Co-based thermochromic coordination polymer gel and preparation method thereof

Abstract

The invention discloses a Co-based thermochromic coordination polymer gel and a preparation method thereof, relates to the technical field of thermochromic functional polymers, and aims to solve the problems that an existing thermochromic material cannot realize simultaneous response of temperature and humidity, and the preparation method often needs to adopt toxic reagents or is complex in preparation process, so that the cost is low. And the method is not suitable for large-scale production. The method comprises the following steps: (1) adding cobalt halide serving as a cobalt source into an aqueous solution of a hydroxyl aqueous polymer, and fully dispersing to obtain a mixed solution; and (2) evaporating the mixed solution to dryness to obtain the Co-based thermochromic coordination polymer gel. The thermal transition temperature of the Co-based thermochromic coordination polymer gel is adjustable within 10-50 DEG C, the humidity is adjustable within 20%-100% RH, and simultaneous response of the temperature and the humidity is achieved. The Co-based thermochromic coordination polymer gel disclosed by the invention can be used for preparing thermochromic glass.

Description

Technical Field

[0001] The present invention relates to the technical field of thermochromic functional polymers, in particular to a Co-based thermochromic coordination polymer gel and a preparation method thereof. Background Art

[0002] As the most critical heat exchange component of a building's exterior envelope, windows are limited by their fixed ability to regulate light and heat. In summer, they struggle to effectively block solar radiation, leading to increased cooling loads; in winter, their insulation capacity is insufficient, increasing heating energy consumption. Research indicates that window-related heat exchange can account for approximately 40%-50% of a building's total cooling and heating loads. Currently, common energy-saving measures, such as low-emissivity glass, are mostly static in design and struggle to adapt to dynamic climate changes. Temperature-responsive smart window materials can dynamically regulate solar transmittance, blocking heat in summer and allowing for optimal daylight in winter, significantly improving energy efficiency and indoor thermal comfort. Developing such highly stable and high-performance dimming materials is a key step in promoting the development of green buildings.

[0003] Thermochromic technology has attracted widespread attention due to its zero energy consumption, zero carbon emissions, and ability to adaptively change its transmittance in response to changes in ambient temperature. Smart windows utilizing thermochromism can adaptively regulate the amount of solar radiation entering a room based on changes in ambient temperature, enabling adaptive regulation of indoor temperature and thus reducing building cooling and heating energy consumption. Currently, materials used in thermochromic technology primarily focus on perovskites, hydrogels, vanadium dioxide, and transition metal ion complexes. Perovskite materials have extremely poor stability and are susceptible to degradation in humid, hot environments and ultraviolet light. They also commonly contain lead, posing a serious environmental pollution risk. Hydrogel materials rely on moisture absorption and desorption to adjust optical properties, but they have low mechanical strength and are prone to cracking and failure, making them difficult to maintain in closed environments for long periods of time. While vanadium dioxide exhibits significant infrared control capabilities, its phase transition temperature is far above ambient temperature, requiring additional energy to trigger, and its poor light transmittance can compromise building lighting.

[0004] Thermochromic transition metal ion complexes are used in smart windows. The essence of this is that temperature stimulates the adsorption and desorption of guest water, inducing changes in the coordination configuration of the central ion to achieve changes in the material's transmittance: the prior art with document number CN118440228A discloses a Ni 2+Thermochromic organic transition metal coordination polymers, which are coordinated by a central ion, oxygen-containing functional groups (=O, -OH) in the polymer matrix, halogen ions, and guest H2O, cannot respond to both temperature and humidity simultaneously, and their phase transition temperature is relatively high. CN108300002A discloses a VO2-based organic polymer thermochromic material in which a liquid-phase thermochromic material containing Fe(II), Co(II), Ni(II), or Cu(II)-based ionic liquids is uniformly dispersed. This improves the material's dimming performance while also enhancing its thermal and chemical stability. However, the VO2 used is toxic, the preparation process is relatively complex, and its optical properties are poor.

[0005] The prior art of document No. CN110305173A discloses a method based on [Co(DMBPY) 0.5 (L)]·H2O containing tricarboxylic acid Co(II) thermochromic complex, the prior art of CN101768433B discloses a thermochromic complex with Co as the component x [R(PO3) m ] y (H2O) z (wherein R is an organic group) and a novel thermochromic material of an organic cobalt phosphonate coordination compound. Both adopt the hydrothermal synthesis method, which has high process requirements and is not suitable for large-scale production. The prior art with document number CN116655708A discloses a Co / Zn(NCS)2(pyz)2 doped with Co(NCS)2 and Zn(NCS)2, which has a humidity-sensitive response to humidity. The thermochromic material disclosed in the prior art is liquid, prone to leakage problems, and cannot respond to temperature and humidity at the same time. The prior art with document number CN115260688A discloses a thermochromic composite film with Co-BTC as a metal organic framework composite polymer. The method disclosed in the prior art requires the use of volatile toxic reagents such as DMF for dissolution. The prior art with document number CN108299515A discloses a method based on [Co2(HL)(H2O)5]·3.5H2O (wherein HL 4- C 23 H 10 O 12 ), but the synthesis method requires a long time and the preparation process is complicated. Summary of the Invention

[0006] The technical problems to be solved by the present invention are:

[0007] Existing thermochromic materials cannot achieve simultaneous response to temperature and humidity, and their preparation methods often require the use of toxic reagents or complex preparation processes, making them unsuitable for large-scale production.

[0008] The present invention is to solve the above technical problems using the following technical solutions:

[0009] The present invention provides a method for preparing a Co-based thermochromic coordination polymer gel, which is characterized by comprising the following steps:

[0010] (1) adding a cobalt halide as a cobalt source to an aqueous solution of a hydroxyl aqueous polymer and fully dispersing the mixture to obtain a mixed solution;

[0011] (2) The mixed solution is evaporated to dryness to obtain a Co-based thermochromic coordination polymer gel.

[0012] Furthermore, the cobalt halide in step (1) is one or more of CoCl2, CoBr2, CoCl2·nH2O or CoBr2·nH2O.

[0013] Furthermore, the hydroxyl-containing aqueous polymer in step (1) is one or more of polyvinyl alcohol, gelatin or polyethylene glycol.

[0014] Furthermore, the mass ratio of the cobalt halide to the hydroxyl-containing aqueous polymer in step (1) is 1:(0.5-20).

[0015] Furthermore, step (1) further comprises adding a cobalt halide and a hygroscopic salt to the aqueous solution of the hydroxyl aqueous polymer to obtain a mixed solution, wherein the hygroscopic salt is one or more of LiCl, MgCl2, LiBr or MgBr2.

[0016] Furthermore, in step (1), the mass ratio of the cobalt halide to the hygroscopic salt is 1:(0.1-0.8).

[0017] Furthermore, the mass fraction of the aqueous solution of the hydroxyl-containing aqueous polymer in step (1) is 5% to 20%.

[0018] Furthermore, the conditions for sufficient dispersion in step (1) are stirring at 200-500 rpm for 0.5-10 h or ultrasonic dispersion for 5-120 min.

[0019] The present invention provides a Co-based thermochromic coordination polymer gel, which is prepared by the method described in any one of the above technical solutions.

[0020] Furthermore, the thermochromic transition temperature of the Co-based thermochromic coordination polymer gel is adjustable in the range of 10 to 50° C., and the humidity response range is 20% to 100% RH.

[0021] The present invention also provides a thermochromic glass comprising the Co-based thermochromic coordination polymer gel described in any one of the above technical solutions.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The Co-based thermochromic coordination polymer gel of the present invention is Co 2+ The material is combined with the polymer matrix by using halogen ions, hydroxyl functional groups in the polymer, and guest H2O for coordinated coordination. The reversible adsorption and desorption of guest H2O induces the change of the coordination configuration of the central ion. The material absorbs water at low temperature to make Co 2+ It exhibits a hexacoordinated octahedral configuration with water and a four-coordinated tetrahedral configuration upon high-temperature dehydration, achieving the material's ultra-high optical contrast. The Co-based thermochromic coordination polymer gel of the present invention has an adjustable thermal transition temperature between 10 and 50°C. It exhibits a pale pink or transparent state at low temperatures and a blue state at high temperatures, with a distinct color change. It also exhibits high light transmittance at low temperatures, excellent thermal insulation at high temperatures, and strong solar regulation capabilities. It can also respond simultaneously to both temperature and humidity.

[0024] The preparation method of the Co-based thermochromic coordination polymer gel of the present invention adopts a hydroxyl-containing aqueous polymer, does not require toxic reagents for dissolution, and adopts a full liquid phase synthesis method, which has a simpler preparation process, shortens the synthesis time, and is easier to mass-produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Graph showing the corresponding time periods of coloration (50°C) and fading (20°C) of the Co-based thermochromic coordination polymer gel in an embodiment of the present invention;

[0026] Figure 2 FTIR spectrum of the Co-based thermochromic coordination polymer gel according to the embodiment of the present invention;

[0027] Figure 3 The electron spin resonance spectra (ESR) of the Co-based thermochromic coordination polymer gel in the embodiment of the present invention at 70° C. and 20° C. are shown;

[0028] Figure 4 Graph showing contact angle test data of the Co-based thermochromic coordination polymer gel in an embodiment of the present invention;

[0029] Figure 5 (a) is the temperature-dependent UV-visible transmission spectrum of the Co-based thermochromic coordination polymer gel in an embodiment of the present invention; Figure 5 (b) shows the temperature-transmittance hysteresis curve of coloration-fading; the red line is the temperature-transmittance change curve with increasing temperature, and the blue curve is the temperature-transmittance change curve with decreasing temperature;

[0030] Figure 6(a) is the temperature-dependent UV-visible transmission spectrum of the Co-based thermochromic coordination polymer gel in an embodiment of the present invention; Figure 6 (b) shows the temperature-transmittance hysteresis curve of coloration-fading; the red line is the temperature-transmittance change curve with increasing temperature, and the blue curve is the temperature-transmittance change curve with decreasing temperature;

[0031] Figure 7 (a) is the temperature-dependent UV-visible transmission spectrum of the Co-based thermochromic coordination polymer gel in an embodiment of the present invention; Figure 7 (b) shows the temperature-transmittance hysteresis curve of coloration-fading; the red line is the temperature-transmittance change curve with increasing temperature, and the blue curve is the temperature-transmittance change curve with decreasing temperature;

[0032] Figure 8 Graph showing transmittance spectra of the Co-based thermochromic coordination polymer gel at different humidity levels in an embodiment of the present invention;

[0033] Figure 9 This is a test of the thermal insulation performance of the thermochromic glass (CCP Glass) and ordinary double-glazing (Normal Glass) in the embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the present invention, exemplary embodiments or examples of the present invention will be described below with reference to the accompanying drawings. Obviously, the described embodiments or examples are only some of the embodiments or examples of the present invention, and not all of them. Based on the embodiments or examples of the present invention, all other embodiments or examples obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] Example 1

[0037] (1) Add 1 g of CoCl2·6H2O to 20 ml of 10 wt% polyvinyl alcohol (PVA) solution and stir at 400 rpm for 0.5 h at room temperature to obtain a mixed solution;

[0038] (2) The mixed solution was evaporated to dryness to obtain a Co-based thermochromic coordination polymer gel film. The optical properties of the gel film were tested and calculated, and the results are shown in Table 1.

[0039] Table 1

[0040]

[0041] The Co-based thermochromic coordination polymer gel film obtained in this example was subjected to temperature-dependent Fourier transform infrared spectroscopy (FTIR) testing. Figure 2 As shown in the figure, the vibration peak of the material in the wavenumber range of 3000-3500 cm-1 continues to weaken with the increase of temperature. This wavenumber range is the vibration peak of hydroxyl (-OH) in water, indicating that the color change mechanism of the material is the reversible adsorption and desorption of guest water.

[0042] The Co-based thermochromic coordination polymer gel film of this embodiment was subjected to electron spin resonance spectroscopy (ESR) tests at high temperature (70°C) and low temperature (20°C). Figure 3 As shown in the figure, the electron spin of Co in the material is in a highly symmetric state at low temperatures, that is, the octahedral coordination structure of Co and water; at high temperatures, the electron spin is in an asymmetric state, that is, the tetrahedral coordination structure of Co and halogen atoms.

[0043] The Co-based thermochromic coordination polymer gel film of this embodiment was subjected to temperature-dependent UV-visible transmission spectroscopy. Figure 5 As shown in Figure 1, under a humidity of 65% RH, when the temperature of the material in Figure (a) rises, the transmittance of the spectrum in the range of 600-750nm shows obvious changes, indicating that the material has thermochromic properties. The transmittance of the material in Figure (b) can be effectively colored and faded in a low-temperature-high-temperature-low-temperature cycle, with a heating phase transition temperature of 25.6°C and a cooling phase transition temperature of 18.2°C.

[0044] Example 2

[0045] (1) Add 2 g of CoCl2·6H2O to 20 ml of 10 wt% polyvinyl alcohol (PVA) solution and stir at 400 rpm for 0.5 h at room temperature to obtain a mixed solution;

[0046] (2) The mixed solution was evaporated to dryness to obtain a Co-based thermochromic coordination polymer gel film. The optical properties of the gel film were tested and calculated, and the results are shown in Table 2.

[0047] Table 2

[0048]

[0049] Example 3

[0050] (1) Weigh 1 g of CoCl2·6H2O and 0.2 g of LiCl, add the CoCl2·6H2O and LiCl to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically disperse for 10 min to obtain a mixed solution;

[0051] (2) The mixed solution was evaporated to dryness to obtain a Co-based thermochromic coordination polymer gel film. The optical properties of the gel film were tested and calculated, and the results are shown in Table 3.

[0052] Table 3

[0053]

[0054] The Co-based thermochromic coordination polymer gel film of this embodiment was subjected to temperature-dependent UV-visible transmission spectroscopy. Figure 6 As shown in Figure (a), when the temperature rises, the material has an obvious transmittance change in the 600-750nm range, indicating that the material has thermochromic properties. The transmittance of the material in Figure (b) can be effectively colored and faded in the low-temperature-high-temperature-low-temperature cycle. The heating phase transition temperature of the material is 33.4℃, and the cooling phase transition temperature of the material is 15℃.

[0055] Example 4

[0056] The difference between this embodiment and embodiment 3 is that:

[0057] In step (1), 1 g of CoCl2·6H2O and 0.1 g of LiCl were weighed, and the CoCl2·6H2O and LiCl were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed for 10 min to obtain a mixed solution.

[0058] Example 5

[0059] The difference between this embodiment and embodiment 3 is that:

[0060] In step (1), 1 g of CoCl2·6H2O and 0.4 g of LiCl were weighed, and the CoCl2·6H2O and LiCl were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed for 10 min to obtain a mixed solution.

[0061] Example 6

[0062] The difference between this embodiment and embodiment 3 is that:

[0063] In step (1), 1 g of CoCl2·6H2O and 0.6 g of LiCl were weighed, and the CoCl2·6H2O and LiCl were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed for 10 min to obtain a mixed solution.

[0064] Example 7

[0065] The difference between this embodiment and embodiment 3 is that:

[0066] In step (1), 1 g of CoCl2·6H2O and 0.8 g of LiCl were weighed, and the CoCl2·6H2O and LiCl were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed for 10 min to obtain a mixed solution.

[0067] The contact angle test was conducted on the Co-based thermochromic coordination polymer gel films of Examples 1, 3 to 7. Figure 4 As shown in the figure, the mass ratios of CoCl2·6H2O to LiCl corresponding to L0 to L5 are 1:0, 1:0.1, 1:0.2, 1:0.4, 1:0.6, and 1:0.8, respectively. It can be seen that the contact angle of the material does not change much after LiCl doping, and is always below 50° (hydrophilic). This indicates that salt doping does not change the hydrophilicity of the material, and the material remains hydrophilic.

[0068] Example 8

[0069] (1) Weigh 1 g of CoCl2·6H2O and 0.6 g of MgCl2, add the CoCl2·6H2O and MgCl2 into 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and disperse them by ultrasonication at room temperature for 30 min to obtain a mixed solution.

[0070] (2) The mixed solution was evaporated to dryness to obtain a Co-based thermochromic coordination polymer gel film. The optical properties of the gel film were tested and calculated, and the results are shown in Table 4.

[0071] Table 4

[0072]

[0073] The Co-based thermochromic coordination polymer gel film of this embodiment was subjected to temperature-dependent UV-visible transmission spectroscopy. Figure 7 As shown, under a humidity of 65% RH, when the temperature of the material in Figure (a) rises, the spectrum has an obvious transmittance change in the range of 600-750nm, indicating that the material has thermochromic properties. The transmittance of the material in Figure (b) can be effectively colored and faded in a low-temperature-high-temperature-low-temperature cycle. The heating phase transition temperature of the material is 31.2°C, and the cooling phase transition temperature of the material is 22°C.

[0074] The transmittance spectrum of the Co-based thermochromic coordination polymer gel film of this embodiment was tested at different humidity levels. Figure 8 As shown in the figure, at 20°C, the material's response humidity range is 20-100% RH, and the material can completely fade at 60% RH and above. Therefore, the transmittance of the material remains unchanged when the humidity is above 60% RH, and is the same as the transmittance at 60% RH; and the material has corresponding transmittance at different humidity levels, indicating that the material has good humidity response characteristics.

[0075] The Co-based thermochromic coordination polymer gel film of this embodiment was coated on one side of a double-layer glass and the film was encapsulated in the double-layer glass to obtain thermochromic glass (CCP Glass). The heat insulation performance of the thermochromic glass (CCP Glass) and ordinary double-layer glass (Normal Glass) was tested. Figure 9 As shown in Figure (a), it can be seen that thermochromic glass can effectively reduce the direct sunlight temperature by 6°C; Figure (b) shows that thermochromic glass can effectively reduce the direct sunlight light power; Figure (c) shows that thermochromic glass can reduce the transmitted radiation energy by 39% in the tinted state.

[0076] Example 9

[0077] The difference between this embodiment and embodiment 3 is that:

[0078] In step (1), 1 g of CoCl2·6H2O and 0.8 g of LiCl were weighed, and the CoCl2·6H2O and LiCl were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed for 10 min to obtain a mixed solution.

[0079] like Figure 1 As shown, it shows that the material can be colored and faded at 80% RH, with a coloring time of 15 minutes and a fading time of 22 minutes.

[0080] Example 10

[0081] The difference between this embodiment and embodiment 8 is that:

[0082] In step (1), 1 g of CoCl2·6H2O and 0.8 g of MgCl2 were weighed, and the CoCl2·6H2O and MgCl2 were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed at room temperature for 30 min to obtain a mixed solution.

[0083] The optical properties of the gel film were tested and calculated, and the results are shown in Table 5.

[0084] Table 5

[0085]

[0086] Example 11

[0087] The difference between this embodiment and embodiment 8 is that:

[0088] In step (1), 0.1 g of CoCl2·6H2O and 0.06 g of MgCl2 were weighed, and the CoCl2·6H2O and MgCl2 were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed at room temperature for 30 min to obtain a mixed solution.

[0089] The optical properties of the gel film were tested and calculated, and the results are shown in Table 6.

[0090] Table 6

[0091]

[0092] Example 12

[0093] The difference between this embodiment and embodiment 8 is that:

[0094] In step (1), 0.2 g of CoCl2·6H2O and 0.12 g of MgCl2 were weighed, and the CoCl2·6H2O and MgCl2 were added to 20 ml of a 10 wt% polyvinyl alcohol (PVA) solution, and ultrasonically dispersed at room temperature for 30 min to obtain a mixed solution.

[0095] The optical properties of the gel film were tested and calculated, and the results are shown in Table 7.

[0096] Table 7

[0097]

[0098] Although the present invention is disclosed as above, the scope of protection disclosed by the present invention is not limited thereto. Those skilled in the art of the present invention may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a Co-based thermochromic coordination polymer gel, characterized in that: The steps include: (1) adding a cobalt halide as a cobalt source to an aqueous solution of a hydroxyl aqueous polymer and fully dispersing the mixture to obtain a mixed solution; (2) The mixed solution is evaporated to dryness to obtain a Co-based thermochromic coordination polymer gel.

2. The method for preparing a Co-based thermochromic coordination polymer gel according to claim 1, wherein: The cobalt halide in step (1) is one or more of CoCl2, CoBr2, CoCl2·nH2O or CoBr2·nH2O.

3. The method for preparing the Co-based thermochromic coordination polymer gel according to claim 2, characterized in that: The hydroxyl-containing aqueous polymer in step (1) is one or more of polyvinyl alcohol, gelatin or polyethylene glycol.

4. The method for preparing a Co-based thermochromic coordination polymer gel according to claim 3, wherein: The mass ratio of the cobalt halide to the hydroxyl-containing aqueous polymer in step (1) is 1:(0.5-20).

5. The method for preparing the Co-based thermochromic coordination polymer gel according to claim 4, characterized in that: Step (1) further comprises adding a cobalt halide and a hygroscopic salt to an aqueous solution of a hydroxyl aqueous polymer, fully dispersing the mixture to obtain a mixed solution; the hygroscopic salt is one or more of LiCl, MgCl2, LiBr or MgBr2.

6. The method for preparing the Co-based thermochromic coordination polymer gel according to claim 5, characterized in that: The mass ratio of the cobalt halide to the hygroscopic salt in step (1) is 1: (0.1 to 0.8).

7. The method for preparing a Co-based thermochromic coordination polymer gel according to claim 6, wherein: The conditions for sufficient dispersion in step (1) are stirring at 200-500 rpm for 0.5-10 h or ultrasonic dispersion for 5-120 min.

8. A Co-based thermochromic coordination polymer gel, characterized in that: The Co-based thermochromic coordination polymer gel is prepared by the method described in any one of claims 1 to 7.

9. The Co-based thermochromic coordination polymer gel according to claim 8, characterized in that: The thermochromic transition temperature of the Co-based thermochromic coordination polymer gel is adjustable in the range of 10 to 50° C., and the humidity response range is 20% to 100% RH.

10. A thermochromic glass comprising the Co-based thermochromic coordination polymer gel according to any one of claims 8 to 9.

Images