Three-dimensional hydrogen bond-metal organic framework composite material constructed based on ultrasonic-solvothermal method and application of three-dimensional hydrogen bond-metal organic framework composite material

Abstract

The invention discloses a three-dimensional hydrogen bond-metal organic framework composite material constructed based on an ultrasonic-solvothermal method and application thereof, and belongs to the technical field of organic framework materials. According to the composite material, a hydrogen bond connected two-dimensional layered precursor is constructed through an ultrasonic-solvothermal method, and Co < 2 + > and acetic acid are introduced to be converted into three-dimensional regular octahedral particles through solvothermal reaction. The composite material has double structure advantages of a hydrogen bond organic framework and a metal organic framework, and has excellent pH stability and visible light response characteristics. By utilizing the composite material, efficient degradation of persistent organic pollutants such as perfluorooctanoic acid can be realized through an adsorption-photodegradation synergistic mechanism, and a new solution is provided for water environment treatment.

Description

Technical Field

[0001] This invention belongs to the field of crystalline porous materials and environmental catalysis technology, specifically relating to a three-dimensional composite material that combines the characteristics of hydrogen-bonded organic frameworks (HOFs) and metal-organic frameworks (MOFs). Background Technology

[0002] Perfluoroalkyl substances (PFAS) are known as "persistent pollutants" due to the high stability of their CF bonds. They exhibit environmental persistence, bioaccumulation, and food chain transmission, posing a serious threat to ecosystems and human health. Currently, PFAS remediation faces three main challenges: 1) Traditional adsorption materials (such as AC and ion exchange resins) have limited adsorption capacity and poor selectivity for PFAS, and are easily affected by coexisting substances; 2) Chemical degradation typically requires high temperature and pressure or strong acid / alkali conditions, resulting in high energy consumption and the potential generation of toxic intermediates; 3) Biodegradation is largely ineffective against long-chain PFAS, limiting its remediation scope. To address these issues, researchers have developed various technologies, including adsorption, photocatalysis, electrochemistry, membrane separation, and biodegradation. While adsorption can enrich PFAS, it suffers from difficulties in desorption and regeneration, and a high risk of secondary pollution. Furthermore, the extremely high chemical stability of PFAS means that traditional degradation technologies (such as incineration, ultrasound, electrochemistry, and supercritical water oxidation) still rely on harsh conditions and high energy consumption. While incineration can effectively mineralize PFAS, it requires temperatures of 600–1000°C, is costly, and may release toxic gases. Therefore, there is an urgent need to develop new methods and strategies for the efficient removal of PFAS.

[0003] MOFs, as crystalline materials with tunable pore structures, high specific surface areas, and well-defined active sites, have shown potential in the integrated enrichment and degradation of PFAS. However, the dynamic nature of their coordination bonds leads to insufficient stability, limiting practical applications. HOFs, as all-organic porous materials, not only circumvent the organic-inorganic compatibility issues of MOFs but also possess advantages such as well-defined structures, tunable functions, and mild synthesis conditions, attracting attention in the field of photocatalysis. The crystal structure of HOFs facilitates anisotropic charge transport, providing ee - -h + Separation provides an ideal platform. However, hydrogen bonding is relatively weak (approximately 4 ~ 60 kJ mol). -1 The inherent limitations of HOFs and MOFs lead to poor stability, limited functionalization methods, and difficulty in large-scale preparation, necessitating reinforcement through the introduction of metal nodes or dynamic covalent bonds. Therefore, this invention aims to construct a method for preparing HOFs-MOFs composite functional materials to overcome the shortcomings of individual HOFs and MOFs materials. Summary of the Invention

[0004] This invention aims to overcome the shortcomings of existing technologies and provide a novel three-dimensional crystalline hydrogen-bonded metal-organic framework composite material. It constructs a synergistic strategy integrating "adsorption-degradation-fluorine recovery" to achieve efficient transfer and complete mineralization of PFAS from water. In particular, it can carry out high-concentration degradation in non-aqueous media, thus broadening the reaction pathway and application scenarios.

[0005] The specific objectives of this invention include:

[0006] (1) Construct a three-dimensional composite material with a regular octahedral morphology, which combines the structural advantages of HOFs and MOFs;

[0007] (2) Controllable synthesis of materials is achieved through an ultrasonic-solvothermal method;

[0008] (3) Introducing Co 2+ / Acetic acid system enhances the structural stability and photocatalytic activity of materials;

[0009] (4) This material is used to achieve efficient adsorption and visible light-driven degradation of PFOA, thereby improving the efficiency of pollutant removal.

[0010] To achieve the above objectives, this invention provides a three-dimensional hydrogen-bonded metal-organic framework composite material, which is made by using Co... 2+ The bridging effect enables the self-assembly of two-dimensional hydrogen-bonded organic framework layers into a three-dimensional interwoven network structure, resulting in a three-dimensional composite material with an octahedral particle morphology, named HOF-Co-MOF. It possesses the following characteristics:

[0011] The precursors HOFs were constructed from organic ligands tricarboxyphenyl six-membered rings or six-membered heterocyclic compounds such as 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (H3TATB) or 2,4,6-tris(4-carboxyanilino)-1,3,5-triazine (H3TATAB) and melamine (MA) via an ultrasonic-solvothermal method, and further processed by hydrogen-bonded two-dimensional layered organic framework precursors via Co 2+ Coordination self-assembly forms a three-dimensional interwoven network structure, achieving an upgrade in structural dimension;

[0012] The material has a regular octahedral morphology with uniform particle size distribution, which is conducive to light capture and mass transfer diffusion.

[0013] Ultrasonic pretreatment promotes crystallization or accelerates self-assembly, followed by solvothermal reaction to complete structural transformation, ensuring reproducibility of the synthesis;

[0014] The Co 2+ The sources are cobalt salts such as cobalt chloride, cobalt nitrate, and cobalt acetate. Acetic acid acts as an auxiliary ligand to participate in coordination, synergistically enhancing structural stability, adsorption performance, and catalytic activity.

[0015] This design integrates "precursor construction, ion coordination, morphology regulation, and stability enhancement" to form a multi-scale synergistic optimization technology system.

[0016] The composite material maintains structural stability in an environment with pH = 3~12.

[0017] In some embodiments of the present invention, the particle size distribution of the octahedral particles of the composite material is 20-50 μm, and the specific surface area is 240-360 m². 2 / g, the pore size of the internal channels is about 3~4 nm.

[0018] This invention also provides a method for preparing the aforementioned three-dimensional hydrogen-bonded metal-organic framework composite material, comprising the following steps:

[0019] (1) The organic ligands used to form the two-dimensional hydrogen bond organic framework layer are placed in an organic solvent and crystallized or self-assembled by ultrasonic treatment to obtain a homogeneous suspension.

[0020] (2) The above suspension was transferred to a reaction vessel for the first solvothermal reaction to obtain a two-dimensional layered HOF precursor;

[0021] (3) Add a cobalt source to the obtained HOF precursor mixed solution, adjust the pH to 2-3 with acetic acid, and carry out the solvothermal reaction again to allow Co to react. 2+ It coordinates with organic ligands to form a three-dimensional composite structure;

[0022] (4) After the reaction is complete, centrifuge, wash and dry to obtain the target product.

[0023] Furthermore, the organic ligands mentioned in step (1) include, but are not limited to, tricarboxyphenyl six-membered ring or six-membered heterocyclic compounds such as H3TATB (or H3TATAB) and melamine (MA), and the organic solvent is preferably methanol.

[0024] The tricarboxyphenyl six-membered ring or six-membered heterocyclic compound is preferably any one of the compounds shown in Formulas I to III:

[0025]

[0026] In Formulas I to III, X represents a single bond or is selected from one of the following linking groups:

[0027]

[0028] G1, G2, and G3 may be the same or different, representing one or more substituents on the benzene ring, selected from amino, imino, mercapto, hydroxyl, carboxyl, C2-C6 alkynyl, azide, guanidinyl, etc. One or more of them.

[0029] Furthermore, in step (1), the temperature of the ultrasonic treatment is controlled below 35°C, and the time is 2-3 hours.

[0030] Furthermore, the temperature of the first solvothermal reaction in step (2) is 130~150°C and the reaction time is 12~24 hours; the temperature of the second solvothermal reaction in step (3) is 120~150°C and the reaction time is 12~24 hours.

[0031] Further, the cobalt source in step (3) is preferably a cobalt salt such as cobalt chloride (CoCl2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), or cobalt acetate (Co(CH3COO)2·4H2O). The amount of cobalt source added is Co 2+ :H3TATB=(3~5):1.

[0032] The three-dimensional crystalline hydrogen-bonded metal-organic framework composite material of the present invention can be used to degrade perfluoroalkyl substances such as perfluorooctanoic acid (PFOA).

[0033] Furthermore, the method for using the composite material to degrade PFOA involves immersing the composite material in a PFOA-containing solution and subjecting it to an adsorption-photodegradation synergistic reaction under visible light irradiation to remove perfluorooctanoic acid (PFOA) from the water. In some embodiments of the present invention, the reaction is carried out under LED light irradiation with a wavelength of 400-800 nm, the pH of the system is adjusted to 12-13, the reaction time is controlled at 12-24 hours, and the PFOA removal rate can reach over 90%.

[0034] This invention is constructed using an ultrasonic-solventothermal synergistic method and introduces Co. 2+ A hydrogen-bonded metal-organic framework composite material, with an acetic acid ligand, forms a crystalline structure with a specific morphology and function. This composite material can persistently adsorb and photocatalytically degrade organic pollutants—especially perfluorooctanoic acid (PFOA)—in water, providing a new material and method for the efficient treatment of recalcitrant organic pollutants. Specifically, the composite material provided by this invention has the following advantages:

[0035] Structural synergy: Combining the designability of HOFs with the structural stability of MOFs, through Co 2+ The bridging effect transforms the two-dimensional HOF layer into a three-dimensional interlaced network, improving the overall material performance;

[0036] Controllable morphology: By adjusting the solvent ratio and reaction temperature, regular octahedral particles with a size of approximately 50 μm were obtained. SEM images showed uniform morphology and a specific surface area of ​​356.2 m². 2 / g, with a pore size of approximately 4nm, which is beneficial for enhancing light absorption efficiency and mass transfer kinetics;

[0037] High stability: After soaking in a buffer solution with pH = 3~12 for 24 hours, the XRD pattern showed no significant change and the mass loss rate was less than 5%, indicating that the material has excellent chemical stability under complex water quality conditions.

[0038] Visible light response: UV-Vis DRS testing shows that Co 2+ After introduction, the material exhibits a new ultraviolet absorption peak in the 430–750 nm range, which can effectively excite electron-hole pairs under simulated sunlight, indicating that Co… 2+ Introducing new energy levels reduces the band gap of materials, allowing for the effective utilization of visible light;

[0039] Synergistic degradation mechanism: The material has an adsorption capacity of 1794.42 mg / g for PFOA (fitted by Langmuir model). Under light irradiation, photogenerated electrons are the main active species that dominate the efficient degradation of PFOA, achieving efficient coupling between adsorption enrichment and in-situ photocatalytic degradation.

[0040] Environmentally friendly: the degradation products are F - The catalyst is recyclable and reusable, meeting the requirements of green chemistry. Attached Figure Description

[0041] Figure 1 The schematic diagram of the synthetic route for preparing the composite material using H3TATB as the organic ligand in Example 2 of this invention illustrates the ultrasonic treatment, initial solvothermal treatment, and Co... 2+ The entire process of introduction and secondary solvothermal treatment.

[0042] Figure 2 The SEM images of the composite material prepared in Example 2 of this invention are shown in the following: a) is a scanning electron microscope image at a scale bar of 100 μm, which shows that the synthesized material has basically the same size; b) is a scanning electron microscope image at a scale bar of 20 μm, which shows that the material has a regular octahedral structure; c) is a scanning electron microscope image of a cross-section of the material, which shows that the cross-section of the material is a layered stack of HOFs; d) is a high-magnification transmission electron microscope image, which shows that the HOFs have hexagonal structural units.

[0043] Figure 3 The XRD pattern of the composite material HOF-Co-MOF prepared in Example 2 of this invention and the comparison of XRD patterns after treatment in different pH buffer solutions.

[0044] Figure 4The UV-Vis diffuse reflectance spectra (UV-Vis DRS) of the composite material HOF-Co-MOF and its precursor HOF measured in Example 3 of this invention show that the composite material has significant absorption in the range of 430–740 nm and has visible light response capability.

[0045] Figure 5 The adsorption and degradation efficiency curves of PFOA for the three-dimensional hydrogen-bonded metal-organic framework composite materials in Examples 4 and 5 of this invention are shown, where a) is the PFOA isothermal adsorption curve, and q e a) represents the maximum adsorption amount at adsorption equilibrium, and Ce represents the concentration of PFOA at adsorption equilibrium; b) is the PFOA degradation and F - Release curve. Detailed Implementation

[0046] The objectives, technical solutions, and effects of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but the scope of the present invention is not limited in any way.

[0047] Example 1: Preparation of two-dimensional layered HOF precursors

[0048] Weigh 0.36–0.72 g of H3TATB or H3TATAB and 0.18–0.48 g of MA, add 35 mL of anhydrous MeOH, and react in an ultrasonic cleaner for 2 hours, ensuring the reaction temperature remains below 35 °C. After ultrasonication, transfer to a 100 mL PTFE reactor and react at 150 °C for 24 hours. Cool to room temperature, wash three times each with N,N-diethylformamide (DEF) and methanol (MeOH), and dry at 80 °C for later use.

[0049] Example 2: Preparation of three-dimensional hydrogen-bonded metal-organic framework composite material HOF-Co-MOF

[0050] like Figure 1 As shown, 0.36–0.72 g of H3TATB and 0.18–0.48 g of MA were weighed and added to 35 mL of anhydrous MeOH. The mixture was reacted in an ultrasonic cleaner for 2 hours, with the reaction temperature maintained below 35 °C. After ultrasonication, the mixture was transferred to a 100 mL PTFE reactor and reacted at 150 °C for 24 hours. After cooling to room temperature, 1.2–2.4 g of CoCl2·6H2O (dissolved in 15 mL of MeOH) and 1–2 mL of acetic acid were added to the above reaction system. The mixed solution was then reacted at 120–150 °C for another 24 hours. After cooling to room temperature, the mixture was washed three times each with DEF and MeOH, and then dried at 80 °C for later use.

[0051] SEM images of the prepared composite material are as follows: Figure 2 As shown, the shape of a regular octahedron is clearly displayed, and the size is uniform.

[0052] like Figure 3 As shown, XRD patterns confirmed that the diffraction peaks at 5.98° and 6.36° correspond to the layered structure of HOF and the periodic channels formed by Co coordination extension; 7.83° and 10.83° are related to ligand arrangement or hydrogen bond network; and the signal at 15.43° originates from the short-range order of metal-ligands in Co-MOFs. Furthermore, the XRD-derived peaks remained unchanged at pH 3–12, indicating that the composite material possesses high crystallinity and excellent pH stability.

[0053] Example 3: Ultraviolet-Vis DRS of the material

[0054] The solid-state UV-Vis absorption of the composite material (HOF-Co-MOF) and its precursor (HOFs) in the 200-800 nm range was scanned using UV-Vis diffuse reflectance spectroscopy. Figure 4 The results show that, unlike HOFs, a significant ultraviolet absorption peak appears at 430-740 nm, verifying the potential applications of the material's visible light response.

[0055] Example 4: Perfluorooctanoic acid adsorption experiment

[0056] PFOA aqueous solutions of different concentrations (20–500 mg / L) were prepared, and 40–100 mg / L of HOF-Co-MOF were added and ultrasonically dispersed to a total volume of 50 mL. The pH was 4–5. The mixture was stirred at 400 rpm at 25 °C. Different solutions were collected within the range of 0–120 min, and the concentration was determined by UPLC-MS. The experiment was repeated in triplicate. Model (R) 2 >0.99), experimental results are as follows Figure 5 As shown in Figure a), the maximum adsorption capacity fitted by Langmuir is 1794.42 mg / g, indicating that the material has high adsorption performance for PFOA and achieves efficient degradation by combining photocatalytic synergy.

[0057] Example 5: Perfluorooctanoic acid degradation experiment

[0058] Add 50–100 mg / L PFOA and 500–1000 mg / L HOF-Co-MOF to a quartz reaction flask, disperse by ultrasonication, and adjust the pH to 12–13 using a NaOH / Na₂CO₃ mixed alkali. The total volume is 15 mL (DMSO:H₂O = 1:1, volume ratio). Stir at 400 rpm at 25°C. The reaction system is catalyzed using a 400–800 nm white light photocatalysis device. Different solutions (filtered at 0.22 μm, diluted with MeOH) are collected at 0–24 hours. The products in the system are detected and analyzed using a Quadrupole-TOF LC-MS / MS system, and the F… - F in the ion-selective electrode real-time monitoring system - And the use of ion chromatography to analyze F in the system - Quantitative analysis was performed, and the experiment was repeated in triplicate. The experimental results are as follows: Figure 5 As shown in b), under the above reaction conditions, a PFOA removal efficiency of over 90% and a PFOA removal efficiency of over 72% were achieved within a 24-hour reaction cycle. - Ion release.

[0059] This invention successfully constructed a three-dimensional crystalline hydrogen-bonded metal-organic framework composite material using an innovative ultrasonic-solvothermal method. This material not only possesses a unique octahedral morphology and excellent structural stability, but also efficiently degrades perfluorooctanoic acid (PFOA) under visible light, achieving an organic unity of adsorption and catalysis. This technology provides a practical new approach for the treatment of persistent organic pollutants, demonstrating promising application prospects and significant potential for widespread adoption.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-dimensional hydrogen-bonded metal-organic framework composite material, characterized in that, Through Co 2+ The bridging effect enables the two-dimensional hydrogen-bonded organic framework layer to self-assemble into a three-dimensional interwoven network structure, resulting in a three-dimensional composite material with a regular octahedral particle morphology.

2. The three-dimensional hydrogen-bonded metal-organic framework composite material as described in claim 1, characterized in that, The composite material is prepared by first obtaining a two-dimensional layered hydrogen-bonded organic framework precursor from organic ligands via an ultrasonic-solvothermal method, and then by Co... 2+ Hydrogen-bonded metal-organic framework composites that coordinate self-assemble to form a three-dimensional interwoven network structure.

3. The three-dimensional hydrogen-bonded metal-organic framework composite material as described in claim 2, characterized in that, The organic ligand is at least one of the compounds shown in Formulas I to III and melamine; In Formulas I to III, X represents a single bond or is selected from one of the following linking groups: G1, G2, and G3 may be the same or different, representing one or more substituents on the benzene ring, selected from amino, imino, mercapto, hydroxyl, carboxyl, C2-C6 alkynyl, azide, guanidinyl, etc. One or more of them.

4. The three-dimensional hydrogen-bonded metal-organic framework composite material as described in claim 3, characterized in that, The organic ligand is 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine or 2,4,6-tris(4-carboxyanilino)-1,3,5-triazine and melamine.

5. The three-dimensional hydrogen-bonded metal-organic framework composite material as described in claim 1, characterized in that, The composite material has octahedral particles with a particle size distribution of 20–50 μm and a specific surface area of ​​240–360 m². 2 / g, with an internal pore size of 3~4nm.

6. The three-dimensional hydrogen-bonded metal-organic framework composite material as described in claim 1, characterized in that, The composite material maintains structural stability in an environment with pH 3 to 12.

7. A method for preparing the three-dimensional hydrogen-bonded metal-organic framework composite material according to any one of claims 1 to 6, comprising the following steps: 1) Organic ligands used to form a two-dimensional hydrogen-bonded organic framework layer are placed in an organic solvent and then subjected to ultrasonic treatment to crystallize or self-assemble to obtain a homogeneous suspension. 2) The suspension was transferred to a reaction vessel for the first solvothermal reaction to obtain a two-dimensional layered hydrogen-bonded organic framework precursor; 3) Add a cobalt source to the precursor mixture solution, adjust the pH to 2-3 using acetic acid, and perform a solvothermal reaction again to allow the Co to... 2+ It coordinates with organic ligands to form a three-dimensional composite structure; 4) After the reaction is complete, centrifuge, wash and dry to obtain a three-dimensional hydrogen bond-metal-organic framework composite material.

8. The preparation method according to claim 7, characterized in that, The organic solvent mentioned in step 1) is methanol, and the temperature of the ultrasonic treatment is controlled below 35°C; the temperature of the first solvothermal reaction in step 2) is 130~150°C, and the reaction time is 12~24 hours; the cobalt source mentioned in step 3) is selected from one or more of cobalt chloride, cobalt nitrate, and cobalt acetate, and the temperature of the solvothermal reaction is 120~150°C, and the reaction time is 12~24 hours.

9. The application of the three-dimensional hydrogen-bonded metal-organic framework composite material according to any one of claims 1 to 6 in the degradation of perfluoroalkyl substances.

10. The application as described in claim 9, characterized in that, The perfluoroalkyl substance is perfluorooctanoic acid (PFOA). The three-dimensional hydrogen-bonded metal-organic framework composite material is immersed in a solution containing PFOA and undergoes an adsorption-photodegradation synergistic reaction under visible light irradiation.

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