Application of zinc-based microporous metal organic framework material in formaldehyde removal

Abstract

The invention belongs to the technical field of formaldehyde adsorption, and particularly relates to application of a zinc-based microporous metal organic framework (BUT-236) material in formaldehyde removal. An environment-friendly zinc element is used as a metal node, 1, 2, 4-triazolyl amino and isophthalic acid are used as organic ligands, synthesis preparation is performed in pure water, a zinc-based microporous metal organic framework material and a binder are mixed, and the mixture is granulated by a granulator to form spherical formaldehyde adsorption particles. The zinc-based MOFs have pore sizes matched with formaldehyde and abundant amino functional groups, and show good formaldehyde adsorption performance, so that the zinc-based MOFs can be suitable for indoor formaldehyde purification.

Description

Technical Field

[0001] The present invention belongs to the technical field of formaldehyde adsorption, and particularly relates to the application of a zinc-based microporous metal-organic framework material in formaldehyde removal. Technical Background

[0002] Formaldehyde (HCHO), as a typical volatile organic pollutant, its release sources are mainly concentrated in urea-formaldehyde resin-based composite materials such as plywood, particleboard, and wallpaper adhesives widely used in indoor decoration materials. Long-term exposure to an HCHO-polluted environment can induce various pathological reactions, including eye conjunctiva and upper respiratory mucosa irritation symptoms, and is significantly positively correlated with nasopharyngeal carcinoma, pregnancy complications, glioma, and hematological system malignancies. Therefore, the development of efficient indoor formaldehyde purification technology has become an important research direction in the field of environmental functional materials. Among many pollutant treatment technologies, the adsorption separation method is regarded as the most promising formaldehyde elimination strategy in practical application scenarios due to its practical advantages such as simple operation and low energy consumption. Although traditional adsorbents such as activated alumina and activated carbon have been applied on a large scale, they generally have inherent defects such as insufficient adsorption site specificity, weak binding energy, and limited dynamic adsorption capacity. Metal-organic frameworks (MOFs), as a new type of crystalline porous material, are self-assembled by metal nodes and organic ligands through coordination bonds. Thanks to their adjustable pore structures and abundant surface functional groups, they show breakthrough application prospects in the field of volatile organic pollutant capture. However, most MOFs are synthesized by solvothermal methods. The synthesis process requires a large amount of toxic and harmful organic solvents, resulting in high production costs and serious pollution, and it is difficult to be promoted to commercial applications. The greatest advantage of this patent is to report the shaping of a zinc-based MOF that can be prepared greenly and on a large scale and its formaldehyde adsorption performance, promoting the commercialization of MOF adsorbents in the field of formaldehyde. Summary of the Invention

[0003] The purpose of the present invention is to provide the application of a zinc-based microporous metal-organic framework material in formaldehyde removal.

[0004] Furthermore, the name of the zinc-based organic framework material is BUT-236, and the organic ligands are 3-amino-1,2,4-triazole and isophthalic acid.

[0005] Furthermore, the preparation method of the zinc-based organic framework material includes the following steps: Prepare Zn(OAC) 2 ·2H 2Aqueous solution; prepare an aqueous solution of 3-amino-1,2,4-triazole; mix NaOH and isophthalic acid, add water to prepare a sodium isophthalate solution; first mix the sodium isophthalate solution and the aqueous solution of 3-amino-1,2,4-triazole, and add Zn(OAC) 2 ·2H 2 O aqueous solution, then stir and react at 60 °C for 2 hours, filter, wash with deionized water, and vacuum dry at 120 °C for 12 hours to obtain the zinc-based organic framework material.

[0006] A formaldehyde adsorption particle, the adsorption particle includes a zinc-based organic framework material and hydroxyethyl cellulose, and the mass ratio of the zinc-based organic framework material to hydroxyethyl cellulose is 97:3. Hydroxyethyl cellulose is used as a binder and is mixed with BUT-236 in a mass ratio of 97:3, and then formed into uniform spherical particles by granulation. This combination enhances the mechanical strength of the MOF material, prevents the powdered MOF from dispersing due to air flow or vibration during use, and ensures the long-term stable use of the material. The addition amount of hydroxyethyl cellulose is relatively low (3%), which does not significantly block the microporous structure of the MOF (the pore size matches the formaldehyde molecule), but may instead optimize the pore distribution of the particles and promote the diffusion of formaldehyde molecules inside the material.

[0007] Furthermore, the zinc-based organic framework material can be regenerated and recycled after adsorbing and removing formaldehyde.

[0008] The present invention also provides a method for adsorbing and removing formaldehyde by the zinc-based organic framework material, including the following steps: adding the zinc-based organic framework material to a formaldehyde-air mixture, waiting for the formaldehyde gas concentration to be stable and unchanged, and then separating the zinc-based organic framework material.

[0009] The present invention also provides a method for regenerating the zinc-based organic framework material after adsorbing and removing formaldehyde, including the following steps: placing the zinc-based organic framework material after adsorbing and removing formaldehyde in the sun for 24 h to achieve regeneration and recycling.

[0010] The present invention also provides a method for regenerating the zinc-based organic framework material after adsorbing and removing formaldehyde, including the following steps: subjecting the zinc-based organic framework material after adsorbing and removing formaldehyde to vacuum drying for desorption to achieve regeneration and recycling.

[0011] Furthermore, the drying temperature is 120 - 150 °C.

[0012] Compared with the prior art, the present invention has the following technical effects: The present invention successfully synthesizes a Zn-MOF (BUT-236) in pure water, which has a porous structure and amino groups (-NH 2It has rich functional groups, good water stability, and is easy to form. The zinc-based metal-organic framework material is synthesized in a "green" and low-cost manner and exhibits excellent performance in the field of formaldehyde removal. It can be desorbed and recycled, making it a potential formaldehyde adsorbent.

[0013] (2) BUT-236 itself has water stability (synthesized in pure water). The hydrophobicity of hydroxyethyl cellulose may further reduce the competitive adsorption of water molecules in the MOF pores in a humid environment, maintaining the formaldehyde adsorption efficiency.

[0014] (3) Water is used as the solvent for the synthesis of BUT-236, and hydroxyethyl cellulose is used as a non-toxic and biodegradable binder. The combination of the two conforms to the concept of green chemistry and reduces the environmental burden during the production process. Description of the Drawings

[0016] Figure 1 It is the synthesis raw materials of BUT-236 and its structural diagram.

[0017] Figure 2 It is the adsorption curve diagram after the static adsorption experiment of formaldehyde in Examples 1 and 2 at room temperature.

[0018] Figure 3 It is the size of the formaldehyde molecule and the molecular spacing between the two N atoms in the -NH in the pores of BUT-236 2 in the pores of BUT-236.

[0019] Figure 4 It is the scanning electron microscope images of Example 1 before (a) and after (b) adsorbing formaldehyde.

[0020] Figure 5 It is the adsorption curve diagram after the static adsorption experiment of formaldehyde by the regenerated material of Example 1. Detailed Description of the Invention

[0021] Example 1 (1) By placing Zn(OAc) 2 ·2H 2 O (34.38 g; 0.157 mol) in a 100 ml volumetric flask and adding water to prepare a 1.57 mol / L zinc salt solution; (2) Placing 3-amino-1,2,4-triazole (22.428 g, 0.267 mol) in a 100 ml volumetric flask and adding water to prepare a 2.67 mol / L 3-amino-1,2,4-triazole solution; (3)NaOH (31.208 g, 0.188 mol) and isophthalic acid (15.04 g, 0.376 mol) were placed in a 100 ml volumetric flask, and water was added to prepare 100 mL of a 1.88 mmol / L sodium isophthalate solution; First, 7.5 ml of 3 - amino - 1,2,4 - triazole solution was mixed with 5.35 ml of sodium isophthalate solution, and then 12.75 ml of zinc salt solution was added. Then, the mixture was stirred and reacted at 60 °C for 2 hours, filtered, washed with deionized water, and vacuum - dried at 120 °C for 12 hours. The obtained MOF product was named BUT - 236.

[0022] The raw material composition and three - dimensional spatial structure of BUT - 236 are as Figure 1 shown. The structure of BUT - 236 has one - dimensional pores, and the intermolecular distance between two N atoms on - NH 2 in the pores is 4.32 Å.

[0023] The sample obtained in Example 1 was post - treated and dried to obtain an adsorption sample for the test of formaldehyde static adsorption.

[0024] Example 2 19.4 g of the product obtained in Example 1 and 0.6 g of hydroxyethyl cellulose were weighed and mixed in a mortar. Deionized water was added dropwise while grinding until the two were evenly mixed to form a paste, which was processed into 3.00 mm spherical particles by a semi - automatic granulator.

[0025] The sample obtained in Example 2 was post - treated and dried to obtain an adsorption sample for the test of formaldehyde static adsorption Example 3 First step: Weigh 0.2944 g of the sample obtained in Example 1 and add it to a container with 1 mg / m 3 formaldehyde - air mixture in 25 L.

[0026] Second step: Wait for the formaldehyde gas concentration to stabilize and then start measuring.

[0027] Third step: Measure the change in formaldehyde concentration in the container with a formaldehyde detector.

[0028] Example 4 First step: Weigh 20 g of the sample of Example 2 and add it to a container with 1 mg / m 3 formaldehyde - air mixture in ≈388 L.

[0029] Second step: Wait for the formaldehyde gas concentration to stabilize and then start measuring.

[0030] Third step: Measure the change in formaldehyde concentration in the container with a formaldehyde detector.

[0031] The adsorption curves obtained after the static adsorption experiments of Examples 1 and 2 are as follows Figure 2 shown. It shows that the BUT-236 and the processed material can respectively adsorb and remove 0.64 mg / m 3 and 0.69 mg / m 3 of formaldehyde within 3 hours, having good trace static adsorption performance. The above shows that this material has good application prospects in the field of adsorbing and removing formaldehyde in the air.

[0032] Figure 3 is the molecular size of formaldehyde and the molecular distance between two N atoms on -NH 2 in the pore channels of BUT-236. It can be seen from the figure that the molecular size of formaldehyde exactly matches the pore size of its channels.

[0033] BUT-236 has a strong adsorption force on formaldehyde molecules. The reasons are as follows: (1) The existence of ammonia sites The characteristics of ammonia sites: For example, the amino group -NH 2 has a lone pair of electrons and can act as a Lewis base to interact with the carbonyl group (C=O) in formaldehyde molecules.

[0034] Hydrogen bond interaction: A hydrogen bond can be formed between the hydrogen atom (H) in the formaldehyde molecule and the nitrogen atom (N) in the ammonia site, and this hydrogen bond interaction enhances the adsorption force.

[0035] The hydroxyl group (-OH) and ether bond (-O-) in the hydroxyethyl cellulose molecule interact with the formaldehyde molecule through weak hydrogen bonds or van der Waals forces, assisting the amino group (-NH 2 ) of the MOF's main adsorption site to capture formaldehyde, forming a multi-level adsorption mechanism.

[0036] (2) The polarity of formaldehyde molecules Formaldehyde (HCHO) is a polar molecule. Its carbonyl group (C=O) has a high electronegativity, resulting in partial positive charges (δ+) and partial negative charges (δ-) in the molecule. This polarity makes formaldehyde molecules easily attracted by the polar sites (such as ammonia sites) in the pore channels, and the adsorption is enhanced through electrostatic interaction.

[0037] (3) The confinement effect of the pore structure Since the molecular size of formaldehyde exactly matches the pore size of its channels, the pore structure of BUT-236 provides a confined space for formaldehyde molecules, making it easier for formaldehyde molecules to contact the ammonia sites in the pore channels and further enhancing the adsorption effect.

[0038] (4) Coordination interaction The oxygen atom (O) in the formaldehyde molecule has lone pairs of electrons and can act as a ligand to coordinate with a metal center (such as Zn²⁺). This coordination further enhances the adsorption stability of the formaldehyde molecule in the pores.

[0039] (5) π-π interaction There are aromatic rings in the structure of BUT-236 (such as the benzene ring in the isophthalic acid ligand), and π-π interactions may occur between the formaldehyde molecule and the aromatic ring, further enhancing the adsorption force.

[0040] Figure 4 SEM images before and after formaldehyde adsorption in Example 1 are compared. As can be seen from the figure, the morphology of BUT-236 did not change before and after formaldehyde adsorption, proving its good stability.

[0041] The sample after the adsorption test in Example 1 was placed in the sun for 24 h or dried under vacuum for desorption. The drying temperature was 120 - 150 °C to achieve the regeneration of the material, and then the formaldehyde adsorption test was repeated. During the regeneration of the material (such as sun drying or vacuum drying), the hydroxyethyl cellulose maintained the integrity of the particle structure, avoiding the pulverization or structural collapse of the MOF caused by repeated desorption-adsorption cycles, thus supporting the recycling of the material. The test conditions were the same as those in Example 2, and the above operations were repeated twice. The results obtained are as Figure 5 shown, indicating that the regenerated material can adsorb and remove 0.57 mg / m 3 , 0.58 mg / m 3 , 0.58 mg / m 3 of formaldehyde within 3 hours, still having good trace static adsorption performance, proving its good recyclability.

Claims

1. Application of a zinc-based microporous metal-organic framework material in formaldehyde removal.

2. The use of the zinc-based microporous metal organic framework material in formaldehyde removal according to claim 1, characterized in that: The preparation method of the zinc-based organic framework material comprises the following steps: A Zn(OAC)2·2H2O aqueous solution is prepared; a 3-amino-1,2,4-triazole aqueous solution is prepared; NaOH and isophthalic acid are mixed, and water is added to prepare a sodium isophthalate solution; firstly, the sodium isophthalate solution and the 3-amino-1,2,4-triazole aqueous solution are mixed, and a Zn(OAC)2·2H2O aqueous solution is added, and then the mixture is stirred and reacted at 60°C for 2 hours, filtered, washed with deionized water, and vacuum dried at 120°C for 12 hours to obtain the zinc-based organic framework material.

3. A formaldehyde adsorption particle, characterized in that: The formaldehyde adsorption particles include the zinc-based organic framework material according to claim 1 and hydroxyethyl cellulose, and the mass ratio of the zinc-based organic framework material to the hydroxyethyl cellulose is 97:

3.

4. The use of the zinc-based microporous metal organic framework material in formaldehyde removal according to claim 1, characterized in that: The zinc-based organic framework material can be regenerated and recycled after formaldehyde is adsorbed and removed.

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