Preparation method and application of MOFs / MWCNTs composite material adsorbent for CO2 / N2 adsorption separation

Abstract

The invention relates to a preparation method and application of an MOFs / MWCNTs composite material adsorbent for CO2 / N2 adsorption separation. According to the method, the high-stability UiO-66-NH2 / MWCNTs composite material is synthesized in situ by adding multi-walled carbon nanotubes (MWCNTs) into the material UiO-66-NH2, and the composite adsorbent is more stable in physical property, higher in adsorption efficiency and better in cycle performance. The UiO series MOFs material selected in the adsorbent disclosed by the invention has good hydrothermal stability, the UiO-66-NH2 / MWCNTs have relatively high BET (Brunauer, Emmett and Teller) surface area and micropore volume, and the adsorbent has good adsorption separation performance.

Description

Technical Field

[0001] This invention belongs to the technical field of adsorption materials, specifically relating to the research on a MOFs / MWCNTs composite adsorbent for CO2 / N2 adsorption and separation. Background Technology

[0002] In recent years, the large-scale development of fossil fuels has resulted in excessive CO2 emissions into the atmosphere. CO2 emissions have become a major cause of global warming and ecological imbalance, making the implementation of a low-carbon emission reduction strategy imperative. How to control CO2 emissions has become a primary concern for researchers. Carbon capture and storage (CCS) technology is a key technological means to significantly reduce CO2 emissions, mitigate climate change, and achieve sustainable development, and it holds great promise for the coming decades. To date, numerous porous materials have been researched and introduced as adsorbents, including activated carbon, zeolite molecular sieves, metal oxides, metal-organic framework materials, porous polymers, carbon nanomaterials, and porous carbon.

[0003] MOFs (Metal-Organic Frameworks) are one-dimensional or multi-dimensional network frameworks formed by bridging of multifunctional organic ligands containing metal ions or small inorganic nanoparticle clusters. MOFs possess excellent thermal stability, large specific surface area, and diverse and modifiable structures. Therefore, MOFs show great potential in catalysts, gas adsorption, and magnetic materials. Currently, the most widely studied MOFs include the IRMOFs series, MILs series, ZIFs series, UiO series, and ZMOFs series. The UiO series is the most acid-, alkali-, hydrothermal-stable metal framework material among MOFs. The UiO series materials are a novel class of 12-coordinate MOFs, and also the MOFs with the highest coordination number discovered to date. UiO-66 is a MOF material with zirconium (Zr) as the metal center and 1,4-phthalic acid (H₂BDC) as the organic ligand. Due to its unique Zr-O structure, UiO-66 not only possesses a high specific surface area but also exhibits significant improvements in thermal, chemical, and mechanical stability. Therefore, UiO-66 demonstrates great application potential in gas adsorption and separation.

[0004] Multi-walled carbon nanotubes (MWCNTs) have been extensively studied due to their advantages such as high specific surface area, high mesoporosity, good electrical conductivity, high mechanical strength, and corrosion resistance. MWCNTs serve as a growth platform for metalloenzymes (MOFs), not only increasing the internal dispersion forces of MOFs but also inhibiting their aggregation and controlling their morphology, structure, and size. Simultaneously, the introduction of MWCNTs can protect the unsaturated metal centers within MOFs, allowing for more unsaturated metal centers to interact more strongly with the adsorbate. Therefore, MOFs / MWCNTs composites have been widely studied due to their unique properties.

[0005] This invention synthesizes a highly stable UiO-66-NH2 / MWCNTs composite material in situ by adding multi-walled carbon nanotubes (MWCNTs) to the material UiO-66-NH2. Compared with the UiO-66-NH2 adsorbent, the composite adsorbent has more stable physical properties, higher adsorption efficiency, and better cycle performance. Summary of the Invention

[0006] [Technical problem to be solved]

[0007] The purpose of this invention is to provide a method for preparing MOFs / MWCNTs composite adsorbents for CO2 / N2 adsorption and separation and their applications.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] Synthesis of UiO-66-NH2:

[0010] UiO-66-NH2 was synthesized in situ via a solvothermal method. 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2) and 1.57 g of ZrCl4 were added to a mixed solution of 60 g DMF and 40 g glacial acetic acid, and the mixture was heated at 125 °C with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, with the supernatant removed by centrifugation every 10 h. Finally, the product was vacuum dried at 120 °C for 15 h to obtain the target product UiO-66-NH2.

[0011] Synthesis of UiO-66-NH2 / MWCNTs:

[0012] First, MWCNTs were added to 60 g of DMF and sonicated for 1 h to obtain a MWCNTs suspension. Then, 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2), 1.57 g of ZrCl4, and 40 g of glacial acetic acid were added to the suspension, and the mixture was heated at 125 ℃ with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, centrifuged and the supernatant was replaced every 10 h. Finally, the product was vacuum dried at 120 ℃ for 15 h to obtain the target product, denoted as UiO-66-NH2 / MWCNTs-x %, where x represents the mass ratio of MWCNTs added to the total amount of H2BDC-NH2 and ZrCl4.

[0013] Adsorption scheme:

[0014] The specific surface area, pore volume, pore size, and CO2 and N2 adsorption performance of the adsorbent material were tested using an adsorption analyzer at 273 K and 298 K. At 298 K, the separation coefficients of the adsorbent for CO2 and N2 were tested using a breakthrough analyzer.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0016] The UiO series MOFs selected in the technical solution of this invention have good hydrothermal stability.

[0017] The sample UiO-66-NH2 / MWCNTs in the technical solution of this invention has a high BET surface area and micropore volume.

[0018] The UiO-66-NH2 / MWCNTs in the technical solution of this invention have good adsorption and separation performance. Attached Figure Description

[0019] Figure 1 The images show SEM characterization diagrams (a) of UiO-66-NH2 and (b, c, d, e, f) of UiO-66-NH2 / MWCNTs prepared in Examples 1 and 2.

[0020] Figure 2 The CO2 adsorption isotherms at 298 K and 273 K for UiO-66-NH2 and UiO-66-NH2 / MWCNTs prepared in Examples 1 and 2 are shown in (a, b).

[0021] Figure 3 The N2 adsorption isotherms and pore size distributions of UiO-66-NH2 and UiO-66-NH2 / MWCNTs prepared in Examples 1 and 2 at 77 K are shown in (a, b).

[0022] Figure 4 Transmission curves (b, c, d, e, f) of UiO-66-NH2 (a) and UiO-66-NH2 / MWCNTs prepared in Examples 1 and 2. Detailed Implementation

[0023] Example 1:

[0024] Synthesis of UiO-66-NH2:

[0025] UiO-66-NH2 was synthesized in situ via a solvothermal method. 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2) and 1.57 g of ZrCl4 were added to a mixed solution of 60 g DMF and 40 g glacial acetic acid, and the mixture was heated at 125 °C with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, with the supernatant removed by centrifugation every 10 h. Finally, the product was vacuum dried at 120 °C for 15 h to obtain the target product UiO-66-NH2.

[0026] Synthesis of UiO-66-NH2 / MWCNTs:

[0027] First, MWCNTs were added to 60 g of DMF and sonicated for 1 h to obtain a MWCNTs suspension. Then, 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2), 1.57 g of ZrCl4, and 40 g of glacial acetic acid were added to the suspension, and the mixture was heated at 125 ℃ with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, centrifuged every 10 h, and the supernatant was replaced. Finally, the product was vacuum dried at 120 ℃ for 15 h to obtain the target product, denoted as UiO-66-NH2 / MWCNTs-1%.

[0028] Adsorption scheme:

[0029] The specific surface area, pore volume, pore size, and CO2 and N2 adsorption performance of the adsorbent material were tested using an adsorption analyzer at 273 K and 298 K. The separation coefficient of the adsorbent was tested using a breakthrough analyzer at 298 K. Results: At 273 K, the CO2 adsorption capacity of UiO-66-NH2 / MWCNTs-1% was 1.79 mmol / g; at 298 K, the CO2 adsorption capacity was 1.04 mmol / g; and the separation coefficient of CO2 for N2 was 21.01.

[0030] Example 2:

[0031] Synthesis of UiO-66-NH2:

[0032] UiO-66-NH2 was synthesized in situ via a solvothermal method. 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2) and 1.57 g of ZrCl4 were added to a mixed solution of 60 g DMF and 40 g glacial acetic acid, and the mixture was heated at 125 °C with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, with the supernatant removed by centrifugation every 10 h. Finally, the product was vacuum dried at 120 °C for 15 h to obtain the target product UiO-66-NH2.

[0033] Synthesis of UiO-66-NH2 / MWCNTs:

[0034] 30 mL of deionized water was added to multi-walled carbon nanotube powder, and the mixture was sonicated for 1 hour to obtain a graphene oxide suspension. Then, 1 g of 2,5-dihydroxyterephthalic acid, 1.5 g of ZrOCl2·8H2O, and 40 mL of glacial acetic acid were added to the suspension, and the mixture was sonicated for 1 hour. The mixture was then placed in a single-necked flask and refluxed at 100 °C for 24 hours to obtain the product. The sample was cooled to below 25 °C, and the precipitate was removed and immersed in water and methanol for 3 days each. The sample was centrifuged twice daily, the supernatant was removed, and the solvent was replaced. After drying at room temperature to remove the methanol solvent, the sample was dried in a vacuum oven at 100 °C for 24 hours to obtain UiO-66-NH2 / MWCNTs-2%.

[0035] Adsorption scheme:

[0036] The specific surface area, pore volume, pore size, and CO2 and N2 adsorption performance of the adsorbent material were tested using an adsorption analyzer at 273 K and 298 K. The separation coefficient of the adsorbent was tested using a breakthrough analyzer at 298 K. Results: At 273 K, the CO2 adsorption capacity of UiO-66-NH2 / MWCNTs was 2.07 mmol / g; at 298 K, the CO2 adsorption capacity was 1.32 mmol / g; and the separation coefficient of CO2 for N2 was 26.13.

[0037] Example 3:

[0038] Synthesis of UiO-66-NH2:

[0039] UiO-66-NH2 was synthesized in situ via a solvothermal method. 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2) and 1.57 g of ZrCl4 were added to a mixed solution of 60 g DMF and 40 g glacial acetic acid, and the mixture was heated at 125 °C with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, with the supernatant removed by centrifugation every 10 h. Finally, the product was vacuum dried at 120 °C for 15 h to obtain the target product UiO-66-NH2.

[0040] Synthesis of UiO-66-NH2 / MWCNTs:

[0041] First, MWCNTs were added to 60 g of DMF and sonicated for 1 h to obtain a MWCNTs suspension. Then, 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2), 1.57 g of ZrCl4, and 40 g of glacial acetic acid were added to the suspension, and the mixture was heated at 125 ℃ with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, centrifuged every 10 h, and the supernatant was replaced. Finally, the product was vacuum dried at 120 ℃ for 15 h to obtain the target product, denoted as UiO-66-NH2 / MWCNTs-3%.

[0042] Adsorption scheme:

[0043] The specific surface area, pore volume, pore size, and CO2 and N2 adsorption performance of the adsorbent material were tested using an adsorption analyzer at 273 K and 298 K. The separation coefficient of the adsorbent was tested using a breakthrough analyzer at 298 K. Results: At 273 K, the CO2 adsorption capacity of UiO-66-NH2 / MWCNTs-3% was 2.74 mmol / g; at 298 K, the CO2 adsorption capacity was 1.51 mmol / g; and the separation coefficient of CO2 for N2 was 32.6.

[0044] Example 4:

[0045] Synthesis of UiO-66-NH2:

[0046] UiO-66-NH2 was synthesized in situ via a solvothermal method. 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2) and 1.57 g of ZrCl4 were added to a mixed solution of 60 g DMF and 40 g glacial acetic acid, and the mixture was heated at 125 °C with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, with the supernatant removed by centrifugation every 10 h. Finally, the product was vacuum dried at 120 °C for 15 h to obtain the target product UiO-66-NH2.

[0047] Synthesis of UiO-66-NH2 / MWCNTs:

[0048] First, MWCNTs were added to 60 g of DMF and sonicated for 1 h to obtain a MWCNTs suspension. Then, 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2), 1.57 g of ZrCl4, and 40 g of glacial acetic acid were added to the suspension, and the mixture was heated at 125 ℃ with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, centrifuged every 10 h, and the supernatant was replaced. Finally, the product was vacuum dried at 120 ℃ for 15 h to obtain the target product, denoted as UiO-66-NH2 / MWCNTs-4%.

[0049] Adsorption scheme:

[0050] The specific surface area, pore volume, pore size, and CO2 and N2 adsorption performance of the adsorbent material were tested using an adsorption analyzer at 273 K and 298 K. The separation coefficient of the adsorbent was tested using a breakthrough analyzer at 298 K. Results: At 273 K, the CO2 adsorption capacity of UiO-66-NH2 / MWCNTs-4% was 2.26 mmol / g; at 298 K, the CO2 adsorption capacity was 1.39 mmol / g; and the separation coefficient of CO2 for N2 was 18.15.

[0051] Example 5:

[0052] Synthesis of UiO-66-NH2:

[0053] UiO-66-NH2 was synthesized in situ via a solvothermal method. 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2) and 1.57 g of ZrCl4 were added to a mixed solution of 60 g DMF and 40 g glacial acetic acid, and the mixture was heated at 125 °C with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, with the supernatant removed by centrifugation every 10 h. Finally, the product was vacuum dried at 120 °C for 15 h to obtain the target product UiO-66-NH2.

[0054] Synthesis of UiO-66-NH2 / MWCNTs:

[0055] First, MWCNTs were added to 60 g of DMF and sonicated for 1 h to obtain a MWCNTs suspension. Then, 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2), 1.57 g of ZrCl4, and 40 g of glacial acetic acid were added to the suspension, and the mixture was heated at 125 ℃ with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively, centrifuged every 10 h, and the supernatant was replaced. Finally, the product was vacuum dried at 120 ℃ for 15 h to obtain the target product, denoted as UiO-66-NH2 / MWCNTs-5%.

[0056] Adsorption scheme:

[0057] The specific surface area, pore volume, pore size, and CO2 and N2 adsorption performance of the adsorbent material were tested using an adsorption analyzer at 273 K and 298 K. The separation coefficient of the adsorbent was tested using a breakthrough analyzer at 298 K. Results: At 273 K, the CO2 adsorption capacity of UiO-66-NH2 / MWCNTs-5% was 1.98 mmol / g; at 298 K, the CO2 adsorption capacity was 1.24 mmol / g; and the separation coefficient of CO2 for N2 was 16.52.

Claims

1. A method for preparing a MOFs / MWCNTs composite adsorbent for CO2 / N2 adsorption and separation, characterized in that... MWCNTs were added to DMF, and a MWCNTs suspension was obtained by ultrasonication. 2-Aminoterephthalic acid, ZrCl4, and glacial acetic acid were added to the suspension, and the mixture was heated under constant temperature stirring. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively. The supernatant was removed by centrifugation every 10 hours, and finally dried under vacuum to obtain the target product, denoted as UiO-66-NH2 / MWCNTs-x %, where x represents the mass ratio of MWCNTs added to the total amount of H2BDC-NH2 and ZrCl4.

2. The method according to claim 1, characterized in that... First, MWCNTs were added to 60 g DMF and sonicated for 1 h to obtain a MWCNTs suspension. Then, 1.1 g of 2-aminoterephthalic acid (H2BDC-NH2), 1.57 g of ZrCl4, and 40 g of glacial acetic acid were added to the suspension. The mixture was heated at 125 ℃ with stirring for 25 h. After the reaction system cooled naturally to room temperature, the solution portion was removed by centrifugation, and the remaining product was soaked in DMF and ethanol for three days respectively. The supernatant was removed by centrifugation every 10 h and replaced. Finally, the product was vacuum dried at 120 ℃ for 15 h to obtain the target product, denoted as UiO-66-NH2 / MWCNTs-x %, where x represents the mass ratio of the amount of MWCNTs added to the total amount of H2BDC-NH2 and ZrCl4.

3. The method according to claims 1 and 2, characterized in that... The mass percentages of MWCNTs added during the preparation of composite materials were 1%, 2%, 3%, 4%, and 5%.

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