Microporous Ni-MOF adsorption material as well as preparation method and application thereof

Abstract

The invention relates to an adsorption material, in particular to a microporous Ni-MOF adsorption material and a preparation method and application thereof. The microporous Ni-MOF material provided by the invention has remarkable advantages in structural stability and aperture matching, and is just matched with the kinetic diameters of hexane isomers and benzene / cyclohexane molecules, so that the microporous Ni-MOF material can realize an efficient molecular sieving effect. Especially, the selective recognition of straight-chain / single-branched-chain and double-branched-chain hexane realizes the'complete cutting 'capability which cannot be achieved by the existing adsorbent.

Description

Technical Field

[0001] This invention relates to an adsorption material, specifically to a microporous Ni-MOF adsorption material, its preparation method, and its application. Background Technology

[0002] The separation of alkane isomers and aromatic / cycloalkanes is a core step in petrochemical processes. In the refining and petrochemical industries, the composition of hexane isomers directly determines the octane number and economic value of downstream products. Straight-chain and monobranched hexane are mainly used as cracking feedstocks, while dibranched hexane can significantly improve the octane number of gasoline and plays an important role in fuels. Therefore, efficient separation of straight-chain, monobranched, and dibranched hexane isomers is of great significance for optimizing petroleum refining and improving fuel quality. On the other hand, the separation of benzene / cyclohexane is equally crucial in processes such as aromatic hydrogenation and the purification of fine chemical feedstocks. Benzene, as an important basic chemical feedstock, is widely used in the synthesis of resins, fibers, and pharmaceuticals; cyclohexane is mainly used as a precursor for adipic acid and hexamethylenediamine in the nylon industry chain. The boiling points of the two are extremely close, differing by only about 0.5 °C, making effective separation difficult with traditional distillation, resulting in huge energy consumption in the separation process.

[0003] Currently, most of the above separation methods rely on cryogenic distillation or multi-stage extraction, which suffer from high energy consumption, large equipment investment, and complex operation. In recent years, adsorbents such as molecular sieves and activated carbon have been applied to separation processes, but their pore size distribution is relatively wide, making it difficult to accurately distinguish molecules with similar sizes and morphologies, resulting in limited separation selectivity.

[0004] Metal-organic frameworks (MOFs) offer new possibilities for the efficient separation of complex hydrocarbon molecules due to their designable pore structures, large specific surface areas, and tunable chemical environments. However, most MOFs still suffer from inaccurate pore size distributions, making it difficult to meet the industrial demands for highly selective alkane separation. This is especially true for hexane isomers, such as 3-methylpentane (3MP, kinetic diameter approximately 5.4 Å) and 2,3-dimethylbutane (23DMB, kinetic diameter approximately 5.8 Å), whose molecular sizes are extremely similar. Existing MOFs are insufficient in their separation capabilities for these isomers, and the same applies to benzene (kinetic diameter approximately 5.6 Å) and cyclohexane (kinetic diameter approximately 6.1 Å), which have similar kinetic diameters. Therefore, there is an urgent need to develop novel MOF materials with stable structures, precisely controllable pore sizes, and excellent molecular recognition properties to solve the challenges of separating hexane isomers and benzene / cyclohexane. Summary of the Invention

[0005] To address the aforementioned issues, the microporous Ni-MOF material provided by this invention exhibits significant advantages in structural stability and pore size matching, precisely matching the kinetic diameters of hexane isomers and benzene / cyclohexane molecules, enabling it to achieve a highly efficient molecular sieving effect. In particular, its selective recognition of straight-chain / single-branched and double-branched hexanes achieves a "complete cleavage" capability unattainable by existing adsorbents.

[0006] First, this invention provides a microporous Ni-MOF adsorbent material, wherein the microporous Ni-MOF adsorbent material has a composition of Ni 2+ The microporous Ni-MOF adsorbent material is a periodic three-dimensional crystal framework constructed through coordination of a metal center, 1,3,5-benzenetricarboxylic acid (H3BTC) and 1,4-diazabicyclo[2.2.2]octane (DABCO) as organic ligands; the pore size range of the microporous Ni-MOF adsorbent material is 5.4-5.6 Å.

[0007] As a preferred embodiment, the material has a specific surface area ≥ 500 m². 2 / g, preferably ≥700 m 2 / g.

[0008] As a preferred embodiment, the stoichiometric molar ratio of Ni:H3BTC:DABCO in the microporous Ni-MOF adsorbent material is 1:(0.90–1.10):(1.10–1.40).

[0009] Secondly, the present invention also provides a method for preparing the microporous Ni-MOF adsorbent material of claim 1, which includes the following steps: (1) Dissolve 1,4-diazabicyclo[2.2.2]octane, 1,3,5-benzenetricarboxylic acid and nickel source in organic solvents to obtain a first solution, a second solution and a metal source solution, and then add the second solution and the metal source solution into the first solution and mix them to form a mixed solution; (2) Add alcohols to the mixed solution to aid dissolution, and continue stirring until the solid is completely dissolved to form a synthetic solution; (3) The synthesis solution is stirred at 70-95 °C for 48-72 h, and after the reaction is completed, the solid-liquid separation, washing and activation are performed to obtain the microporous Ni-MOF adsorbent material.

[0010] As a preferred embodiment, in step (1), the nickel source is selected from one of Ni(NO3)2·6H2O, NiCl2·6H2O, and NiSO4·6H2O; and the organic solvent is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

[0011] As a preferred embodiment, in step (2), the alcohol auxiliary is at least one of methanol, ethanol or isopropanol, preferably methanol; the volume fraction of the alcohol auxiliary in the synthesis solution is 50-70 vol.

[0012] As a preferred embodiment, in step (2), the molar concentrations of 1,4-diazabicyclo[2.2.2]octane, 1,3,5-benzenetricarboxylic acid, and the nickel source in the organic solvent in the synthesis solution are each independently 0.35-0.50 mol·L⁻¹. -1 .

[0013] As a preferred embodiment, in step (3), the washing is performed by sequentially washing with the organic solvent and dichloromethane; the activation includes at least one of solvent replacement and vacuum heating drying.

[0014] Finally, the microporous Ni-MOF adsorbent material provided by this invention can be used in the separation of hexane isomers or the separation of benzene and cyclohexane. When applied to the separation of hexane isomers, the microporous Ni-MOF adsorbent material preferentially adsorbs straight-chain and monobranched hexanes and repels dibranched isomers. When applied to the separation of benzene and cyclohexane, the microporous Ni-MOF adsorbent material preferentially adsorbs benzene.

[0015] As a preferred method, the separation temperature is 20-50℃, and a bubbling adsorption-desorption cycle is adopted, wherein the desorption method is at least one of heating or inert gas purging.

[0016] Compared with the prior art, the present invention has the following advantages: (1) The significant beneficial effects of the Ni-MOF adsorbent material obtained in this invention stem from the use of Ni 2+ The Ni-MOF adsorbent material, with a metal center, is a specific ligand combination consisting of a rigid planar structure of 1,3,5-benzenetricarboxylic acid (H3BTC) and a linearly bridged 1,4-diazabicyclo[2.2.2]octane (DABCO). The Ni-MOF adsorbent material prepared by this specific combination exhibits a uniform micropore size distribution and a large specific surface area, typically not less than 500 m². 2 ·g -1 This material maintains a stable crystal structure up to 390 °C and does not exhibit significant framework collapse in common organic solvents, demonstrating excellent thermal and chemical stability. Furthermore, the material described in this invention maintains good structure and performance even after multiple adsorption-desorption cycles, demonstrating excellent cycle life and industrial application potential.

[0017] (2) In separation applications, the Ni-MOF material provided by this invention exhibits significant advantages. Thanks to the precise control of the material's main pore size (approximately 5.5 Å) by H3BTC and DABCO, which highly matches the target molecule's kinetic diameter, the material effectively achieves selective adsorption of straight-chain and single-branched isomers while completely rejecting dibranched isomers during hexane isomer separation, resulting in highly efficient separation. This characteristic overcomes the limitation of traditional adsorbents in insufficient separation of 3-methylpentane (3MP) and 2,3-dimethylbutane (23DMB), achieving precise cutting of hexane isomers. In benzene / cyclohexane separation, the material exhibits significant preferential adsorption of benzene molecules. Even though benzene (5.6 Å) and cyclohexane (6.1 Å) differ in kinetic diameter by only about 0.5 Å, efficient separation can still be achieved, thus avoiding the high energy consumption and low efficiency problems caused by traditional distillation due to a boiling point difference of only 0.5 °C. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the method for preparing Ni-MOF adsorbent materials according to the present invention and a schematic diagram of the structure of Ni-MOF adsorbent materials; Figure 2 The image shows the powder X-ray diffraction (PXRD) pattern of the Ni-MOF adsorbent material prepared in Example 1, with a comparison between the measured pattern and the simulated pattern. Figure 3 The nitrogen adsorption-desorption isotherm curve of the Ni-MOF adsorbent material prepared in Example 1 at 77 K; Figure 4 Thermogravimetric analysis (TGA) curves of the Ni-MOF adsorbent material prepared in Example 1; Figure 5 The PXRD spectra of the Ni-MOF adsorbent material prepared in Example 1 after immersion in different solvents (including water, methanol, n-hexane and dichloromethane) for 48 h are compared. Figure 6 The single-component adsorption isotherm of the Ni-MOF adsorbent material prepared in Example 1 in the hexane isomer separation experiment; Figure 7 The adsorption curve of the Ni-MOF adsorbent material prepared in Example 1 in the dynamic separation experiment of hexane isomers; Figure 8 The desorption curve of the Ni-MOF adsorbent material prepared in Example 1 in the dynamic separation experiment of hexane isomers; Figure 9 The single-component adsorption isotherm of the Ni-MOF adsorbent material prepared in Example 1 for the benzene and cyclohexane system; Figure 10The breakthrough curve of the Ni-MOF adsorbent material prepared in Example 1 in the benzene / cyclohexane separation experiment; Figure 11 Breakthrough curve of Al-bttotb material prepared for Comparative Example 1 in hexane isomer separation experiment; Figure 12 The single-component adsorption isotherm of the Al-bttotb material prepared for Comparative Example 1 for the five-component hexane isomers is shown.

[0019] Figure 13 A schematic diagram of the crystal structure of Ni-MOF-py prepared in Comparative Example 2; Figure 14 The single-component adsorption isotherm of a typical three-component hexane isomer prepared by Ni-MOF-py in Comparative Example 2 is shown. Figure 15 Breakthrough curves of Ni-MOF-py prepared for Comparative Example 2 against typical three-component hexane isomers. Detailed Implementation

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention, and not all embodiments. Any other embodiments obtained by those skilled in the art based on these drawings without creative effort are within the protection scope of the present invention.

[0021] Example 1 like Figure 1 As shown, this embodiment provides a Ni-MOF adsorbent, and the specific preparation method is as follows: In a three-necked flask, weigh 6.8 g (60 mmol) of 1,4-diazabicyclohexane. Octane (DABCO) was dissolved in 50 mL of N,N-dimethylformamide (DMF) to obtain a clear solution. Separately, 10.5 g (50 mmol) of 1,3,5-benzenetricarboxylic acid (H3BTC) and 14.8 g (50 mmol) of Ni(NO3)2·6H2O were dissolved in 50 mL of DMF respectively, and then added sequentially to the aforementioned DABCO solution, stirring for 10 minutes. Then, 200 mL of methanol was added to the mixture, and stirring continued until the solid was completely dissolved, resulting in a homogeneous reaction system. The reaction solution was heated at 95 °C for 48 h, with low-speed stirring at 100 rpm for the first 40 h, and thorough stirring at 300 rpm for the last 8 h. After the reaction was completed, the mixture was cooled to room temperature, and the precipitated green crystals were collected by filtration and washed twice with 100 mL each of DMF and DCM. The resulting solid was replaced with DCM and then dried under vacuum at 100 °C for 12 h to obtain the target Ni-MOF material.

[0022] Example 2 This example demonstrates the application of the Ni-MOF prepared in Example 1 in the separation of hexane isomers: For the dynamic competitive adsorption separation evaluation, 1-2 g of the prepared Ni-MOF material was ground into powder and packed into a stainless steel adsorption column with quartz wool at both ends. The column was 20 cm long and 6 mm in inner diameter. Before the adsorption test, the stainless steel column containing the Ni-MOF adsorbent material was purged with N2 in a 100°C oven for 5 h. It was then cooled to 35°C for the adsorption test. The feed gas mixture was prepared using a nitrogen bubbling method, with a nitrogen flow rate set to 1 mL / min. -1 The mixture was bubbled through a liquid mixture containing different hexane isomers, and the resulting gaseous components were verified to be in equimolar proportions by gas chromatography (GC). The liquid phase feed amounts for the pentagonal equimolar mixture (nHEX / 2MP / 3MP / 23DMB / 22DMB, 1 / 1 / 1 / 1 / 1) were: 4.212 g nHEX, 3.014 g 2MP, 3.604 g 3MP, 2.72 g 23DMB, and 2.04 g 22DMB, with a partial pressure of approximately 5.46 kPa for each gaseous component. The above mixed gas was bubbled at 35 °C at a rate of 1 mL / min. -1 The total flow rate was fed into the Ni-MOF packed column for breakthrough experiments, and data was collected using gas chromatography every 6 minutes.

[0023] Example 3 This example demonstrates the application of the Ni-MOF prepared in Example 1 in the separation of benzene / cyclohexane: Using the same apparatus and conditions as in Example 2, an adsorption separation experiment was conducted at 35°C with an equimolar mixture of benzene and cyclohexane as the feed. The difference was that helium was used for bubbling tests during the operation, and the liquid phase feed amounts corresponding to the equimolar benzene / cyclohexane mixture (Be / Cy, 1 / 1) were 5.8 g Be and 5.68 g Cy.

[0024] Comparative Example 1 This comparative example is used to synthesize Al-bttotb adsorbent materials and apply them to the separation of hexane isomers: Al-bttotb is a class of aluminum ions (Al... 3+As a metal node, H3bttotb polycarboxylic acid ligands serve as organic linkers in a metal-organic framework (MOF) material. This material has been widely reported in the literature and, due to its regular pore structure, is considered a "star material" for the adsorption and separation of hexane isomers, often used as a typical control system in related studies. Previous studies have shown that Al-bttotb has a certain adsorption capacity for straight-chain and monobranched alkanes, showing good application prospects in the separation of hexane isomers, thus becoming a commonly used comparative standard in this field. However, in comparative experiments, this invention found that although Al-bttotb can achieve partial separation, its pore selectivity is insufficient, especially exhibiting significant adsorption of 23DMB, failing to completely exclude dibranched isomers, which is detrimental to the hexane separation process.

[0025] Synthesis steps: 2g Al(NO3)2·9H2O and 1.25g organic ligand H3bttotb were added to a mixed solvent consisting of 50mL LDM and 25mL formic acid, and stirred at room temperature for 30 minutes to ensure complete dissolution. The resulting solution was transferred to a 100mL polytetrafluoroethylene-lined reactor and reacted at 150℃ for 5 days to obtain colorless crystals. After the reaction was completed and cooled, post-treatment was performed using the same method as for Ni-MOF. Subsequently, the obtained Al-bttotb crystals were ground and packed into a stainless steel adsorption column. An equimolar mixture of hexane isomers was subjected to adsorption at 305K and a N2 flow rate of 1mL·min⁻¹. -1 Breakthrough experiments were conducted under these conditions.

[0026] Comparative Example 2 This comparative example was used to synthesize another Ni-MOF adsorbent (Ni-MOF-py) and applied it in the separation of hexane isomers. The only difference between the synthetic method and Example 1 is the replacement of 1,4-diazabicyclo with an equimolar amount of pyrazine (py). Octane (DABCO) was dissolved in 50 mL of N,N-dimethylformamide (DMF).

[0027] Characterization results like Figure 2 As shown, PXRD testing revealed that the diffraction peaks of the Ni-MOF prepared in Example 1 were completely consistent with the simulated pattern, indicating that the prepared material has a highly ordered crystal structure and high purity. Figure 3 As shown, this Ni-MOF exhibits high nitrogen adsorption capacity at 77 K, with the adsorption capacity increasing rapidly in the low-pressure region, exhibiting typical microporous adsorption characteristics. Its specific surface area is calculated to be 715–725 m². 2 ·g -1 The pore size is mainly concentrated in the range of 5.4-5.6 Å. For example... Figure 4As shown, the thermal decomposition temperature of this Ni-MOF is approximately 390℃, exhibiting excellent thermal stability. Figure 5 The PXRD spectra of the Ni-MOF material of this invention after immersion in different solvents (including water, methanol, n-hexane, and dichloromethane) show that the diffraction peak positions and intensities of each sample remain basically unchanged, proving that the material has good chemical stability in various solvent environments. To evaluate the adsorption capacity for hexane isomers, the Ni-MOF adsorbent was degassed under vacuum at 100°C for 5 h, and then its adsorption capacity for five hexane isomers was evaluated using a vapor adsorption instrument. The results are as follows: Figure 6 As shown, single-component adsorption isotherm tests of hexane isomers at 308 K indicate that the Ni-MOF material prepared in Example 1 exhibits significant adsorption differences for different isomers. nHEX shows the highest adsorption capacity, reaching approximately 145 mg·g⁻¹. -1 The adsorption capacities of the single-branched isomers 2-MP and 3-MP are approximately 105 mg·g⁻¹. -1 and 90 mg·g -1 It still exhibits strong ability to enter the pores. However, the adsorption capacities of the dibranched isomers 23-DMB and 22-DMB are both below 10 mg·g⁻¹. -1 There is almost no noticeable adsorption.

[0028] like Figure 7 As shown, at 305K and an N2 flow rate of 1 mL·min -1 Under specific conditions, breakthrough experiments were conducted on an equimolar mixture of hexane isomers. The breakthrough order of different isomers on a Ni-MOF stainless steel breakthrough column showed significant differences. The dibranched isomers 22DMB and 23DMB were almost completely retained in the column and broke through simultaneously, indicating that they were hardly adsorbed. With time, the single-branched isomers 3MP and 2MP broke through sequentially, with breakthroughs occurring at approximately 30 min·g⁻¹. -1 and 40 min·g -1 The occurrence of saturation breakthrough indicates that the single-branched isomer exhibits moderate adsorption in the material. nHEX, on the other hand, shows adsorption at approximately 90 min·g. -1 The adsorption gradually penetrated later, exhibiting the strongest adsorption effect. The breakthrough order shows that the Ni-MOF prepared in Example 1 exhibits significant selectivity for hexane isomers: straight-chain molecules are preferentially retained, followed by monobranched molecules, while bibranched molecules are almost completely repelled. This result is consistent with the pattern of single-component adsorption isotherms. Simultaneously, the octane number (RON) curve plotted in the figure shows that the RON value of the effluent remained above 90 for the first 30 minutes during adsorption separation, reaching close to 100 in the pre-breakthrough phase, indicating that the material can effectively enrich high-octane monobranched isomers, possessing potential application value in improving fuel quality. Figure 8As shown, at 373K and an N2 flow rate of 1 mL·min -1 Under the specified conditions, temperature-programmed desorption experiments were conducted on Ni-MOF after adsorption saturation. It was observed that the desorption order of different hexane isomers on the material differed significantly: the dibranched isomers 22DMB and 23DMB were completely desorbed first in the initial time period, with almost no retention in the material channels; the monobranched isomers 2MP and 3MP were gradually released in the intermediate temperature range; the linear isomer nHEX showed the most delayed desorption, with the peak value appearing in the later stage. Notably, in the range of 15-65 min·g... -1 Within the desorption range, the product stream consisted almost entirely of three isomers: nHEX, 2MP, and 3MP, with a purity exceeding 97.2%, making it particularly suitable as a high-quality feedstock for ethylene cracking. This result demonstrates that the Ni-MOF prepared in Example 1 possesses both excellent adsorption selectivity and controllable desorption characteristics, enabling efficient separation and high-purity recovery. It is suitable for application in petroleum refining processes to enhance gasoline octane number and for targeted feedstock separation.

[0029] The results of the steam adsorption experiment are as follows Figure 9 As shown, the adsorption curve for benzene (Bz) exhibits a clear monotonic upward trend under low pressure, a typical Type I adsorption isotherm, indicating that the Ni-MOF prepared in Example 1 has a strong adsorption effect on benzene molecules and possesses high pore affinity. The cyclohexane (Cy) curve shows low adsorption capacity across the entire pressure range and a slow increase without a clear inflection point, indicating that the material has weak adsorption capacity for cyclohexane and poor matching between the pore structure and the molecular shape or polarity. Figure 11 The figure shows the dynamic competitive adsorption isotherm of the multicomponent mixture. The results indicate that a breakthrough experiment was conducted on an equimolar Be / Cy mixture, and there was a significant difference in the breakthrough time between the two molecules. The Cy concentration was approximately 5 min·g. -1 The concentration of Bz began to rise at that time, indicating an earlier breakout and the occurrence of size exclusion; while the concentration of Bz was delayed until approximately 90 min·g. -1 The adsorption of benzene only begins later, indicating that it has a stronger adsorption capacity and a longer retention time in the Ni-MOF channels. Through adsorption-desorption cycling verification, the Ni-MOF prepared in Example 1 maintained its selective adsorption capacity for benzene and good structural stability after five consecutive cycles. The results demonstrate that the material of this invention can effectively distinguish between benzene (5.6 Å) and cyclohexane (6.1 Å), whose kinetic diameters differ by only about 0.5 Å, thus achieving efficient separation.

[0030] like Figure 12 As shown, at 305 K and a nitrogen flow rate of 1 mL / min... -1Under the specified conditions, breakthrough experiments were conducted on an equimolar mixture of hexane isomers using the Al-bttotb material prepared in Comparative Example 1. It was observed that the material exhibited insufficient selectivity for the separation of each isomer, particularly the dibranched isomer 23DMB, which showed a significantly delayed breakthrough time and prolonged retention. This indicates that 23DMB was not effectively repelled but instead entered the material's pores and competed for adsorption with other molecules, failing to maintain a high separation efficiency for the overall hexane separation process. Single-component adsorption isotherms further confirmed this, showing a significant adsorption capacity of approximately 38 mg / g for the dibranched 23DMB, higher than the 8 mg / g of Ni-MOF, indicating that the pores did not completely sieve all dibranched molecules.

[0031] like Figure 13 Therefore, the Ni-MOF-py material prepared in Comparative Example 2, after the removal of the cubic ligands, exhibits its framework along... b A more open pore structure is formed along the axial direction. This enlarged pore size weakens the spatial constraint on molecular movement within the pores, simultaneously reducing the original "geometric sieving" and "shape-selective adsorption" effects. Figure 14 The adsorption isotherms provide a more intuitive view of the single-component adsorption isotherms of Ni-MOF-py for the typical three components (linear, monobranched, and bibranched) in hexane. The adsorption capacities of linear nHEX, monobranched 3MP, and bibranched 22DMB at 308 K show a decreasing difference in adsorption capacity in that order, but all maintain high adsorption capacity (all > 100 mg / g). This indicates that after structural adjustment, the material lost its effective molecular sieving effect on branched isomers, and the enlarged pore size led to reduced selectivity. Figure 15 As shown, the Ni-MOF-py material exhibits non-molecular sieving thermodynamically controlled adsorption behavior in a typical three-component hexane isomer mixed gas separation experiment. The breakthrough order is 22DMB-3MP-nHEX. Among them, branched alkanes have larger steric hindrance and smaller molecular-surface contact area, so they penetrate earlier. Linear alkanes penetrate last. The overall retention time is relatively long (all > 150 min / g), resulting in low process efficiency.

[0032] The above results show that Al-bttotb, the material in Comparative Example 1, cannot repel the bibranched isomers, exhibiting insufficient separation and thus failing to achieve precise cleavage of the hexane isomers. This contrasts sharply with the "preferential adsorption of straight and single-branched molecules, and complete repulsion of bibranched molecules" achieved by the Ni-MOF of this invention in Example 2, fully demonstrating the unique advantages of the material of this invention in isomer separation. The Ni-MOF-py material in Comparative Example 2 exhibits pore relaxation and increased effective pore size, completely losing its molecular sieving effect on the hexane isomers, highlighting the importance of the combination of H3BTC and DABCO.

Claims

1. A microporous Ni-MOF adsorbent material, characterized in that: The microporous Ni-MOF adsorbent material has a periodic three-dimensional crystal framework constructed by coordination of Ni²⁺ as the metal center and 1,3,5-benzenetricarboxylic acid (H3BTC) and 1,4-diazabicyclo[2.2.2]octane (DABCO) as organic ligands; the pore size of the microporous Ni-MOF adsorbent material is in the range of 5.4-5.6 Å.

2. The microporous Ni-MOF adsorbent material according to claim 1, characterized in that: The specific surface area of ​​the material is ≥500 m². 2 / g.

3. The microporous Ni-MOF adsorbent material according to claim 1, characterized in that: The stoichiometric molar ratio of Ni:H3BTC:DABCO in the microporous Ni-MOF adsorbent material is 1:(0.90–1.10):(1.10–1.40).

4. A method for preparing the microporous Ni-MOF adsorbent material according to claim 1, characterized in that, Includes the following steps: (1) Dissolve 1,4-diazabicyclo[2.2.2]octane, 1,3,5-benzenetricarboxylic acid and nickel source in organic solvents to obtain a first solution, a second solution and a metal source solution, and then add the second solution and the metal source solution into the first solution and mix them to form a mixed solution; (2) Add alcohols to the mixed solution to aid dissolution, and continue stirring until the solid is completely dissolved to form a synthetic solution; (3) The synthesis solution is stirred at 70-95℃ for 48-72h, and after the reaction is completed, the solid-liquid separation, washing and activation are performed to obtain the microporous Ni-MOF adsorbent material.

5. The method according to claim 4, characterized in that, In step (1), the nickel source is selected from one of Ni(NO3)2·6H2O, NiCl2·6H2O, and NiSO4·6H2O; the organic solvent is selected from one of N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide.

6. The method according to claim 4, characterized in that, In step (2), the alcohol auxiliary is at least one of methanol, ethanol or isopropanol; the volume fraction of the alcohol auxiliary in the synthesis solution is 50-70 vol.

7. The method according to claim 4, characterized in that, In step (2), the molar concentrations of 1,4-diazabicyclo[2.2.2]octane, 1,3,5-benzenetricarboxylic acid, and the nickel source in the organic solvent in the synthesis solution are each independently 0.35-0.50 mol·L⁻¹. -1 .

8. The method according to claim 4, characterized in that, In step (3), the washing is a sequential washing with the organic solvent and dichloromethane; the activation includes at least one of solvent replacement and vacuum heating drying.

9. The application of the microporous Ni-MOF adsorbent material according to claim 1 in the separation of hexane isomers or the separation of benzene and cyclohexane, wherein, When applied to the separation of hexane isomers, the microporous Ni-MOF adsorbent material preferentially adsorbs straight-chain and monobranched hexanes and repels dibranched isomers; when applied to the separation of benzene and cyclohexane, the microporous Ni-MOF adsorbent material preferentially adsorbs benzene.

10. The application according to claim 9, characterized in that: The separation temperature is 20-50℃, and a bubbling adsorption-desorption cycle is adopted, wherein the desorption method is at least one of heating or inert gas purging.

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