Two-dimensional copper chloride perovskite reversible phase change material and preparation method thereof

Abstract

The invention relates to a thermochromic material, in particular to a two-dimensional copper chloride perovskite reversible phase change material and a preparation method thereof. The preparation method of the two-dimensional copper chloride perovskite reversible phase change material comprises the following steps: S1, putting 2-fluoroethylamine into a reaction container, adding concentrated hydrochloric acid, and fully dissolving; step S2, taking anhydrous copper chloride, adding the anhydrous copper chloride into the clarified solution obtained in the step S1, heating the solution to boiling after the solution becomes turbid, and stopping heating after the solution is recovered to be clarified; the feeding molar ratio of the 2-fluoroethylamine to the anhydrous copper chloride is 1: 1; and S3, the solution obtained after the reaction is subjected to standing, and after precipitation, the [2-FCH2CH2NH3] 2CuCl4 material is obtained. The two-dimensional copper chloride perovskite reversible phase-change material with the phase-change temperature of 351 K is prepared by assembling anhydrous copper chloride anions and 2-fluoroethylamine cations through a hydrogen-fluorine substitution strategy, and the two-dimensional copper chloride perovskite reversible phase-change material is a two-dimensional copper-based perovskite phase-change material of which the known phase-change conversion temperature belongs to a lower class at present. The method is simple in process, low in cost, energy-saving and environment-friendly, and enriches the family of thermochromic materials.

Description

Technical Field

[0001] The present invention relates to a thermochromic material, in particular to a two-dimensional copper chloride perovskite reversible phase change material and a preparation method thereof. Background Art

[0002] Thermochromic materials have become increasingly important due to their great potential in applications such as intelligent photovoltaic windows and temperature sensors. Currently, most common thermochromic materials are two-dimensional lead-based perovskite materials. However, due to the great toxicity of lead elements to the human body and the environment, the leaked lead elements can cause harm to many organs such as the human nervous system, blood system, and kidneys. Therefore, there is an urgent need to develop new thermochromic materials to replace two-dimensional lead-based perovskite materials. Currently, the research on lead-free two-dimensional perovskite materials (such as Sn 2+ , Ge 2+ , Ba 2+ , Cu 2+ , and Sr 2+ , etc.) has gradually emerged. Research shows that although Sn 2+ and Ge 2+ are widely used in the preparation of lead-free perovskite single crystals due to their efficient charge transport and lower toxicity than Pb²⁺, Sn- and Ge-based perovskites face the risk of failure due to easy oxidation to Sn 4+ and Ge 4+ . Among them, copper-based perovskites have become potential materials to replace lead-based perovskites due to their non-toxicity, stability, and significant cost-effectiveness.

[0003] Two-dimensional hybrid perovskite materials have attracted much attention in the fields of photovoltaics, optoelectronics, and photocatalysis in recent years due to their excellent optoelectronic properties. The main two-dimensional hybrid perovskite is the RP-phase perovskite, that is, organic cations and inorganic perovskite layers are alternately arranged.

[0004] Multi-stimulus responsive hybrid perovskite materials can trigger reversible physical property changes, such as color transitions, fluorescence, phase transitions, etc., through external stimuli such as sound, light, electricity, and temperature. These excellent properties enable their applications in many fields such as aerospace, architectural design, and energy storage. Among them, thermochromic smart windows are particularly attracting attention, which can effectively reduce building energy consumption and play a huge role in energy conservation and environmental protection. Currently, there are few reports on two-dimensional thermochromic response switching materials, and even fewer reports on lead-free materials. In addition, a single response behavior or an extremely high response temperature is difficult to meet the various requirements of smart electronic devices. For example, (2-chloroethylammonium)2CuCl4 exhibits reversible thermochromic behavior between yellow and light red at a thermochromic temperature of 393K, and the thermochromic temperature of (N-phenylethylenediamine)CuCl4 is 383K. The too-high thermochromic temperature interferes with the application of the material. The internal temperature of some smart electronic devices cannot reach the phase transition temperature. When the phase transition temperature is reached, the internal part of the device may be damaged, and even the device may be scrapped. At the same time, some thermochromic materials can only change color through temperature stimulation and are insensitive to other external stimuli. These two factors jointly limit the application of thermochromic materials, and new thermochromic materials need to be developed. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a two-dimensional copper chloride perovskite reversible phase change material [2-FCH2CH2NH3]2CuCl4, enriching the family of thermochromic materials; The preparation method of the two-dimensional copper chloride perovskite reversible phase change material of the present invention uses a hydrofluoro substitution strategy to assemble an anhydrous copper chloride anion and a 2-fluoroethylamine cation to prepare a two-dimensional copper chloride perovskite reversible phase change material with a phase transition temperature of 351K, which is a two-dimensional copper-based perovskite phase change material with a relatively low phase transition temperature known so far.

[0006] The technical solution adopted by the present invention is as follows: A two-dimensional copper chloride perovskite reversible phase change material is prepared by assembling an anhydrous copper chloride anion and a 2-fluoroethylamine cation, and its molecular formula is as follows: [2-FCH2CH2NH3]2CuCl4.

[0007] The preparation method of the two-dimensional copper chloride perovskite reversible phase change material includes the following steps: Step S1, place 2-fluoroethylamine in a reaction vessel, and add concentrated hydrochloric acid to the reaction vessel to fully dissolve 2-fluoroethylamine; Step S2: Weigh anhydrous copper chloride and add it to the clarified solution obtained in Step S1. After the solution becomes turbid, heat it to boiling. After the solution becomes clear again, stop heating. The molar feeding ratio of 2-fluoroethylamine to anhydrous copper chloride is 1:1. Step S3: Let the reacted solution stand still. After precipitation, the [2-FCH2CH2NH3]2CuCl4 material is obtained.

[0008] In the preparation method of the two-dimensional copper chloride perovskite reversible phase change material, in Step S1, weigh 2-fluoroethylamine (5 mmol, 0.498 g) and place it in a 50 ml beaker. Take 20 ml of concentrated hydrochloric acid and add it to the beaker to fully dissolve the solid. Step S2: Weigh anhydrous copper chloride (5 mmol, 0.672 g) and add it to the clarified solution obtained in the first step. After the solution becomes turbid, heat it to boiling. After the solution becomes clear again, stop heating. Step S3: Place the reacted solution on a hot stage at 40 °C and volatilize it in the open air. The obtained solid product is the two-dimensional copper chloride perovskite reversible phase change material [2-FCH2CH2NH3]2CuCl4 material.

[0009] Advantages of the invention: 1. The present invention designs the material by modifying organic cations, and proposes a two-dimensional copper chloride perovskite reversible phase change material, enriching the family of materials with multiple stimulus-responsive thermochromic switching characteristics. This material can be applied in the fields of new energy, energy storage, photovoltaic materials, heat storage, and intelligent buildings, etc., and has broad application prospects.

[0010] 2. The preparation method of the two-dimensional copper chloride perovskite reversible phase change material of the present invention has the characteristics of high yield and high purity. Through the hydrofluoro substitution strategy, the two-dimensional copper chloride perovskite reversible phase change material [2-FCH2CH2NH3]2CuCl4 is prepared by assembling the anions of anhydrous copper chloride and the cations of 2-fluoroethylamine.

[0011] 3. The preparation method of the two-dimensional copper chloride perovskite reversible phase change material of the present invention has a simple synthesis process, is easy to process, energy-saving and environment-friendly. By modifying organic cations to design the material, the reaction solution is crystallized by the evaporation solvent method. The preparation process is simple, highly operable, and has low energy consumption, achieving the purpose of reducing costs and energy conservation and environmental protection.

[0012] 4. The preparation method of the two-dimensional copper chloride perovskite reversible phase change material of the present invention regulates the occurrence of phase change by using the hydrofluoro substitution strategy. On the basis of the parent body without phase change, a two-dimensional lead-free thermochromic perovskite material with multiple stimulus-responsive thermochromic switching characteristics is designed, verifying the effectiveness of the hydrofluoro substitution strategy. The phase change transition temperature is lower than that of similar products, and it has broad application prospects in the field of smart wear. Description of the drawings

[0013] Figure 1 Shown is the crystal structure of [2-FCH2CH2NH3]2CuCl4 at 300 K; Figure 2 Shown is the crystal structure of [2-FCH2CH2NH3]2CuCl4 at 353 K; Figure 3 Shown is the DSC heating-cooling schematic diagram of [2-FCH2CH2NH3]2CuCl4. Detailed implementation manners

[0014] To make the technical concept and advantages of the present invention for achieving its invention purpose clearer and more understandable, the technical solution of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the following embodiments are only for explaining and illustrating the preferred implementation manners of the present invention, and should not be regarded as and do not constitute a limitation to the scope of patent protection required by the present invention.

[0015] The present invention provides a two-dimensional copper chloride perovskite reversible phase change material, which is prepared by assembling an anhydrous copper chloride anion and a 2-fluoroethylamine cation, and its molecular formula is as follows: [2-FCH2CH2NH3]2CuCl4.

[0016] The preparation method of the two-dimensional copper chloride perovskite reversible phase change material includes the following steps: Step S1, weigh 2-fluoroethylamine (5 mmol, 0.498 g) and place it in a 50 ml beaker, take 20 ml of concentrated hydrochloric acid and add it to the beaker to fully dissolve the solid; Step S2, weigh anhydrous copper chloride (5 mmol, 0.672 g), add it to the clarified solution in the first step, heat the solution to boiling after it becomes turbid, and stop heating after the solution returns to clarity; Step S3, place the reaction solution on a hot stage at 40 °C and volatilize it open to the air to obtain the product [2-FCH2CH2NH3]2CuCl4 material.

[0017] As Figure 1 Shown is the crystal structure of the two-dimensional copper chloride perovskite reversible phase change material of [2-FCH2CH2NH3]2CuCl4 obtained; Figure 2 Shown is the crystal structure of [2-FCH2CH2NH3]2CuCl4 at 353 K; In the low-temperature phase at 300 K, (2-FEA)2CuCl4 crystallizes in the monoclinic P 21 / C space group, and the unit cell parameters are a =10.8712(10) Å, b =7.6440(7) Å, c= 7.1837(8) Å, Z = 2, β = 104.46(1)° and V = 578.05(11) Å 3 。

[0018] The crystal structure contains inorganic [CuCl4] 2- layers of corner-sharing CuCl6 octahedra, separated by organic [2-FEA] + bilayers, showing a two-dimensional organic-inorganic A2BX4 perovskite structure, where [2-FEA] + , Cu 2+ and Cl - ions correspond to the A, B, and X sites, respectively. Thus, (2-FEA)2CuCl4 can be regarded as a two-dimensional halide perovskite. The distances of the Cu-Cl bonds are 2.2902(18), 2.305(2), and 2.969(2) Å and the adjacent Cl-Cu-Cl angles are 89.15(2)° - 90.85(2)°, where two Cu-Cl bond lengths (2.969(2) Å) are significantly longer than the other four (2.2902(18) Å, 2.305(2) Å), which causes Jahn-Teller distortion of the CuCl6 octahedra. In addition, the [2-FEA] + cations between the layers are orientationally ordered, with the C-N bonds arranged along a single direction, and the polar [2-FEA] + cations show an orientational arrangement along the c-axis. All the C-N groups of the [2-FEA] + cations are arranged along the c-axis, and the nitrogen and hydrogen atoms in the organic framework have weak intermolecular interactions with the chlorine atoms in the inorganic layered framework.

[0019] In the high-temperature phase at 358 K, the crystal structure of (2-FEA)2CuCl4 undergoes a transformation, and the space group becomes Cmce , and the unit cell parameters are a = 7.3757(7) Å, b = 21.394(3) Å, c = 7.5343(6) Å, Z = 4, β = 90° and V = 1188.9(2) Å 3 。In the crystal structure, the organic component becomes severely disordered. Due to the organic cation [2-FEA] + occupying the symmetry mirror plane, the [2-FEA] + cations exhibit 2-fold orientational disorder, and the C-N bonds have 2 orientations.

[0020] Figure 3The figure shows the DSC heating-cooling schematic diagram of the two-dimensional copper chloride perovskite reversible phase change material [2-FCH2CH2NH3]CuCl4. Through DSC testing, it was found that [2-FCH2CH2NH3]2CuCl4 exhibited obvious endothermic / exothermic behavior near 351K and 340K during heating and cooling processes respectively, and the thermal hysteresis was about 11K. The occurrence of the phase change of [2-FCH2CH2NH3]2CuCl4 was verified, indicating that it can achieve phase transformation under the stimulation of external temperature change. The phase change temperature was determined to be 351K, belonging to a two-dimensional copper-based perovskite phase change material with a relatively low phase change transformation temperature among the currently known ones.

[0021] The preparation method of the two-dimensional copper chloride perovskite reversible phase change material of the present invention uses a hydrofluoro substitution strategy to assemble the anhydrous copper chloride anion with the 2-fluoroethylamine cation to prepare the two-dimensional copper chloride perovskite reversible phase change material [2-FCH2CH2NH3]CuCl4, enriching the family of materials with multiple stimulus-responsive thermochromic switch characteristics. This material can be applied in the fields of new energy, energy storage, photovoltaic materials, thermal storage, and intelligent buildings, etc., and has broad application prospects.

[0022] The preparation method of the two-dimensional copper chloride perovskite reversible phase change material of the present invention designs the material by modifying the organic cation. The reaction solution is crystallized by the evaporation solvent method. The preparation process is simple, highly operable, low in energy consumption, low in cost, energy-saving and environment-friendly.

[0023] The preparation method of the two-dimensional copper chloride perovskite reversible phase change material of the present invention designs a two-dimensional lead-free thermochromic perovskite material with multiple stimulus-responsive thermochromic switch characteristics on the basis of a parent body without phase change, verifies the effectiveness of the hydrofluoro substitution strategy, and the phase change transformation temperature is lower than that of similar products, and has broad application prospects in the field of smart wear.

Claims

1. A two-dimensional copper chloride perovskite reversible phase change material, characterized in that: The molecular formula of the reversible phase change material is as follows: [2-FCH2CH2NH3]2CuCl4.

2. The two-dimensional copper chloride perovskite reversible phase change material according to claim 1, characterized in that: The reversible phase change material is prepared by assembling anhydrous copper chloride anions and 2-fluoroethylamine cations.

3. The method for preparing a two-dimensional copper chloride perovskite reversible phase change material according to claim 1 or 2, characterized in that the process include: Step S1, placing 2-fluoroethylamine in a reaction container, adding concentrated hydrochloric acid to fully dissolve the 2-fluoroethylamine; Step S2, taking anhydrous copper chloride and adding it to the clear solution of step S1, heating the solution to boiling after it becomes turbid, and stopping heating after the solution becomes clear again; the molar ratio of 2-fluoroethylamine to anhydrous copper chloride is 1:1; Step S3, allowing the solution after the reaction to stand, and obtaining the [2-FCH2CH2NH3]2CuCl4 material after precipitation.

4. The method for preparing a two-dimensional copper chloride perovskite reversible phase change material according to claim 3, characterized in that: Step S1, weigh 2-fluoroethylamine (5 mmol, 0.498 g) and place it in a 50 ml beaker, add 20 ml of concentrated hydrochloric acid to the beaker to fully dissolve the solid; Step S2, weigh anhydrous copper chloride (5 mmol, 0.672 g), add it to the clear solution of the first step, heat it to boiling after the solution becomes turbid, and stop heating after the solution becomes clear again; Step S3, placing the solution after the reaction on a hot plate at 40°C for open volatilization, and the obtained solid product is a two-dimensional copper chloride perovskite reversible phase change material [2-FCH2CH2NH3]2CuCl4 material.

Images