Metal phthalocyanine-based conductive covalent organic framework material with high conjugation and preparation method of metal phthalocyanine-based conductive covalent organic framework material

Abstract

The invention provides a metal phthalocyanine-based conductive covalent organic framework material with high conjugation and a preparation method of the metal phthalocyanine-based conductive covalent organic framework material. The metal-containing phthalocyanine-based conductive covalent organic framework material with a highly conjugated topological structure is synthesized by selecting a phthalocyanine compound with a pi conjugated system and a metal-containing organic ligand as construction units, and the covalent organic framework material disclosed by the invention has relatively high specific surface area, high crystallinity, stability and high electron mobility; meanwhile, the conductivity of the covalent organic framework material is improved.

Description

Technical Field

[0001] This application relates to the technical field of conductive covalent organic framework materials, and particularly to a metal phthalocyanine-based conductive covalent organic framework material with high conjugation and a preparation method thereof. Background Art

[0002] Covalent organic frameworks are a class of porous materials with a periodic framework formed by covalently connecting small molecule monomers. They have a high specific surface area, good chemical stability, regular and ordered pore structures, and flexible and adjustable structural characteristics. They are widely used in various fields such as gas adsorption and separation, drug delivery, and catalysis.

[0003] Traditional covalent organic framework materials have the problem of poor conductivity. Therefore, it is of great significance to develop covalent organic frameworks with high conductivity. Summary of the Invention

[0004] This application provides a metal phthalocyanine-based conductive covalent organic framework material with high conjugation and a preparation method thereof to solve the above problems mentioned in the background art.

[0005] On the one hand, this application provides a metal phthalocyanine-based conductive covalent organic framework material with high conjugation. The metal phthalocyanine-based conductive covalent organic framework material includes a structural unit shown in Formula I:

[0006]

[0007] In Formula 1, "R1" is any one of C, N, and O; R2 is any one of C, N, and O; M is any one of Fe, Co, Ni, Cu, Zn, Cr, Mn, V, and Ti.

[0008] On the other hand, this application provides a preparation method of a metal phthalocyanine-based conductive covalent organic framework material with high conjugation. This preparation method is used to prepare the covalent organic framework material of the above claim 1. The preparation method is to synthesize by solvothermal method with an octaamino phthalocyanine monomer and a metal-containing organic ligand in a molar ratio of 1-8:2-8.

[0009] Optionally, the structure of the octaamino phthalocyanine monomer includes any one of Formulas 2 - 5:

[0010]

[0011]

[0012] Optionally, the metal-containing organic ligand includes the structure shown in Formula 6:

[0013]

[0014] Optionally, the preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material includes the following steps:

[0015] (1) Take octaamino phthalocyanine monomer and catalyst in proportion in a reaction kettle, add an organic solvent, and add a metal-containing organic ligand under stirring to obtain a reaction precursor;

[0016] (2) Seal the reaction kettle and carry out a condensation reaction. After the reaction is completed, naturally cool to room temperature, filter by suction, and take the filter cake to obtain a crude covalent organic framework material;

[0017] (3) Wash the crude covalent organic framework material with DMF and absolute ethanol in sequence, and then dry to obtain the metal phthalocyanine-based conductive covalent organic framework material.

[0018] Optionally, the organic solvent includes a mixture of 1,4-dioxane and n-butanol, or a mixture of 1,4-dioxane and mesitylene. The volume-mass ratio of the added amount of the organic solvent to the sum of the masses of the octaamino phthalocyanine monomer and the metal-containing organic ligand is 0.4 - 0.5 mL / mg;

[0019] The volume ratio of 1,4-dioxane to n-butanol or mesitylene is 1 - 5:5 - 20.

[0020] Optionally, the catalyst uses trifluoroacetic acid, and the volume ratio of the added amount of trifluoroacetic acid to the organic solvent is 1 - 2:20.

[0021] Optionally, the temperature of the condensation reaction is 180 - 200 °C, and the reaction time is 5 days.

[0022] Optionally, the mass ratios of DMF (N,N-dimethylformamide), absolute ethanol to the crude covalent organic framework material are all 100:1.

[0023] Optionally, the drying temperature is 70 - 85 °C.

[0024] The highly conjugated metal phthalocyanine-based conductive covalent organic framework material and its preparation method provided by this application realize the preparation of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material. Compared with the prior art, it has the following beneficial effects:

[0025] (1) Select phthalocyanine compounds with a π-conjugated system and metal-containing organic ligands as building units to synthesize a highly conjugated topological structure and metal-containing phthalocyanine-based conductive covalent organic framework material. This covalent organic framework material has a high specific surface area, high crystallinity, stability, high electron mobility, and excellent catalytic performance.

[0026] (2) In this application, the covalent organic framework material is synthesized by the solvothermal method using octaamino phthalocyanine monomer and metal-containing organic ligand as raw materials. By controlling the molar ratio of the octaamino phthalocyanine monomer to the metal-containing organic ligand, a phthalocyanine-based conductive covalent organic framework material with a highly conjugated topological structure and containing metal is synthesized, enabling the covalent organic framework material to have a relatively high conductivity and excellent catalytic performance.

[0027] (3) The preparation method of the covalent organic framework material provided by this application is simple, convenient to operate, and has a certain universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is the synthesis route diagram of the copper phthalocyanine-based conductive covalent organic framework material in Embodiment 3 of this application;

[0030] Figure 2 It is the structural schematic diagram of the copper phthalocyanine-based conductive covalent organic framework material provided in Embodiment 3 of this application;

[0031] Figure 3 It is the X-ray diffraction pattern of the copper phthalocyanine-based conductive covalent organic framework material provided in Embodiment 3 of this application;

[0032] Figure 4 It is the morphology diagram of the copper phthalocyanine-based conductive covalent organic framework material provided in Embodiment 3 of this application;

[0033] Figure 5 It is the conductivity diagram of the copper phthalocyanine-based conductive covalent organic framework material provided in Embodiment 3 of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following provides a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without making creative efforts also fall within the scope of protection of this application. Additionally, for those steps or conditions of specific technical operations not specified in the embodiments, they are all carried out according to the techniques or conditions described in general documents in this field or according to the product specifications. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained commercially. Furthermore, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0035] On the one hand, this application provides a metal phthalocyanine-based conductive covalent organic framework material with a high degree of conjugation. The metal phthalocyanine-based conductive covalent organic framework material includes a structural unit shown in Formula 1:

[0036]

[0037] In Formula 1, "R1" is any one of C, N, and O; R2 is any one of C, N, and O; and M is any one of Fe, Co, Ni, Cu, Zn, Cr, Mn, V, and Ti.

[0038] Specifically, phthalocyanine compounds with a π-conjugated system and metal-containing organic ligands are selected as building units to synthesize a metal phthalocyanine-based conductive covalent organic framework material with a high degree of conjugated topological structure and containing metal. This covalent organic framework material has a relatively high specific surface area, high crystallinity, stability, and high electron mobility, and has excellent catalytic performance.

[0039] On the other hand, this application provides a preparation method for a metal phthalocyanine-based conductive covalent organic framework material with a high degree of conjugation. This preparation method is used to prepare the covalent organic framework material of the above claim 1. The preparation method is to synthesize octaamino phthalocyanine monomers and metal-containing organic ligands by a solvothermal method in a molar ratio of 1-8:2-8.

[0040] Through the above solution, the present application realizes the preparation of a metal phthalocyanine-based conductive covalent organic framework material with high conjugation. By using an octaamino phthalocyanine monomer and a metal-containing organic ligand as raw materials, the covalent organic framework material is synthesized by a solvothermal method. By controlling the molar ratio of the octaamino phthalocyanine monomer to the metal-containing organic ligand, a phthalocyanine-based conductive covalent organic framework material with a highly conjugated topological structure and containing metal is synthesized, so that the covalent organic framework material has a high conductivity and excellent catalytic performance. At the same time, the preparation method provided by the present application is simple to operate and has a certain universality.

[0041] Optionally, the structure of the octaamino phthalocyanine monomer includes any one of Formula 2 - Formula 5:

[0042]

[0043]

[0044] Optionally, the metal-containing organic ligand includes the structure shown in Formula 6:

[0045]

[0046] Optionally, the preparation method of the metal phthalocyanine-based conductive covalent organic framework material with high conjugation includes the following steps:

[0047] (1) Take the octaamino phthalocyanine monomer and the catalyst in proportion in a reaction kettle, add an organic solvent, and add the metal-containing organic ligand under stirring to obtain a reaction precursor;

[0048] (2) Seal the reaction kettle and carry out a condensation reaction. After the reaction is completed, naturally cool to room temperature, filter by suction, take the filter cake to obtain a crude covalent organic framework material;

[0049] (3) Take DMF and absolute ethanol in sequence to wash the crude covalent organic framework material, and then dry it to obtain the metal phthalocyanine-based conductive covalent organic framework material.

[0050] Specifically, octaaminophthalocyanine monomer and a catalyst are placed in a reaction kettle, an organic solvent is added, and the mixture is stirred for 3 - 5 min. Then, an organometallic ligand is added under stirring, and the mixture is stirred for 5 - 20 min to uniformly disperse the reaction raw materials and the catalyst in the organic solvent, which helps the efficient progress of the condensation reaction to obtain a reaction precursor. The reaction kettle is sealed and the condensation reaction is carried out. After the reaction is completed, the reaction kettle is allowed to cool naturally to room temperature. The reaction product is filtered by suction. The obtained filter cake is the crude product of the covalent organic framework material, and the crude product of the covalent organic framework material is washed successively with DMF and absolute ethanol. DMF and absolute ethanol are used to wash the crude product of the covalent organic framework material at least 3 times each to remove impurities therein. Finally, the solvent in the crude product is removed by drying to obtain a metal phthalocyanine-based conductive covalent organic framework material. The preparation method of the covalent organic framework material provided by this application is simple and convenient to operate.

[0051] Optionally, the organic solvent includes a mixture of 1,4 - dioxane and n - butanol, or a mixture of 1,4 - dioxane and mesitylene. The volume - mass ratio of the added amount of the organic solvent to the sum of the masses of the octaaminophthalocyanine monomer and the organometallic ligand is 0.4 - 0.5 mL / mg.

[0052] The volume ratio of 1,4 - dioxane to n - butanol or mesitylene is 1 - 5:5 - 20.

[0053] Specifically, the organic solvent is a mixture of 1,4 - dioxane and n - butanol, or a mixture of 1,4 - dioxane and mesitylene, which provides a reaction medium for the condensation reaction, enables the octaaminophthalocyanine monomer, the catalyst, and the organometallic ligand to form a uniform precursor, makes the reaction raw materials evenly distributed, and improves the condensation reaction efficiency at the same time.

[0054] Optionally, the catalyst is trifluoroacetic acid, and the volume ratio of the added amount of trifluoroacetic acid to the organic solvent is 1 - 2:20.

[0055] Optionally, the temperature of the condensation reaction is 180 - 200 °C, and the reaction time is 5 days.

[0056] Optionally, the mass ratios of DMF (N,N - dimethylformamide), absolute ethanol to the crude product of the covalent organic framework material are both 100:1.

[0057] Optionally, the drying temperature is 70 - 85 °C.

[0058] The technical solutions of this application will be described in detail below with specific examples.

[0059] Example 1

[0060] A metal phthalocyanine - based conductive covalent organic framework material with high conjugation and its preparation method, the method comprising the following steps:

[0061] Preparation of copper phthalocyanine-based conductive covalent organic framework material: The synthesis route diagram is as Figure 1 shown, and the structural schematic diagram is as Figure 2 shown.

[0062] (1) Take octaamino phthalocyanine monomer and catalyst in proportion in a reaction kettle, add an organic solvent, and add a metal-containing organic ligand under stirring to obtain a reaction precursor;

[0063] The molar ratio of octaamino phthalocyanine monomer to the metal-containing copper organic ligand is 1:8, the organic solvent is a mixture of 1,4-dioxane and n-butanol, and the volume-mass ratio of the added amount of the organic solvent to the sum of the masses of the octaamino phthalocyanine monomer and the metal-containing organic ligand is 0.4 mL / mg; the volume ratio of 1,4-dioxane to n-butanol is 1:5;

[0064] The catalyst uses trifluoroacetic acid, and the volume ratio of the added amount of trifluoroacetic acid to the organic solvent is 1:20;

[0065] (2) Seal the reaction kettle, and carry out a condensation reaction at a temperature of 180 °C for 5 days. After the reaction is completed, naturally cool to room temperature, filter by suction, take the filter cake to obtain a crude covalent organic framework material;

[0066] (3) Take DMF and absolute ethanol in turn to wash the crude covalent organic framework material, and dry it to constant weight at 70 °C to obtain a metal phthalocyanine-based conductive covalent organic framework material with a yield of 87%. The mass ratio of DMF, absolute ethanol to the crude covalent organic framework material is 100:1.

[0067] Example 2

[0068] A metal phthalocyanine-based conductive covalent organic framework material with high conjugation and its preparation method, the method includes the following steps:

[0069] Preparation of copper phthalocyanine-based conductive covalent organic framework material:

[0070] (1) Take octaamino phthalocyanine monomer and catalyst in proportion in a reaction kettle, add an organic solvent, and add a metal-containing copper organic ligand under stirring to obtain a reaction precursor;

[0071] The molar ratio of octaamino phthalocyanine monomer to the metal-containing organic ligand is 1:8, the organic solvent is a mixture of 1,4-dioxane and n-butanol, and the volume-mass ratio of the added amount of the organic solvent to the sum of the masses of the octaamino phthalocyanine monomer and the metal-containing organic ligand is 0.45 mL / mg; the volume ratio of 1,4-dioxane to n-butanol is 1:5;

[0072] The catalyst uses trifluoroacetic acid, and the volume ratio of the added amount of trifluoroacetic acid to the organic solvent is 1.5:20;

[0073] (2) Seal the reaction kettle and carry out the condensation reaction at a temperature of 185 °C for 5 days. After the reaction, cool it naturally to room temperature, carry out suction filtration, take the filter cake to obtain the crude product of the covalent organic framework material;

[0074] (3) Take DMF and absolute ethanol in sequence to wash the crude product of the covalent organic framework material, and then dry it to constant weight at 70 °C to obtain the metal phthalocyanine-based conductive covalent organic framework material, with a yield of 87%. The mass ratio of DMF, absolute ethanol to the crude product of the covalent organic framework material is 100:1.

[0075] Example 3

[0076] A metal phthalocyanine-based conductive covalent organic framework material with high conjugation and its preparation method. The method includes the following steps:

[0077] Preparation of copper phthalocyanine-based conductive covalent organic framework material:

[0078] (1) Take octaamino phthalocyanine monomer and catalyst in proportion in the reaction kettle, add organic solvent, and add the metal copper-containing organic ligand under stirring to obtain the reaction precursor;

[0079] The molar ratio of octaamino phthalocyanine monomer to the metal-containing organic ligand is 2:8, the organic solvent is a mixture of 1,4-dioxane and mesitylene, and the volume-mass ratio of the added amount of the organic solvent to the sum of the masses of the octaamino phthalocyanine monomer and the metal-containing organic ligand is 0.5 mL / mg; the volume ratio of 1,4-dioxane to mesitylene is 1:10;

[0080] The catalyst is trifluoroacetic acid, and the added amount of trifluoroacetic acid to the volume of the organic solvent is 2:20;

[0081] (2) Seal the reaction kettle and carry out the condensation reaction at a temperature of 190 °C for 5 days. After the reaction, cool it naturally to room temperature, carry out suction filtration, take the filter cake to obtain the crude product of the covalent organic framework material;

[0082] (3) Take DMF and absolute ethanol in sequence to wash the crude product of the covalent organic framework material, and then dry it to constant weight at 80 °C to obtain the metal phthalocyanine-based conductive covalent organic framework material, with a yield of 89%. The mass ratio of DMF, absolute ethanol to the crude product of the covalent organic framework material is 100:1.

[0083] Example 4

[0084] A metal phthalocyanine-based conductive covalent organic framework material with high conjugation and its preparation method. The method includes the following steps:

[0085] Preparation of copper phthalocyanine-based conductive covalent organic framework material:

[0086] (1) Take octaamino phthalocyanine monomer and catalyst in a reaction kettle, add an organic solvent, and add a metal-containing organic ligand under stirring to obtain a reaction precursor;

[0087] The molar ratio of octaamino phthalocyanine monomer to the metal copper-containing organic ligand is 2:8, the organic solvent is a mixture of 1,4-dioxane and mesitylene, and the volume-mass ratio of the added amount of the organic solvent to the sum of the masses of octaamino phthalocyanine monomer and the metal-containing organic ligand is 0.5 mL / mg; the volume ratio of 1,4-dioxane to mesitylene is 5:10;

[0088] The catalyst is trifluoroacetic acid, and the volume ratio of the added amount of trifluoroacetic acid to the organic solvent is 2:20;

[0089] (2) Seal the reaction kettle and carry out a condensation reaction at a temperature of 200 °C for 5 days. After the reaction is completed, naturally cool to room temperature, filter by suction, take the filter cake to obtain a crude covalent organic framework material;

[0090] (3) Take DMF and absolute ethanol in turn to wash the crude covalent organic framework material, and dry it to constant weight at 85 °C to obtain a metal phthalocyanine-based conductive covalent organic framework material with a yield of 86%. The mass ratio of DMF, absolute ethanol to the crude covalent organic framework material is 100:1.

[0091] Example 5

[0092] A metal phthalocyanine-based conductive covalent organic framework material with high conjugation and its preparation method, the method comprising the following steps:

[0093] The difference from Example 3 is:

[0094] Preparation of cobalt phthalocyanine-based conductive covalent organic framework material:

[0095] (1) Take octaamino phthalocyanine monomer and catalyst in a reaction kettle, add an organic solvent, and add a metal cobalt-containing organic ligand under stirring to obtain a reaction precursor.

[0096] Example 6

[0097] A metal phthalocyanine-based conductive covalent organic framework material with high conjugation and its preparation method, the method comprising the following steps:

[0098] The difference from Example 3 is:

[0099] Preparation of iron phthalocyanine-based conductive covalent organic framework material:

[0100] (1) Weigh octaamino phthalocyanine monomer and catalyst in proportion in a reaction kettle, add an organic solvent, and add an organic ligand containing iron metal under stirring to obtain a reaction precursor.

[0101] Example 7

[0102] A highly conjugated metal phthalocyanine-based conductive covalent organic framework material and a preparation method thereof. The method comprises the following steps:

[0103] The difference from Example 3 is as follows:

[0104] Preparation of nickel phthalocyanine-based conductive covalent organic framework material:

[0105] (1) Weigh octaamino phthalocyanine monomer and catalyst in proportion in a reaction kettle, add an organic solvent, and add an organic ligand containing nickel metal under stirring to obtain a reaction precursor.

[0106] Experimental Example 1

[0107] Through the solutions provided in Examples 1 to 7, the highly conjugated metal phthalocyanine-based conductive covalent organic framework material of the present application can be successfully synthesized. Taking the copper phthalocyanine-based conductive covalent organic framework material as an example, the structure of the covalent organic framework material provided in Example 3 of the present application was characterized by an X-ray diffractometer, and the obtained X-ray diffraction pattern is as Figure 3 shown, indicating that the copper phthalocyanine-based conductive covalent organic framework material is a two-dimensional covalent organic framework material with high crystallinity.

[0108] Experimental Example 2

[0109] The morphology of the covalent organic framework material provided in Example 3 was characterized by a transmission electron microscope (TEM), and the obtained results are as Figure 4 shown.

[0110] It can be seen from Figure 4 that the morphology of the covalent organic framework material prepared in Example 3 is a relatively thin sheet structure.

[0111] Experimental Example 3

[0112] The conductivity of the copper phthalocyanine-based conductive covalent organic framework material provided in Example 3 was detected by the four-probe method, with a voltage range of 2 - 30 MPa, and at least 3 parallel experiments were conducted for each experiment. The obtained results are as Figure 5 shown.

[0113] It can be seen from Figure 5 that under DC stimulation, the conductivity of the copper phthalocyanine-based conductive covalent organic framework material provided in Example 3 reaches about 0.9×10 -3 S cm -1, indicating that the strong π-π stacking with high conjugation in the covalent organic framework material provided by this application endows it with high conductivity, and this material can be used as a catalyst in the field of electrocatalysts.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, rather than to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A metal phthalocyanine-based conductive covalent organic framework material with high conjugation, characterized in that The metal phthalocyanine-based conductive covalent organic framework material comprises a structural unit shown in Formula 1: In Formula 1, "R1” is any one of C, N, and O; R2 is any one of C, N, and O; M is any one of Fe, Co, Ni, Cu, Zn, Cr, Mn, V, and Ti.

2. A preparation method of a metal phthalocyanine-based conductive covalent organic framework material with high conjugation, characterized in that, The preparation method is used to prepare the covalent organic framework material described in Claim 1 above. The preparation method is to synthesize the octaamino phthalocyanine monomer and the metal-containing organic ligand by a solvothermal method in a molar ratio of 1-8:2-8.

3. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 2, wherein, The structure of the octaamino phthalocyanine monomer includes any one of Formulas 2-5:

4. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 2, characterized in that, The metal-containing organic ligand includes the structure shown in Formula 6:

5. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 2, wherein The preparation method includes the following steps: (1) Take the octaamino phthalocyanine monomer and the catalyst in proportion in a reaction kettle, add an organic solvent, and add the metal-containing organic ligand under stirring to obtain a reaction precursor; (2) Seal the reaction kettle and carry out a condensation reaction. After the reaction is completed, naturally cool to room temperature, filter by suction, take the filter cake to obtain a crude covalent organic framework material; (3) Wash the crude covalent organic framework material with DMF and absolute ethanol in sequence, and then dry to obtain the metal phthalocyanine-based conductive covalent organic framework material.

6. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 5, characterized in that, The organic solvent includes a mixture of 1,4-dioxane and n-butanol, or a mixture of 1,4-dioxane and mesitylene. The volume-mass ratio of the added amount of the organic solvent to the total mass of the octaamino phthalocyanine monomer and the metal-containing organic ligand is 0.4-0.5 mL / mg; The volume ratio of 1,4-dioxane to n-butanol or mesitylene is 1-5:5-20.

7. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 5, wherein The catalyst uses trifluoroacetic acid, and the volume ratio of the added amount of trifluoroacetic acid to the organic solvent is 1-2:

20.

8. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 5, wherein The temperature of the condensation reaction is 180-200 °C, and the reaction time is 5 days.

9. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 5, characterized in that, The mass ratios of DMF, absolute ethanol, and the crude covalent organic framework material are all 100:

1.

10. The preparation method of the highly conjugated metal phthalocyanine-based conductive covalent organic framework material according to claim 5, characterized in that, The drying temperature is 70-85 °C.

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