Regenerable moF-based gas adsorbent materials, methods of making and applications thereof

Abstract

This invention relates to the field of gas adsorption materials technology, and particularly to renewable MOF-based gas adsorption materials, their preparation methods, and applications. Starting with 1,3-xylene, this invention utilizes a multi-step synthetic pathway involving Friedel-Crafts alkylation, potassium permanganate oxidation, regioselective nitration, iron powder reduction, and diazotization-methoxylation to prepare the bifunctional organic ligand 2-tert-butyl-5-methoxy-1,3-phthalic acid, which possesses a hydrophobic tert-butyl group and a hydrogen bond acceptor methoxy group. A solvothermal method with alkali-modified solution is employed to achieve in-situ coordination assembly of the aluminum metal salt and the bifunctional ligand. By precisely controlling the pH and temperature of the reaction system, an Al-MOF-TBOMe material with a one-dimensional pore structure, a hydrophobic microenvironment, and specific recognition sites is finally obtained. This material exhibits high efficiency in adsorbing isopropanol, stable hydrophobic properties, and high reversibility with isopropanol.

Claims

1. A method for preparing renewable MOF-based gas adsorbent materials, characterized in that, The preparation method is as follows: A mixture of aluminum nitrate nonahydrate, 2-tert-butyl-5-methoxy-1,3-phthalic acid, N,N-dimethylformamide, ethanol and sodium hydroxide aqueous solution was dissolved by ultrasonic treatment to obtain a mixed solution. The mixed solution was placed in a high-pressure reactor and reacted at 140–165 °C for 30–40 h. After natural cooling, the resulting solid product was washed with N,N-dimethylformamide and then soaked in acetone for 3–5 days. Subsequently, it was taken out and activated by heating at 140–160 °C under vacuum for 6–10 h to obtain MOF-based gas adsorbent material.

2. The preparation method according to claim 1, characterized in that, The molar ratio of aluminum nitrate nonahydrate, 2-tert-butyl-5-methoxy-1,3-phthalic acid, and sodium hydroxide is 1:(1-2):(2-3.6); and / or, The concentration of the sodium hydroxide aqueous solution is 1 mol / L; and / or, The volume ratio of N,N-dimethylformamide to ethanol is (3-5):

1.

3. The preparation method according to claim 1, characterized in that, The preparation method of the 2-tert-butyl-5-methoxy-1,3-phthalic acid is as follows: Weigh 2-tert-butyl-5-amino-1,3-phthalic acid and add it to sulfuric acid solution. Heat to 55-65°C and stir until completely dissolved. Then cool to 0-5°C and add sodium nitrite solution dropwise while maintaining the temperature and stirring. After the addition is complete, continue stirring for 1-2 hours to obtain a diazonium salt solution. Add methanol and concentrated sulfuric acid in a volume ratio of 100:1 to a three-necked flask, heat to reflux, and then add the diazonium salt solution dropwise to the refluxed methanol through a constant pressure dropping funnel. After the addition is complete, continue stirring and refluxing for 2-4 hours. Remove the methanol by rotary evaporation, pour the remaining reaction solution into ice water to precipitate the solid, filter, wash with water until the filtrate is neutral, and recrystallize with a 50% ethanol solution to obtain white needle-like crystals, namely 2-tert-butyl-5-methoxy-1,3-phthalic acid.

4. The preparation method according to claim 3, characterized in that, The molar ratio of 2-tert-butyl-5-amino-1,3-phthalic acid to sodium nitrite is 1:1.2; and / or, The sulfuric acid solution is a mixture of water and concentrated sulfuric acid in a volume ratio of 3:20; and / or, The concentration of the sodium nitrite solution is 3–5 mol / L.

5. The preparation method according to claim 3, characterized in that, The preparation method of the 2-tert-butyl-5-amino-1,3-phthalic acid is as follows: Mix 2-tert-butyl-5-nitro-1,3-phthalic acid, iron powder, water and ethanol, add concentrated hydrochloric acid dropwise while stirring, then heat to 75-90℃ and stir under reflux for 3-5 hours. Filter, wash the filter cake, combine the filtrates and adjust the pH to 7-8 with saturated Na2CO3 solution to precipitate solid. Filter the precipitate, wash and dry it to obtain 2-tert-butyl-5-amino-1,3-phthalic acid. The molar ratio of 2-tert-butyl-5-nitro-1,3-phthalic acid to iron powder is 1:

6.

6. The preparation method according to claim 5, characterized in that, The preparation method of the 2-tert-butyl-5-nitro-1,3-phthalic acid is as follows: Mix 2-tert-butyl-1,3-phthalic acid and concentrated sulfuric acid, cool to 0-5°C in an ice-salt bath, add the pre-cooled mixed acid dropwise, controlling the dropwise rate to keep the temperature below 10°C, and after the dropwise addition is complete, raise the temperature to room temperature, then heat to 55-65°C and stir the reaction for 5-8 hours. Pour the resulting reaction solution into crushed ice, precipitate the solid, filter and wash with ice water until the filtrate is neutral, and dry the resulting solid, which is 2-tert-butyl-5-nitro-1,3-phthalic acid. The molar volume ratio of 2-tert-butyl-1,3-phthalic acid to concentrated sulfuric acid is (10–15) mol: 6 L; and / or, The mixed acid is prepared by mixing concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 3:

8.

7. The preparation method according to claim 6, characterized in that, The preparation method of the 2-tert-butyl-1,3-phthalic acid is as follows: Mix 2-tert-butyl-1,3-xylene, water, and pyridine, heat to 85–90 °C, and add potassium permanganate in batches while stirring, controlling the addition rate to prevent bumping. After the potassium permanganate is added, reflux the mixture at 85–90 °C for 10–15 h. After the reaction is complete, filter while hot, wash, combine the filtrate and washings, and acidify with concentrated hydrochloric acid to pH=2 under ice-water bath cooling, precipitating a white solid. Then filter under vacuum, wash the solid with cold water, dry under vacuum, and recrystallize with a 1:1 volume ratio of ethanol and water to obtain 2-tert-butyl-1,3-phthalic acid. In this step, the molar ratio of 2-tert-butyl-1,3-xylene to potassium permanganate is 4:9.6; and / or, The molar volume of 2-tert-butyl-1,3-xylene and pyridine is (0.4–1.2) mol: 5 mL.

8. The preparation method according to claim 7, characterized in that, The preparation method of the 2-tert-butyl-1,3-xylene is as follows: Mix 1,3-xylene and anhydrous aluminum trichloride, place in an ice-water bath, and slowly add tert-butyl chloride dropwise under stirring. Control the dropping rate to maintain the reaction temperature below 20°C. After the addition is complete, heat the resulting reaction solution to 35–40°C and stir for 3–5 hours. Pour the resulting reaction solution into a mixture containing crushed ice and concentrated hydrochloric acid, stir to quench the reaction, separate the organic layer, extract the aqueous layer with petroleum ether, combine the organic phases, wash successively with saturated NaHCO3 solution and water, dry the organic phase with anhydrous MgSO4, filter, remove the solvent by rotary evaporation, and collect the fraction at 110–115°C / 20 mmHg by vacuum distillation to obtain a colorless liquid. The molar ratio of 1,3-xylene, anhydrous aluminum trichloride, and tert-butyl chloride is 5:5.5:

6.

9. A renewable MOF-based gas adsorbent material, characterized in that, The MOF-based gas adsorbent material is prepared using the preparation method described in any one of claims 1-8.

10. The application of the renewable MOF-based gas adsorbent material according to claim 9 in isopropanol adsorbent materials.

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