Application of zeolite imidazate framework structure material in solid-state refrigeration

Abstract

The invention discloses application of a zeolite imidazate framework structure material in solid-state refrigeration, and belongs to the field of solid-state refrigeration. The zeolite imidazate skeleton structure material is used for a solid-state refrigeration working medium, and can induce phase change of a structure involving pore diameter change in a frame by hydrostatic pressure to generate a remarkable heat effect for solid-state refrigeration. The zeolite imidazate framework structure material is ZIF-4 (Zn) and the like, the ZIF-4 (Zn) can generate adiabatic temperature changes of-9.6 K and-15.1 K under the pressure of 100 MPa and 180 MPa respectively, the corresponding isothermal entropy changes are 268 J kg <-1 > K <-1 > and 426 J kg <-1 > K <-1 > respectively, and refrigeration stability can be kept in pressure circulation. In addition, the refrigeration temperature range of the material is 140-298K, and the material is suitable for diversified refrigeration requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state refrigeration, and in particular to application of a zeolite imidazolate framework structure material in solid-state refrigeration. Background Art

[0002] Refrigeration technology plays a vital role in modern society. The current dominant refrigeration technology is gas compression refrigeration. This technology consumes 20% of the world's electrical energy, and this figure is still increasing rapidly. On the other hand, the refrigerants that this technology primarily relies on have a high global warming potential (often thousands of times that of CO2). Therefore, the development of environmentally friendly and energy-saving alternative refrigeration technologies is crucial to achieving a sustainable future. In this context, refrigeration technology based on the compression effect has become a potential solution. This is because its typical materials, such as neopentyl glycol, can produce an entropy change comparable to that of traditional gas refrigerants.

[0003] However, existing compression card refrigeration materials face the problem of difficulty in simultaneously optimizing the refrigeration temperature range and isothermal entropy change, which limits the development of this refrigeration technology. Specifically, in order to achieve effective refrigeration, the normal pressure phase transition temperature of the compression card material needs to be lower than room temperature, and the difference between the two is the refrigeration temperature range. Among existing compression card materials, the phase transition temperature of materials with an entropy change equivalent to neopentyl glycol is generally higher than room temperature and cannot meet refrigeration needs; and the entropy change value of compression card materials with a phase transition temperature below room temperature is generally low. Therefore, in order to promote the practical refrigeration application of compression card materials, the current core issue is to achieve high entropy change value and wide refrigeration temperature range at the same time. Summary of the Invention

[0004] The purpose of the present invention is to provide an application of a zeolite imidazolate framework structure material in solid-state refrigeration. Using the zeolite imidazolate framework structure material as a refrigerant can produce a significant refrigeration effect under the drive of hydrostatic pressure.

[0005] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0006] The invention discloses an application of a zeolite imidazolate framework material in solid-state refrigeration. The zeolite imidazolate framework material is used as a refrigerant in solid-state refrigeration to achieve a refrigeration effect based on a phase change thermal effect.

[0007] The zeolite imidazolate framework structure material belongs to a metal organic framework material, which undergoes a structural phase transition involving a change in the pore size within the framework under hydrostatic pressure.

[0008] The structure of the zeolite imidazolate framework material at room temperature and pressure is a porous three-dimensional network framework formed by bonding of a metal center and an imidazole linker. Hydrostatic pressure can drive it to undergo a structural phase change and generate a thermal effect, thereby achieving solid-state refrigeration. The zeolite imidazolate framework material is ZIF-1(M), ZIF-2(M), ZIF-4(M), ZIF-5(M), ZIF-7(M), ZIF-8(M), ZIF-9(M), ZIF-10(M), ZIF-11(M), ZIF-12(M), ZIF-14(M), ZIF-20(M), ZIF-23(M), ZIF-60(M), ZIF-61(M), ZIF-62(M), ZIF-64(M), ZIF-6 ...7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), ZIF-7(M), Z One or more of ZIF-67(M), ZIF-68(M), ZIF-69(M), ZIF-70(M), ZIF-71(M), ZIF-72(M), ZIF-73(M), ZIF-74(M), ZIF-75(M), ZIF-77(M), ZIF-78(M), ZIF-90(M), ZIF-95(M), ZIF-100(M), ZIF-224(M), and ZIF-268(M), wherein M is one or more of metal centers such as Zn and Co.

[0009] When ZIF-4(Zn) is used as a refrigerant, the preparation process employs a solvothermal method. Specifically, Zn(NO₃)₂·6H₂O and imidazole are dissolved in N,N-dimethylformamide (DNDM) at a molar ratio of 2.5:1 to 3.5:1, with the Zn(NO₃)₂·6H₂O concentration ranging from 0.02 to 0.3 mol / L. The solution is then reacted in a sealed container at a temperature of 343 to 423 K for 12 to 120 hours. The resulting solid product, ZIF-4(Zn), contains residual solvent. The solid is then washed with DNDM, then rinsed with dichloromethane, and finally dried to yield the solvent-free ZIF-4(Zn) refrigerant. The refrigeration range of ZIF-4(Zn) as a refrigerant is 158 K. The applied driving pressure ranged from 70 to 600 MPa. When the hydrostatic pressures of 100 MPa and 180 MPa were applied at 298 K, the adiabatic temperature changes of the ZIF-4(Zn) phase transition were -9.6 K and -15.1 K, respectively, and the corresponding entropy changes were 268 J kg -1 K -1 and 426J kg -1 K -1 ; and the adiabatic temperature change value of ZIF-4(Zn) is stable in high-pressure cycles.

[0010] The advantages and beneficial effects of the present invention are as follows:

[0011] 1. The present invention uses zeolite imidazolate framework material as a working fluid and adopts hydrostatic drive to achieve the refrigeration effect. ZIF-4 (Zn) is used as a solid-state refrigeration working fluid. The refrigeration effect comes from the fact that the vibration entropy dominated by the low-frequency rigid unit vibration mode of the zeolite imidazolate framework material can be regulated by pressure. When hydrostatic pressure (70-600MPa) is applied, the Ponzi-Card effect (defined as a maximum entropy change greater than 100J kg) can be exhibited. -1 K -1 This pang-pressure-card effect remains stable even under high-pressure cycles, with adiabatic temperature fluctuations of only 0.2K after 100 cycles at 100 MPa, offering potential for the development of durable solid-state refrigeration technology. Furthermore, ZIF-4(Zn) has a refrigeration temperature range of up to 158K, adapting to diverse cooling needs.

[0012] 4. The pressure cycle refrigeration of the present invention is similar to the existing gas cycle compression refrigeration, but does not emit greenhouse gases, which is conducive to replacing the existing gas cycle compression refrigeration technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a process flow chart for a compression refrigeration cycle using zeolite imidazolate framework structure materials;

[0014] Figure 2 1 is the heat flow curve of ZIF-4(Zn) under normal pressure;

[0015] Figure 3 The in situ high-pressure Raman spectrum of ZIF-4 (Zn) at 298K is shown in Example;

[0016] Figure 4 The in situ high-pressure Raman spectrum of ZIF-4 (Zn) at 200K is shown in Example;

[0017] Figure 5 The distribution of vibration entropy of the low-pressure open-pore phase and the high-pressure closed-pore phase along with the vibration mode energy of ZIF-4(Zn) at 300K obtained from the tested phonon state density curve is shown in FIG.

[0018] Figure 6 The distribution of vibration entropy of the low-pressure open-pore phase and the high-pressure closed-pore phase along with the vibration mode energy of ZIF-4(Zn) at 200K obtained from the tested phonon state density curve is shown in FIG.

[0019] Figure 7 This is the adiabatic temperature change test curve of ZIF-4 (Zn) in Example 1 at 298K and 100MPa pressure cycle;

[0020] Figure 8 is the specific heat curve of ZIF-4(Zn) in Example;

[0021] Figure 9 This is the adiabatic temperature change test curve of ZIF-4 (Zn) in Example 1 at 298K and 180MPa pressure cycle;

[0022] Figure 10 This is the adiabatic temperature change test curve of ZIF-4(Zn) in Example 1 at 298K and 100 cycles of 100 MPa pressure; DETAILED DESCRIPTION

[0023] In order to further understand the present invention, the present invention is described below with reference to examples. However, the examples are only for further elaboration of the features and advantages of the present invention, rather than for limitation of the claims of the present invention.

[0024] The present invention uses zeolite imidazolate skeleton structure material as refrigerant, applies isostatic pressure to drive it to undergo phase change to produce thermal effect, thereby performing solid-state refrigeration. Figure 1 The refrigeration cycle shown.

[0025] The present invention adopts hydrostatic pressure and is applicable to various high-pressure systems such as piston systems and high-pressure systems.

[0026] When ZIF-4(Zn) is used as a refrigerant, the preparation process employed is a solvothermal method. Specifically, Zn(NO₃)₂·6H₂O and imidazole are dissolved in an N,N-dimethylformamide solvent at a molar ratio of 2.5:1 to 3.5:1 (4.03:1.32 in the examples), wherein the concentration of Zn(NO₃)₂·6H₂O is in the range of 0.02 to 0.3 mol / L (0.046 mol / L in the examples). The solution is then placed in a sealed container for reaction at a temperature of 343 to 423 K (373 K in the examples) and a reaction time of 12 to 120 hours (72 hours in the examples). After completion of the reaction, a solid product containing residual solvent, ZIF-4(Zn), is obtained. The solid product is then washed with N,N-dimethylformamide solvent, then rinsed with dichloromethane, and finally dried to obtain the solvent-free ZIF-4(Zn) used as a refrigerant.

[0027] Example 1

[0028] Refrigeration applications of ZIF-4(Zn):

[0029] (1) Refrigeration temperature range of ZIF-4(Zn): ZIF-4(Zn), a typical material of zeolitic imidazolate framework structure material, has the molecular formula Zn(C3H3N2)2, and its English name is zeolitic imidazolate framework-4(Zn), abbreviated as ZIF-4(Zn). The structure of ZIF-4(Zn) at room temperature and pressure is a porous three-dimensional network framework formed by the bonding of metal center and imidazole linker, which is a low-pressure open-pore phase. A ZIF-4(Zn) sample with a mass of 4.73 mg was placed in an aluminum sample cell with an inner diameter of 5 mm. An empty aluminum sample cell was used as a reference. The heat flow curves of the cooling and heating processes were tested in the temperature range of 103 to 298 K at a rate of 20 K / min using a Q1000 (produced by Netzsch, Germany). Figure 2 The phase transition extreme temperatures corresponding to cooling and heating are 137 K and 140 K, respectively. Based on the phase transition extreme temperature point of heating, it can be seen that the cooling temperature range of ZIF-4(Zn) is 158 K.

[0030] (2) ZIF-4(Zn) can undergo a phase transition induced by hydrostatic pressure in the refrigerated temperature range: In the refrigerated temperature range, hydrostatic pressure can be used to drive the pores in the ZIF-4(Zn) framework to close, transforming it into a high-pressure closed-pore phase. In situ high-pressure Raman spectroscopy can be used to demonstrate the occurrence of this phase transition. The seal was pre-pressed and a hole was drilled in the center (the seal was made of beryllium copper alloy, with a diameter (outer diameter) of 50 mm, an initial thickness of 300 μm, and a central hole diameter (inner diameter) of 300 μm). The ZIF-4(Zn) sample was placed flat in the center hole, and ruby ​​powder was placed to calibrate the pressure. Silicone oil was dripped as a pressure medium to immerse the ZIF-4(Zn) sample and ruby, with a volume ratio of solid to silicone oil of approximately 1:1. The seal was then clamped between the upper and lower anvil surfaces of a diamond anvil (anvil surface diameter of 1000 μm). Finally, the screw is used to push the upper and lower anvil surfaces of the diamond anvil closer together to achieve in-situ pressurization of the sample in the center of the gasket. 4 In situ high-pressure Raman spectra were collected at two temperature points in the refrigeration zone, 298 K and 200 K, using a Raman spectrometer (LabRAM HR Evolution, Horiba) in a He cryostat (S-300, Physike). Figure 3 、 Figure 4 Compared with the low-pressure spectrum, the high-pressure spectrum at 1175 cm -1 and 1280cm -1 The nearby vibration mode is significantly red-shifted, 1160cm -1 A new vibration mode appears nearby, which corresponds to the transition from the low-pressure open-pore phase to the high-pressure closed-pore phase of ZIF-4(Zn).

[0031] (3) The phase transition of ZIF-4(Zn) under hydrostatic pressure in the refrigeration temperature range is accompanied by a significant entropy change: the vibrational entropy of the low-pressure open-pore phase and the high-pressure closed-pore phase of ZIF-4(Zn) can be compared at 300K and 200K respectively using inelastic neutron scattering technology. The inelastic neutron scattering experiment was carried out on the cold neutron time-of-flight spectrometer PELICAN at the Australian Neutron Scattering Center (ANSTO). The incident neutron wavelength of the instrument is The incident energy is 3.72 meV, and the energy resolution of the elastic line is 0.135 meV. A ZIF-4 (Zn) sample with a mass of 0.86 g and 0.24 g of pressure-transmitting medium Fomblin oil are sealed in a piston-cylinder high-pressure sample cell (made of high-strength aluminum alloy, with an inner diameter of the cylinder and an outer diameter of the piston of 10 mm, and a Teflon sample tube can be inserted into the cylinder. The inner diameter of the Teflon sample tube is 8 mm and the height is 22 mm). The phonon state density of ZIF-4 (Zn) at 0.1 MPa and 200 MPa was obtained by testing at 300 K and 200 K, respectively, and then converted into vibrational entropy, as shown in Figure 2. Figure 5 、 Figure 6 As shown. Furthermore, a standard vanadium sample was measured for detector normalization and determination of the energy resolution function. It can be seen that at 300K and 200K, there is a significant difference in the vibrational entropy between the low-pressure open-pore phase and the high-pressure closed-pore phase. Due to the transition from the high-pressure closed-pore phase to the low-pressure open-pore phase, the entropy of ZIF-4(Zn) increases, manifesting itself as a significant endothermic effect, thus enabling solid-state refrigeration.

[0032] Example 2

[0033] Refrigeration applications of ZIF-4(Zn):

[0034] (1) Refrigeration effect of ZIF-4(Zn) at 100 MPa: 1 g of refrigerant ZIF-4(Zn) mixed with pressure-transmitting medium silicone oil (volume ratio of 4:1) was placed in a piston cylinder sample cell (made of beryllium copper alloy, with an inner diameter of the cylinder and an outer diameter of the piston of 10 mm, and a Teflon sample tube that can be inserted into the cylinder. The inner diameter of the Teflon sample tube is 9 mm and the height is 11 mm). One end of an E-type thermocouple (produced by OMEGA, USA, model TT-E-30, error: ±1K) was connected to a temperature recorder (Lakeshore 336), and the other end was extended through the bottom of the sample cell to the center of the sample to record the change of sample temperature over time. A high-pressure electric syringe pump (produced by Shanghai Neste, model HP350A) was used to apply and maintain a specified pressure to the above piston cylinder sample cell in situ, and the change of sample temperature during this pressurization process was recorded in real time. After the sample temperature stabilizes, use a high-pressure electric injection pump to release the pressure to 0.1 MPa in situ, and record the change of sample temperature over time during this pressure relief process in real time. The above process is a pressure cycle. Figure 7As shown, under the pressure cycle of 100MPa, the adiabatic temperature change value T ad During pressurization, it reaches 10.6K, and during depressurization, it is -9.6K. Figure 8 Specific heat, calculated entropy change at 100 MPa is 268 J kg -1 K -1 .

[0035] (2) Refrigeration effect of ZIF-4(Zn) at 180 MPa: Next, the pressure is raised to 180 MPa and the above process is repeated to obtain Figure 9 The data shown. Under the pressure cycle of 180MPa, T ad During pressurization, it reaches 15.8K, and during depressurization, it is -15.1K. Figure 8 Specific heat, calculated entropy change at 180 MPa is 426 J kg -1 K -1 This reflects the compressive cooling capability of ZIF-4(Zn).

[0036] (3) Durability of the refrigeration effect of ZIF-4(Zn): Next, the pressure cycle was repeated 100 times at a pressure of 100 MPa. After 100 cycles, Figure 10 The absolute value of the adiabatic temperature change of the sample |T ad During the decompression process, the temperature slightly decreased from the initial 9.7 K to 9.5 K. This indicates that the compression cooling capacity of ZIF-4(Zn) is still stable under high cycle fatigue.

[0037] (4) Refrigeration cycle of ZIF-4(Zn): The refrigerant ZIF-4(Zn) is loaded into Figure 1 In the cavity of the compression refrigeration cycle system shown, under adiabatic conditions, a pressure of 160 MPa is applied to a ZIF-4 (Zn) refrigerant having a temperature of 298 K and a pressure of 0.1 MPa, thereby raising its temperature to 308 K. Maintaining the pressure at 160 MPa, the ZIF-4 (Zn) refrigerant is brought into contact with the environment through a heat exchange fluid, transferring heat to the environment so that the temperature reaches equilibrium with the environment and is cooled to 298 K. Under adiabatic conditions, the pressure of the ZIF-4 (Zn) refrigerant is reduced to 0.1 MPa, thereby reducing its temperature to 288 K. The ZIF-4 (Zn) refrigerant is brought into contact with a load, whereby the refrigerant absorbs heat from the load to achieve the purpose of cooling the load.

Claims

1. Application of a zeolite imidazolate framework material in solid-state refrigeration, characterized in that: The zeolite imidazolate skeleton structure material is used as a refrigerant in solid-state refrigeration, and refrigeration is achieved based on the solid-state phase change thermal effect.

2. The use of the zeolite imidazolate framework material according to claim 1 in solid-state refrigeration, characterized in that: The zeolite imidazolate framework structure material belongs to a metal organic framework material, which undergoes a structural phase transition involving a change in the pore size within the framework under hydrostatic pressure.

3. The use of the zeolite imidazolate framework material according to claim 1 in solid-state refrigeration, characterized in that: The structure of the zeolite imidazolate skeleton structure material at room temperature and pressure is a porous three-dimensional network framework formed by bonding a metal center and an imidazole linker. Hydrostatic pressure can drive it to undergo a structural phase change and generate a thermal effect, thereby achieving solid-state refrigeration.

4. The use of the zeolite imidazolate framework material according to claim 1 in solid-state refrigeration, characterized in that: The zeolite imidazolate framework material is ZIF-1(M), ZIF-2(M), ZIF-4(M), ZIF-5(M), ZIF-7(M), ZIF-8(M), ZIF-9(M), ZIF-10(M), ZIF-11(M), ZIF-12(M), ZIF-14(M), ZIF-20(M), ZIF-23(M), ZIF-60(M), ZIF-61(M), ZIF-62(M), ZIF-64(M), ZIF-6 ... One or more of ZIF-67(M), ZIF-68(M), ZIF-69(M), ZIF-70(M), ZIF-71(M), ZIF-72(M), ZIF-73(M), ZIF-74(M), ZIF-75(M), ZIF-77(M), ZIF-78(M), ZIF-90(M), ZIF-95(M), ZIF-100(M), ZIF-224(M), and ZIF-268(M), wherein M is one or more of metal centers such as Zn and Co.

5. The use of the zeolite imidazolate framework material according to claim 4 in solid-state refrigeration, characterized in that: When ZIF-4(Zn) is used as a refrigerant, the preparation process employed is a solvothermal method. Specifically, Zn(NO₃)₂·6H₂O and imidazole at a molar ratio between 2.5:1 and 3.5:1 are dissolved in N,N-dimethylformamide (DNDF) with a Zn(NO₃)₂·6H₂O concentration ranging from 0.02 to 0.3 mol / L. The solution is then reacted in a sealed container at a temperature of 343 to 423 K for 12 to 120 hours. The resulting solid product, ZIF-4(Zn), contains residual solvent. The solid is then washed with DNDF, then rinsed with dichloromethane, and finally dried to yield the solvent-free ZIF-4(Zn) refrigerant.

6. Use of the zeolite imidazolate framework material according to claim 3 or 4 in solid-state refrigeration, characterized in that: When the ZIF-4 (Zn) is used as a refrigerant, the applied driving pressure is 70-600 MPa, and the refrigeration range is 140-298K. 、 7. Use of the zeolite imidazole framework material according to claim 3 or 4 in solid-state refrigeration, characterized in that: When ZIF-4(Zn) is used as a refrigerant, the adiabatic temperature changes of the ZIF-4(Zn) phase transition are -9.6K and -15.1K, respectively, when a hydrostatic pressure of 100MPa and 180MPa is applied at 298K, and the corresponding isothermal entropy changes are 268J kg -1 K -1 and 426J kg -1 K -1 ; and the adiabatic temperature change value of ZIF-4(Zn) is stable in high-pressure cycles.

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