JP2012240873A - Layered double hydroxide having i3-, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a layered double hydroxide and a method for producing the same, to put it in detail, a layered double hydroxide having Iand a method for producing the same.SOLUTION: This layered double hydroxide comprises a laminated structure of a host layer containing M1ion and M2ion, and an intermediate layer containing anions. The element M1 of the M1ion is at least one transition metal selected from a group comprising Co, Fe Ni and Zn, and the element M2 of the M2ion is a transition metal of Co and/or Fe, and the mol ratio (M2/M1) is 1/2, and the anions contain Iion and Iion.

Description

The present invention relates to a layered double hydroxide and a method for producing the same, and more particularly to a layered double hydroxide having I ₃ ⁻ and a method for producing the same.

  Layered double hydroxides (LDH), known as hydrotalcite compounds or anionic clay minerals, are anion exchange materials, adsorbents, catalysts, nanoreactors, molecular sieves, polymer composites, biomaterials Application to such as is expected. In addition, construction of a novel nanodevice using a cationic nanosheet obtained by peeling a layered double hydroxide into a single layer is also expected.

  As such a layered double hydroxide, a layered double hydroxide which is a cobalt hydroxide (II) / (III) crystal has been developed (see, for example, Patent Document 1). As another layered double hydroxide, a layered double hydroxide which is a cobalt hydroxide (II) / iron (III) crystal has been developed (see, for example, Patent Document 2). As another layered double hydroxide, a layered double hydroxide that is a cobalt hydroxide / nickel crystal is known (see, for example, Non-Patent Document 1).

  According to Patent Document 1, a Co-based layered double hydroxide composed of cobalt hydroxide (II) and cobalt (III) and bromine intercalated as an anion is obtained. However, bromine used for production has an irritating odor and is extremely toxic, and there is a concern about the influence on the human body. In addition, bromine used for production required 40 times the starting material and was also inefficient.

According to Patent Document 2, a Co—Fe system comprising cobalt hydroxide (II) and iron (III), hexagonal plate-like and layered crystals, and intercalated with iodine (I ⁻ ) as an anion. A layered double hydroxide is obtained. However, according to Patent Document 2, since the atomic ratio (molar ratio) between iron and cobalt in the starting material is limited to ½, the layered double hydroxide can be formed using starting materials having different atomic ratios. It is desirable to be obtained.

  Further, according to Non-Patent Document 1, a Co—Ni-based layered double hydroxide composed of cobalt (II), nickel (II), and cobalt (III) and bromine intercalated as an anion is obtained. It is desirable to obtain a layered double hydroxide composed of another transition metal using an oxidizing agent other than bromine.

As described above, an object of the present invention is to provide a layered double hydroxide and a method for producing the same, and more specifically, to provide a layered double hydroxide having I ₃ ⁻ and a method for producing the same.

The layered double hydroxide according to the present invention has a laminated structure of a host layer containing M1 ²⁺ ions and M2 ³⁺ ions and an intermediate layer containing anions. The element M1 of the M1 ²⁺ ions is Co, Fe A transition metal selected from the group consisting of Ni and Zn, and the element M2 of the M2 ³⁺ ion is a transition metal of Co and / or Fe, and the M2 ³⁺ ion and the M1 ²⁺ ion The molar ratio (M2 ³⁺ / M1 ²⁺ ) is ½, and the anion contains I ⁻ ion and I ₃ ⁻ ion, thereby solving the above problem.
The molar ratio (I ₃ ⁻ / I ⁻ ) between the I ₃ ⁻ ion and the I ⁻ ion may be ½.
The host layer is represented by the general formula _{^{[M1 2+ 2/3 M2 3+ 1/3 (}} OH) 2] represented ^{1/3 +,} the intermediate layer is represented by the general formula _{^{[(I - 2/3 + I 3}} - 1/3 ^{_{) 1/3 · mH 2 O] 1}} / 3- (m may be represented by a is) 0.1 to 0.5.
The layered double hydroxide may have a hexagonal plate shape.
The peak intensity of primary bottom reflection in the X-ray diffraction pattern of the layered double hydroxide may be lower than the peak intensity of secondary bottom reflection.
The method for producing a layered double hydroxide according to the present invention comprises M1 ′ _1-x M2 ′ _x (OH) ₂ (M1 ′ is a transition metal of Co and / or Fe, and optionally Ni and / or Zn. M2 ′ is a transition metal of Co and / or Fe, and x is a brucite type metal hydroxide represented by 0 ≦ x <1/3), or M1 ′ _1-x M2 ′ _x (OH) ₂ (M1 ′ includes a transition metal selected from the group consisting of Co, Fe, Ni and Zn, and M2 ′ is a transition metal of Co and / or Fe , X is x = 1/3), and a step of adding and stirring the solution of the brucite type metal hydroxide to the solution in which the iodine is dissolved, the iodine and the brucite type metal water is included. Molar ratio with oxide (iodine / brucite metal hydroxide) ) Is, 2.5 × 1 / 3~40 × 1/3 (where the range of the iodine and I), a by solving the above problems.
The content of Co and / or Fe that becomes trivalent may be 1/3 or more of the metal content in the brucite type metal hydroxide in molar ratio.
The molar ratio of the iodine to the brucite metal hydroxide (iodine / brucite metal hydroxide) is in the range of 10 × 1/3 to 25 × 1/3 (where iodine is I). It may be.
In the step of adding and stirring, the solution to which the brucite metal hydroxide is added may be stirred at room temperature for 1 to 7 days.
The solvent of the solution in which iodine is dissolved may be chloroform.

The layered double hydroxide according to the present invention comprises M1 ²⁺ ions (the element M1 of the M1 ²⁺ ions is a transition metal selected from the group consisting of Co, Fe, Ni and Zn) and M2 ³⁺ ions (M2 ³⁺ ion element M2 is a laminated structure of a host layer containing a transition metal of Co and / or Fe) and an intermediate layer containing an anion containing I ⁻ ions and I ₃ ⁻ ions, Since the molar ratio of M2 ³⁺ ions to M1 ²⁺ ions (M2 ³⁺ / M1 ²⁺ ) only needs to satisfy 1/2, various combinations and various compositions as M1 and M2 can be realized. If such a layered double hydroxide is peeled off, a novel nanosheet can be obtained as a building block.

According to the method for producing a layered double hydroxide according to the present invention, M1 ′ _1-x M2 ′ _x (OH) ₂ (M1 ′ represents a transition metal of Co and / or Fe, optionally Ni and / or Or a transition metal of Zn, M2 ′ is a transition metal of Co and / or Fe, and x is a brucite metal hydroxide represented by 0 ≦ x <1/3), Or M1 ′ _1-x M2 _x ′ (OH) ₂ (M1 ′ includes a transition metal selected from the group consisting of Co, Fe, Ni and Zn, and M2 ′ is a transition metal of Co and / or Fe. And x is a topo chemical method including a step of adding and stirring a brucite-type metal hydroxide represented by x) to a solution in which iodine is dissolved. Molar ratio of bluesite-type metal hydroxide (iodine / blue rhino -Type metal hydroxide) is, 2.5 × 1 / 3~40 × 1/3 (where satisfies the range of the iodine and I). According to the production method of the present invention, a desired brucite-type metal hydroxide is simply added to a solution in which iodine is excessively dissolved and stirred, which is convenient and advantageous for mass production. Moreover, since the above-mentioned layered double hydroxide can be obtained without requiring a special technique and apparatus, it can be provided at low cost.

Schematic diagram showing a layered double hydroxide according to the present invention Another schematic diagram showing a layered double hydroxide according to the present invention Schematic showing anion-exchanged layered double hydroxide according to the invention The figure which shows the flowchart which manufactures the layered double hydroxide by this invention The figure which shows the XRD pattern of the product by Example 1 and Comparative Example 1 The figure which shows the XRD pattern of product BD by Comparative Examples 2-4 Figure 2 shows the XRD pattern of products 2-4 according to Examples 2-4 The figure which shows the TEM image (a) and electron diffraction pattern (b) of the product 3 by Example 3. Figure 2 shows the XPS spectrum of product 1-4 according to Example 1 FIG. 5 shows an XPS spectrum of product 4 according to Example 4. Figure 2 shows UV-vis spectra of products 2-4 according to Examples 2-4 Figure 5 shows the XRD pattern of anion exchanged product 3 according to example 3 FIG. 5 shows a UV-vis spectrum of the product 3ds according to Example 3. FIG. 5 shows a TG curve of product 3 and product 3p according to Example 3. The figure which shows the TG curve of the product B by the comparative example 2, and the product Bp Schematic diagram of the superlattice structure of product 3 according to Example 5 The figure which shows the distribution of the iodine of the intermediate | middle layer of the product 3 by Example 5, and a simulation low angle XRD pattern The figure which shows another distribution of the iodine of the intermediate | middle layer of the product 3 by Example 5, and a simulation low angle XRD pattern The figure which shows further another distribution of the iodine of the intermediate | middle layer of the product 3 by Example 5, and a simulation low angle XRD pattern The figure which shows further another distribution of the iodine of the intermediate | middle layer of the product 3 by Example 5, and a simulation low angle XRD pattern FIG. 6 shows another further distribution of iodine in the intermediate layer of the product 3 according to Example 5 and a simulated low angle XRD pattern.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same number is attached | subjected to the same element and the description is abbreviate | omitted.

  FIG. 1 is a schematic view showing a layered double hydroxide according to the present invention.

  The layered double hydroxide 100 according to the present invention has a laminated structure of a host layer 110 and an intermediate layer 120.

The host layer 110 contains M1 ²⁺ ions and M2 ³⁺ ions. The element M1 of the M1 ²⁺ ion is a transition metal selected from at least one selected from the group consisting of Co, Fe, Ni, and Zn. The element M2 of the M2 ³⁺ ion is a transition metal of Co and / or Fe. Furthermore, the molar ratio (M2 ³⁺ / M1 ²⁺ ) between M2 ³⁺ ions and M1 ²⁺ ions satisfies 1/2. Here, M1 and M2 may be the same element.

The intermediate layer 120 includes I ⁻ ions and I ₃ ⁻ ions as anions. More preferably, the molar ratio (I ₃ ⁻ / I ⁻ ) between I ₃ ⁻ ions and I ⁻ ions is ½.

Since the molar ratio of M2 ³⁺ ions to M1 ²⁺ ions (M2 ³⁺ / M1 ²⁺ ) only needs to satisfy 1/2, various combinations and various compositions as M1 and M2 can be realized. For example, the same transition metal may be selected for M1 and M2, Co and Ni may be selected as M1, and Co may be selected as M2. In addition, as long as the above molar ratio is satisfied, there is no limitation on the combination and composition of M1 and M2, so the degree of freedom in design is high.

Further, the host layer 110, the general formula ^{_{[M1 2+ 2/3 M2 3+ 1/3 (}} OH) 2] represented ^{1/3 +,} an intermediate layer 120, the general formula ^{_{[(I - 2/3 + I 3}} - 1 ^{_{/ 3) 1/3 · mH 2 O}} ] expressed ^1/3 in the general formula a layered double hydroxide of the present invention ^{_{[M1 2+ 2/3 M2 3+ 1/3 (}} OH) 2] 1/3 + [ ^{_{(I - 2/3 + I 3 -}} 1/3) 1/3 · mH 2 O] 1 / 3- or formula ^{_{M1 2+ 2/3 M2 3+ 1/3 (OH}} ) 2 I 5/9 · mH 2 O It may be expressed as Here, m is in the range of 0.1 to 0.5, and is stable within this range.

  In the present specification, the molar ratio 1/2, or the number of ions in the general formula and composition formula (2/3, 1/3, etc.) may include an error, and substantially 1/2, 2 / It is intended to satisfy the general formula when the value is 3, 1/3, 5/9, or the like.

  FIG. 2 is another schematic view showing a layered double hydroxide according to the present invention.

  The layered double hydroxide 100 according to the present invention has a hexagonal plate shape. This hexagonal plate shape reflects the shape of the brucite type metal hydroxide used as a starting material in the manufacturing method described later. In the layered double hydroxide 100 of the present invention, a host layer 110 and an intermediate layer 120 are laminated in a hexagonal plate-like thickness direction d.

The layered double hydroxide according to the present invention exhibits an X-ray diffraction pattern different from existing layered double hydroxides (for example, Patent Documents 1 and 2) by containing I ₃ ^{− in the} intermediate layer. It is known that a so-called layered double hydroxide exhibits a peculiar bottom reflection derived from a laminated structure of a host layer and an intermediate layer in an X-ray diffraction pattern. The peak intensity of bottom reflection in the X-ray diffraction pattern of the existing layered double hydroxide gradually decreases as the first order, second order, and order increase. However, according to the layered double hydroxide according to the present invention, the peak intensity of the primary bottom reflection is lower than the peak intensity of the secondary bottom reflection. If such a feature is utilized, it can be easily determined whether or not the layered double hydroxide of the present invention has been obtained by measuring X-ray diffraction.

  FIG. 3 is a schematic diagram showing an anion-exchanged layered double hydroxide according to the present invention.

According to the layered double hydroxide 100 according to the invention (FIGS. 1 and 2), the anions (I ⁻ and I ₃ ⁻ ) of the intermediate layer 120 (FIGS. 1 and 2) can be exchanged for different anions 310, The layered double hydroxide can be functionalized. For example, the anion-exchanged layered double hydroxide 300 according to the present invention comprises an inorganic anion consisting of ClO ₄ ⁻ , Cl ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ and HPO ₄ ²⁻ , and organic It is exchanged for an anion selected from the group consisting of organic anions derived from carboxylic acids and organic sulfonic acids. Representative organic carboxylic acids include, but are not limited to, CH ₃ COO ⁻ and representative organic sulfonic acids include C ₁₂ H ₂₅ OSO ₃ ^— .

  In addition, according to the anion-exchanged layered double hydroxide 300 according to the present invention, the peak intensity of the primary bottom surface reflection is higher than the peak intensity of the secondary bottom surface reflection, and is reversed from that of the layered double hydroxide 100 of the present invention. Can do. By utilizing such a feature, it is possible to easily determine whether or not the layered double hydroxide of the present invention has been anion-exchanged by measuring X-ray diffraction.

For example, when the anion of the layered double hydroxide according to the present invention is exchanged with carbonic acid (CO ₃ ²⁻ ), the layered double hydroxide after the anion exchange is heated at a temperature of 500 ° C., etc., and dehydrated / decarbonated. An oxide can be obtained.

For example, when the anion of the layered double hydroxide according to the present invention is exchanged with perchloric acid (ClO ₄ ⁻ ), the host compound can be obtained by simply dispersing the layered double hydroxide after anion exchange in an aprotic solvent such as formamide. A layer and an intermediate layer can be peeled apart to obtain a nanosheet.

  Next, the method for producing the layered double hydroxide according to the present invention will be described in detail.

  FIG. 4 is a diagram showing a flowchart for producing a layered double hydroxide according to the present invention.

Step S410: M1 ′ _1-x M2 ′ _x (OH) ₂ (M1 ′ includes a transition metal of Co and / or Fe, and optionally includes a transition metal of Ni and / or Zn, and M2 ′ A transition metal of Co and / or Fe, and x is a brucite type metal hydroxide represented by 0 ≦ x <1/3), or M1 ′ _1-x M2 ′ _x (OH ) ₂ (M1 ′ includes a transition metal selected from the group consisting of Co, Fe, Ni and Zn, M2 ′ is a transition metal of Co and / or Fe, and x is x = 1/3 The brucite-type metal hydroxide represented by (A) is added to a solution in which iodine is dissolved, and stirred. In the following, for simplicity, the former brucite metal hydroxide is the first metal hydroxide, the latter brucite metal hydroxide is the second metal hydroxide, and both brucite metals. The hydroxides are generically referred to simply as metal hydroxides.

  In the first metal hydroxide that is the starting material, M1 ′ is divalent, but contains Co and / or Fe transition metals that can be all or partly trivalent after the reaction, and is necessary Accordingly, when the layered double hydroxide 100 (FIGS. 1 and 2) to be finally obtained contains a transition metal of Ni and / or Zn, the divalent Ni and / or Zn which is divalent after the reaction A transition metal is included, and M2 ′ is a transition metal of Co and / or Fe that is divalent but all trivalent after the reaction.

  In the second metal hydroxide that is the starting material, M1 ′ is divalent but contains a transition metal selected from the group consisting of Co, Fe, Ni, and Zn that is divalent after the reaction, and , M2 ′ is a transition metal of Co and / or Fe which is divalent but becomes trivalent after the reaction.

Here, the molar ratio of iodine to metal hydroxide (iodine / metal hydroxide) satisfies the range of 2.5 × 1/3 to 40 × 1/3 (however, iodine is calculated as I) To do). Note that when calculating the iodine as _{I 2,} the molar ratio satisfies the range of 2.5 × 1 / 6~40 × 1/ 6. Below this range, it is difficult to produce a layered double hydroxide single phase according to the present invention. When this range is exceeded, excessive iodine is required, leading to high costs. More preferably, the molar ratio satisfies a range of 10 × 1/3 to 25 × 1/3 (however, iodine is calculated as I). If it is this range, the production | generation of the layered double hydroxide by this invention will be accelerated | stimulated, and the metal hydroxide of a starting material will not remain. In addition, the solvent of the solution in which iodine is dissolved may be an organic solvent with low polarity, and specifically, chloroform can be used.

In step S410, specifically, the stirring may be performed by stirring the solution to which the starting metal hydroxide is added at room temperature for 1 to 7 days. As a result, a layered double hydroxide in which iodine is intercalated as I ⁻ and I ₃ ⁻ and M2 ′ (optionally M1 ′) is oxidized from divalent to trivalent is obtained. It is done. The longer the stirring period is, the more effective it is, and 5 days or more is preferable, but the effect does not change even if it exceeds 7 days.

The solution in which iodine in Step S410 is dissolved contains excess iodine exceeding the amount of iodine (1.0 × 1/3 to 2.0 × 1/3) used in Patent Document 2, for example. By using a solution in which excess iodine in the above-mentioned range is dissolved, the inventors of the present invention make M2 ′ always trivalent in the starting metal hydroxide, and M1 ′ Co and / or As necessary, the transition metal of Fe may have a molar ratio of M2 ³⁺ ions to M1 ²⁺ ions (M2 ³⁺ / M1 ²⁺ ) in the finally obtained layered double hydroxide 100 satisfying 1/2. We found that it can be trivalent. That is, the content (molar ratio) of transition metal Co and / or Fe that can be trivalent in the brucite-type metal hydroxide that is the starting material is 1/3 or more of the total metal content.

  It should be noted that M1 'and M2' in the metal hydroxide are not necessarily the same as M1 and M2 in the layered double hydroxide 100 of the present invention described with reference to FIG. M1 ′ and M2 ′ may be completely the same as M1 and M2, and a part of M1 ′ becomes M1, a part of M1 ′ and all of M2 become M2, and all of M2 ′ becomes M2. In some cases. Next, an example will be described.

For example, in the first metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ , assume that M1 ′ is Co, M2 ′ is Fe, and x is ¼. In this case, the first metal hydroxide of the starting material is represented by Co _3/4 Fe _1/4 (OH) ₂ . When step S401 is performed using this first metal hydroxide, Fe _1/4 is oxidized from divalent to trivalent. Of Co _3/4 , Co _1/12 is oxidized from divalent to trivalent, and Co _2/3 remains divalent. As a result, the molar ratio of M2 ³⁺ (M2 is Co and Fe) and M1 ²⁺ (M1 is Co) becomes 1/2. Layered double hydroxide to be finally ^{_{obtained, [Co 2+ 2/3 (Co 3+}} 1/12 Fe 3+ 1/4) (OH) 2] 1/3 + [(I - 2/3 + I 3 - 1 / ^{_{3) 1/3 · mH 2 O]}} 1 / 3- becomes (m is in the range of 0.1 to 0.5).

Similarly, in the first metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ , it is assumed that M1 ′ is Co, M2 ′ is Fe, and x is 1/5. . In this case, the first metal hydroxide as the starting material is represented by Co _4/5 Fe _1/5 (OH) ₂ . When step S401 is performed using this first metal hydroxide, Fe _1/5 is oxidized from divalent to trivalent. Of Co _4/5 , Co _2/15 is oxidized from divalent to trivalent, and Co _2/3 remains divalent. As a result, the molar ratio of M2 ³⁺ (M2 is Co and Fe) and M1 ²⁺ (M1 is Co) becomes 1/2. Layered double hydroxide to be finally ^{_{obtained, [Co 2+ 2/3 (Co 3+}} 2/15 Fe 3+ 1/5) (OH) 2] 1/3 + [(I - 2/3 + I 3 - 1 / ^{_{3) 1/3 · mH 2 O]}} 1 / 3- becomes (m is in the range of 0.1 to 0.5).

The same applies to other combinations, so that all of M2 ′ and part or all of M1 ′ in the first metal hydroxide so that the molar ratio of M2 ³⁺ to M1 ²⁺ is finally ½. Is oxidized.

On the other hand, for example, in the second metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ , when M1 ′ is Co and M2 ′ is Fe, the second metal hydroxide of the starting material The product is represented by Co _2/3 Fe _1/3 (OH) ₂ . When step S401 is performed using this second metal hydroxide, Fe _1/3 is oxidized from divalent to trivalent. Co _2/3 remains divalent. As a result, the molar ratio of M2 ³⁺ (M2 is Fe) and M1 ²⁺ (M1 is Co) becomes 1/2. Layered double hydroxide to be finally ^{_{obtained, [Co 2+ 2/3 Fe 3+ 1/3}} ) (OH) 2] 1/3 + [(I - 2/3 + I 3 - 1/3) 1/3 · ^{_{mH 2 O] 1 / 3- (}} m is in the range of 0.1 to 0.5) it becomes.

Similarly, in the second metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ , when M1 ′ is Ni and M2 ′ is Fe, the starting second metal hydroxide Is represented by Ni _2/3 Fe _1/3 (OH) ₂ . When step S401 is performed using this second metal hydroxide, Fe _1/3 is oxidized from divalent to trivalent. Ni _2/3 remains divalent. As a result, the molar ratio of M2 ³⁺ (M2 is Fe) and M1 ²⁺ (M1 is Ni) becomes 1/2. Layered double hydroxide to be finally ^{_{obtained, [Ni 2+ 2/3 Fe 3+ 1/3}} ) (OH) 2] 1/3 + [(I - 2/3 + I 3 - 1/3) 1/3 · ^{_{mH 2 O] 1 / 3- (}} m is in the range of 0.1 to 0.5) it becomes.

  As described above, according to the topochemical method of the present invention, it is easy to add a desired metal hydroxide to a solution in which iodine satisfying the above molar ratio is excessively dissolved and stir, so that it is simple and mass production. Is advantageous. Moreover, since the above-mentioned layered double hydroxide can be obtained without requiring a special technique and apparatus, it can be provided at low cost.

In the production method of the present invention, the layered double hydroxide of the present invention, which is the product obtained in step S401, is converted into ClO ₄ ⁻ , Cl ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ and HPO _4. A step of adding an inorganic anion composed of ^2- and an anion selected from the group consisting of an organic anion derived from an organic carboxylic acid and an organic sulfonic acid to a dissolved solution and stirring the solution may be further included. Thereby, the anion (I ⁻ and I ₃ ⁻ ) of the layered double hydroxide of the present invention can be anion exchanged. Specifically, the stirring is performed by sealing the solution in which the anion to which the layered double hydroxide is added is sealed (the air in the container is purged with an inert gas such as nitrogen), and at room temperature for 10 hours to 24 hours. Shake for hours. For such anion exchange, for example, an ethanol-added anion exchange method (see, for example, Non-Patent Document 1) can be applied.

Representative organic carboxylic acids include, but are not limited to, CH ₃ COO ⁻ and representative organic sulfonic acids include C ₁₂ H ₂₅ OSO ₃ ^— . The molar ratio between the anion to be exchanged and the layered double hydroxide of the present invention is preferably in the range of 3 × 10 ² : 1 to 1 × 10 ² : 1.

Further, the layered double hydroxide of the present invention, by appropriate soft chemical treatment, are single layer peeling in the host layer ^{_{110 [M1 2+ 2/3 M2 3+ 1/3}} (OH) 2] 1/3 +, the positive charge A nanosheet is obtained. For example, a layered double hydroxide that has been anion-exchanged with perchloric acid is dispersed in an aprotic solvent typified by formamide and sealed (the air in the container is purged with an inert gas such as nitrogen). It may be mechanically shaken or sonicated at room temperature.

  The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

In Example 1, in step S410 of FIG. 4, as (first) metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ , M1 ′ is Co and Co = 0H where x = 0. ₂ ) The layered double hydroxide of the present invention was produced by using a molar ratio of various iodine I and metal hydroxide.

Co (OH) ₂ was produced, for example, by the method for producing brucite-type cobalt (II) hydroxide described in Patent Document 1. Using a 1000 cm ³ three-necked flask, cobalt chloride hexahydrate (CoCl ₂ .6H ₂ O) was dissolved in milli-Q water. At this time, the concentration of Co cation was 7.5 mM. The three neck flask was purged with nitrogen gas. Using the same route that was purged with nitrogen gas, a hexamethylenetetramine (HMT) solution (1.2 M, 50 cm ³ ) was introduced into one neck of the three-necked flask and held in a separation valve. After purging overnight, the separation valve was opened and the HMT solution was placed in a three-necked flask. At this time, outside air / O ₂ impurities were not mixed. The mixed solution of cobalt chloride hexahydrate and the HMT solution was refluxed for about 5 hours while stirring with a magnetic stirrer. It was confirmed that a pink solid product was precipitated in the three-necked flask. The precipitate was then filtered in a glove box filled with nitrogen gas to collect a pink solid product. The recovered solid product (Co (OH) ₂ ) was washed several times with degassed MilliQ water and absolute ethanol. In this way, Co (OH) ₂ was produced.

Next, metal hydroxide Co (OH) ₂ was added to a solution of iodine dissolved in chloroform (50 cm ³ ) (hereinafter referred to as chloroform solution for simplicity) and stirred at room temperature (step of FIG. 4). S410). Here, the molar ratio of iodine to Co (OH) ₂ and the stirring time (hours) are 2.5 × 1/3 and 24, 10 × 1/3 and 24, 25 × 1/3 and 24, And 25 × 1/3 and 120. The dark product was collected by filtration and washed repeatedly with absolute ethanol until the filtrate was colorless.

The products thus obtained are collectively referred to as a product 1 or individually as products 1-1 to 1-4. The products 1-1 to 1-4 have a molar ratio of iodine to Co (OH) ₂ and a stirring time (hour) of 2.5 × 1/3 and 24, 10 × 1/3 and Products obtained by stirring under the conditions of 24, 25 × 1/3 and 24, and 25 × 1/3 and 120.

  Product 1 was identified by an X-ray diffraction pattern using a powder X-ray diffractometer (Rigaku RINT-2200, a monochromator CuKα ray (λ = 0.15405 nm)). The results are shown in FIG.

  The X-ray photoelectron spectroscopy (XPS) spectrum of the product 1-4 was measured using PHI XPS 5700 (Al Kα ray (200 W, 1486.6 eV)). The results are shown in FIG. All spectra were calibrated using C 1s and O 1s peaks.

  The contents of Co and I in the product 1 were analyzed by an energy dispersive X-ray analyzer (EDS) to obtain a composition formula. The results are shown in Table 1.

  The molar ratio of the divalent and trivalent metal cations of product 1 was determined by titration. Product 1 (0.030 g) was dissolved in diluted HCl and aliquoted. One HCl solution was titrated directly with sulfate of ethylenediaminetetraacetic acid (EDTA) using murexide as an indicator. As a result, a total amount of divalent metal cations in the product 1 was obtained. During the titration, the pH value was adjusted to about 10 with diluted ammonium. At the end of the titration, the color of the solution changed from yellow to purple.

To the other HCl solution was added potassium iodide (KI). The stoichiometric amount of iodine produced from the oxidation of I ⁻ by trivalent metal cation (Co ³⁺ ) in HCl solution was determined by back titration with Na ₂ S ₂ O ₃ using starch as an indicator. Since intercalated iodine can inhibit KI titration, the product 1 iodine was exchanged for other anions, which were titrated using a similar procedure and the results were calibrated. The determined molar ratio is shown in Table 1.

In Example 2, in step S410 of FIG. 4, as (second) metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ , M1 ′ is Co, M2 ′ is Fe, x By using Co _2/3 Fe _1/3 (OH) _{2 in} which = _1/3 , the molar ratio of iodine I to metal hydroxide is 10 × 1/3, and the stirring time is 120 hours The layered double hydroxide of the present invention was produced.

In Example 1, in addition to CoCl ₂ .6H ₂ O, a mixed solution in which iron chloride tetrahydrate (FeCl ₂ .4H ₂ O) is added (the molar ratio of Fe and Co is 1: 2). The metal hydroxide Co _2/3 Fe _1/3 (OH) ₂ was obtained in the same manner as in Example 1 except that the above was prepared. The metal hydroxide Co _2/3 Fe _1/3 (OH) ₂ thus obtained was set to a molar ratio of iodine I to metal hydroxide of 10 × 1/3, and the stirring time was 120 hours. In the same manner as in Example 1, it was added to a chloroform solution in which iodine was dissolved and stirred. The resulting product is referred to as Product 2.

  Similar to Example 1, the XRD pattern was measured for product 2. The results are shown in FIG. The UV-vis absorption spectrum of product 2 was measured using a U-4100 spectrophotometer (Hitachi). For the measurement, a quartz cell (path length: 10 mm) containing a diluted ethanol dispersion of product 2 was used. The results are shown in FIG. Moreover, the composition of the product 2 was calculated | required by EDS similarly to Example 1, and the molar ratio of a bivalent and a trivalent metal cation was determined by the titration method. The composition and molar ratio are shown in Table 1.

In Example 3, M1 ′ is Co, M2 ′ is Fe as ( _first ) metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ in Step S410 of FIG. = _Same as Example 2 except that Co _3/4 Fe _1/4 (OH) ₂ was used. The resulting product is referred to as Product 3.

Product 3 was anion exchanged using an ethanol-added anion exchange method. NaClO ₄ (0.3 mol) and C ₁₂ H ₂₅ OSO ₃ Na (0.3 mol) were respectively added to an ethanol-water mixed solution (volume ratio of ethanol (v) and water (v) was 1: 1). After dissolving, a perchlorate (ClO ₄ ⁻ ) solution (1.5 M) and a dodecyl sulfate (C ₁₂ H ₂₅ OSO ₃ ⁻ ) solution (1.5 M) were prepared. Product 3 (0.25 g) was dispersed in perchlorate solution and dodecyl sulfate solution, respectively, and the vessel was purged with nitrogen gas. The container was sealed and mechanically shaken at room temperature for 24 hours. The anion exchanged product 3 was filtered, washed with degassed MilliQ water and absolute ethanol and dried in air. The product 3 anion-exchanged with perchlorate is referred to as product 3p, and the product 3 anion-exchanged with dodecyl sulfate is referred to as product 3ds.

  As in Example 2, XRD patterns and UV-vis spectra were measured for product 3, product 3p and product 3ds. The results are shown in FIGS. 7 and 11 to 13.

  The product 3 was observed with a transmission electron microscope (TEM) using an energy filter transmission electron microscope (JEOL, JEM-3100F). The results are shown in FIG.

  Thermogravimetric (TG) measurements were performed on product 3 and product 3p using a TGA-8120 apparatus (Rigaku). The measurement was performed in the air at a temperature rising rate of 5 ° C./min for a temperature range of 25 ° C. to 1000 ° C. The results are shown in FIG.

  Moreover, the composition of the product 3 was calculated | required by EDS similarly to Example 1, and the molar ratio of a bivalent and a trivalent metal cation was determined by the titration method. The composition and molar ratio are shown in Table 1.

In Example 4, M1 ′ is Co, M2 ′ is Fe, as ( _first ) metal hydroxide M1 ′ _1-x M2 ′ _x (OH) ₂ in Step S410 of FIG. = _{1/5 Same} as Example 2 except that Co _4/5 Fe _1/5 (OH) ₂ was used. The resulting product is referred to as Product 4.

  As in Example 1, the XRD pattern and XPS spectrum of product 4 were measured. The results are shown in FIG. 7 and FIG. As in Example 2, the UV-vis spectrum of product 4 was measured. The results are shown in FIG. Moreover, the composition of the product 4 was calculated | required by EDS similarly to Example 1, and the molar ratio of the trivalent and bivalent metal cation was determined by the titration method. The composition and molar ratio are shown in Table 1.

Comparative Example 1

In Comparative Example 1, the same procedure as in Example 1 was performed except that the molar ratio of iodine I to metal hydroxide was 1.2 × 1/3 and the stirring time was 24 hours. Co (OH) ₂ was added to the chloroform solution and stirred. The resulting product is referred to as Product A.

  As in Example 1, the XRD pattern was measured for product A. The results are shown in FIG.

Comparative Example 2

In Comparative Example 2, the procedure of Example 2 was followed except that the molar ratio of iodine I to metal hydroxide was 1.2 × 1/3 and the stirring time was 12 hours. Co _2/3 Fe _1/3 (OH) ₂ was added to the chloroform solution and stirred. The resulting product is referred to as Product B. Furthermore, as in Example 3, the product B was anion exchanged using a perchlorate solution. The anion exchanged product B is referred to as product Bp.

  The XRD pattern was measured for product B as in Example 1. The results are shown in FIG. In the same manner as in Example 3, TG measurement was performed on the product B and the product Bp. The results are shown in FIG. Further, as in Example 1, the composition of the product B was determined by EDS, and the molar ratio of trivalent and divalent metal cations was determined by a titration method. The composition and molar ratio are shown in Table 1.

Comparative Example 3

In Comparative Example 3, the same procedure as in Example 3 was followed, except that the molar ratio of iodine I to metal hydroxide was 1.2 × 1/4, and the stirring time was 12 hours. Co _3/4 Fe _1/4 (OH) ₂ was added to the chloroform solution and stirred. The resulting product is referred to as Product C. The XRD pattern was measured for product C as in Example 1. The results are shown in FIG.

Comparative Example 4

In Comparative Example 4, the same procedure as in Example 4 was followed except that the molar ratio of iodine I to metal hydroxide was 1.2 × 1/5, and the stirring time was 12 hours. Co _4/5 Fe _1/5 (OH) ₂ was added to the chloroform solution and stirred. The resulting product is referred to as Product D. As in Example 1, the XRD pattern was measured for product D. The results are shown in FIG.

  The product 3 obtained in Example 3 was simulated by the multipurpose pattern fitting program RIEtan-2000. The results of the structural model and XRD simulation are shown in FIGS. 16 to 21 and will be described later.

  The experimental conditions of Examples 1-5 and Comparative Examples 1-4 and the product composition formulas are shown in Table 1 for simplicity.

  Next, the measurement results of Examples 1 to 5 and Comparative Examples 1 to 4 are shown and described in detail.

  FIG. 5 is a diagram showing XRD patterns of the products according to Example 1 and Comparative Example 1.

XRD patterns a to e are XRD patterns of product A, product 1-1, product 1-2, product 1-3, and product 1-4, respectively. The XRD pattern a coincides with the XRD pattern (JCPDS card No. 74-1057) of Brucite-type Co (OH) ₂ which is the starting material of the products A to 1, and the primary bottom surface reflection is 4.6 mm. Showed a peak. According to the XRD pattern b, in addition to the primary bottom surface reflection peak at 4.6% of Brusite-type Co (OH) ₂ , another peak at 4.3% was shown. Referring to the XRD patterns c to e, as the amount of iodine in step S410 increases, the peak of the brucite-type Co (OH) ₂ disappears and a plurality of different peaks having 4.3 Å as the main peak appear. .

Further, in the XRD pattern e, the peak of the brucite type Co (OH) ₂ disappeared completely, and an XRD pattern completely different from the brucite type Co (OH) ₂ was shown. More specifically, any peak of the XRD pattern e has a bottom surface separation of about 8.7 mm (primary bottom surface reflection peak 8.7 mm, secondary bottom surface reflection peak 4.3 mm, tertiary bottom surface reflection peak 2.9 mm, quaternary bottom surface reflection. A layered structure having a peak of 2.23 Å, a fifth order bottom reflection peak of 1.75 Å, and a sixth order bottom reflection peak of 1.48 Å was shown. In addition, according to the XRD pattern e, unlike the XRD pattern a, the peak intensity of the primary bottom surface reflection was found to be lower than the peak intensity of the secondary bottom surface reflection.

As mentioned above, although the product 1-1 contained the brucite type Co (OH) ₂ which is a starting material, it showed a layered structure having a bottom face distance of about 8.7 mm different from the starting material. Therefore, in step S410 (FIG. 4) of the production method of the present invention, it was confirmed that the lower limit of the molar ratio of iodine to metal hydroxide was 2.5 × 1/3. In addition, since the product 1-2 clearly showed a 4.3 peak main peak (bottom distance of about 8.7 inches) different from the starting material, in step S410 (FIG. 4) of the production method of the present invention, It was confirmed that the molar ratio of iodine to metal hydroxide is preferably 10 × 1/3 or more.

Further, the product 1-4 was found to be a layered material having a layered structure having a bottom surface distance of about 8.7 mm different from the starting material without containing the starting material, brucite-type Co (OH) _2. It was. Therefore, in step S410 (FIG. 4) of the production method of the present invention, it was confirmed that the preferable upper limit of the molar ratio of iodine to metal hydroxide was 25 × 1/3.

  FIG. 6 is a diagram showing XRD patterns of products B to D according to Comparative Examples 2 to 4.

XRD patterns a to c are XRD patterns of products B to D, respectively. The XRD pattern a shows a layered structure having a bottom surface interval of 8.3 mm, and is similar to the XRD pattern b of FIG. Specifically, it is known that Fe ²⁺ is more likely to be oxidized than Co ²⁺ in the brucite-type metal hydroxide, and the molar ratio of iodine and metal hydroxide having a nearly stoichiometric composition (Comparative Example 2). 1.2 × 1/3) is reacted with Co ²⁺ _1-x Fe ²⁺ _x (OH) ₂ (x = 1/3), whereby Fe ²⁺ is oxidized to Fe ³⁺ , and Fe ³⁺ The molar ratio of / Co ²⁺ satisfies 1/2, and I ₂ becomes I ^{− and} is intercalated. This reaction formula is expressed as follows.
Co ²⁺ _1-x Fe ²⁺ _x (OH) + x / 2I ₂ → Co ²⁺ _1-x Fe ³⁺ _x (OH) ₂ I _x (where x = 1/3)
Therefore, it was found that the product B was a layered double hydroxide composed of cobalt hydroxide (II) and iron (III) intercalated with iodine (I ⁻ ) as anions.

On the other hand, according to the XRD patterns b and c, the peaks of the starting materials _Brusite- type Co _3/4 Fe _1/4 (OH) ₂ and Co _4/5 Fe _1/5 (OH) ₂ , and the XRD pattern In addition to the peak of the crystal consisting of cobalt hydroxide (II) and iron (III) intercalated with iodine (I ⁻ ) similar to a, a layered structure having a bottom surface spacing of about 12.9% was shown. This suggests that in products C and D, a phenomenon called staging where iodide ions intercalate every other layer occurred. That is, slabs intercalated with iodide ions (I ⁻ ) (bottom spacing 8.3 mm) and brucite-type slabs (bottom spacing 4.6 mm) which are remaining starting materials are alternately stacked, It shows that it has a periodic structure with an interval of 12.9 cm (8.3 cm + 4.6 cm). In Comparative Examples 3 and 4, it was confirmed that a brucite-type slab was also present in the products having a stirring time of 120 hours.

From this, iodine and Co ²⁺ _1-x Fe ²⁺ _x (OH) satisfying a molar ratio of iodine to metal hydroxide (1.2 × 1/3 of Comparative Examples 3 and 4) having a nearly stoichiometric composition. ₂ (x is 0 ≦ x <1/3), the molar ratio of Fe ³⁺ / Co ²⁺ does not become ½, and it is understood that a single-phase layered double hydroxide cannot be obtained. It was.

  FIG. 7 shows the XRD patterns of products 2-4 according to Examples 2-4.

  XRD patterns a to c are XRD patterns of products 2 to 4, respectively. All of the XRD patterns a to c were the same as the XRD pattern e in FIG. That is, all of the peaks show a layered structure having a bottom surface interval of about 8.6 to 8.7 inches, and the peak intensity of the primary bottom surface reflection is higher than that of the secondary bottom surface reflection (4.3 to 4.4 inches). Was found to be low.

Here, the XRD pattern a (product B) in FIG. 6 is compared with the XRD pattern a (product 2) in FIG. Product 2 showed a layered structure with a bottom spacing of about 8.6 mm, unlike Product B, although it exhibited a slight layered structure with a bottom spacing of about 8.3 mm, similar to Product B. From this, it became clear that the product 2 is different from the product B (that is, the layered double hydroxide intercalated with I ⁻ ).

Further, the peak intensity of the primary bottom surface reflection of the XRD pattern a of FIG. 6 is higher than that of the secondary bottom surface reflection, but the peak intensity of the primary bottom surface reflection of the XRD pattern a of FIG. Was also low. This suggests that another anion species having an X-ray scattering ability stronger than I ⁻ is intercalated between the layers of the product 2 exhibiting a layered structure, and the production method of the present invention. Therefore, it can be said that the other anionic species can be I ₃ ⁻ . In the present specification, it should be noted that “an anion intercalated between layers” is synonymous with “an intermediate layer has an anion”.

From the above, for the metal hydroxide that is M1 ′ _1-x M2 ′ _x (OH) ₂ (x is 0 ≦ x ≦ 1/3), in step S410 (FIG. 4) of the production method of the present invention, It was shown that when the molar ratio of iodine to metal hydroxide is in the range of 2.5 × 1/3 to 40 × 1/3, a layered material having a single-phase layered structure can be obtained. Further, the peak intensity of the primary bottom reflections resulting layered material is lower than that of the secondary bottom reflection, the layers of the layered material, I ^- that is intercalated ^- in addition to I ₃ It was suggested.

If the layered double hydroxide of the present invention contains I ⁻ and I ₃ ⁻ as an anion ion of the intermediate layer, the product A which is an I ⁻ single layered double hydroxide as the anion ion of the intermediate layer, In comparison, it can be inferred that the layer spacing of the layered double hydroxide of the present invention is expanded and the bottom spacing increases from 8.3 mm to about 8.6 cm to 8.7 mm.

  FIG. 8 is a diagram showing a TEM image (a) and an electron diffraction pattern (b) of the product 3 according to Example 3.

According to Fig.8 (a), it turned out that the product 3 has a hexagonal plate shape. Specifically, it was confirmed that the product 3 has a size of 2 to 4 μm in the lateral direction (in the spreading direction of the plate-like surface) and several tens of nm in the thickness direction. This shape and size were almost the same as those of the Co ²⁺ _3/4 Fe ²⁺ _1/4 (OH) ₂ metal hydroxide used as the starting material. Although not shown, the products 1, 2 and 4 also had the same morphology.

  According to FIG.8 (b), the hexagonal symmetry (lattice length a = 3.1?) Was shown in the surface, and it confirmed that the product 3 was a single crystal.

  From the above, in the production method of the present invention, the molar amount of iodine and metal hydroxide far exceeding the molar ratio of iodine and metal hydroxide described in Patent Document 2 (at most 2 × 1/3). It has been found that even if the ratio is employed, a topotactic reaction from the starting material is possible.

  FIG. 9 is a diagram showing an XPS spectrum of the product 1-4 according to Example 1.

XPS spectrum a is the XPS spectrum of Co (OH) ₂ which is the starting material used in Example 1, and XPS spectrum b is the XPS spectrum of product 1-4.

According to the XPS spectrum a, the Co2p core line of Co (OH) ₂ is split into Co2p _3/2 (780.2 eV) and Co2p _1/2 (796.6 eV). These main peaks are accompanied by satellite bands of 785.5 eV and 802.1 eV, respectively. The satellite band of Co2p _3/2 shows a high spin Co ²⁺ state.

According to XPS spectrum b, the main peaks of Co2p _3/2 and Co2p _1/2 were shifted to the lower energy side of 780.2 eV to 779.7 eV and 796.6 eV to 795.5 eV, respectively. Also, the intensity of the satellite band in the XPS spectrum b was slightly reduced compared to that of the XPS spectrum a.

The spectroscopic differences in these XPS spectra a and b suggest a partial valence change from Co ²⁺ to Co ³⁺ . That is, it is shown that oxidation of Co ²⁺ can be caused by concentration effect, for example, by using much more iodine than that described in Patent Document 2 in the production method of the present invention.

5 and 9, the product 1-4 is a layered compound in which a part of Co in Co (OH) ₂ is oxidized from Co ²⁺ to Co ³⁺ , and I ⁻ and I ₃ ⁻ are intercalated. It was suggested to be a hydroxide. That is, in the production method of the present invention, in M1 ′ _1-x M2 ′ _x (OH) ₂ (x = 0) as a starting material, M1 ′ is oxidized from divalent to trivalent as necessary. I understood.

  FIG. 10 shows the XPS spectrum of product 4 according to Example 4.

XPS spectra a and b in FIG. 10A are XPS spectra for Co (OH) ₂ and Co of product 4, respectively. The XPS spectra a and b in FIG. 10B are XPS spectra for Co (OH) ₂ and Fe of the product 4, respectively.

As shown in the XPS spectrum a in FIG. 10B, it is difficult to accurately analyze the valence due to the overlap from the CoLMN Auger peak in the vicinity of 715 eV, but the XPS spectrum b in FIG. The appearance of a satellite band in the vicinity of the Fe2p main peak in shows the Fe ³⁺ state.

Similarly, in the XPS spectrum b of FIG. 10A, the FeLMN Auger peak in the vicinity of 785 eV overlaps the energy region of the Co core line, which makes it difficult to analyze the Co valence. The main peaks of Co2p _3/2 and Co2p _1/2 of the XPS spectrum b were both shifted to the lower energy side as compared with that of the XPS spectrum a. Also, the intensity of the satellite band in the XPS spectrum b was slightly reduced compared to that of the XPS spectrum a.

Similar to FIG. 9, spectroscopic differences in these XPS spectra suggest a complete valence changes to ^{Fe 3+} from ^{Fe 2+,} a partial valence changes from ^{Co 2+} to ^{Co 3+} . That is, in the production method of the present invention, by using much excess iodine than the iodine described in Patent Document 1, in addition to complete oxidation of Fe ²⁺ , oxidation of Co ²⁺ can occur kinetically. Show. That is, in the production method of the present invention, in M1 ′ _1-x M2 ′ _x (OH) ₂ (0 ≦ x ≦ 1/3) which is a starting material, M1 ′ is added as necessary in addition to M2 ′. It was found to oxidize from divalent to trivalent.

Further referring to Table 1, the molar ratio of trivalent and divalent metal cations of the products 1 to 4 obtained by titration is the molar ratio (atomic ratio) between M2 ′ and M1 ′ in the starting material. Regardless, both were found to be ½. In addition, when the composition formulas of the products 1 to 4 by elemental analysis in Table 1 are seen, in Example 1, Examples 3 and 4, a part of Co ²⁺ that is M1 ′ in the starting material becomes Co ³⁺ . I found out. Therefore, according to the production method of the present invention, in M1 ′ _1-x M2 ′ _x (OH) ₂ (0 ≦ x ≦ 1/3) which is the starting material, in addition to M2 ′, M1 ′ is It was confirmed that oxidation was performed from divalent to trivalent as necessary.

  FIG. 11 is a diagram showing UV-vis spectra of products 2-4 according to Examples 2-4.

Spectra a to c are UV-vis spectra of products 2 to 4, respectively. All the spectra had peaks showing absorption at wavelengths of 290 nm and 360 nm. These peaks are all due to I ₃ ⁻ and correspond to σ → σ ^* transition and π → σ ^* transition. On the other hand, the spin-forbidden singlet-triplet transition of I ₃ ⁻ at 440 nm and 560 nm, which is prominent when I ₃ ⁻ is low-symmetric, was not observed. This suggests that linear I ₃ ⁻ is intercalated between the layers of the products 2 to 4.

Note that the peak near the wavelength of 230 nm is ignored because it is caused by charge transfer between cobalt and oxygen and is not involved in I ₃ ⁻ .

  FIG. 12 is an XRD pattern of anion-exchanged product 3 according to Example 3.

  XRD patterns a to c are XRD patterns of the product 3, the product 3p, and the product 3ds, respectively. According to XRD patterns b and c, the products 3p and 3ds after anion exchange also showed a single phase. More specifically, the primary bottom surface reflection peak 9.2 生成 of the product 3p and the primary bottom surface reflection peak 23.7Å of the product 3ds coincided with, for example, FIG.

  In addition, a prominent feature of the XRD pattern by anion exchange is an intensity ratio between the peak intensity of the primary bottom surface reflection peak and the peak intensity of the secondary bottom surface reflection peak. According to the XRD pattern a before anion exchange, the peak intensity of the primary bottom surface reflection peak (about 8.7Å) is lower than that of the secondary bottom surface reflection peak (4.3Å). On the other hand, according to the XRD patterns b and c after the anion exchange, the peak intensity of the primary bottom surface reflection peaks (9.2９ and 23.7Å) is higher than that of the secondary bottom surface reflection peak. That is, it was found that the intensity ratio between the primary bottom surface reflection peak and the secondary bottom surface reflection peak was reversed before and after anion exchange.

From such a reversal of the intensity ratio, the product (layered double hydroxide) obtained by the production method of the present invention is capable of anion exchange, and the layered double water obtained by the production method of the present invention. The unique XRD pattern found in the oxide (ie, the peak intensity of the primary bottom reflection is lower than the peak intensity of the secondary bottom reflection) is the triiodide intercalated between the layers of the layered double hydroxide. It has been found that it can be attributed to ions (I ₃ ⁻ ).

  13 shows the UV-vis spectrum of the product 3ds according to Example 3. FIG.

Spectrum d is the UV-vis spectrum of product 3ds, and spectra ac are identical to UV-vis spectra ac of FIG. Spectrum d did not have absorption peaks at wavelengths 290 nm and 360 nm seen in spectra ac. That is, it was confirmed that the spectrum d does not have I ₃ ⁻ . This also indicates that the product (layered double hydroxide) obtained by the production method of the present invention can be easily anion-exchanged.

FIG. 14 is a diagram showing TG curves of product 3 and product 3p according to Example 3.
FIG. 15 is a diagram showing TG curves of product B and product Bp according to Comparative Example 2.

  Curves a and b in FIG. 14 are TG curves of product 3 and product 3p, respectively. Curves c and d in FIG. 15 are TG curves of product B and product Bp, respectively.

  Comparing curve a and curve c, product 3 showed a weight loss of about 50% and product B showed a weight loss of about 34%. On the other hand, when curve b and curve d were compared, both product 3p and product Bp after anion exchange showed similar weight loss. The curves a to c all have the same behavior.

From this, the product (layered double hydroxide) obtained by the production method of the present invention has an existing layered compound except that it has a high content of anions (I ⁻ and I ₃ ⁻ ) between layers. It was found to have a layered structure similar to hydroxide.

Referring to the elemental analysis by EDS in Table 1, the average molar ratio of iodine in the products 1 to 4 is about 1.6 times that of iodine in the product B (about 1/3). Similar to the 15 results, a high content of iodine is included. That is, in the layered double hydroxide obtained by the production method of the present invention, the average content of iodine per chemical formula is 1.6 × 1/3 mol, and although there is an error, the composition formula M1 ²⁺ _2/3 It was confirmed that M2 ³⁺ _1/3 (OH) ₂ I _5/9 · mH ₂ O (m is in the range of 0.1 to 0.5) was satisfied.

At high concentrations of iodine / iodide ion solution, as shown in the following equation, iodine (I ₂₎ is an iodide ion ^- combine with triiodide ions ^(I) (I 3 _-) form a.
I ₂ + I ⁻ → I ₃ ⁻
In the iodine-iodide ion system, a number of one-electron reduction reactions can occur. By this one-electron reduction reaction, the iodide ion / triiodide ion pair is used as an effective redox mediator in, for example, a dye-sensitized solar cell (DSSC). In the production method of the present invention, oxidation of Co ²⁺ to Co ³⁺ in addition to complete oxidation of Fe ²⁺ to Fe ³⁺ by generating triiodide ions (I ₃ ⁻ ) using high concentration iodine. Also became possible. That is, in M1 ′ _1-x M2 ′ _x (OH) ₂ (0 ≦ x ≦ 1/3) which is a starting material, in addition to M2 ′, M1 ′ is divalent to trivalent as necessary. It is considered that the effect of promoting the formation of the layered double hydroxide was obtained by enabling the oxidation of.

  FIG. 16 is a schematic diagram of the superlattice structure of the product 3 according to Example 5.

The structure of the layered double hydroxide is determined by the arrangement of metal cations in the host layer that controls the charge distribution and the corresponding anion distribution in the intermediate layer. The M1 and M2 ions in the host layer are considered to appear as superlattice arrays by avoiding the proximity of the higher valence M2 ³⁺ . The superlattice aspect is closely related to the charge (M2 ³⁺ / (M1 ²⁺ + M2 ³⁺ )) of the host layer. FIG. 16 shows a possible superlattice structure for the product 3 obtained in Example 3 (when the starting material is Co ²⁺ _3/4 Fe ²⁺ _1/4 (OH) ₂ ). In FIG. 16, a solid diamond represents a basic unit cell, and a dotted diamond represents a superlattice. The lattice length is a, which corresponds to the distance between metal cations. Each superlattice has one positive charge.

Assuming that only Fe ²⁺ out of Co ²⁺ _3/4 Fe ²⁺ _1/4 (OH) ₂ is oxidized by the manufacturing method of the present invention, the host layer has [Co ²⁺ _3/4 Fe ³⁺ _1/4 (OH ₂ ] ^{1/4 +} . In this case, a superlattice (referred to as a 2a × 2a superlattice) as shown in FIG. This 2a × 2a superlattice (a is the distance between metal cations) has three M1 ²⁺ (ie Co ²⁺ ) and one M2 ³⁺ (ie Fe ³⁺ ) for one positive charge, M2 ³⁺ / M1 ²⁺ = 1/3 is satisfied.

On the other hand, by the production method of the present ^invention, in addition to all of the ^{Fe 2+} of _{^{Co 2+ 3/4 Fe 2+ 1/4 (OH}} ) 2, assuming that some of ^{Co 2+} is oxidized, the host layer [ Co ²⁺ _2/3 (Co ³⁺ _1/12 Fe ³⁺ _1/4 ) (OH) ₂ ] ^{1/3 +} . In this case, a superlattice (referred to as √3a × √3a superlattice) as shown in FIG. This √3a × √3a superlattice has two M1 ²⁺ (ie, Co ²⁺ ) and one M2 ³⁺ (ie, Co ³⁺ and Fe ³⁺ ) for one positive charge, and M2 ³⁺ / M1 ^{Satisfies 2+} = 1/2.

Both the 2a × 2a superlattice and the √3a × √3a superlattice generate one anion site in the intermediate layer. Each anion shares its charge with one M2 ³⁺ cation in the underlying host layer and one M2 ³⁺ cation in the underlying host layer. There are six equivalent sites around each anion site, which form a hexagonal array of anions.

Next, using the superlattice structures (I) and (II) of FIG. 16, the distribution of possible iodide ions (I ⁻ ) and triiodide ions (I ₃ ⁻ ) in the intermediate layer was examined.

FIG. 17 is a diagram showing the iodine distribution in the intermediate layer of the product 3 according to Example 5 and the simulated low-angle XRD pattern.
FIG. 18 is a diagram showing another distribution of iodine in the intermediate layer of the product 3 according to Example 5 and a simulation low-angle XRD pattern.
FIG. 19 is a diagram showing still another distribution of iodine in the intermediate layer of the product 3 according to Example 5 and a simulation low-angle XRD pattern.
FIG. 20 is a diagram showing still another distribution of iodine in the intermediate layer of the product 3 according to Example 5 and a simulation low-angle XRD pattern.
FIG. 21 is a diagram showing another further distribution of iodine in the intermediate layer of the product 3 according to Example 5 and a simulated low-angle XRD pattern.

17 to 19 show that the iodide ion and triiodide ion in the intermediate layer for the superlattice structure (I) in FIG. 16 are 1 / 4I ⁻ , 1/4 (2 / 3I ⁻ + 1 / 3I ₃ ^{−), respectively.} ) And 1/4 (1 / 2I ⁻ + 1 / 2I ₃ ⁻ ) distributions and the corresponding simulated low angle XRD patterns.

20 and 21 show that the iodide ion and triiodide ion in the intermediate layer for the superlattice structure (II) in FIG. 16 are 1 / 3I ⁻ and 1/3 (2 / 3I ⁻ + 1 / 3I ₃ ^{−, respectively.} ) Distribution and the corresponding simulated low angle XRD pattern.

The ion diameter of I ⁻ (4.32 Å) is much larger than the distance between metal cations (about 3.1 Å). However, considering the 2a × 2a superlattice in FIG. 16 (I) and the √3a × √3a superlattice in FIG. 16 (II), both generate one anion site in the intermediate layer. In the 2a × 2a superlattice of FIG. 16 (I), 2a (6.2６), or in the √3a × √3a superlattice of FIG. 16 (II), √3a (5.37Å), the I ⁻ ion diameter Each superlattice can be charged neutral by one iodide ion, separated by a distance greater than (4.32 cm). Thus, the interlayer iodide ion alignment is consistent with the long-range order of the metal cations in the host layer.

As shown in FIG. 17A, when the anion site is occupied only by I ⁻ , the model composition formula of the product 3 is Co ²⁺ _3/4 Fe ³⁺ _1/4 (OH) ₂ I _1/4 · 0.2H ₂ O (that is, the iodine content in the composition formula is I _0.25 ). This iodine content was found to be extremely low compared to the iodine content obtained by composition analysis (for example, the composition formula in Table 1). Furthermore, as shown in FIG. 17B, according to the low-angle XRD pattern simulated from the model composition formula, the peak intensity of the primary bottom surface reflection is higher than the peak intensity of the secondary bottom surface reflection. This was found to be different from the experimental results (eg, FIG. 7). Therefore, the superlattice structure and composition formula corresponding to FIG. 17 do not correspond to the layered double hydroxide of the present invention.

When the anion site is linearly occupied by I ₃ ⁻ , the XRD pattern changes dramatically due to the extremely high X-ray scattering ability by I ₃ ⁻ . The size of the linear triiodide ion (I ₃ ⁻ ) described with reference to FIG. 11 is estimated to be 4.32 × 9.64 ² .

As shown in FIG. 18A, when the anion site is occupied by 2 / 3I ⁻ and 1 / 3I ₃ ⁻ , the model composition formula of the product 3 is Co ²⁺ _3/4 Fe ³⁺ _1/4 ( OH) ₂ (2 / 3I + 1 / 3I ₃ ) _1/4 · 0.2H ₂ O (that is, the iodine content in the composition formula is I _0.42 ). The iodine content was found to be lower than the iodine content obtained by composition analysis (for example, the composition formula in Table 1). On the other hand, as shown in FIG. 18B, according to the low angle XRD pattern simulated from the model composition formula, the peak intensity of the primary bottom surface reflection is the peak of the secondary bottom surface reflection as in the experimental result (FIG. 7). Although lower than the intensity, the peak of the primary bottom reflection is clearly shown.

As shown in FIG. 19A, when the anion site is occupied by 1 / 2I ⁻ and 1 / 2I ₃ ⁻ , the model composition formula of the product 3 is Co ²⁺ _3/4 Fe ³⁺ _1/4 ( OH) ₂ (1 / 2I + 1 / 2I ₃ ) _1/4 · 0.2H ₂ O (that is, the iodine content in the composition formula is I _0.50 ). Although the iodine content was slightly lower than the iodine content obtained by the composition analysis (for example, the composition formula in Table 1), the iodine content was relatively good. Further, as shown in FIG. 19B, according to the low angle XRD pattern simulated from the model composition formula, the peak intensity of the primary bottom surface reflection is the peak of the secondary bottom surface reflection as in the experimental result (FIG. 7). It became lower than the strength. However, compared to FIG. 18B, the peak intensity of the primary bottom reflection is low but still clearly shown.

17 to 19 suggest that the product 3 has triiodide ions (I ₃ ⁻ ) in the intermediate layer. Assuming that only Fe ²⁺ out of Co ²⁺ _3/4 Fe ²⁺ _1/4 (OH) ₂ is oxidized, the host layer is [Co ²⁺ _3/4 Fe ³⁺ _1/4 (OH) ₂ ] _1/4 ⁺ . And the intermediate layer is expected to be [(1 / 2I + 1 / 2I ₃ ) _1/4 · 0.2H ₂ O] ^{1 / 4−} .

As shown in FIG. 20A, when the anion site is occupied only by I ⁻ , the model composition formula of the product 3 is Co ²⁺ _2/3 (Co ³⁺ _1/12 Fe ³⁺ _1/4 ) (OH ) ₂ I _1/3 · 0.2H ₂ O (that is, the iodine content in the composition formula is I _0.33 ). This iodine content was found to be extremely low compared to the iodine content obtained by composition analysis (for example, the composition formula in Table 1). Furthermore, as shown in FIG. 20B, according to the low-angle XRD pattern simulated from the model composition formula, the peak intensity of the primary bottom surface reflection is somewhat lower than the peak intensity of the secondary bottom surface reflection. It was in good agreement with the XRD pattern a (product B) in FIG. Therefore, the superlattice structure and composition formula corresponding to FIG. 20 do not correspond to the layered double hydroxide of the present invention.

As shown in FIG. 21A, when the anion site is occupied by 2 / 3I ⁻ and 1 / 3I ₃ ⁻ , the model composition formula of the product 3 is Co ²⁺ _2/3 (Co ³⁺ _1/12 Fe ³⁺ _1/4 ) (OH) ₂ (2 / 3I + 1 / 3I ₃ ) _1/4 · 0.2H ₂ O (that is, the iodine content in the composition formula is I _0.555 ). This iodine content was in good agreement with the iodine content (for example, the composition formula in Table 1) obtained by composition analysis. Further, as shown in FIG. 21B, according to the low angle XRD pattern simulated from the model composition formula, the peak intensity of the primary bottom reflection is lower than the peak intensity of the secondary bottom reflection, and the primary bottom The peak intensity of reflection was negligibly low, which was in good agreement with the experimental result (FIG. 7).

20 to 21 suggest that the product 3 has triiodide ions (I ₃ ⁻ ) in the intermediate layer. Assuming that a part of Co ²⁺ is oxidized in addition to Fe ²⁺ in Co ²⁺ _3/4 Fe ²⁺ _1/4 (OH) ₂ , the host layer is [Co ²⁺ _2/3 (Co ³⁺ _1/12 Fe ^{_{3+ 1/4) (OH) 2]}} 1/3 is ^+, the intermediate layer is expected to _{[(2 / 3I + 1 /} 3I 3) 1/3 · 0.2H 2 O] 1 / 3- is.

Further, when FIG. 19 is compared with FIG. 21, it is more consistent with the experimental result in FIG. 21 (FIG. 17 and Table 1), so that the product 3 has a host layer of [Co ²⁺ _2/3 (Co ^{3 +} _{1). ^{/ 12 Fe 3+ 1/4) (OH}} ) 2] 1/3 is ^+, the intermediate layer is _{[(2 / 3I + 1 /} 3I 3) 1/4 · 0.2H 2 O] 1 / 3- layered double water is Suggested oxide.

16 to 21, the layered double hydroxide of the present invention has M2 ³⁺ / M, regardless of the molar ratio of M2 ′ to M1 ′ of the starting material M1 ′ _1-x M2 ′ _x (OH) _2. The molar ratio of M1 ²⁺ was 1/2, and the intermediate layer was shown to contain I ⁻ and I ₃ ⁻ ions. Furthermore, in the layered double hydroxide of the present invention, it was shown that the content of iodine in the intermediate layer was 1/3 (2 / 3I + 1 / 3I ₃ ).

  Since the XRD pattern is significantly affected by the iodine content in the intermediate layer, it goes without saying that the above-described model composition formula and XRD simulation can be similarly applied to the products of other examples.

  The layered double hydroxide according to the present invention is applied to a fine device utilizing the electrical and magnetic properties resulting from selected M1 and M2. The layered double hydroxide according to the present invention can be applied to an anion exchange material, an adsorbent, a catalyst, a nanoreactor, a molecular sieve, a polymer composite material, a biomaterial and the like in the same manner as the existing layered double hydroxide. Moreover, if the layered double hydroxide according to the present invention is peeled off, a nanosheet that can function as a building block can be provided.

100, 300 Layered double hydroxide 110 Host layer 120 Intermediate layer 310 Anion

JP 2008-290913 A JP 2009-203081 A

Liang et al., Chem. Mater. 2010, 22, 371

Claims (10)

A layered double hydroxide comprising a laminated structure of a host layer containing M1 ²⁺ ions and M2 ³⁺ ions and an intermediate layer containing anions,
The element M1 of the M1 ²⁺ ion is a transition metal selected from at least one selected from the group consisting of Co, Fe, Ni, and Zn,
The element M2 of the M2 ³⁺ ion is a transition metal of Co and / or Fe,
The molar ratio (M2 ³⁺ / M1 ²⁺ ) between the M2 ³⁺ ion and the M1 ²⁺ ion is 1/2,
The anion is a layered double hydroxide containing I ⁻ ions and I ₃ ⁻ ions. 2. The layered double hydroxide according to claim 1, wherein a molar ratio (I ₃ ⁻ / I ⁻ ) between the I ₃ ⁻ ion and the I ⁻ ion is ½. The host layer is represented by the general formula [M1 ²⁺ _2/3 M2 ³⁺ _1/3 (OH) ₂ ] _1/3 ⁺
The intermediate layer general formula ^{1 / 3-} (m is in the range of _{^{0.1~0.5) [1/3 · mH 2 O}} (I - 1/3 - 2/3 + I 3)] The layered double hydroxide according to claim 1 represented.   The layered double hydroxide according to claim 1, wherein the layered double hydroxide has a hexagonal plate shape.   The layered double hydroxide according to claim 1, wherein the peak intensity of primary bottom reflection in the X-ray diffraction pattern of the layered double hydroxide is lower than the peak intensity of secondary bottom reflection. A method for producing the layered double hydroxide according to any one of claims 1 to 5,
M1 ′ _1-x M2 ′ _x (OH) ₂ (M1 ′ includes a transition metal of Co and / or Fe, and optionally includes a transition metal of Ni and / or Zn, and M2 ′ includes Co and / or Or a transition metal of Fe, and x is a brucite-type metal hydroxide represented by 0 ≦ x <1/3), or M1 ′ _1-x M2 ′ _x (OH) ₂ ( M1 ′ comprises a transition metal selected from the group consisting of Co, Fe, Ni and Zn, M2 ′ is a transition metal of Co and / or Fe, and x is x = 1/3) Including the step of adding and stirring the represented brucite-type metal hydroxide to the iodine-dissolved solution;
The molar ratio of the iodine to the brucite metal hydroxide (iodine / brucite metal hydroxide) is 2.5 × 1/3 to 40 × 1/3 (where iodine is I) Is the range of methods.   The method according to claim 6, wherein the content of Co and / or Fe that becomes trivalent is 1/3 or more of the metal content in the brucite metal hydroxide in molar ratio.   The molar ratio of the iodine to the brucite metal hydroxide (iodine / brucite metal hydroxide) is in the range of 10 × 1/3 to 25 × 1/3 (where iodine is I). The method of claim 6, wherein   The method according to claim 6, wherein in the adding and stirring, the solution to which the brucite-type metal hydroxide is added is stirred at room temperature for 1 to 7 days.   The method according to claim 6, wherein a solvent of the iodine-dissolved solution is chloroform.