on the graphene surface and increase the density of gas molecule adsorption sites.

[0020] 7. Through plasma treatment parameters, chemical bonding defects are formed on the heterojunction interface to further improve structural stability.

[0021] 8. Through mineralization treatment conditions, hydroxyapatite is promoted to grow preferentially along the (002) crystal plane to form a continuous protective layer, while eliminating crystal agglomeration. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 The present invention provides a flow chart of a method for preparing a nano-olefin-based gas desorbent according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] Figure 1 A flow chart of a method for preparing a nano-olefin-based gas desorbent provided in an embodiment of the present application is shown.

[0027] like Figure 1 As shown, the present application provides a method for preparing a nano-olefin-based gas desorbent, comprising the following steps: S10, mixing a graphene oxide (GO) aqueous solution with 1-butyl-3-methylimidazolium hexafluorophosphate, ultrasonically treating the mixture, freezing the mixture with liquid nitrogen, and freeze-drying the mixture to obtain a three-dimensional graphene aerogel, wherein the mass of the 1-butyl-3-methylimidazolium hexafluorophosphate is 15% of the mass of the graphene oxide; S20, immersing the three-dimensional graphene aerogel in Zn(NO 3 ) 2 6H 2 O ethanol solution was vacuum infiltrated, and then transferred to 2-methylimidazole aqueous solution, and then subjected to hydrothermal reaction and plasma treatment to obtain a graphene / MOF heterojunction. The Zn(NO 3 ) 2 6H 2 The molar ratio of O to the 2-methylimidazole is 1: (3.8-4.2); S30, dispersing the graphene / MOF heterojunction in water to obtain an aqueous phase, mixing mineral oil with Span80 to obtain an oil phase, and passing the aqueous phase and the oil phase into a microfluidic device to prepare microcapsules; S40, sequentially passing the microcapsules through CaCl 2 The desorbent particles are obtained by solution impregnation, simulated body fluid mineralization treatment and drying.

[0028] In step S10, the graphene oxide aqueous solution and 1-butyl-3-methylimidazolium hexafluorophosphate are ultrasonically dispersed and then rapidly frozen by liquid nitrogen to form an ice crystal template. During the freeze-drying process, the ice crystals sublime to leave a three-dimensional porous network structure. The ionic liquid acts as a cross-linking agent to enhance the connection strength between graphene sheets, forming an aerogel matrix with high specific surface area and pores.

[0029] When the graphene oxide aqueous solution is mixed with the ionic liquid, the rapid freezing of liquid nitrogen (-196℃) causes the water in the solution to instantly form multi-scale ice crystals. The rapid cooling causes the ice crystal nucleation rate to be much greater than the growth rate, resulting in nanoscale (50-200nm) ice crystals; while the local unfrozen liquid phase area forms micron-scale (200nm-5μm) ice crystals during the continuous freezing process. During the freeze-drying stage, the ice crystals are removed by sublimation, and the space occupied by the original ice crystals is converted into pores, where the difference in ice crystal size directly determines the pore size distribution of the final aerogel. The introduction of ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) cross-links with the graphene oxide sheets through π-π interactions, restricting the disordered stacking of graphene sheets during the growth of ice crystals, thereby stabilizing the multi-level pore structure.

[0030] In step S20, the aerogel is subjected to vacuum infiltration to make Zn(NO 3 ) 2 6H 2 O ethanol solution fully infiltrates the pores and then undergoes a coordination reaction with 2-methylimidazole aqueous solution. The hydrothermal environment promotes the in situ growth of metal organic framework (MOF) crystals on the graphene surface. Plasma treatment forms chemical bonds on the heterojunction interface through high-energy particle bombardment, enhancing the structural stability.

[0031] In step S30, microfluidic technology is used to achieve structural encapsulation. The graphene / MOF heterojunction particles in the water phase form monodisperse droplets under the shear force of the oil phase. Span80 acts as a surfactant to reduce the interfacial tension between the two phases. The uniformity of the microcapsule particle size is controlled by adjusting the flow rate ratio of the water phase to the oil phase.

[0032] In step S40, CaCl 2 Solution impregnation enriches the surface of the microcapsules with calcium ions, and then a hydroxyapatite mineralization layer is formed by ion deposition in simulated body fluid. This biomineralization process builds a dense protective layer on the surface of the particles and fills the internal defects of the material through crystal growth.

[0033] This method constructs pores through three-dimensional graphene aerogel, significantly improving the gas adsorption capacity; the in-situ growth of MOF heterojunction realizes the synergistic effect of physical adsorption and chemical bonding, enhancing the adsorption of CO 2 The selective adsorption capacity of the material is excellent; the microfluidic encapsulation technology forms regular particles with uniform particle size, ensuring effective retention in the cracks of the coal seam; the surface mineralized layer not only improves the mechanical strength to resist stratum stress, but its hydroxyapatite component can also neutralize acidic mine water and prevent the dissolution of metal ions.

[0034] In some embodiments, in S10, the graphene oxide aqueous solution has a concentration of 8 mg / mL. The freeze-drying conditions are -50°C and 10 Pa for 48 hours.

[0035] The concentration of 8mg / mL graphene oxide aqueous solution forms a dynamic balance with the addition of 15% 1-butyl-3-methylimidazolium hexafluorophosphate - the former ensures that the dispersion of the sheets is sufficient to build a continuous three-dimensional network, and the latter enhances the cross-linking of the sheets through the π-π interaction between ionic liquid and graphene. At the same time, its hydrophobic properties guide the ice crystals to grow directional along the edges of the sheets during liquid nitrogen freezing, forming a multi-level pore channel; while the freeze-drying conditions of -50℃ and 10Pa form a matching mechanism with the 48h processing time. The low temperature and low pressure environment slows down the sublimation rate of ice crystals, avoids the collapse of the pores caused by rapid phase change, and fully removes the solvent to stabilize the aerogel skeleton. The concentration determines the initial sheet distribution, the ionic liquid regulates the pore morphology, and the drying parameters lock the final structure, together achieving a gradient pore size distribution from 50-200nm to 2-5μm and high mechanical stability.

[0036] In some embodiments, in S20, the Zn(NO 3 ) 2 6H 2 The concentration of the O ethanol solution is 0.1 mol / L, the concentration of the 2-methylimidazole aqueous solution is 0.4 mol / L, and the Zn(NO 3 ) 2 6H 2 The molar ratio of O to the 2-methylimidazole is 1:(3.8-4.2).

[0037] In some embodiments, the Zn(NO 3 ) 2 6H 2 The molar ratio of O to the 2-methylimidazole is 1:4.

[0038] 0.1 mol / L Zn(NO 3 ) 2 6H 2 The 0.0 mol / L ethanol solution ensures that zinc ions fully penetrate and are evenly distributed in the aerogel pores, while the 0.4 mol / L 2-methylimidazole aqueous solution provides excess ligands to drive the coordination reaction toward the formation of MOF crystals. The 1:4 molar ratio matches the stoichiometric requirements of zinc ions and ligands, forming a continuous and dense ZIF-8 type MOF layer on the aerogel skeleton while avoiding the unreacted precursor from remaining in the pores, thereby constructing a stable graphene / MOF heterojunction interface. The synergistic effect of concentration and ratio enables MOF crystals to grow in a directional manner on the graphene surface, forming a composite structure with a high specific surface area and enhancing the density of gas molecule adsorption sites.

[0039] In some embodiments, in S20, the parameters of the plasma treatment are power 200W, time 90s, argon gas flow rate 5L / min, vacuum infiltration pressure -0.1MPa, infiltration time 30min, hydrothermal reaction temperature 80°C, hydrothermal reaction time 5-7h.

[0040] In some embodiments, the hydrothermal reaction time is 6 hours.

[0041] The vacuum infiltration was continued at -0.1 MPa pressure for 30 min to make Zn(NO 3 ) 2 6H 2 The ethanol solution fully infiltrates the multi-level channels of the three-dimensional graphene aerogel to ensure that the zinc ions are evenly anchored on the surface of the graphene sheets; then the hydrothermal reaction is carried out at 80°C for 6 hours, and the zinc ions are thermodynamically driven to coordinate with the 2-methylimidazole ligands to form a high-crystallinity ZIF-8 type MOF crystal layer on the aerogel skeleton; the plasma treatment is carried out at a power of 200W and an argon flow rate of 5L / min for 90 seconds. The high-energy argon ion bombardment causes defect sites at the interface between the MOF crystal and the graphene, and at the same time stimulates the surface active groups to form chemical bonds. The three-way vacuum infiltration provides uniform precursor distribution for heterojunction growth, the hydrothermal reaction constructs the main crystal structure, and the plasma treatment strengthens the interface bonding strength through the dual physical and chemical effects.

[0042] In some embodiments, in S30, the flow rate of the water phase is 0.2 mL / min, and the flow rate of the oil phase is 0.8-1.0 mL / min. Preferably, the flow rate of the oil phase is 1.0 mL / min.

[0043] In the microfluidic device, the water phase (dispersion containing graphene / MOF heterojunction) was injected at a flow rate of 0.2mL / min, and the oil phase (mineral oil containing Span80) was injected at a flow rate of 1.0mL / min, and a shear force field was formed when the two phases met in the T-shaped microchannel. The low flow rate of the water phase caused it to be stretched into a thin stream under the shearing action of the high flow rate of the oil phase, and it broke at the balance point of interfacial tension and inertial force to form monodisperse droplets; Span80 was adsorbed on the water / oil interface as a surfactant, reducing the interfacial tension and preventing the droplets from coalescing, and the 5:1 oil / water phase flow rate ratio ensured the stability of droplet generation frequency and size by regulating the viscosity difference between the two phases (mineral oil viscosity 35cP) and momentum transfer efficiency.

[0044] In some embodiments, the microfluidic device is a T-type microchannel microfluidic device.

[0045] In some embodiments, in S40, the mineralization treatment is carried out at 37° C. and 100-120 rpm shaking for 24 h. Preferably, the mineralization treatment is carried out at 37° C. and 120 rpm shaking for 24 h.

[0046] 37°C is close to the optimal temperature for biomineralization, which promotes the preferential growth of hydroxyapatite crystals along the (002) crystal plane to form a dense and uniformly oriented mineralized layer; 120rpm oscillation enhances ion transfer efficiency through forced convection, avoids uneven mineralization caused by local concentration gradients, and periodic shear force eliminates crystal agglomeration; 24-hour treatment time ensures that the mineralization reaction is fully completed, and the continuous protective layer formed not only improves the compressive strength of the microcapsules to resist coal seam stress, but its alkaline hydroxyapatite component can also neutralize acidic mine water and prevent the dissolution of zinc ions in the MOF skeleton, thereby achieving a dual improvement in structural stability and corrosion resistance.

[0047] The present application also provides an application of a nano-olefin-based gas desorbent prepared by any of the aforementioned methods in coal mine drainage.

[0048] When the desorbent particles are injected into the coal seam fissures, the multi-level pores of the three-dimensional graphene / MOF heterojunction preferentially adsorb methane molecules through van der Waals forces, while the zinc nodes in the MOF crystals bind to CO 2 The coordination effect occurs to achieve the selective separation of gas components. The surface hydroxyapatite mineralization layer forms a water film in a humid environment, which promotes the diffusion of gas molecules into the pores through capillary action; at the same time, the alkaline properties of the mineralization layer can neutralize the acidic mine water and prevent the dissolution of zinc ions in the MOF framework. Under periodic gas pressure fluctuations, the elastic deformation of the microcapsules keeps the structure intact under coal seam stress, avoiding pore blockage caused by crushing.

[0049] The method of the present invention will be described in detail below with reference to embodiments, comparative examples and experimental data.

[0050] Example 1: This example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a multi-level pore structure.

[0051] Step 2: Immerse the aerogel obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H2 In an ethanol solution, under a vacuum condition of -0.1 MPa, infiltrate for 30 minutes to fully load zinc ions into the pores of the aerogel. After taking it out, transfer it to an aqueous solution of 0.4 mol / L 2-methylimidazole (the molar ratio of Zn(NO 3 ) 2 ·6H 2 O to 2-methylimidazole is 1:4), place it in a hydrothermal reactor at 80 °C and react for 6 hours to form a ZIF-8 type MOF crystal layer. Put the product into a plasma treatment chamber and treat it for 90 seconds at a power of 200 W and an argon gas flow rate of 5 L / min to form a heterojunction interface with enhanced chemical bonding.

[0052] Step 3: Disperse the product of Step 2 in deionized water to prepare an aqueous solution with a solid content of 2 wt%. Separately, mix mineral oil (viscosity 35 cP) and Span80 in a volume ratio of 98:2 as the oil phase. Pass the aqueous phase at a flow rate of 0.2 mL / min and the oil phase at a flow rate of 1.0 mL / min into a T-shaped microfluidic channel. Monodisperse droplets are generated under the action of shear force, collected and cured at 60 °C for 2 hours to obtain microcapsules.

[0053] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 solution and let it stand for 2 hours. After centrifuging to remove the excess solution, transfer it to a simulated body fluid (containing Ca 2+ 2.5 mmol / L, HPO 4 2- 1.0 mmol / L, pH = 7.4), and treat it in a constant temperature oscillator at 37 °C at a rotation speed of 120 rpm for 24 hours. After mineralization is completed, vacuum dry at 60 °C for 6 hours to obtain desorbent particles with a hydroxyapatite layer covering the surface.

[0054] Example 2. This example provides a preparation method of a nano-ene-based gas desorbent, and the method includes the following steps: Step 1: Take 100 mL of an aqueous solution of graphene oxide at 8 mg / mL, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonic instrument to treat it at a power of 300 W and a frequency of 40 kHz for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196 °C for 2 hours, and then transfer it to a freeze dryer and dry it at -50 °C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a hierarchical pore structure.

[0055] Step 2: Immerse the aerogel obtained in Step 1 in 0.1 mol / L Zn(NO 3 ) 2 ·6H 2O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2 O and 2-methylimidazole (molar ratio 1:4) were placed in a hydrothermal reactor at 80°C for 5 hours to generate a ZIF-8 type MOF crystal layer. The product was placed in a plasma treatment chamber and treated for 90 seconds at a power of 200W and an argon gas flow rate of 5L / min to form a chemically bonded enhanced heterojunction interface.

[0056] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the aqueous phase into the T-shaped microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 1.0mL / min, and generate monodisperse droplets under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain microcapsules.

[0057] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 The solution was allowed to stand for 2 hours, and after centrifugation to remove excess solution, it was transferred to simulated body fluid (containing Ca 2+ 2.5mmol / L, HPO 4 2- 1.0mmol / L, pH=7.4), and treated at 37℃ constant temperature oscillator at 120rpm for 24 hours. After mineralization, it was vacuum dried at 60℃ for 6 hours to obtain desorbent particles covered with hydroxyapatite layer on the surface.

[0058] Example 3: This example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a multi-level pore structure.

[0059] Step 2: Immerse the aerogel obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H 2O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2 O and 2-methylimidazole (molar ratio 1:4) were placed in a hydrothermal reactor at 80°C for 6 hours to generate a ZIF-8 type MOF crystal layer. The product was placed in a plasma treatment chamber and treated for 90 seconds at a power of 200W and an argon gas flow rate of 5L / min to form a chemically bonded enhanced heterojunction interface.

[0060] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the aqueous phase into the T-type microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 0.8mL / min. Monodisperse droplets are generated under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain microcapsules.

[0061] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 The solution was allowed to stand for 2 hours, and after centrifugation to remove excess solution, it was transferred to simulated body fluid (containing Ca 2+ 2.5mmol / L, HPO 4 2- 1.0mmol / L, pH=7.4), and treated at 37℃ constant temperature oscillator at 120rpm for 24 hours. After mineralization, it was vacuum dried at 60℃ for 6 hours to obtain desorbent particles covered with hydroxyapatite layer on the surface.

[0062] Example 4: This example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a multi-level pore structure.

[0063] Step 2: Immerse the aerogel obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H 2O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2 O and 2-methylimidazole (molar ratio 1:3.8) were placed in a hydrothermal reactor at 80°C for 6 hours to generate a ZIF-8 type MOF crystal layer. The product was placed in a plasma treatment chamber and treated for 90 seconds at a power of 200W and an argon gas flow rate of 5L / min to form a chemically bonded enhanced heterojunction interface.

[0064] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the aqueous phase into the T-shaped microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 1.0mL / min, and generate monodisperse droplets under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain microcapsules.

[0065] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 The solution was allowed to stand for 2 hours, and after centrifugation to remove excess solution, it was transferred to simulated body fluid (containing Ca 2+ 2.5mmol / L, HPO 4 2- 1.0mmol / L, pH=7.4), and treated at 37℃ constant temperature oscillator at 120rpm for 24 hours. After mineralization, it was vacuum dried at 60℃ for 6 hours to obtain desorbent particles covered with hydroxyapatite layer on the surface.

[0066] Example 5. This example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a multi-level pore structure.

[0067] Step 2: Immerse the aerogel obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H 2O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2 O and 2-methylimidazole (molar ratio 1:4.2) were placed in a hydrothermal reactor at 80°C for 6 hours to generate a ZIF-8 type MOF crystal layer. The product was placed in a plasma treatment chamber and treated for 90 seconds at a power of 200W and an argon gas flow rate of 5L / min to form a chemically bonded enhanced heterojunction interface.

[0068] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the aqueous phase into the T-shaped microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 1.0mL / min, and generate monodisperse droplets under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain microcapsules.

[0069] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 The solution was allowed to stand for 2 hours, and after centrifugation to remove excess solution, it was transferred to simulated body fluid (containing Ca 2+ 2.5mmol / L, HPO 4 2- 1.0mmol / L, pH=7.4), and treated at 37℃ constant temperature oscillator at 120rpm for 24 hours. After mineralization, it was vacuum dried at 60℃ for 6 hours to obtain desorbent particles covered with hydroxyapatite layer on the surface.

[0070] Comparative Example 1: This comparative example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a multi-level pore structure.

[0071] Step 2: Immerse the aerogel obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H 2O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2 O and 2-methylimidazole (molar ratio 1:3) were placed in a hydrothermal reactor at 80°C for 6 hours to generate a ZIF-8 type MOF crystal layer. The product was placed in a plasma treatment chamber and treated for 90 seconds at a power of 200W and an argon gas flow rate of 5L / min to form a chemically bonded enhanced heterojunction interface.

[0072] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the aqueous phase into the T-shaped microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 1.0mL / min, and generate monodisperse droplets under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain microcapsules.

[0073] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 The solution was allowed to stand for 2 hours, and after centrifugation to remove excess solution, it was transferred to simulated body fluid (containing Ca 2+ 2.5mmol / L, HPO 4 2- 1.0mmol / L, pH=7.4), and treated at 37℃ constant temperature oscillator at 120rpm for 24 hours. After mineralization, it was vacuum dried at 60℃ for 6 hours to obtain desorbent particles covered with hydroxyapatite layer on the surface.

[0074] Comparative Example 2: This comparative example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a multi-level pore structure.

[0075] Step 2: Immerse the aerogel obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H 2O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2 O and 2-methylimidazole (molar ratio of 1:4) were placed in a hydrothermal reactor at 80 °C for 6 hours to generate a ZIF-8 type MOF crystal layer.

[0076] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the aqueous phase into the T-shaped microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 1.0mL / min, and generate monodisperse droplets under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain microcapsules.

[0077] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 The solution was allowed to stand for 2 hours, and after centrifugation to remove excess solution, it was transferred to simulated body fluid (containing Ca 2+ 2.5mmol / L, HPO 4 2- 1.0mmol / L, pH=7.4), and treated at 37℃ constant temperature oscillator at 120rpm for 24 hours. After mineralization, it was vacuum dried at 60℃ for 6 hours to obtain desorbent particles covered with hydroxyapatite layer on the surface.

[0078] Comparative Example 3: This comparative example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Pour the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a preliminary product.

[0079] Step 2: Immerse the preliminary product obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H 2 O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2O and 2-methylimidazole (molar ratio 1:4) were placed in a hydrothermal reactor at 80°C for 6 hours to generate a ZIF-8 type MOF crystal layer. The product was placed in a plasma treatment chamber and treated for 90 seconds at a power of 200W and an argon gas flow rate of 5L / min to form a chemically bonded enhanced heterojunction interface.

[0080] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the aqueous phase into the T-shaped microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 1.0mL / min, and generate monodisperse droplets under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain microcapsules.

[0081] Step 4: Immerse the microcapsules in 0.1 mol / L CaCl 2 The solution was allowed to stand for 2 hours, and after centrifugation to remove excess solution, it was transferred to simulated body fluid (containing Ca 2+ 2.5mmol / L, HPO 4 2- 1.0mmol / L, pH=7.4), and treated at 37℃ constant temperature oscillator at 120rpm for 24 hours. After mineralization, it was vacuum dried at 60℃ for 6 hours to obtain desorbent particles covered with hydroxyapatite layer on the surface.

[0082] Comparative Example 4: This comparative example provides a method for preparing a nano-olefin-based gas desorbent, the method comprising the following steps: Step 1: Take 100 mL of 8 mg / mL graphene oxide aqueous solution, add 120 mg of 1-butyl-3-methylimidazolium hexafluorophosphate, and place it in an ultrasonicator at 300 W power and 40 kHz frequency for 30 minutes. Inject the mixed solution into a polytetrafluoroethylene mold, quickly immerse it in liquid nitrogen and freeze it at -196°C for 2 hours, then transfer it to a freeze dryer and dry it at -50°C and 10 Pa for 48 hours to obtain a three-dimensional graphene aerogel with a multi-level pore structure.

[0083] Step 2: Immerse the aerogel obtained in step 1 in 0.1 mol / L Zn(NO 3 ) 2 6H 2 O ethanol solution, and infiltrated under -0.1 MPa vacuum conditions for 30 minutes to fully load the zinc ions into the aerogel pores. After removal, transfer to a 0.4 mol / L 2-methylimidazole aqueous solution (Zn(NO 3 ) 2 6H 2O and 2-methylimidazole (molar ratio 1:4) were placed in a hydrothermal reactor at 80°C for 6 hours to generate a ZIF-8 type MOF crystal layer. The product was placed in a plasma treatment chamber and treated for 90 seconds at a power of 200W and an argon gas flow rate of 5L / min to form a chemically bonded enhanced heterojunction interface.

[0084] Step 3: Disperse the product of step 2 in deionized water to prepare an aqueous solution with a solid content of 2wt%. In addition, mix mineral oil (viscosity 35cP) and Span80 at a volume ratio of 98:2 as the oil phase. Pass the water phase into the T-type microfluidic channel at a flow rate of 0.2mL / min and the oil phase at a flow rate of 1.0mL / min, and generate monodisperse droplets under the action of shear force. After collection, solidify at 60°C for 2 hours to obtain desorbent particles.

[0085] Experimental methods

[0086] 1. Adsorption capacity: Using a high-pressure static volumetric adsorption instrument (model 3H-2000PH, Best Instruments), 0.5 g of sample was vacuum degassed at 150 °C for 6 hours before testing, and pure CO was introduced. 2 Gas (99.999%), balanced adsorption for 2 hours at 25℃, 0.5MPa, and the adsorption per unit mass is calculated by pressure change, which conforms to GB / T 19587-2017 standard.

[0087] 2. Cycle decay rate: The dynamic penetration curve method was used to conduct CO 2 In the adsorption and desorption stages, nitrogen purge (50 mL / min) was used and the temperature was raised to 120 °C for 30 min. After 10 cycles, the decay percentage of the ratio of the 10th adsorption capacity to the first was calculated.

[0088] 3. Compressive strength: Use a microcomputer-controlled electronic universal testing machine (WDW-100E, Jinan Shijin) to randomly select 50 intact particles, apply vertical pressure at a rate of 1 mm / min until the particles break, record the maximum load value and convert it into compressive strength, and control the test environment humidity at 40±5%.

[0089] 4. Particle size CV value: The microcapsules were dispersed in 0.1% Tween 80 aqueous solution using a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical). The ultrasonic dispersion was performed for 5 minutes and the standard deviation percentage of the volume average particle size was calculated. The average value was obtained by repeating the analysis three times.

[0090] 5. Zn 2+Dissolution rate: 1 g of sample was placed in 50 mL of deionized water, ultrasonically treated (40 kHz, 300 W) for 30 minutes, centrifuged (8000 rpm, 10 min), and the supernatant was taken for determination of Zn by inductively coupled plasma optical emission spectrometry (ICP-OES, Agilent 5110). 2+ concentration and calculate the dissolution mass percentage.

[0091] 6. Metal dissolution: 1g of particles were immersed in 50mL of acetic acid-sodium acetate buffer at pH=5, and oscillated at 37℃ (120rpm) for 72 hours. After filtration, ICP-OES was used to detect Zn in the solution. 2+ The calibration curve covers the range of 0.01-10 mg / L, and the detection limit is 0.005 mg / L.

[0092] The experimental results are shown in Table 1. Table 1 Comparison of key performance indicators of the embodiments and comparative examples

[0093] Experimental results analysis

[0094] Comparative Example 1: Zn(NO 3 ) 2 6H 2 The molar ratio of O to 2-methylimidazole is unbalanced (1:3), and the MOF crystal growth is incomplete, resulting in the aggregation of unreacted zinc ions in the aerogel pores, which not only reduces the density of adsorption active sites (the adsorption capacity is only 8.2 mmol / g), but also accelerates the adsorption of Zn in an acidic environment due to structural defects. 2+ The dissolution rate (2.3 mg / L) was much higher than 0.08 mg / L in Example 1. Although Comparative Example 1 was still prepared by microfluidics (CV value 12.3%), its cyclic decay rate was as high as 42%, indicating that the physical uniformity of the microcapsules could not make up for the defects of the chemical structure, highlighting the key role of the 1:4 molar ratio in Example 1 on the integrity of the MOF heterojunction.

[0095] In Example 2, the hydrothermal reaction time was shortened to 5 hours, the MOF crystal size distribution was slightly wider, and the adsorption capacity was reduced to 11.8 mmol / g, but the cycle attenuation rate (18%) was still significantly better than that of Comparative Example 1 (42%). This is attributed to the fact that Zn(NO 3 ) 2 6H 2The molar ratio of O to 2-methylimidazole is in a reasonable range, so that the MOF crystals form a continuous heterojunction interface on the aerogel surface, and the integrity of the heterojunction (even if the crystallinity is slightly lower) can still effectively maintain the structural stability during the dynamic adsorption process. In contrast, in comparative example 1, the MOF layer has local defects due to the unbalanced molar ratio (1:3), and the defective area preferentially collapses under cyclic stress, accelerating capacity decay.

[0096] Comparative Example 2 was not subjected to plasma treatment, and MOF and graphene were only combined by physical adsorption. 2+ The dissolution rate increased to 18%, which directly led to the degradation of the cycle performance (attenuation rate of 35%). However, the chemical bonding interface formed by 200W plasma treatment in Example 1 controlled the dissolution rate at 3.1%, confirming the necessity of the power and time parameters in Example 1 for interface stability.

[0097] In Example 3, the microfluidic oil phase flow rate was adjusted to 0.8 mL / min, and the CV value of the microcapsule particle size increased to 9.8%, and the compressive strength (4.1 MPa) was close to that of Example 1 (4.3 MPa), indicating that the flow rate ratio (oil phase 1.0 mL / min: water phase 0.2 mL / min) is the core parameter of particle uniformity, but slight adjustments can still be maintained within the effective range.

[0098] In Example 4, the amount of 2-methylimidazole was slightly reduced, resulting in a slowdown in the growth rate of MOF crystals, the appearance of submicron-sized holes in some areas, the adsorption capacity dropped to 11.9 mmol / g, and the cycle attenuation rate increased to 16%. However, since it was still close to the 1:4 ratio of claim 4, the MOF crystal shedding rate (3.8%) and compressive strength (4.0 MPa) were still better than those of Comparative Example 1.

[0099] In Example 5, the excess 2-methylimidazole (1:4.2) locally enriched the ligand in the aerogel pores, slightly inhibiting the diffusion of zinc ions, resulting in a slightly uneven distribution of MOF crystal size, but the adsorption capacity (12.1 mmol / g) was close to that in Example 1, and the cycle decay rate (15%) increased by only 1 percentage point, proving that Zn(NO 3 ) 2 6H 2 The molar ratio of O to 2-methylimidazole in the range of 1:3.8-1:4.2 can maintain the basic integrity of the heterojunction structure.

[0100] In Comparative Example 3, 1-butyl-3-methylimidazolium hexafluorophosphate was not added, resulting in a lack of cross-linking between graphene sheets. After freeze-drying, the aerogel pores collapsed (the proportion of pores with a diameter > 2μm dropped to 5%), and the specific surface area decreased by 60%. Although MOF crystals can still partially grow, the insufficient strength of the aerogel skeleton (compressive strength 1.2MPa) causes the microcapsules to rupture during the encapsulation process (CV value 19.4%), and the MOF crystals are more likely to fall off due to the loose base structure (falling rate 32%). Although the zinc dissolution in an acidic environment is low (0.05mg / L), the adsorption capacity is only 6.7mmol / g, and the cyclic attenuation rate is as high as 58%, proving that 1-butyl-3-methylimidazolium hexafluorophosphate is a necessary condition for constructing stable multi-level pores.

[0101] After step 4 is omitted in comparative example 4, there is no hydroxyapatite protective layer on the surface of the microcapsule, the compressive strength is reduced to 2.1 MPa, and it is easy to break and release fine powder under coal seam stress (cycle attenuation rate 37%). Although the initial adsorption capacity (12.0 mmol / g) is close to that of Example 1, the amount of zinc ion dissolution in the acidic environment surges to 3.6 mg / L (0.08 mg / L in Example 1), indicating that mineralization treatment is the core means to inhibit metal dissolution. In addition, the unmineralized particles swell due to water absorption in a high humidity environment (RH>90%), resulting in pore blockage, further exacerbating capacity attenuation.

[0102] The compressive strength data further reveals the linkage effect between mineralization and MOF structure: in Example 1, due to the incomplete MOF layer, hydroxyapatite cannot evenly cover the defective area during the mineralization process, and the compressive strength is only 2.8MPa; while in Example 1, the complete heterojunction interface provides a uniform base for the mineralized layer, so that the compressive strength reaches 4.3MPa, meeting the stress requirements of the coal seam. These results show that the parameter system given in this application achieves a comprehensive improvement in adsorption capacity, stability and mechanical strength through multi-level synergy of physical structure control (microfluidics), chemical bonding enhancement (plasma) and functional layer construction (mineralization).

[0103] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0104] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a nano-olefin-based gas desorbent, characterized in that: The following steps are involved: S10, mixing the graphene oxide aqueous solution with 1-butyl-3-methylimidazolium hexafluorophosphate, performing ultrasonic treatment, freezing by liquid nitrogen and freeze-drying to obtain a three-dimensional graphene aerogel, wherein the mass of the 1-butyl-3-methylimidazolium hexafluorophosphate is 15% of the mass of the graphene oxide; S20, immersing the three-dimensional graphene aerogel in a Zn(NO3)2·6H2O ethanol solution for vacuum infiltration, and then transferring it to a 2-methylimidazole aqueous solution, and subjecting it to a hydrothermal reaction and plasma treatment to obtain a graphene / MOF heterojunction, wherein the molar ratio of the Zn(NO3)2·6H2O to the 2-methylimidazole is 1:(3.8-4.2); S30, dispersing the graphene / MOF heterojunction in water to obtain a water phase, mixing mineral oil with Span80 to obtain an oil phase, and passing the water phase and the oil phase into a microfluidic device to prepare microcapsules; S40, sequentially immersing the microcapsules in a CaCl2 solution and subjecting them to a simulated body fluid mineralization treatment, and drying them to obtain desorbent particles.

2. The preparation method according to claim 1, characterized in that: In the S10, the concentration of the graphene oxide aqueous solution is 8 mg / mL.

3. The preparation method according to claim 1, characterized in that: In the S10, the freeze-drying conditions are -50°C and 10Pa for 48 hours.

4. The preparation method according to claim 1, characterized in that: In the S20, the concentration of the Zn(NO3)2·6H2O ethanol solution is 0.1 mol / L, and the concentration of the 2-methylimidazole aqueous solution is 0.4 mol / L.

5. The preparation method according to claim 1, characterized in that: In S20, the parameters of the plasma treatment are power 200 W, time 90 s, and argon gas flow rate 5 L / min.

6. The preparation method according to claim 1, characterized in that: In the S20, the vacuum penetration pressure is -0.1 MPa, and the penetration time is 30 min.

7. The preparation method according to claim 1, characterized in that: In S20, the temperature of the hydrothermal reaction is 80° C., and the time of the hydrothermal reaction is 5-7 hours.

8. The preparation method according to claim 1, characterized in that: In the S30, the flow rate of the water phase is 0.2 mL / min, and the flow rate of the oil phase is 0.8-1.0 mL / min.

9. The preparation method according to claim 1, characterized in that: In the S40, the mineralization treatment is carried out at 37° C. and 100-120 rpm shaking for 24 hours.

10. Use of the nano-olefin-based gas desorbent prepared by the method according to any one of claims 1 to 9 in coal mine drainage.

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