Anion shielding type porous organic cage and preparation method thereof

Abstract

The invention discloses an anion shielding type porous organic cage and a preparation method thereof, and belongs to the technical field of porous material chemistry and functional materials. According to the invention, triaminoguanidine salt and tetraformyl resorcinol [4] arene (C4RACHO) are used as reaction monomers, and the porous organic cage material with the anion encapsulation characteristic is synthesized in one step. Single crystal X-ray diffraction analysis, infrared spectroscopy, solid nuclear magnetism and other representations prove that the organic cage is successfully synthesized. A single-crystal structure proves that anions are all packaged in intrinsic holes of a molecular cage, and the anions in the cage cannot escape due to the fact that the window size of the molecular cage is small. Thermogravimetric analysis shows that the material has high thermal stability. Through nitrogen adsorption-desorption test analysis, the organic cage material shows a developed pore structure and a high specific surface area characteristic. The anion-encapsulated porous organic cage is expected to be industrially popularized and applied in the fields of capacitors, energy storage, catalysis, gas adsorption and separation, pollutant treatment and the like.

Description

Technical Field

[0001] This invention belongs to the fields of porous materials chemistry, supramolecular chemistry, functional materials and separation technology, and energy materials, and specifically relates to the preparation of an anion-shielded porous organic cage. Background Technology

[0002] Existing ionic materials are usually synthesized in situ by modifying the framework with anions / cations or using ionic ligands. The anions, which are usually counterions, are mostly free in the pores of the material. This leads to the following problems: (1) Anions are easily lost: external anions are easily dissociated in solvents, which destroys the structural stability; (2) Thermal stability is reduced: the dynamic movement of anions is intensified at high temperatures, which may cause them to detach from the material body, especially limiting their high-temperature applications in gas adsorption or catalytic reactions; (3) Pore blockage and limited mass transfer: free anions may accumulate disorderly in the pores, blocking the mass transfer path and reducing the gas / molecule diffusion efficiency; (4) Signal interference: in sensing applications, free anions may non-specifically bind with other analytes, reducing the detection signal-to-noise ratio; (5) Short cycle life: in applications such as battery electrolytes or electrocatalysis, the loss of anions will accelerate the failure of the material and significantly reduce the cycle stability. Summary of the Invention

[0003] To address the shortcomings and deficiencies of existing materials and technologies, this invention aims to provide a porous organic cage with anion-shielding properties, and also provides a method for preparing this porous organic cage. This invention completely encapsulates anions within the internal cavity of the organic cage by designing a rigid three-dimensional cavity for cations and strong electrostatic interactions.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: An anion-shielded porous organic cage material was prepared by reacting triaminoguanidine salt and C4RACHO as monomers, using ethanol, 1,4-dioxane, etc. as solvents, and acid as a catalyst. The structural diagram is shown below. The organic cage framework exhibits a [6+8] cage-like structure, with six C4RACHO units and eight triaminoguanidine salt linkers bridged by imine bonds formed by Schiff base reactions.

[0005] This invention provides a method for preparing anion-shielded porous organic cage material, the preparation reaction equation and structure of which are as follows.

[0006] The synthetic reaction used is a Schiff base formation reaction between an amino group and an aldehyde group.

[0007] Specifically, it includes the following steps: (1) Triaminoguanidine salt and tetraformylresorcinol[4] ligand (C4RACHO) were added to the reaction vessel, and then the reaction solvent and catalyst were added to the vessel in sequence; (2) Sonicate the reaction solution in step (1) for 5 to 60 minutes and shake well to make the reaction solution evenly mixed. Then, perform freezing-vacuuming-thawing operation in an inert gas atmosphere, repeating the cycle multiple times, and then seal the reaction container. (3) The sealed reaction vessel from step (2) is reacted at 50–200°C for 1–10 days; (4) After the reaction is complete, the reaction vessel of step (3) is cooled to room temperature and filtered to obtain the target product. The product is repeatedly soaked and washed with a mixture of water and methanol, and then dried.

[0008] Preferably, the molar ratio of triaminoguanidine salt to C4RACHO ligand is (1-10):1; more preferably, the molar ratio of triaminoguanidine salt to C4RACHO ligand is 4:3.

[0009] Preferably, the triaminoguanidine salt is triaminoguanidine hydrochloride, triaminoguanidine bromate, or triaminoguanidine iodide.

[0010] The reaction solvents include, but are not limited to, one or more combinations of N-methylpyrrolidone, 1,4-dioxane, trimethylbenzene, toluene, xylene, dichlorobenzene, ethanol, methanol, and water.

[0011] The catalyst includes, but is not limited to, one or more of the following: trifluoromethanesulfonic acid, glacial acetic acid, p-toluenesulfonic acid, hydrochloric acid, and trifluoroacetic acid.

[0012] The reaction vessel includes, but is not limited to: reaction vessel, flask, glass tube or glass bottle.

[0013] The present invention can be scaled up on a gram scale by using a molar ratio of triaminoguanidine salt to C4RACHO ligand of 4:3.

[0014] Tests show that the organic cage obtained by the present invention has a clear anion shielding structure: all anions are confined within the internal cavity of the molecular cage. The window size of the molecular cage is smaller than the van der Waals radius of the anion, so the anions cannot pass through the cage window and are permanently sealed in the cavity of the organic cage, thereby forming an anion shielding system. The guanidino cations exposed on the cage surface form cation pores through the stacking of cage layers.

[0015] Tests show that each vertex of the octahedral organic cage obtained by this invention has four hydrophobic groups (isobutyl groups), thereby forming a hydrophobic barrier and exhibiting excellent hydrophobic properties.

[0016] Tests show that the material obtained by this invention has good thermal stability and porous properties, with guanidinium cations in the pores, and its specific surface area can reach ~1000 m². 2 / g. The material of this invention can be applied in fields such as capacitors, energy storage, catalysis, gas adsorption and separation, and pollutant treatment.

[0017] Compared with existing ionic materials, the beneficial effects of this invention are: (1) Preventing the loss of anions: The anions are completely sealed in the cavity inside the organic cage, and are not easily lost in solvent or high temperature environments, thus maintaining structural stability. (2) Preventing channel blockage and mass transfer limitation: Free anions may accumulate disorderly in the channels, blocking the mass transfer path and reducing the gas / molecule diffusion efficiency, while the material of the present invention will not avoid such problems; (3) Avoid signal interference: In sensing applications, avoid non-specific binding of free anions with other analytes to reduce the detection signal-to-noise ratio; (4) In applications such as battery electrolytes or electrocatalysis, anions are not easily lost, and cycle stability is enhanced.

[0018] (5) The organic cage material of the present invention has a simple reaction operation and can be obtained in one step, which has obvious economic advantages and industrial application potential. Attached Figure Description

[0019] Figure 1 : A schematic diagram of the stacked structure of the anion-shielded porous organic cage synthesized in Example 1 of this invention (the anions in the organic cage are ignored for easy observation).

[0020] Figure 2 Powder X-ray diffraction pattern of the anion-shielded porous organic cage synthesized in Example 1 of this invention.

[0021] Figure 3 Infrared spectrum of the anion-shielded porous organic cage synthesized in Example 1 of this invention.

[0022] Figure 4 Solid-state NMR spectrum of the anion-shielded porous organic cage synthesized in Example 1 of this invention.

[0023] Figure 5 Thermogravimetric analysis diagram of the anion-shielded porous organic cage synthesized in Example 1 of this invention.

[0024] Figure 6 The nitrogen adsorption-desorption isotherm (77K) of the anion-shielded porous organic cage synthesized in Example 1 of this invention.

[0025] Figure 7Pore ​​size distribution diagram of the anion-shielded porous organic cage synthesized in Example 1 of this invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Example 1

[0027] First, 7.4 mg of triaminoguanidine hydrochloride and 20.5 mg of C4RACHO were added to a glass tube. Then, 0.2 mL of water, 0.5 mL of toluene, and 0.5 mL of ethanol were added sequentially to the glass tube. The mixture was sonicated for 10 min. A freeze-vacuum-thaw cycle was performed under liquid nitrogen three times. The glass tube was then evacuated and flame-sealed. The sealed glass tube was placed in a 100°C oven for 3 days. The reaction solution was filtered to obtain yellow crystals. After rinsing the crystals with a mixture of methanol and water, the crystals were vacuum-dried at 120°C for 12 hours to obtain the product of this invention.

[0028] Figure 1 The diagram shows a stacked structure of the anion-shielded porous organic cage of the present invention. The molecular cages are stacked through the hydrophobic interaction of the isobutyl groups on the surface to form a three-dimensional channel rich in cations.

[0029] Figure 2 The image shows the powder X-ray diffraction pattern of the anion-shielded porous organic cage of this invention. The dried and activated organic cage sample exhibits peak width expansion, which may be due to the fragmentation of some crystals during solvent removal. However, its main peak (2θ=4.14°) did not change significantly compared with the sample before drying, confirming that the structural integrity of the material was maintained after activation treatment.

[0030] Figure 3 The image shows the infrared spectrum of the anion-shielded porous organic cage of the present invention. No characteristic peaks of amino and aldehyde groups are observed in the spectrum. Instead, characteristic peaks of NH and CN of triaminoguanidine hydrochloride, as well as OH of C4RACHO and characteristic peaks of the benzene ring are shown, confirming the successful synthesis of the organic molecular cage.

[0031] Figure 4 The image shows the solid-state NMR spectrum of the anion-shielded porous organic cage of the present invention. No impurity peaks were observed in the spectrum, which proves the phase purity of the organic cage.

[0032] Figure 5 The thermogravimetric analysis (TGA) diagram of the anion-shielded porous organic cage of the present invention is shown. The TGA analysis shows that the thermal decomposition temperature of the material of the present invention is close to 300 °C, indicating that it has high thermal stability.

[0033] Figure 6The figure shows the nitrogen adsorption-desorption isotherm (77 K) of the anion-shielded porous organic cage of this invention, confirming that the synthesized organic cage has a nitrogen adsorption-desorption isotherm of ~1000 m. 2 / g high specific surface area.

[0034] Figure 7 The diagram shown is a pore size distribution of the anion-shielded porous organic cage of the present invention. The main pore size of the material of the present invention is in the range of 0.4-1.3 nm. Example 2

[0035] Unlike Example 1, in this example, the triaminoguanidine salt is selected as triaminoguanidine bromate or triaminoguanidine iodate. Example 3

[0036] Unlike Example 1, in this example, in addition to toluene, ethanol, and water, the reaction solvent can also be one or more combinations of N-methylpyrrolidone, 1,4-dioxane, trimethylbenzene, toluene, xylene, dichlorobenzene, ethanol, methanol, and water. Example 4

[0037] Unlike Example 1, this example may use one or more of the following catalysts: trifluoromethanesulfonic acid, glacial acetic acid, p-toluenesulfonic acid, hydrochloric acid, and trifluoroacetic acid. Example 5

[0038] Unlike Example 1, the heating reaction conditions in this example are: 50°C for 10 days. Example 6

[0039] Unlike Examples 1 or 5, the heating reaction conditions in this example are: reaction at 200°C for 1 day.

[0040] It should be further noted that the above embodiments are merely for understanding the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. Any obvious adjustments and modifications made to the technical solution of the present invention that fall within the inventive concept should also fall within the scope of protection of the present invention.

Claims

1. A porous anion-shielded organic cage, characterized by: The structural diagram is shown as follows: The organic cage skeleton presents a [6+8] cage structure, six C4RACHO units and eight triaminoguanidine salt connectors are bridged by imine bonds formed by Schiff base reaction.

2. The preparation method of the anion shielding type porous organic cage of claim 1, comprising the following steps: adding triaminoguanidine salt, tetracarboxylic resorcinol [4] arene C4RACHO and a reaction solvent into a reaction container; optionally adding or not adding a catalyst; ultrasonicating the reaction solution for 5-60 min and shaking to mix the reaction solution uniformly, then performing freeze-vacuum-thaw operation in an inert gas atmosphere for multiple cycles, and then sealing the reaction container; heating the sealed reaction container for a certain period of time, cooling to room temperature after the reaction is completed, filtering the obtained product, and washing and drying.

3. The method for preparing an anion-shielded porous organic cage according to claim 2, characterized by, The reaction container includes but is not limited to a reaction kettle, a flask, a glass tube or a glass bottle; and the washing method is to immerse the product in a mixture of methanol and water, and replace the solution regularly for 3-5 times.

4. The method for preparing an anion-shielded porous organic cage according to claim 2, characterized by, The molar ratio of C4RACHO: triaminoguanidine salt is 1: (1-10).

5. The method for preparing anion-shielded porous organic cage according to claim 2, characterized in that, The triaminoguanidine salt includes but is not limited to triaminoguanidine hydrochloride, triaminoguanidine bromide or triaminoguanidine iodide.

6. The method for preparing anion-shielded porous organic cage according to claim 2, characterized in that, The reaction solvent includes but is not limited to one or more of N-methylpyrrolidone, 1,4-dioxane, mesitylene, toluene, xylene, dichlorobenzene, ethanol, methanol and water.

7. The method for preparing anion-shielded porous organic cage according to claim 2, characterized in that, The catalyst includes but is not limited to one or more of triflic acid, glacial acetic acid, p-toluenesulfonic acid, hydrochloric acid and trifluoroacetic acid.

8. The method for preparing anion-shielded porous organic cage according to claim 2, characterized in that, The heating reaction condition is 50-200°C for 1-10 days.

9. The method for preparing an anion-shielded porous organic cage according to claim 2 or 4, characterized by, The molar ratio of triaminoguanidine salt: C4RACHO ligand is 4:

3.

10. The method for preparing an anion-shielded porous organic cage according to claim 2 or 4, characterized by, The amplification preparation can be performed in a gram-scale under the molar ratio of triaminoguanidine salt: C4RACHO ligand = 4:3.

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