A porous liquid based on ldh interface engineering stabilization and preparation and application thereof

Abstract

This invention discloses a porous liquid stabilized by LDH interface engineering, its preparation, and its application. The porous liquid comprises mesoporous SiO2@LDH composite nanoparticles and an ionic liquid. The mesoporous SiO2@LDH composite nanoparticles have a composite structure formed by the self-assembly of mesoporous silica and layered bimetallic hydroxide nanosheets, with the layered bimetallic hydroxide nanosheets serving as the interface layer. The ionic liquid and the LDH surface –OH groups exhibit hydrogen bonding and electrostatic interactions. This invention solves the problems of weak electrostatic bonding, poor mass transfer due to pore closure, and high solvent toxicity in existing technologies. By constructing a SiO2@LDH composite material and obtaining mesoporous SiO2@LDH through alkali treatment followed by etching, the LDH nanosheets achieve a dual-functional interface, unifying pore protection and system stability. It exhibits high adsorption capacity, good selectivity, and excellent regeneration performance in CO2 capture.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite materials and gas capture technology, specifically to a porous liquid stabilized by LDH interface engineering and its preparation and application. Background Technology

[0002] Layered bimetallic hydroxides (LDHs) have shown significant potential in CO2 adsorption due to their tunable layer metals, rich hydroxyl content, and good chemical stability. However, traditional LDH materials often suffer from low accessibility to active sites and limited mass transfer due to aggregation, making it difficult to achieve efficient gas capture. In recent years, combining porous solids with liquid media to construct "porous liquids" has become an emerging research direction. These liquids combine the permanent pores of solids with the fluidity of liquids, potentially achieving integrated adsorption and transport. However, the core challenges facing porous liquids are: the liquid medium easily invades and blocks the solid pores, leading to pore deactivation; and solid particles tend to aggregate and settle in the liquid phase, resulting in poor system stability.

[0003] Existing literature 1 (Chinese invention patent application with publication number CN112934196A) uses HCS as a core, coated with long-chain organic matter; the mass fractions of the two are: 5%~15% HCS and 85%~95% long-chain organic matter; the long-chain organic matter is an organic long chain obtained by anion exchange of polymeric ionic liquids (PILs) and 4-nonylphenol-polyethylene ether sulfonate (PEGS), with a molar ratio of PILs to PEGS of 1:1. It combines the characteristics of porous solids (such as zeolites and metal-organic frameworks, which have permanent, rigid, and well-defined pores) and liquids (which have fluidity, rapid heating, and mass transfer). By modifying the surface of polymeric ionic liquids (PILs) and then grafting organic oligomers with opposite charges (such as 4-nonylphenol-polyethylene ether sulfonate (PEGS)) onto the surface of HCS through anion exchange, a porous liquid is prepared, which is liquid at room temperature, and the HCS is monodisperse. The method for preparing HCS porous liquid of the present invention is simple and easy to implement. Since the hollow carbon sphere nanoparticles are monodisperse in the porous liquid at room temperature, they have potential application prospects in gas adsorption, photothermal conversion and catalytic conversion.

[0004] However, the hollow carbon spheres in Reference 1 have a closed hollow structure that lacks open channels, and the micropores are not conducive to CO2 mass transfer; the nonylphenol polyoxyethylene ether sulfonate used has obvious endocrine-related properties and poor biodegradability; the imidazole polymer ionic liquid has high viscosity, which affects its fluidity; the surface modification mechanism is simple and lacks hydrogen bonding, resulting in insufficient long-term stability; the CO2 adsorption performance and rheological data are not disclosed, and the carbon material relies only on physical adsorption and lacks basic site chemical adsorption; the preparation process uses hydrofluoric acid etching, which has strong corrosiveness and environmental risks, and the high-temperature carbonization has high energy consumption, which is not conducive to green large-scale production. Summary of the Invention

[0005] The purpose of this invention is to provide a porous liquid based on LDH interface engineering, its preparation and application, which solves the problems of weak electrostatic bonding, poor mass transfer due to pore closure and high solvent toxicity in the prior art. By constructing a mesoporous SiO2@LDH composite material, a dual-functional interface is achieved by utilizing the self-assembly of LDH nanosheets on the SiO2 surface. This porous liquid can achieve the unity of pore protection and system stability without complex surface grafting modification. It exhibits high adsorption capacity, good selectivity and excellent recycling performance in CO2 capture.

[0006] To achieve the above objectives, the present invention provides a porous liquid stabilized by LDH interface engineering, the porous liquid comprising the following components: Mesoporous SiO2@LDH composite nanoparticles and ionic liquid; the mesoporous SiO2@LDH composite nanoparticles have a composite structure formed by the self-assembly of mesoporous silica and layered bimetallic hydroxide nanosheets, i.e., the layered bimetallic hydroxide nanosheets serve as the interface layer; the hydrogen bonds and electrostatic interactions between the ionic liquid and the –OH groups on the LDH surface.

[0007] Preferably, the ionic liquid is [Bmin]BF4.

[0008] Preferably, the layered bimetallic hydroxide nanosheets are LDH nanosheets.

[0009] This invention provides a method for preparing a porous liquid stabilized by LDH interface engineering as described above, the method comprising: S1. Synthesis of SiO2 microspheres; S2. SiO2 microspheres were pretreated with surfactants and then LDH nanosheets were added. The LDH nanosheets were self-assembled on the surface of the SiO2 microspheres by electrostatic interaction to form a continuous and dense shell. After the reaction, the mixture was post-treated (centrifuged, washed and dried) to obtain a solid SiO2@LDH composite material. S3. The solid SiO2@LDH composite material is placed in a dilute alkaline solution for selective etching. The SiO2 core part in the solid SiO2@LDH composite material can be dissolved to form a uniform mesoporous channel. After centrifugation, washing to neutrality, and drying, mesoporous SiO2@LDH composite particles with a multi-level pore structure are obtained. S4. Add the mesoporous SiO2@LDH composite particles to the ionic liquid, and stir and ultrasonically disperse them at a constant temperature to make the particles uniformly dispersed in the liquid phase system and form a stable porous liquid. The hydrogen bond and electrostatic interaction between the ionic liquid and the -OH groups on the LDH surface help to enhance the dispersibility and compatibility of the particles in the system, prevent the aggregation and sedimentation of the particles, and obtain the mesoporous SiO2@LDH-based porous liquid.

[0010] Preferably, in step S1, the SiO2 microspheres are obtained by adding tetraethyl orthosilicate to a mixed solution of ethanol and ammonia via the Stöber method, followed by centrifugation, washing, and drying.

[0011] Preferably, in step S2, the surfactant is sodium dodecylbenzenesulfonate; the mass ratio of SiO2 microspheres to LDH nanosheets is 1:(0.1~0.3); and the self-assembly time is 5 hours.

[0012] Preferably, in step S3, the dilute alkaline solution is a 1M NaOH solution; the etching time is 2 hours and the temperature is 25 °C.

[0013] Preferably, in step S4, the mass fraction of the mesoporous SiO2@LDH-based porous liquid mesoporous SiO2@LDH composite particles is 0.1%~10%; the ultrasonic treatment time is 10 minutes.

[0014] This invention provides an application of a porous liquid stabilized by LDH interface engineering as described above in gas trapping.

[0015] Preferably, the gas is CO2.

[0016] This invention discloses a porous liquid stabilized by LDH interface engineering, its preparation, and its application. This invention solves the problems of weak electrostatic bonding, poor mass transfer due to closed pores, and high solvent toxicity in existing technologies, and has the following advantages: 1. By constructing a mesoporous SiO2@LDH composite material, a dual-functional interface is achieved through the self-assembly of LDH nanosheets on the SiO2 surface: First, the cross-grown LDH nanosheets form a dense interface layer with steric hindrance on the SiO2 surface, which can effectively block large steric solvent molecules (such as ionic liquids) from entering the mesoporous channels of the SiO2 core, thereby preserving pores to accommodate small molecule gases such as CO2; Second, the abundant hydroxyl functional groups on the surface of LDH nanosheets can form strong hydrogen bond interactions with steric solvent molecules, significantly enhancing the dispersibility and interfacial compatibility of nanoparticles in the liquid phase, thereby greatly improving the kinetic stability of the porous liquid system and preventing particle sedimentation and pore blockage.

[0017] 2. The self-assembled LDH nanosheets on the surface of mesoporous SiO2 effectively improve the layered stacking and aggregation problem of LDH, and significantly improve the structural stability and interfacial bonding strength of the material. At the same time, the high specific surface area and open pore structure of mesoporous SiO2 provide sufficient diffusion and storage space for CO2 molecules, enhancing the mass transfer and adsorption capacity of the gas in the system.

[0018] 3. Using ionic liquid as the dispersion medium replaces the traditional organic solvent system, forming a stable porous liquid, which significantly improves the fluidity and dispersion uniformity of the system, while also having good environmental compatibility; through the hydrogen bond interaction between the hydroxyl groups on the LDH surface and the ionic liquid, the compatibility and stability of nanoparticles in the liquid phase system are enhanced, preventing sedimentation and stratification during long-term use.

[0019] 4. The mesoporous SiO2@LDH-based porous liquid prepared by this invention has low viscosity, high fluidity and excellent CO2 adsorption and recycling performance, providing a new technical route for developing efficient, green and renewable CO2 capture and utilization materials. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of the method for preparing mesoporous SiO2@LDH-based porous liquid according to the present invention.

[0021] Figure 2 This is a schematic diagram of the solid SiO2@LDH composite material of the present invention.

[0022] Figure 3 This is a characterization diagram of the pore structure of the mesoporous SiO2@LDH composite material of the present invention.

[0023] Figure 4 This is a CO2 adsorption-desorption isotherm diagram of the mesoporous SiO2@LDH-based porous liquid and the control sample of this invention.

[0024] Figure 5 This is a diagram showing the CO2 / N2 separation performance of the mesoporous SiO2@LDH-based porous liquid of the present invention.

[0025] Figure 6 This is a graph showing the CO2 adsorption cycle performance of the mesoporous SiO2@LDH-based porous liquid of the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The specific source information for the reagents and instruments involved in the following examples is as follows: Anhydrous ethanol (99.5%), NH3∙H2O solution (25wt.%~28wt.%), and sodium dodecylbenzenesulfonate (analytical grade) were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; TEOS (analytical grade, tetraethyl orthosilicate) was purchased from Tianjin Kemeo Chemical Reagent Co., Ltd.

[0028] The surface morphology of the composite material was determined using a field emission scanning electron microscope (FET) with a JSM-7610F from NEC Corporation. The pore size distribution was measured using a Micromeritics ASAP 2460 adsorption analyzer. The CO2 adsorption performance, CO2 / N2 separation performance, and adsorption cycle stability were measured using a Bestech high-temperature and high-pressure adsorption analyzer (3H-2000PH).

[0029] Example 1 The preparation method of LDH-NS is as follows: First, LDH is prepared by co-precipitation. Magnesium nitrate and aluminum nitrate (total amount of magnesium nitrate and aluminum nitrate is 0.03 mol) in a molar ratio of 2:1 are dissolved in 100 mL of deionized water. Then, 80 mL of 7 wt.% NH3·H2O solution is added, and the mixture is stirred at 80 °C for 10 min. During this process, the pH of the mixed solution is maintained at 10. The precipitate is collected by centrifugation at 12,000 rpm and washed three times to produce LDH gel. The LDH gel is freeze-dried to prepare solid LDH. Second, LDH-NS is exfoliated. The LDH gel is dispersed in water by ultrasonic treatment for 30 min to obtain LDH-NS dispersion (1 mg / mL).

[0030] A method for preparing a porous liquid (mesoporous SiO2@LDH-based porous liquid) based on LDH interface engineering, such as Figure 1 The diagram shows a flow chart of the method for preparing mesoporous SiO2@LDH-based porous liquids according to the present invention. The method includes: S1. Mix 128 g of anhydrous ethanol and 54 mL of NH3∙H2O solution (25 wt.%~28 wt.%), heat to 30 °C, add 8.4 mL of TEOS, and stir for 1 h at 500 rpm / min to generate uniformly sized SiO2 nanospheres. Centrifuge five times with deionized water, each time at 4900 rpm for 10 min. Dry the centrifuged solid sample at 60 °C for 12 h to obtain SiO2 microspheres, denoted as SLDH-2.

[0031] S2. Disperse 0.1 g of the obtained SiO2 microspheres in 20 mL of ethanol by ultrasonication for 15 min, add 0.01 g of sodium dodecylbenzenesulfonate (analytical grade), stir for 1 h, centrifuge and discard the supernatant; disperse the obtained precipitate by ultrasonication in 20 mL of ethanol, add LDH-NS dispersion (the mass of LDH nanosheets in the added LDH-NS dispersion is 0.01 g), stir the solution at 25°C for 5 h, and use electrostatic interaction to allow LDH nanosheets to self-assemble on the SiO2 surface; after the reaction is complete, centrifuge at 8000 rpm, collect the precipitate and dry it at 70°C overnight to obtain a solid SiO2@LDH composite material, denoted as SLDH-2-2h. Figure 2 The diagram shows a schematic representation of the solid SiO2@LDH composite material of this invention. Figure 2 It can be seen that the solid SiO2 nanospheres have a smooth surface, uniform particle distribution, and concentrated size. The SiO2@LDH surface has LDH nanosheets with a certain degree of extension, which indicates that LDH-NS is assembled on the SiO2 surface.

[0032] S3. Take 1g of the solid SiO2@LDH composite material obtained above, disperse it in 1M NaOH solution, let it stand at 25 °C for 2 h, and wash it with deionized water until the supernatant is neutral. Finally, dry it at 70 °C for 12 h to obtain mesoporous SiO2@LDH composite particles, as shown below. Figure 3 The diagram shown illustrates the pore structure characterization of the mesoporous SiO2@LDH composite material of this invention. Figure 3 It can be seen that the mesopore size distribution of mesoporous SiO2@LDH is between 18 nm and 19 nm.

[0033] S4. Add 0.1 g of mesoporous SiO2@LDH composite particles to 1.0 g of [Bmim]BF4 ionic liquid and stir magnetically at 25 °C for 10 min to uniformly disperse the particles in the liquid phase system, thereby obtaining a mesoporous SiO2@LDH-based porous liquid, denoted as SLDH-2-2h-10%BF4.

[0034] Comparative Example 1 A porous liquid (SiO2-based porous liquid) stabilized by LDH interface engineering is basically the same as that in Example 1, except that: Steps S3-4 are omitted; in step S2, 0.1 g of SiO2 microspheres are added to 1.0 g of [Bmim]BF4 ionic liquid and magnetically stirred at 25 °C for 10 min to uniformly disperse the particles in the liquid phase system, thereby obtaining a SiO2-based porous liquid, denoted as SiO2-10%BF4.

[0035] Comparative Example 2 A porous liquid (SiO2-based porous liquid) stabilized by LDH interface engineering is basically the same as that in Example 1, except that: Step S4 is omitted; in step S3, 0.1 g of solid SiO2@LDH composite material is added to 1.0 g of [Bmim]BF4 ionic liquid and magnetically stirred at 25 °C for 10 min to uniformly disperse the particles in the liquid phase system, thereby obtaining solid SiO2@LDH-based porous liquid, denoted as SLDH-2-10%BF4.

[0036] Experiment Example 1: Performance Testing The samples prepared in Example 1 and Comparative Examples 1 and 2 were subjected to performance testing. The specific procedure was as follows: First, the weighed and recorded sample was placed in the sample tube. Then, the sample test parameters were set (25 °C, 10 bar), and the measurement was started. The instrument first performed a vacuum tightness test. After the air tightness check was passed, the sample tube was kept at the same temperature as the reference chamber to begin testing the temperature zone volume. After the temperature zone volume test, a pre-adsorption vacuum was performed to remove residual gaseous impurities in the adsorbent. Then, the test was carried out according to the set maximum adsorption pressure (10 bar) until the test was completed.

[0037] like Figure 4 As shown, the CO2 adsorption-desorption isotherms of the mesoporous SiO2@LDH-based porous liquid and the control sample of the present invention are displayed. SLDH-2-10%BF4 is the solid SiO2@LDH-based porous liquid of Comparative Example 2; SiO2-10%BF4 is the SiO2-based porous liquid of Comparative Example 1; and SLDH-2-2h-10%BF4 is the mesoporous SiO2@LDH-based porous liquid of Example 1. Figure 4 The results show that, under CO2 adsorption conditions of 25°C and 10 bar, the adsorption capacity of the SiO2-based porous liquid is 0.95 mmol / g; the adsorption capacity of the solid SiO2@LDH-based porous liquid is increased to 1.31 mmol / g. The CO2 adsorption capacity of the mesoporous SiO2@LDH-based porous liquid is further increased to 1.5 mmol / g, indicating that the composite structure has a significant synergistic enhancement effect. These results confirm that the introduction of the LDH nanosheet interface layer not only improves the pore accessibility of the material but also enhances its chemisorption capacity for CO2.

[0038] like Figure 5 The figure shows the CO2 / N2 separation performance of the mesoporous SiO2@LDH-based porous liquid of this invention. (From...) Figure 5To evaluate the actual separation potential of the material under different CO2 / N2 compositions, the adsorption isotherms of the porous liquid for pure CO2 and pure N2 at 25 °C (pressure range 0-10 bar) were tested, and its adsorption selectivity was calculated. The mesoporous SiO2@LDH-based porous liquid showed significantly higher adsorption capacity for CO2 than for N2, exhibiting excellent gas separation performance.

[0039] like Figure 6 The figure shows the CO2 adsorption cycle performance of the mesoporous SiO2@LDH-based porous liquid of this invention. (From...) Figure 6 It can be seen that in the cyclic stability test, under the same conditions (25 °C, 10 bar), 10 adsorption-desorption cycles were performed, and material regeneration was achieved solely through vacuuming without additional heating. The results show that the CO2 adsorption capacity remained above 95% of the initial value, indicating that the porous liquid possesses excellent cyclic stability and structural reversibility. Its low viscosity and open pore structure effectively reduced the CO2 mass transfer resistance, allowing both adsorption and regeneration processes to quickly reach equilibrium.

[0040] like Figures 4-6 It can be seen that the mesoporous SiO2@LDH-based porous liquid prepared in Example 3 was used to study the CO2 adsorption and recycling process. This porous liquid system is composed of a composite structure formed by the self-assembly of mesoporous silica and layered bimetallic hydroxide nanosheets and an ionic liquid. Each component plays a synergistic role in the adsorption behavior.

[0041] In summary, this mesoporous SiO2@LDH-based porous liquid achieves high-capacity capture, highly selective separation, and low-temperature efficient regeneration of CO2 through the synergistic effect of hierarchical pore structure, surface chemisorption, and ionic liquid medium, providing a new material system and methodological approach for developing low-energy CO2 adsorption and separation technologies.

[0042] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A porous liquid stabilized based on LDH interface engineering, characterized in that, This porous liquid contains the following components: Mesoporous SiO2@LDH composite nanoparticles and ionic liquids; The mesoporous SiO2@LDH composite nanoparticles have a composite structure formed by the self-assembly of mesoporous silica and layered bimetallic hydroxide nanosheets. The hydrogen bonds and electrostatic interactions between the ionic liquid and the –OH groups on the LDH surface.

2. The porous liquid stabilized by LDH interface engineering according to claim 1, characterized in that, The ionic liquid is [Bmin]BF4.

3. The porous liquid stabilized by LDH interface engineering according to claim 1, characterized in that, The layered bimetallic hydroxide nanosheets are LDH nanosheets.

4. A method for preparing a porous liquid based on LDH interface engineering stability as described in any one of claims 1 to 3, characterized in that, The method includes: S1. Synthesis of SiO2 microspheres; S2. SiO2 microspheres are pretreated with surfactants, and LDH nanosheets are added. The LDH nanosheets are then self-assembled on the surface of SiO2 microspheres by electrostatic interaction to obtain solid SiO2@LDH composite material. S3. The solid SiO2@LDH composite material was placed in a dilute alkaline solution for selective etching. After centrifugation, washing to neutrality, and drying, mesoporous SiO2@LDH composite particles with a multi-level pore structure were obtained. S4. Add the mesoporous SiO2@LDH composite particles to the ionic liquid, and stir and ultrasonically disperse them at a constant temperature to obtain a mesoporous SiO2@LDH-based porous liquid.

5. The preparation method according to claim 4, characterized in that, In step S1, the SiO2 microspheres are obtained by adding tetraethyl orthosilicate to a mixed solution of ethanol and ammonia via the Stöber method, followed by centrifugation, washing, and drying.

6. The preparation method according to claim 4, characterized in that, In step S2, the surfactant is sodium dodecylbenzenesulfonate; the mass ratio of SiO2 microspheres to LDH nanosheets is 1:(0.1~0.3); and the self-assembly time is 5 hours.

7. The preparation method according to claim 4, characterized in that, In step S3, the dilute alkaline solution is a 1M NaOH solution; the etching time is 2 hours and the temperature is 25 °C.

8. The preparation method according to claim 4, characterized in that, In step S4, the mass fraction of the mesoporous SiO2@LDH-based porous liquid mesoporous SiO2@LDH composite particles is 0.1%~10%; the stirring time is 10 minutes.

9. The application of a porous liquid stabilized by LDH interface engineering as described in any one of claims 1 to 3 in gas trapping.

10. The application according to claim 9, characterized in that, The gas is CO2.

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