ADSORBENT AND USE THEREOF

Abstract

An adsorbent and a use thereof are provided. The adsorbent is a metal-organic framework (MOF) MIL-125; the MOF MIL-125 has an external specific surface area (SSA) of 160 m.sup.2/g to 220 m.sup.2/g; and the MOF MIL-125 includes a micropore with an area of 1,000 m.sup.2/g to 1,500 m.sup.2/g. The external SSA of the MOF MIL-125 is much higher than an external SSA of the traditional MIL-125, which has promising application prospects in the adsorptive separation of xylene isomers and exhibits high selectivity for p-xylene.

Claims

1. An adsorbent, comprising a metal-organic framework (MOF) MIL-125, wherein the MOF MIL-125 has an external specific surface area (SSA) of 160 m.sup.2/g to 220 m.sup.2/g; and the MOF MIL-125 comprises a micropore with an SSA of 1,000 m.sup.2/g to 1,500 m.sup.2/g.

2. The adsorbent according to claim 1, wherein a mass content of particles with a particle size of 1.6 μm to 1.8 μm in the MOF MIL-125 is 85% to 95%.

3. The adsorbent according to claim 1, wherein the MOF MIL-125 is a round cake-like crystal.

4. The adsorbent according to claim 1, wherein the micropore has a pore size of 0.35 nm to 0.5 nm.

5. A method for an adsorptive separation of xylene isomers, comprising: using the adsorbent according to claim 1 to conduct the adsorptive separation of the xylene isomers.

6. The method according to claim 5, wherein the xylene isomers are at least two selected from the group consisting of p-xylene, m-xylene, and o-xylene.

7. The method according to claim 5, wherein the adsorbent is used after an activation; and a method for the activation comprises: placing the adsorbent in an inert atmosphere for the activation to obtain an activated adsorbent.

8. The method according to claim 7, wherein the activation is conducted at 150° C. to 200° C. for 3 h to 12 h; and a flow rate of an inert gas in the inert atmosphere is 50 mL/min to 100 mL/min.

9. The method according to claim 5, wherein a molar ratio of two isomers among the xylene isomers is 1:1 to 10:1.

10. The method according to claim 5, comprising: loading the adsorbent into a packed column, allowing a feed solution comprising the xylene isomers to pass through the packed column, and controlling an effusion time of an effluent to separate the xylene isomers.

11. The method according to claim 10, wherein the feed solution comprising the xylene isomers has a concentration of 0.1 wt % to 1 wt %; and a flow rate of the feed solution comprising the xylene isomers to pass through the packed column is 0.2 mL/min to 2 mL/min.

12. The method according to claim 10, wherein the feed solution comprising the xylene isomers comprises a first solvent; and the first solvent is at least one selected from the group consisting of mesitylene, p-diethylbenzene, triisopropylbenzene (TIPB), cyclooctane, and n-heptane.

13. The method according to claim 12, comprising: loading the adsorbent into the packed column, rinsing the packed column with a second solvent, allowing the feed solution comprising the xylene isomers to pass through the packed column, and controlling the effusion time of the effluent to separate the xylene isomers.

14. The method according to claim 5, wherein a mass content of particles with a particle size of 1.6 μm to 1.8 μm in the MOF MIL-125 is 85% to 95%.

15. The method according to claim 5, wherein the MOF MIL-125 is a round cake-like crystal.

16. The method according to claim 5, wherein the micropore has a pore size of 0.35 nm to 0.5 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0100] FIG. 1 is an X-ray diffractometry (XRD) pattern of the product synthesized in Example 1 of the present disclosure.

[0101] FIG. 2 is a scanning electron microscopy (SEM) image of the product synthesized in Example 1 of the present disclosure.

[0102] FIG. 3 is a physical adsorption isotherm (BET) of the product synthesized in Example 1 of the present disclosure.

[0103] FIG. 4 shows a particle size distribution of the product synthesized in Example 1 of the present disclosure.

[0104] FIG. 5 to FIG. 7 show dynamic breakthrough curves of the samples A1, A2, and A8 for xylene isomers.

[0105] FIG. 8 shows the comparison of the separation performance of the adsorbent of the present application with a xylene adsorbent in the prior art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0106] The present application will be described in detail below with reference to examples, but the present application is not limited to these examples.

[0107] Unless otherwise specified, the raw materials in the examples of the present application are all purchased from commercial sources.

[0108] In the examples of the present application, XRD of a product is conducted by an X'Pert PRO X-ray diffractometer of Netherlandish PANalytical under the following conditions: Cu target, Kα radiation source (λ=0.15418 nm), voltage: 40 KV, and current: 40 mA.

[0109] In the examples of the present application, the SEM of a product is conducted by an SU8020 scanning electron microscope of Hitachi.

[0110] In the examples of the present application, the physical adsorption and pore distribution of a product are analyzed by an ASAP2020 automatic physical instrument of Micromeritics.

[0111] In the examples of the present application, the adsorption performance is evaluated by Agilent gas chromatography (GC) under the following conditions: capillary column: polar PEG stationary phase capillary column, such as FFAP/DB-WAX; front inlet gasification chamber temperature: 150° C. to 200° C.; temperature programming is adopted for the column temperature; detector temperature: 200° C. to 220° C.; carrier gas flow rate: 1 mL/min to 5 mL/min; and H.sub.2 flow rate: 10 mL/min to 30 mL/min, and air flow rate: 200 mL/min to 400 mL/min.

[0112] In the examples of the present application, a conversion rate of a transesterification reaction is calculated in the following way:

[0113] According to a mole number n of alcohol distilled during the reaction, a number of groups participating in the transesterification reaction is determined to be n, and a total mole number of the titanate in the reaction raw material is m, such that the conversion rate of the transesterification reaction is: n/4m.

[0114] According to an embodiment of the present application, a preparation method of an MOF MIL-125 includes: [0115] a) a titanate and a polyol are thoroughly mixed in a three-necked flask, the three-necked flask is connected to a distillation device, nitrogen is introduced for protection, and a resulting mixture is subjected to a transesterification reaction for 2 h to 10 h at 80° C. to 180° C. under stirring, where a conversion rate of the transesterification reaction is 60% to 80%; [0116] b) the device obtained after the reaction in step a) is connected to a water pump or oil pump, and a resulting reaction system is subjected to vacuum distillation for 0.5 h to 5 h at a vacuum degree of 0.01 KPa to 5 KPa and a temperature of 170° C. to 230° C. to make the transesterification reaction more complete to obtain the titanium-ester polymer, where a conversion rate of the transesterification reaction is greater than 90%; [0117] c) the titanium-ester polymer obtained in step b) is mixed with the terephthalic acid and the organic solvent, and a resulting mixture is stirred for 0 h to 100 h at a temperature not higher than 120° C. to obtain a gel mixture; [0118] d) the gel mixture obtained in step c) is placed in a high-pressure reactor, the high-pressure reactor is sealed, and the gel mixture is heated to 100° C. to 200° C. and then subjected to crystallization for 0 d to 30 d at an autogenous pressure; and [0119] e) after the crystallization is completed, a solid product is separated, rinsed with an organic solvent, and dried to obtain the microporous MOF MIL-125.

[0120] The titanate in step a) is one or more selected from the group consisting of tetraethyl titanate, TIPT, tetrabutyl titanate, tetrahexyl titanate, and tetraisooctyl titanate.

[0121] The polyol in step a) has a general formula of R−(OH).sub.x, where x≥2; and the polyol includes any one or a mixture of two or more selected from the group consisting of EG, DEG, TEG, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, PEG 200, PEG 400, PEG 600, PEG 800, 1,4-cyclohexanediol, 1,4-CHDM, 1,4-benzenedimethanol, glycerol, trimethylolpropane, pentaerythritol, xylitol, and sorbitol.

[0122] Preferably, a molar ratio of the titanate to the polyol in step a) is:

Ti(OR).sub.4/R—(OH).sub.x=(0.8-1.2)x/4

[0123] Preferably, the reaction in step a) is conducted for 2 h to 10 h at 80° C. to 180° C. under nitrogen protection.

[0124] Preferably, a conversion rate of the transesterification reaction in step a) is 65% to 80%.

[0125] Preferably, the step b) is conducted under vacuum distillation at a vacuum degree of 0.05 KPa to 3 KPa.

[0126] Preferably, the reaction in step b) is conducted at 170° C. to 230° C. for 0.5 h to 5 h.

[0127] Preferably, a conversion rate of the transesterification reaction in step b) is greater than 90%.

[0128] Preferably, a molar ratio of the terephthalic acid to the titanium-ester polymer in step c) is:

terephthalic acid: titanium-ester polymer=(0.8-2):1, [0129] where a mole number of the titanium-ester polymer is calculated based on a titanium content in the titanium-ester polymer; and [0130] the titanium content in the titanium-ester polymer is calculated based on a mole number of TiO.sub.2.

[0131] Preferably, the organic solvent in step c) is a mixture of DMF and methanol, and a volume ratio of the two meets the following condition:

DMF:methanol=(6-15):1.

[0132] Preferably, the crystallization in step d) is conducted at 120° C. to 180° C. for 1 d to 15 d.

[0133] Preferably, the crystallization in step d) is conducted in a dynamic or static state.

[0134] Preferably, the MOF MIL-125 obtained in step e) has a large number of microporous structures and less non-skeleton titanium.

EXAMPLE 1

[0135] A specific preparation process was as follows: 5 g of tetraethyl titanate and 10 g of PEG 200 were added to a three-necked flask and thoroughly mixed, the three-necked flask was connected to a distillation device, nitrogen was introduced for protection, and a resulting mixture was subjected to a transesterification reaction for 5 h at 175° C. under stirring, where a conversion rate of the transesterification reaction was 75%; a water pump was connected to the device, and a resulting reaction system was subjected to vacuum distillation for 1 h at a vacuum degree of 3 KPa and a temperature of 200° C. to make the transesterification reaction more complete to obtain a titanium-PEG ester polymer, where a conversion rate of the transesterification reaction was 92%; 6 g of the titanium-PEG ester polymer, 5 g of terephthalic acid, 18 mL of DMF, and 2 mL of methanol were mixed and stirred for 2 h at room temperature, and a resulting mixture was then transferred to a stainless steel high-pressure reactor; the high-pressure reactor was sealed and placed in an oven that had been heated to 120° C., and crystallization was conducted for 2 d at an autogenous pressure; and after the crystallization was completed, a solid product was separated through centrifugation, rinsed with acetone, and dried at 110° C. in air to obtain the microporous MOF MIL-125, which was denoted as A1.

EXAMPLE 2

[0136] A specific preparation process was as follows: 5 g of tetraethyl titanate and 3.13 g of EG were added to a three-necked flask and thoroughly mixed, the three-necked flask was connected to a distillation device, nitrogen was introduced for protection, and a resulting mixture was subjected to a transesterification reaction for 5 h at 100° C. under stirring, where a conversion rate of the transesterification reaction was 70%; a water pump was connected to the device, and a resulting reaction system was subjected to vacuum distillation for 1 h at a vacuum degree of 3 KPa and a temperature of 170° C. to make the transesterification reaction more complete to obtain a titanium-EG ester polymer, where a conversion rate of the transesterification reaction was 90%; 3 g of the titanium-EG ester polymer, 2 g of terephthalic acid, 9 mL of DMF, and 1.2 mL of methanol were mixed and stirred for 2 h at room temperature, and a resulting mixture was then transferred to a stainless steel high-pressure reactor; the high-pressure reactor was sealed and placed in an oven that had been heated to 150° C., and crystallization was conducted for 15 d at an autogenous pressure; and after the crystallization was completed, a solid product was separated through centrifugation, rinsed many times with DMF and methanol, and dried at 110° C. in air to obtain the MOF MIL-125, which was denoted as A2.

EXAMPLE 3

[0137] A specific preparation process was as follows: 5 g of tetrabutyl titanate and 11.35 g of 1,4-benzenedimethanol were added to a three-necked flask and thoroughly mixed, the three-necked flask was connected to a distillation device, nitrogen was introduced for protection, and a resulting mixture was subjected to a transesterification reaction for 5 h at 160° C. under stirring, where a conversion rate of the transesterification reaction was 80%; a water pump was connected to the device, and a resulting reaction system was subjected to vacuum distillation for 1 h at a vacuum degree of 3 KPa and a temperature of 230° C. to make the transesterification reaction more complete to obtain a titanium-1,4-benzenedimethanol ester polymer, where a conversion rate of the transesterification reaction was 95%; 5 g of the titanium-1,4-benzenedimethanol ester polymer, 3 g of terephthalic acid, 24 mL of DMF, and 3 mL of methanol were mixed and stirred for 2 h at room temperature, and a resulting mixture was then transferred to a stainless steel high-pressure reactor; the high-pressure reactor was sealed and placed in an oven that had been heated to 170° C., and crystallization was conducted for 1 d at an autogenous pressure; and after the crystallization was completed, a solid product was separated through centrifugation, rinsed many times with DMF and methanol, and dried at 110° C. in air to obtain the MOF MIL-125, which was denoted as A3.

EXAMPLE 4

[0138] An MOF MIL-125 was prepared by the same method as in Example 1, and specific preparation conditions were different from Example 1 as in Table 1 and Table 2. Samples A4, A5, A6, and A7 were prepared in this example.

TABLE-US-00001 TABLE 1 Condition parameters for the synthesis of a titanium-ester polymer Temperature Time Vacuum degree Titanate, polyol, and a Reaction Reaction for vacuum for vacuum for vacuum No. molar ratio thereof temperature time distillation distillation distillation 1# TIPT:glycerol = 2.4:0.6  80° C. 10 h  180° C. 3 h 0.01 KPa 2# Tetrahexyl  90° C. 8 h 210° C. 2.5 h 0.05 KPa titanate:pentaerythritol = 0.75:0.25 3# Tetraisooctyl titanate:1,2- 120° C. 4 h 170° C. 5 h 5 KPa propanediol = 0.8:0.2 4# Tetrahexyl titanate:1,4- 180° C. 2 h 230° C. 0.5 h 1.5 KPa cyclohexanediol = 0.7:0.3

TABLE-US-00002 TABLE 2 Conditions for synthesis of the MOF MIL-125 Titanium-ester polymer, terephthalic acid, Temperature and a molar ratio thereof; and organic and time for No. solvents, and a volume ratio thereof crystallization A4 Terephthalic acid:1# = 1:1; and 100° C., 30 d DMF:methanol = 10:1 A5 Terephthalic acid:2# = 1:0.9; and 120° C., 10 d DMF:methanol = 12:1 A6 Terephthalic acid:3# = 1:0.7; and 200° C., 5 d DMF:methanol = 13:1 A7 Terephthalic acid:4# = 1:0.5; and 180° C., 8 d DMF:methanol = 9:1

[0139] The crystallization in Examples 1 to 4 was static crystallization.

EXAMPLE 5

[0140] A specific preparation process was as follows: 5 g of tetraethyl titanate and 12.5 g of PEG 400 were added to a three-necked flask and thoroughly mixed, the three-necked flask was connected to a distillation device, nitrogen was introduced for protection, and a resulting mixture was subjected to a transesterification reaction for 5 h at 170° C. under stirring, where a conversion rate of the transesterification reaction was 70%; a water pump was connected to the device, and a resulting reaction system was subjected to vacuum distillation for 1 h at a vacuum degree of 3 KPa and a temperature of 200° C. to make the transesterification reaction more complete to obtain a titanium-PEG ester polymer, where a conversion rate of the transesterification reaction was 92%; 6 g of the titanium-PEG ester polymer, 3 g of terephthalic acid, 54 mL of DMF, and 6 mL of methanol were mixed and stirred for 2 h at room temperature, and a resulting mixture was then transferred to a stainless steel high-pressure reactor; the high-pressure reactor was sealed and placed in a rotary oven that had been heated to 150° C. through temperature programming, and crystallization was conducted for 3 d; and after the crystallization was completed, a solid product was separated through centrifugation, rinsed many times with acetone, and dried at 110° C. in air to obtain the microporous MOF MIL-125, which was denoted as A8.

EXAMPLE 6

[0141] A specific preparation process was as follows: 5 g of tetraethyl titanate and 8.6 g of 1,4-CHDM were added to a three-necked flask and thoroughly mixed, the three-necked flask was connected to a distillation device, nitrogen was introduced for protection, and a resulting mixture was subjected to a transesterification reaction for 3 h at 200° C. under stirring, where a conversion rate of the transesterification reaction was 75%; an oil pump was connected to the device, and a resulting reaction system was subjected to vacuum distillation for 1 h at 200° C. to make the transesterification reaction more complete to obtain a titanium-CHDM ester polymer, where a conversion rate of the transesterification reaction was 90%; 6.5 g of the titanium-CHDM ester polymer, 2.5 g of terephthalic acid, 45 mL of DMF, and 5 mL of methanol were mixed and stirred for 2 h at room temperature, and a resulting mixture was then transferred to a stainless steel high-pressure reactor; the high-pressure reactor was sealed and placed in a rotary oven that had been heated to 180° C. through temperature programming, and crystallization was conducted for 24 h; and after the crystallization was completed, a solid product was separated through centrifugation, rinsed many times with methanol and DMF, and dried overnight in a vacuum oven to obtain the microporous MOF MIL-125, which was denoted as A9.

EXAMPLE 7

[0142] A specific preparation process was as follows: 5 g of tetraethyl titanate and 4 g of 1,3-propanediol were added to a three-necked flask and thoroughly mixed, the three-necked flask was connected to a distillation device, nitrogen was introduced for protection, and a resulting mixture was subjected to a transesterification reaction for 5 h at 165° C. under stirring, where a conversion rate of the transesterification reaction was 75%; a water pump was connected to the device, and a resulting reaction system was subjected to vacuum distillation for 1 h at a vacuum degree of 2 KPa and a temperature of 200° C. to make the transesterification reaction more complete to obtain a titanium-propanediol ester polymer, where a conversion rate of the transesterification reaction was 92%; 3 g of the titanium-propanediol ester polymer, 2 g of terephthalic acid, 36 mL of DMF, and 4 mL of methanol were mixed and stirred for 2 h at room temperature, and a resulting mixture was then transferred to a stainless steel high-pressure reactor; the high-pressure reactor was sealed and placed in a rotary oven that had been heated to 160° C. through temperature programming, and crystallization was conducted for 900 min; and after the crystallization was completed, a solid product was separated through centrifugation, rinsed many times with acetone, and dried at 110° C. in air to obtain the microporous MOF MIL-125, which was denoted as A10.

[0143] The crystallization involved in Examples 5 to 7 was dynamic crystallization conducted in a rotary oven with a rotational speed of 40 rpm.

EXAMPLE 8 PHASE STRUCTURE ANALYSIS

[0144] The samples A1 to A10 in Examples 1 to 7 each were subjected to XRD analysis, with Example 1 as a typical representative. FIG. 1 is an XRD pattern of the sample A1 synthesized in Example 1, and it can be seen from the figure that the sample A1 is a microporous MOF MIL-125.

[0145] Test results of the other samples are only slightly different from the pattern of the sample A1 in Example 1 in the intensity of the diffraction peak, and all of these samples are microporous MOF MIL-125.

EXAMPLE 9 MORPHOLOGY ANALYSIS

[0146] The samples A1 to A10 in Examples 1 to 7 each were subjected to SEM analysis, with Example 1 as a typical representative. FIG. 2 is an SEM image of the sample A1 synthesized in Example 1, and it can be seen from the figure that the sample A1 has intact MOF MIL-125 grains with a grain size of about 1 μm to 1.5 μm.

[0147] The other samples have the same morphology as the sample A1 in Example 1 and have a grain size slightly different from the grain size of the sample A1, and all of these samples are microporous MOF MIL-125.

EXAMPLE 10 LOW-TEMPERATURE NITROGEN PHYSICAL ADSORPTION ANALYSIS

[0148] The samples A1 to A10 in Examples 1 to 7 each were subjected to low-temperature nitrogen physical adsorption analysis, with Example 1 as a typical representative. FIG. 3 shows a physical adsorption isotherm of the sample A1 prepared in Example 1, and it can be seen from the figure that the nitrogen adsorption-desorption curve of the sample A1 is a typical type I adsorption isotherm, and the rapid increase in adsorption capacity at a low relative pressure reflects the significant micropore characteristics, indicating that the sample has a microporous structure.

[0149] Test results of the other samples are similar to the test results of the sample 1 in Example 1, and an adsorption curve of the sample has obvious micropore characteristics, indicating a typical microporous structure.

EXAMPLE 11 PORE DISTRIBUTION ANALYSIS

[0150] The samples A1 to A10 in Examples 1 to 4 each were subjected to physical adsorption and pore distribution analysis, with Example 1 as a typical representative. Table 3 shows the physical adsorption and pore distribution results of the sample A1 prepared in Example 1, and it can be seen from the table that the sample has an SSA of 1,350 m.sup.2/g and a micropore size of about 0.4 nm.

TABLE-US-00003 TABLE 3 SSA and pore distribution of the sample in Example 1 t-Plot external Sample BET SSA/m.sup.2g−.sup.1 SSA/m.sup.2g−.sup.1 Pore distribution/nm Example 1 1350 167 0.4

[0151] Test results of the other samples are similar to the test results of the sample A1 in Example 1, and these samples each have a micropore SSA of 1,000 m.sup.2/g to 1,500 m.sup.2/g and an external SSA of 160 m.sup.2/g to 220 m.sup.2/g.

EXAMPLE 12 PARTICLE SIZE ANALYSIS

[0152] The samples A1 to A10 in Examples 1 to 4 each were subjected to particle size analysis, with Example 1 as a typical representative. FIG. 4 shows a particle size distribution of the sample A1 prepared in Example 1, and it can be seen from the figure that the particle size distribution of the sample is mainly concentrated in a range of 1.6 μm to 1.8 μm.

EXAMPLE 13 ADSORBENT PERFORMANCE EVALUATION

[0153] A two-component xylene static adsorption experiment and a dynamic breakthrough experiment were conducted on the sample A1 of Example 1.

a) Two-Component Xylene Static Adsorption Experiment

[0154] The adsorbent MIL-125 (namely, sample A1) was pretreated with a 200° C. nitrogen gas flow, 0.2 g of the pretreated adsorbent MIL-125 was taken and added to 2 mL of a solution of 2 wt % p-xylene and m-xylene in mesitylene, and an adsorption experiment was conducted in a shaker; a blank control group was set; and 1 h after adsorption, a resulting supernatant was collected and analyzed by GC to determine a concentration of each component in a blank sample and a concentration of each component in an adsorbed sample. The following adsorption data are acquired according to calculation and listed in Table 4, and it can be seen from Table 4 that an adsorption capacity for p-xylene is much greater than an adsorption capacity for m-xylene, indicating that the sample can selectively adsorb p-xylene. According to the adsorption capacity data, the p-xylene/m-xylene selectivity can be further calculated to be 5.84.

TABLE-US-00004 TABLE 4 Xylene isomer adsorption capacity data for the sample A1 in Example 1 Sample Q.sub.PX (mg/g) Q.sub.MX (mg/g) α.sub.PX/MX A1 45 7.71 5.84

b) Dynamic Breakthrough Experiment

[0155] 0.6 g of the adsorbent MIL-125 (namely, sample A1) was taken, activated in a 200° C. N.sub.2(100 mL/min) atmosphere for 3 h, and then filled into a stainless steel column; before the start of the breakthrough experiment, pure mesitylene was pumped by a pump at a specified flow rate of 1 mL/min to rinse the pipeline and column; when the pipeline was fully filled with pure mesitylene, the feed solution was changed from mesitylene to a 0.1 wt % two-component xylene mixed solution in a molar ratio of 1:1, and the feed solution was fed at a flow rate of 0.2 mL/min; and starting from the outflow of the first drop of liquid, 11 samples were taken at an interval of 1 min, and then a sample was taken every five minutes until the adsorbent in the column was completely penetrated by the two components xylene. After the experiment was completed, the column was further rinsed with pure mesitylene at a flow rate of 2 mL/min for 2 h. A concentration of the sample was detected by GC, and a curve illustrating a change of the sample concentration over time was plotted and shown in FIG. 5. It can be seen from FIG. 5 that, during the breakthrough experiment, m-xylene is first adsorbed, and after the adsorption saturation is achieved, m-xylene is detected in an effluent, indicating that the adsorption of the sample for m-xylene is weak; and about 5 min later, p-xylene penetrates out, indicating that the sample has a high adsorption capacity and a strong adsorption effect for the p-xylene isomer, which is consistent with the conclusion of the results of the static adsorption experiment.

EXAMPLE 14 ADSORBENT PERFORMANCE EVALUATION

[0156] A two-component xylene static adsorption experiment and a dynamic breakthrough experiment were conducted on the sample A2 of Example 2.

a) Two-Component Xylene Static Adsorption Experiment

[0157] The adsorbent MIL-125 (namely, sample A2) was pretreated through vacuum-pumping with 200° C. nitrogen, 0.1 g of the pretreated adsorbent MIL-125 was taken and added to 1 mL of a solution of 5 wt % p-xylene and m-xylene in n-heptane, and an adsorption experiment was conducted in a shaker; a blank control group was set; and 12 h after adsorption, a resulting supernatant was collected and analyzed by GC to determine a concentration of each component in a blank sample and a concentration of each component in an adsorbed sample. The following adsorption data were acquired according to calculation and listed in Table 5.

TABLE-US-00005 TABLE 5 Xylene isomer adsorption capacity data for the sample A2 in Example 2 Sample Q.sub.PX (mg/g) Q.sub.MX (mg/g) α.sub.PX/MX A2 80 9.80 8.16

b) Dynamic Breakthrough Experiment

[0158] 1 g of the adsorbent MIL-125 was taken, activated in a 200° C. N.sub.2(80 mL/min) atmosphere for 5 h, and then filled into a stainless steel column; before the start of the breakthrough experiment, pure mesitylene was pumped by a pump at a specified flow rate of 2 mL/min to rinse the pipeline and column; when the pipeline was fully filled with pure mesitylene, the feed solution was changed from mesitylene to a 0.3 wt % p-xylene and m-xylene two-component mixed solution in a molar ratio of 1:1, and the feed solution was fed at a flow rate of 0.5 mL/min; and starting from the outflow of the first drop of liquid, 10 samples were taken at an interval of 1 min, and then a sample was taken every five minutes until the adsorbent in the column was completely penetrated by the two components xylene. After the experiment was completed, the column was further rinsed with pure mesitylene at a flow rate of 5 mL/min for 2 h. A concentration of the sample was detected by GC, and a curve illustrating a change of the sample concentration over time was plotted and shown in FIG. 6.

EXAMPLE 15 ADSORBENT PERFORMANCE EVALUATION

[0159] A two-component xylene static adsorption experiment and a dynamic breakthrough experiment were conducted on the sample A8 of Example 5.

a) Two-Component Xylene Static Adsorption Experiment

[0160] The adsorbent MIL-125 (namely, sample A8) was pretreated through vacuum-pumping with 200° C. nitrogen, 0.5 g of the pretreated adsorbent MIL-125 was taken and added to 5 mL of a solution of 5 wt % p-xylene and m-xylene in TIPB, and an adsorption experiment was conducted in a shaker; a blank control group was set; and 24 h after adsorption, a resulting supernatant was collected and analyzed by GC to determine a concentration of each component in a blank sample and a concentration of each component in an adsorbed sample. The following adsorption data were acquired according to calculation and listed in Table 6.

TABLE-US-00006 TABLE 6 Xylene isomer adsorption capacity data for the sample A8 in Example 5 Sample Q.sub.PX (mg/g) Q.sub.MX (mg/g) α.sub.PX/MX A8 107.70 7.70 13.60

b) Dynamic Breakthrough Experiment

[0161] 4 g of the adsorbent MIL-125 was taken, activated in a 200° C. N2 (100 mL/min) atmosphere for 3 h, and then filled into a stainless steel column; before the start of the breakthrough experiment, pure mesitylene was pumped by a pump at a specified flow rate of 5 mL/min to rinse the pipeline and column; when the pipeline was fully filled with pure mesitylene, the feed solution was changed from mesitylene to a 0.5 wt % p-xylene and m-xylene two-component mixed solution in a molar ratio of 1:1, and the feed solution was fed at a flow rate of 1 mL/min; and starting from the outflow of the first drop of liquid, 10 samples were taken at an interval of 1 min, and then a sample was taken every five minutes until the adsorbent in the column was completely penetrated by the two components xylene. After the experiment was completed, the column was further rinsed with pure mesitylene at a flow rate of 5 mL/min for 2 h. A concentration of the sample was detected by GC, and a curve illustrating a change of the sample concentration over time was plotted and shown in FIG. 7.

EXAMPLE 16 SINGLE/MULTI-COMPONENT STATIC ADSORPTION EXPERIMENT

[0162] The same static adsorption experimental method as in Example 13 was used to evaluate the adsorption performance of the MOF MIL-125, and specific static adsorption experimental conditions were different from that in Examples 13, 14, and 15 as in Tables 7 and 8.

TABLE-US-00007 TABLE 7 Condition parameters for a single-component xylene static adsorption experiment Xylene Xylene Mass ratio composition in content in Adsorption of adsorbate No. an adsorbate Solvent an adsorbate time to adsorbent 1# p-Xylene Mesitylene 2 wt % 3 h 3:2 2# p-Xylene p-Diethylbenzene 5 wt % 2.5 h 3:1 3# p-Xylene TIPB 3 wt % 5 h 5:1 4# p-Xylene Cyclooctane 5 wt % 0.5 h 4:1 5# p-Xylene n-Heptane 6 wt % 2 h 2:1

TABLE-US-00008 TABLE 8 Condition parameters for a multi-component xylene competitive adsorption experiment Xylene Xylene Mass ratio composition in content in Adsorption of adsorbate No. an adsorbate Solvent an adsorbate time to adsorbent 6# p-Xylene:m-xylene = 1:1 Mesitylene 2 wt % 3 h 3:2 7# p-Xylene:m-xylene = 1:1 p-Diethylbenzene 5 wt % 2.5 h 3:1 8# p-Xylene:m-xylene = 1:1 TIPB 3 wt % 5 h 5:1 9# p-Xylene:m-xylene = 1:1 Cyclooctane 5 wt % 0.5 h 4:1 10#  p-Xylene:m-xylene = 1:1 n-Heptane 6 wt % 2 h 2:1 11#  p-Xylene:m-xylene:o- Isooctane 4 wt % 1.5 h 3:2 xylene = 1:1:1

[0163] The test results of the above sample are slightly different from the test results of the sample A1 in Example 1 only in adsorption selectivity, and these samples can selectively adsorb p-xylene with adsorption performance far better than the adsorption performance of MIL-125 prepared by the traditional method.

EXAMPLE 17 TWO-COMPONENT XYLENE DYNAMIC BREAKTHROUGH EXPERIMENT

[0164] The same dynamic experimental method as in Example 13 was used to evaluate the adsorption performance of the MOF MIL-125, and a specific breakthrough experimental process was different from that in Examples 13, 14, and 15 as in Table 9.

TABLE-US-00009 TABLE 9 Condition parameters for the two-component xylene dynamic breakthrough experiment Xylene composition Xylene content in a breakthrough in a breakthrough No. feed solution feed solution Solvent 12# p-Xylene:m-xylene = 1:1 1 wt %, 1 wt % Mesitylene 13# p-Xylene:m-xylene = 2:1 1 wt %, 0.5 wt % p-Diethylbenzene 14# p-Xylene:m-xylene = 5:1 1 wt %, 0.2 wt % TIPB 15# p-Xylene:m-xylene = 10:1 1 wt %, 0.1 wt % n-Heptane

[0165] The breakthrough results of the above sample are slightly different from the test results of the sample A1 in Example 1 only in adsorption selectivity, which is reflected by a slight difference in breakthrough time; and these samples can selectively adsorb p-xylene with adsorption performance far better than the adsorption performance of MIL-125 prepared by the traditional method.

[0166] EXAMPLE 18 COMPARISON OF ADSORPTIVE SEPARATION PERFORMANCE OF THE ADSORBENT OF THE PRESENT APPLICATION WITH A XYLENE ADSORBENT IN THE PRIOR ART

[0167] According to the existing literature, a molecular sieve adsorbent widely studied and MIL-125 series materials synthesized according to the existing techniques were selected for comparison, and the comparison results of separation performance were shown in FIG. 8. The breakthrough experiments of the MIL-125 series materials synthesized according to the existing techniques show that MIL-125-NH.sup.2 (a) has selectivity of 3 for p-xylene/m-xylene and selectivity of 2.2 for p-xylene/o-xylene at 298 K; and MIL-125 (b) has selectivity of 1.5 for p-xylene/m-xylene and selectivity of 1.6 for p-xylene/o-xylene at 313 K. It can be seen from the figure that the selectivity of the MIL-125 material synthesized by the method of the present application is higher than the selectivity of each of MIL-125 and MIL-125-NH.sub.2 synthesized by the conventional methods under the experimental conditions of the present application. It can be seen that, compared with the molecular sieve adsorbent widely studied, the MIL-125 material synthesized by the method of the present application exhibits higher selectivity for p-xylene/m-xylene. The HZSM-5 molecular sieve has a high adsorption capacity, but cannot be reused, and p-xylene will be strongly adsorbed on the molecular sieve. Therefore, HZSM-5 cannot be used for separation of p-xylene. [0168] a) M. A. Moreira, J. C. Santos, A. F. P. Ferreira, J. M. Loureiro, F. Ragon, P. Horcajada, P. G. Yot, C. Serre and A. E. Rodrigues, Langmuir 2012, 28, 3494-3502; and [0169] b) F. Vermoortele, M. Maes, P. Z. Moghadam, M. J. Lennox, F. Ragon, M. Boulhout, S. Biswas, K. G. M. Laurier, I. Beurroies, R. Denoyel, M. Roeffaers, N. Stock, T. Dueren, C. Serre and D. E. De Vos, Journal of the American Chemical Society 2011, 133, 18526-18529.

[0170] The above examples are merely few examples of the present application, and do not limit the present application in any form. Although the present application is disclosed as above with preferred examples, the present application is not limited thereto. Some changes or modifications made by any technical personnel familiar with the profession using the technical content disclosed above without departing from the scope of the technical solutions of the present application are equivalent to equivalent implementation cases and fall within the scope of the technical solutions.