Biomass MOF (Metal Organic Framework) material as well as synthesis method and application thereof

Abstract

The invention discloses a biomass MOF (Metal Organic Framework) material as well as a synthesis method and water absorption application thereof. The biomass MOF material is formed by self-assembly of fumarate ions, metal Cu < 2 + > ions and biomass nitrogen-containing ligand adenine. The synthesis method comprises the following steps: (1) reacting Cu < 2 + > salt, adenine and fumaric acid in water at 50-90 DEG C to obtain a solid product; and (2) washing and drying the solid product, and removing solvent molecules under a vacuum condition to obtain the biomass MOF material. The biomass MOF material can be used for adsorbing and separating ethanol and water.

Description

Technical Field

[0001] This invention relates to the field of porous material synthesis and adsorption separation technology, specifically to a low-cost metal-organic framework (MOF) material prepared from biomass raw materials, its preparation method, and its application in the separation of ethanol and water. Background Technology

[0002] With the increasing depletion of non-renewable fossil fuels and the escalating environmental pollution, bioethanol has received widespread attention as a sustainable energy source. However, in high-value-added fields such as lithium-ion battery electrolyte production, drug synthesis, and semiconductor processing, traditional fuel-grade bioethanol (with a water content of less than 1%) cannot meet the requirements. These fields typically require ultra-dry ethanol with a water content of less than 100 ppm. Trace amounts of moisture can lead to catalyst deactivation, trigger side reactions, or cause product failure.

[0003] When producing anhydrous ethanol from biomass fermentation broth (initial water content 5%-12%), efficient separation using only distillation is difficult due to the formation of an azeotrope between ethanol and water (ethanol concentration approximately 95.6%). Currently, commonly used separation methods include membrane separation, azeotropic distillation, and adsorption separation. Membrane separation is limited by the trade-off between permeate flux and selectivity, as well as membrane fouling issues; azeotropic distillation requires the introduction of entrainers such as benzene or cyclohexane, which can easily cause product contamination and has high energy consumption. In contrast, adsorption separation utilizes the selective adsorption of porous adsorbents, eliminating the need for a third component, and offers advantages such as a clean process and simple operation.

[0004] Metal-organic frameworks (MOFs) are a class of crystalline porous materials formed by coordination between metal ions / clusters and organic linkers. They possess high specific surface area, tunable pore structure, and surface chemical properties. However, traditional MOF materials often use precious metals or expensive ligands, and their synthesis often relies on toxic organic solvents (such as N,N-dimethylformamide), limiting their large-scale application.

[0005] The following existing technologies were found through a search: The patent specification with publication number CN113426416A discloses a MOFs material with high efficiency in water collection, its preparation method and air water collection application. The preparation process uses a low-boiling-point solvent acid anhydride solution.

[0006] The patent specification with publication number CN112495345A discloses a zirconium-organic composite for water adsorption, its preparation method and application. The zirconium-organic composite material is obtained by complexing zirconium metal compound with fumaric acid, and its structure can be effectively modified by metal salt, solvent and additives, wherein the solvent is water.

[0007] Although the above-mentioned prior art discloses that its materials have water absorption function, it does not clearly explain the adsorption effect on ethanol, or whether it can be further used for ethanol / water separation. Summary of the Invention

[0008] This invention proposes a green and low-cost synthesis strategy: using biomass-derived adenine and fumaric acid as ligands, and reacting with Cu... 2+ A bio-based MOF material, Cu2(Ade)2FA (named ZNU-68), was prepared in aqueous phase via self-assembly, where Ade represents adenine and FA represents fumarate ion. This method utilizes inexpensive and readily available raw materials, requires no organic solvents, and is environmentally friendly and simple. The material possesses specific pore sizes, enabling selective adsorption of water molecules while excluding ethanol molecules, thus achieving efficient separation of ethanol and water.

[0009] The specific technical solution is as follows: In a first aspect, the present invention provides a biomass MOF material composed of fumarate ions and metallic Cu. 2+ It is formed by the self-assembly of ions and the nitrogen-containing ligand adenine from biomass.

[0010] Furthermore, in the biomass MOF material, fumarate ions and metallic Cu are present. 2+ The molar ratio of ions and the biomass nitrogen-containing ligand adenine is 1:2:2.

[0011] Furthermore, the biomass MOF material is composed of fumarate ions and metallic Cu. 2+ Ions and the nitrogen-containing ligand adenine from biomass self-assemble in the aqueous phase to form the adenine.

[0012] Furthermore, the biomass MOF material has a composition of Cu 2+ It is a three-dimensional network structure formed by adenine and fumarate ions linked by coordination bonds. It has zigzag channels along the a-axis and a linear one-dimensional through-channel structure along the b-axis.

[0013] Furthermore, the biomass MOF material has three-dimensional channels with periodically alternating contraction and expansion sections, wherein the narrowest effective pore diameter is 2.43 Å and the widest effective pore diameter is 5.15 Å.

[0014] Furthermore, the aforementioned biomass MOF material, Cu 2+ It exists in two chemical environments: one where four adenine ligands are bridged to form a binuclear paddlewheel cluster structure; and the other where a single copper center coordinates with two adenine and two fumarate ions.

[0015] In a second aspect, the present invention provides a method for synthesizing the biomass MOF material described in the first aspect, comprising the steps of: (1) Cu 2+ Salt, adenine, and fumaric acid react in water at 50–90°C (e.g., 60°C) to give a solid product; (2) The solid product is washed and dried, and then solvent molecules are removed under vacuum to obtain the biomass MOF material.

[0016] In some embodiments, in step (1), the Cu 2+ Salts include at least one of chlorides, sulfates, and nitrates, such as copper nitrate.

[0017] In some embodiments, in step (1), the Cu 2+ Cu in salt 2+ The molar ratio of adenine to fumaric acid is 4:(2~3):(1~2).

[0018] In some embodiments, the reaction time in step (1) is 4 to 48 hours.

[0019] In some embodiments, the conditions for removing solvent molecules under vacuum in step (2) include: a temperature of 70~130°C (e.g., 120°C) and a time of 10~24 hours.

[0020] Thirdly, the present invention provides the application of the biomass MOF material described in the first aspect for water absorption.

[0021] Fourthly, the present invention provides the application of the biomass MOF material described in the first aspect for the adsorption and separation of ethanol and water.

[0022] In the applications described in the third and fourth aspects, the adsorption temperature can be 278~308 K and the adsorption pressure can be 1 bar.

[0023] In the applications described in the third and fourth aspects, the adsorption method can be one or a combination of two or more of the following: fixed bed adsorption, fluidized bed adsorption, and moving bed adsorption.

[0024] In some embodiments, the applications described in the third and fourth aspects employ fixed-bed adsorption, comprising: passing a gas containing water or a mixture of ethanol and water through a fixed-bed adsorption column packed with the biomass MOF material, wherein water is adsorbed by the biomass MOF material, and other substances such as ethanol preferentially permeate through, and anhydrous ethanol or other substances are directly obtained from the outlet of the adsorption column.

[0025] The biomass MOF material of this invention is an inexpensive and green porous metal-organic framework material. Under conditions of 298 K and 1 bar, ZNU-68 achieves a saturated water adsorption capacity of 117.5 cm⁻¹. 3 / g, while the adsorption capacity for ethanol is only 1.7 cm. 3 The material exhibits excellent selectivity, with a density of / g. It maintains stable adsorption performance even after multiple adsorption-desorption cycles and demonstrates good chemical stability, preserving its structural integrity in aqueous, weakly acidic, and weakly alkaline environments.

[0026] Compared with the prior art, the beneficial effects of this invention are as follows: 1) The raw materials are derived from biomass, which is inexpensive and the synthesis process is carried out in an aqueous phase, making it green and environmentally friendly.

[0027] 2) The material has a specific pore structure, which enables specific adsorption of water molecules and high selectivity for ethanol / water separation.

[0028] 3) The material has a stable structure, is easy to desorb and regenerate, and can be reused.

[0029] 4) The preparation process is simple and the conditions are mild, making it suitable for large-scale production. Attached Figure Description

[0030] Figure 1 Photographs of the gram-scale aqueous phase synthesis apparatus of ZNU-68 and the resulting crystals.

[0031] Figure 2 This is a schematic diagram of the single crystal structure of ZNU-68.

[0032] Figure 3 This is a single-component adsorption isotherm diagram of ZNU-68 for water and ethanol at 298 K.

[0033] Figure 4 The dynamic breakthrough curve of ZNU-68 at a volume ratio of 95 / 5 ethanol / water vapor is shown.

[0034] Figure 5 The dynamic breakthrough curve of ZNU-68 at an ethanol / water volume ratio of 88 / 12 vapor is shown.

[0035] Figure 6 The dynamic breakthrough curve of ZNU-68 at a volume ratio of 75 / 25 ethanol / water vapor is shown. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0037] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer.

[0038] Example 1: 14.8 mmol of adenine, 20 mmol of Cu(NO3)2·3H2O, and 8.6 mmol of fumaric acid were added to a 1.2 L Erlenmeyer flask, followed by 1 L of water. The resulting reaction mixture was sonicated for 10 minutes and then transferred to a 60 °C incubator for 48 hours. After the reaction was complete, dark blue blocky crystals were collected, washed with deionized water, and dried overnight at 80 °C to obtain approximately 1.2 g of ZNU-68 product. Its single crystal structure data are shown in Table 1.

[0039] Table 1 Figure 1 The gram-scale aqueous phase synthesis apparatus of ZNU-68 and the resulting crystals are shown in the photograph.

[0040] Figure 2 The single-crystal structure of ZNU-68 is shown, revealing its specific pore structure that enables selective adsorption of water molecules, achieving efficient separation of ethanol / water mixtures. This material boasts low raw material costs, a green synthesis process, and excellent separation performance, making it suitable for bioethanol dehydration and related separation processes.

[0041] Example 2: The ZNU-68 material prepared according to Example 1 was activated under vacuum at 120°C for 10 hours, and its single-component adsorption isotherms for water and ethanol at 298 K were measured on a Bestar 660 adsorption instrument. Figure 3 At 1 bar, the saturated adsorption capacity for water can reach 117.5 cm⁻¹. 3 / g, the saturated adsorption capacity of ethanol is 1.7 cm⁻¹. 3 / g.

[0042] Example 3: The ZNU-68 material prepared according to Example 1 was packed into an adsorption column with an inner diameter of 4.6 mm and a length of 10 cm, and activated under vacuum at 120°C for 10 hours. At 25°C, N2 was introduced into containers containing ethanol and water via two separate streams through a bubbler, and the water / ethanol vapor ratio was adjusted by controlling the N2 flow rate. Figure 4 As shown, when the water / ethanol vapor volume ratio is 5 / 95 and the total flow rate is 20 mL / min, ethanol immediately breaks through the permeation column, while water can be retained for 270 min / g, indicating that ZNU-68 has excellent separation effect on water / ethanol.

[0043] Example 4: The ZNU-68 material prepared according to Example 1 was packed into an adsorption column with an inner diameter of 4.6 mm and a length of 10 cm, and activated under vacuum at 120°C for 10 hours. At 25°C, N2 was introduced into containers containing ethanol and water via two separate streams through a bubbler, and the water / ethanol vapor ratio was adjusted by controlling the N2 flow rate. Figure 5 As shown, when the water / ethanol vapor volume ratio is 12 / 88 and the total flow rate is 20 mL / min, ethanol immediately breaks through the permeation column, while water can be retained for 200 min / g, indicating that ZNU-68 has excellent separation effect on water / ethanol.

[0044] Example 5: The ZNU-68 material prepared according to Example 1 was packed into an adsorption column with an inner diameter of 4.6 mm and a length of 10 cm, and activated under vacuum at 120°C for 10 hours. At 25°C, N2 was introduced into containers containing ethanol and water via two separate streams through a bubbler, and the water / ethanol vapor ratio was adjusted by controlling the N2 flow rate. Figure 6 As shown, when the water / ethanol vapor volume ratio is 25 / 75 and the total flow rate is 20 mL / min, ethanol immediately breaks through the permeation column, while water can be retained for 220 min / g, indicating that ZNU-68 has excellent separation effect on water / ethanol.

[0045] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A biomass MOF material, characterized in that, Composed of fumarate ions and metallic Cu 2+ It is formed by the self-assembly of ions and the nitrogen-containing ligand adenine from biomass.

2. The biomass MOF material according to claim 1, characterized in that, In the biomass MOF material, fumarate ions and metallic Cu are present. 2+ The molar ratio of ions and the biomass nitrogen-containing ligand adenine is 1:2:

2.

3. The biomass MOF material according to claim 1, characterized in that, The biomass MOF material has a composition of Cu 2+ It is a three-dimensional network structure formed by adenine and fumarate ions linked by coordination bonds. It has zigzag channels along the a-axis and a linear one-dimensional through-channel structure along the b-axis.

4. The biomass MOF material according to claim 1, characterized in that, The biomass MOF material has three-dimensional channels with periodically alternating contraction and expansion sections, wherein the narrowest effective pore diameter is 2.43 Å and the widest effective pore diameter is 5.15 Å.

5. The biomass MOF material according to any one of claims 1 to 4, characterized in that, Cu 2+ It exists in two chemical environments: one where four adenine ligands are bridged to form a binuclear paddlewheel cluster structure; and the other where a single copper center coordinates with two adenine and two fumarate ions.

6. The method for synthesizing biomass MOF materials according to any one of claims 1 to 5, characterized in that, Including the following steps: (1) Cu 2+ Salt, adenine, and fumaric acid react in water at 50–90 °C to give a solid product. (2) The solid product is washed and dried, and then solvent molecules are removed under vacuum to obtain the biomass MOF material.

7. The synthesis method according to claim 6, characterized in that, In step (1): The Cu 2+ Salts include at least one of chlorides, sulfates, and nitrates; The Cu 2+ Cu in salt 2+ The molar ratio of adenine to fumaric acid is 4:(2~3):(1~2); The reaction time is 4 to 48 hours.

8. The synthesis method according to claim 6, characterized in that, In step (2), the conditions for removing solvent molecules under vacuum include: temperature 70~130℃ and time 10~24 hours.

9. The application of the biomass MOF material according to any one of claims 1 to 5 for water absorption.

10. The application of the biomass MOF material according to any one of claims 1 to 5 for the adsorption and separation of ethanol and water.

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