Preparation method of MOF disordered material with weak ferromagnetism

Abstract

The invention discloses a weak ferromagnetism MOF disordered material and a preparation method thereof, the weak ferromagnetism MOF disordered material comprises a metal source and an organic ligand, the chemical formula of the weak ferromagnetism MOF disordered material is M (1-x-y) OL1xOL2y, 0 < = x < = 1, 0 < = y < = 1, and M is the metal source: Fe, Co or Ni; and OL is an organic ligand: imidazole (C3H4N2), benzimidazole (C7H6N2), indole (C8H7N) or 2-ethylimidazole (C5H8N2). On the basis of structure disordering, magnetic switching is directly achieved through external field induction metal source self-rotation structure change of a temperature field and a pressure field and the magnetic exchange effect between a nearest neighbor metal source and a ligand, and compared with a composite magnetic particle (Fe3O4 and the like) technology, the method is easy to operate, high in regulation and control speed, easy in process control and suitable for large-scale industrial production. And the prepared MOF disordered material with weak ferromagnetism is more uniform in composition.

Description

Technical Field

[0001] The invention belongs to the technical field of metal-organic framework (MOFs) materials, and in particular relates to a method for preparing a weakly ferromagnetic MOF disordered material. Background Art

[0002] Weak ferromagnetic materials have unique advantages in the field of spintronic devices due to their unique spin ordering mechanism (antiparallel arrangement of spin centers or spin tilt), especially in devices such as micro-nano magnetic sensors and high-density storage media. At present, commercial magnets generally use metal oxides or alloy systems. Their performance is limited by the non-adjustability of chemical composition and structure, making it difficult to achieve dynamic adjustment of magnetic properties, and unable to meet the needs of emerging scenarios such as flexible electronics and biocompatible devices for programmability and adjustability of materials. Based on the modular construction characteristics of MOF materials, combined with the external field-assisted "order-disorder coordinated regulation" strategy, multi-dimensional magnetic coupling regulation is carried out to change the coordination environment, orientation and orbital hybridization of metal nodes, and then the intensity of magnetic exchange interaction is enhanced by constructing the hybridization of ligand π orbitals and metal d orbitals and controlling the distance between metal nodes in the framework structure. Different from the guest doping method, this technology achieves a weak ferromagnetic state at room temperature by directional construction of topological structures and controllable disorder.

[0003] In the past few decades, there have been many reports on MOF magnetism research, but there are almost no cases showing weak ferromagnetism at room temperature. This is mainly limited by the strength of magnetic coupling, which mainly involves the following difficulties: first, the magnetic exchange capacity of the selected building units is weak, and second, the selected magnetic control methods cannot effectively improve the magnetic exchange effect. Therefore, it is necessary to select suitable building units and develop effective magnetic control methods. Breakthroughs in this area will help promote the development of magnetic MOF materials, and then promote the development of spin electronics and flexible electronic devices. Summary of the invention

[0004] In order to solve the defects in the prior art, the present invention provides a weak ferromagnetic MOF disordered material.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The first object of the present invention is to provide a weak ferromagnetic MOF disordered material, wherein the weak ferromagnetic MOF disordered material is composed of a metal source and an organic ligand, and its chemical formula is M (1-x-y) OL1 x OL2 y , wherein 0≤x≤1, 0≤y≤1, the metal source comprises one or more of Fe, Co or Ni, and the organic ligand comprises one or more of imidazole, benzimidazole, indole or 2-ethylimidazole.

[0007] The second object of the present invention is to provide a method for preparing a weakly ferromagnetic MOF disordered material, comprising the following steps:

[0008] S1. Mix a metal source and an organic ligand, and place them in a sealed reaction vessel in a non-oxidizing environment, and heat to 80-300 °C for reaction;

[0009] S2. After the reaction is completed, cool to room temperature, wash, and then dry in a non-oxidizing environment to obtain an antiferromagnetic MOF ordered material;

[0010] S3. Place the antiferromagnetic MOF ordered material in a reaction vessel in a non-oxidizing environment, and carry out disordering treatment with the assistance of a set external pressure field and temperature field system to obtain a weakly ferromagnetic MOF disordered material.

[0011] Preferably, in step S1, the non-oxidizing environment is any one of argon, vacuum, nitrogen, and hydrogen, and the reaction time in step S1 is 24-96 h.

[0012] Preferably, in step S2, the non-oxidizing environment for drying is vacuum, the drying temperature is 80-120 °C, and the drying time is 8-12 h.

[0013] Preferably, in step S3, the non-oxidizing environment for the disordering treatment is any one of argon, vacuum, nitrogen or hydrogen.

[0014] Preferably, the external temperature field in step S3 is: heating to 200-220 °C at a rate of 10-40 °C / min and holding for 10-40 min, then heating to 280-300 °C at a rate of 5-40 °C / min and holding for 10-30 min, then heating to 430-500 °C at a rate of 5-40 °C / min and holding for 10-30 min, and finally cooling to room temperature at a rate of 5-40 °C / min.

[0015] Preferably, the pressure of the external pressure field is: 0.1-1 MPa in the heating stage and 1-1.5 MPa in the cooling stage.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The external field-assisted disordering engineering treatment method used in the present invention solves the problem that room-temperature weak ferromagnetism cannot be obtained due to the too long distance between adjacent metal nodes. The obtained weakly ferromagnetic MOF disordered material has uniform composition and high purity. The method provided by the present invention uses the coupling of a specific temperature field and a pressure field to change the orientation, electronic configuration of metal nodes and the magnetic exchange interaction with organic ligands. Compared with composite magnetic particles, the operation is simple and the regulation process is easy to control.

[0018] The solvent-free synthesis method adopted by the present invention effectively eliminates the process of dissolving reactants in a solvent and the subsequent homogenization process, and avoids the interference of the solvent on the reaction process. It only requires weighing and mixing raw materials according to a ratio and reacting under specific reaction conditions. The externally field-assisted magnetic regulation method adopted controls the degree of disorder, and then controls the orientation, spin, and orbital hybridization degree of metal nodes to obtain a MOF disordered material with weak ferromagnetism at room temperature. Description of the Drawings

[0019] Figure 1 Optical morphology diagram of the antiferromagnetic MOF ordered material in Example 1

[0020] Figure 2 Magnetization intensity - magnetic field curve of the antiferromagnetic MOF ordered material in Example 1

[0021] Figure 3 Optical morphology diagram of the weak ferromagnetic MOF disordered material in Example 2

[0022] Figure 4 XRD pattern of the weak ferromagnetic MOF disordered material in Example 2

[0023] Figure 5 Magnetization intensity - magnetic field curve of the weak ferromagnetic MOF disordered material in Example 2. Detailed Description of the Invention

[0024] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0025] It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0026] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0027] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of the present invention are obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0028] Regarding the use of "comprising", "including", "having", "containing", etc. in this text, they are all open-ended terms, meaning including but not limited to.

[0029] Example 1: Preparation of an antiferromagnetic MOF ordered material.

[0030] Weigh 3.72 g of ferrocene and 2.72 g of imidazole, mix them and place them in a hydrothermal reaction kettle with a polytetrafluoroethylene liner under an argon atmosphere; keep this hydrothermal reaction kettle at 150 °C for 48 h to induce the synthesis reaction, and after naturally cooling to room temperature, obtain the reaction product; use N,N-dimethylformamide to wash away the unreacted raw materials until the supernatant is clear and transparent, and dry the above product in a vacuum drying oven at 80 °C for 12 h to obtain a dried brownish-yellow powder, which is the prepared antiferromagnetic MOF ordered material.

[0031] Figure 1 Figure of the optical morphology of the antiferromagnetic MOF ordered material prepared in Example 1. From Figure 1 it can be seen that the product is brownish-yellow and the average size is 500 μm.

[0032] Figure 2 Magnetization intensity - magnetic field curve of the antiferromagnetic MOF ordered material prepared in Example 1. From Figure 2 it can be seen that the curve is approximately a straight line and there is no obvious hysteresis phenomenon, proving the existence of antiferromagnetic interaction.

[0033] Example 2: Preparation of a weak ferromagnetic MOF disordered material.

[0034] Weigh 300 mg of the antiferromagnetic MOF ordered material obtained in Example 1, put it into a customized hot pressing mold, and place this hot pressing mold in a vacuum hot press. Apply an external pressure field of 1 MPa and assist the temperature field with the following regime: heat up to 220 °C at a rate of 20 °C / min and keep it for 20 min, then heat up to 300 °C at a rate of 10 °C / min and keep it for 20 min, and then heat up to 480 °C at a rate of 10 °C / min; apply an external pressure field of 1.2 MPa and assist the temperature field with the following regime: cool down to room temperature at a rate of 20 °C / min, and remove the pressure field to obtain a weak ferromagnetic Fe-MOF disordered material.

[0035] Figure 3Optical morphology map of the weakly ferromagnetic MOF disordered material prepared in Example 2. It can be seen from Figure 3 that the average size of the product is 40 μm.

[0036] Figure 4 XRD pattern of the weakly ferromagnetic MOF disordered material prepared in Example 2. It can be seen from Figure 4 that there are no obvious diffraction peaks in the pattern, proving its long-range disorder state.

[0037] Figure 5 Magnetization intensity - magnetic field curve of the weakly ferromagnetic MOF disordered material prepared in Example 2. It can be seen from Figure 5 that the curve has an obvious hysteresis phenomenon, its coercivity is 501 Oe, and the remanent magnetization intensity is 0.50 emu / g, proving the existence of ferromagnetic interactions. In the range of -20 kOe to 20 kOe, the magnetization intensity does not reach saturation, proving the existence of antiferromagnetic interactions. Therefore, the MOF disordered material exhibits weak ferromagnetism from the canted antiferromagnetic order.

[0038] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A weakly ferromagnetic MOF disordered material, characterized in that, The weakly ferromagnetic MOF disordered material is composed of a metal source and an organic ligand, and its chemical formula is M (1-x-y) OL1 x OL2 y , where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1. The metal source includes one or more of Fe, Co, or Ni, and the organic ligand includes one or more of imidazole, benzimidazole, indole, or 2-ethylimidazole.

2. A method for preparing a weakly ferromagnetic disordered MOF material as described in claim 1, characterized in that, It includes the following steps: S1. Mix the metal source and the organic ligand and place them in a sealed reaction vessel in a non-oxidizing environment, and heat to 80 - 300 °C for reaction; S2. After the reaction is completed, cool to room temperature, wash, and then dry in a non-oxidizing environment to obtain an antiferromagnetic MOF ordered material; S3. Place the antiferromagnetic MOF ordered material in a reaction vessel in a non-oxidizing environment, and carry out disordering treatment with the assistance of a set external pressure field and temperature field regime to obtain a weakly ferromagnetic MOF disordered material.

3. The preparation method of the weakly ferromagnetic MOF disordered material according to claim 2, characterized in that, In step S1, the non-oxidizing environment is any one of argon, vacuum, nitrogen, and hydrogen, and the reaction time in step S1 is 24 - 96 h.

4. The preparation method of the weakly ferromagnetic MOF disordered material according to claim 2, wherein In step S2, the non-oxidizing environment for drying is vacuum, the drying temperature is 80 - 120 °C, and the drying time is 8 - 12 h.

5. The preparation method of the weakly ferromagnetic MOF disordered material according to claim 2, wherein, In step S3, the non-oxidizing environment for disordering treatment is any one of argon, vacuum, nitrogen, or hydrogen.

6. The preparation method of the weakly ferromagnetic MOF disordered material according to claim 2, characterized in that, The external temperature field in step S3 is: heat up to 200 - 220 °C at a rate of 10 - 40 °C / min and keep warm for 10 - 40 min, then heat up to 280 - 300 °C at a rate of 5 - 40 °C / min and keep warm for 10 - 30 min, then heat up to 430 - 500 °C at a rate of 5 - 40 °C / min and keep warm for 10 - 30 min, and finally cool down to room temperature at a rate of 5 - 40 °C / min.

7. The preparation method of the weakly ferromagnetic MOF disordered material according to claim 2, wherein The pressure of the external pressure field is: 0.1 - 1 MPa in the heating stage and 1 - 1.5 Mpa in the cooling stage.

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