CN112778536B

CN112778536B - Dawson type polyacid-based metal-BBPTZ organic framework material and preparation method and application thereof

Info

Publication number: CN112778536B
Application number: CN202110063528.3A
Authority: CN
Inventors: 郝秀丽; 贾士芳; 温艳珍
Original assignee: Taiyuan University of Science and Technology
Current assignee: Taiyuan University of Science and Technology
Priority date: 2021-01-18
Filing date: 2021-01-18
Publication date: 2022-09-27
Anticipated expiration: 2041-01-18
Also published as: CN112778536A

Abstract

The invention belongs to the technical field of metal-organic framework materials, and provides a Dawson type polyacid-BBPTZ organic framework material and a preparation method and application thereof, aiming at solving the problem that the catalytic activity is reduced because active sites of polyacid are easily covered when the polyacid-based metal-organic framework material is used. The molecular formula is as follows: [ H ] ₂ BBPTZ] ₂ Co(BBPTZ) ₂ [P ₂ W ₁₈ O ₆₂ ]·3H ₂ O; a monoclinic crystal system,C2/cspace group, the basic unit includes one [ P ₂ W ₁₈ O ₆₂ ] ^6‑ Polyanion, one co (ii) cation, two protonated BBPTZ ligands and three crystalline water molecules; simple process, easy obtaining of high-quality single crystal, simple and feasible structural analysis, easy repetition of materials and higher yield. The crystal structure is stable, the catalyst is a heterogeneous catalyst, the concerted catalysis is realized, and the 1+1 is obtained>2'; the service life and efficiency of the catalyst are improved.

Description

Dawson type polyacid-based metal-BBPTZ organic framework material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of metal organic framework materials, and particularly relates to a Dawson type polyacid-based metal-BBPTZ organic framework material, and a preparation method and application thereof.

Background

As a unique oxygen cluster of early transition metals (comprising Mo, W, V, Nb, Ta and the like), polyacid is widely researched in the field of catalysis due to adjustable composition structure, charge, acidity, stability, oxidation-reduction property and oxidation resistance. However, the polyacid is not suitable to be recovered in the reaction system as a homogeneous catalyst, and some polyacid is easy to hydrolyze in solutions with different pH values, which becomes a problem which must be overcome in the polyacid homogeneous system.

When used as heterogeneous catalysts, polyacids exhibit a low specific surface area: (<10 m ² ·g ^-1 ) And has only relatively low loading when compounded with various types of supporting materials. These problems have prevented the polyacid from exerting greater value in the field of catalysis. Therefore, the development of a novel polyacid-based catalytic material with good stability, easy recovery and high catalytic activity is an important research in today's society.

The design and synthesis of polyacid-based metal-organic framework materials is currently considered to be an effective strategy to achieve heterogeneous catalysis of polyacids. By using the material, the specific surface area of the polyacid catalyst can be increased, and the polyacid is monodisperse at the molecular level, so that the catalytic reaction of the heterogeneous catalyst is realized. Only a few of the polyacid-based metal-organic framework materials reported to date have been successfully used as heterogeneous catalysts, and the reaction models catalyzed by these materials are limited. This is because the design of a high efficiency catalyst is usually designed directionally for a particular reaction. Therefore, designing and synthesizing a polyacid-based metal-organic framework material with high catalytic activity to meet specific catalytic reactions is still an important research in the field.

Meanwhile, the metal organic coordination polymer material can also be used as a carrier of polyacid. The polyacid is introduced into the metal-organic coordination network, so that the polyacid can be supported and dispersed on a molecular level, and the redox characteristic of the polyacid can be maintained. A series of polyacid-based metal organic coordination polymer materials are used as heterogeneous catalytic systems for research. Of these compounds, the catalytic properties as heterogeneous catalysts are mostly far from being developed. The main problem is how to release or expose the polyacid active sites in the material to the maximum extent, and contact the polyacid active sites with a reaction substrate to perform a catalytic reaction.

Disclosure of Invention

The invention provides a Dawson type polyacid-based metal-BBPTZ organic framework material, a preparation method and application thereof, aiming at solving the problems that active sites of polyacid are easily covered when the polyacid-based metal organic framework material is contacted with a substrate, so that the active sites are reduced and the catalytic activity is reduced.

The invention is realized by the following technical scheme: a Dawson type polyacid-based-BBPTZ organic framework material has a molecular formula as follows: [ H ] ₂ BBPTZ] ₂ Co(BBPTZ) ₂ [P ₂ W ₁₈ O ₆₂ ]·3H ₂ O; namely: i.e. C ₇₂ H ₇₄ N ₂₄ O ₆₅ P ₂ W ₁₈ Co, a monoclinic system,C2/cspace group, the basic unit includes one [ P ₂ W ₁₈ O ₆₂ ] ^6- A polyanion, one co (ii) cation, two BBPTZ ligands, two protonated BBPTZ ligands, and three crystalline water molecules; the unit cell parameters are as follows:a＝26.675(2)Å，b＝16.1311(12)Å，c＝30.321(2)Å，α＝90°，β＝104.396(8)°，γ＝90°，V＝12637.4(16)Å ³ ，Z＝4，μ＝16.557mm ^-1 ，F(000)= 10332。

the preparation method of the Dawson type polyacid-base metal-BBPTZ organic framework material comprises the following specific steps:

(1) synthesis of 4, 4' -bis (1,2, 4-triazole-1-methylene) biphenyl, BBPTZ: dissolving 20mmol of 1,2, 4-triazole in 50ml of acetone, sequentially adding 4g of PEG-400, 5g of anhydrous potassium carbonate and 0.5g of potassium iodide, stirring for 30min at normal temperature, uniformly stirring, adding 10mmol of biphenyl dichlorobenzyl, uniformly stirring, refluxing for 12h, cooling, filtering, distilling the filtrate to obtain white residue, and recrystallizing with water for 2-3 times to obtain a pure organic ligand BBPTZ;

(2) synthesis of K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ O: 0.31mol of Na ₂ WO ₄ ·2H ₂ Dissolving O in 200ml water, adding 84ml phosphoric acid 1.24mol with mass concentration of 85%, heating the solution to 100 deg.C, refluxing, maintaining for 8 hr, adding into the solutionAdding H ₂ O ₂ Removing the pale green color of the solution; cooling, adding 40g ammonium chloride, stirring for 10-15min to obtain precipitate, vacuum filtering to obtain light yellow powder, dissolving the light yellow powder in 240ml water, adding 40g ammonium chloride, stirring for 10-15min to obtain precipitate, vacuum filtering, and drying; dissolving the dried precipitate in 100ml water, adding 0.27mol KCl to obtain precipitate, filtering, and drying to obtain light yellow K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ O；

(3) Synthesis of Dawson-type polyacid-based metal-BBPTZ organic framework material: 0.25 mmol of Co (NO) ₃ ) ₂ ·3H ₂ O, 0.15 mmol of K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ Mixing O and 0.16 mmol BBPTZ, adding 12mL distilled water into the mixture, stirring for 15min, adjusting pH to 2.5 with 1M NaOH, continuing stirring at room temperature for 0.5h, transferring the uniformly stirred suspension into a 25mL reaction kettle with a polytetrafluoroethylene lining, keeping the temperature at 130 ℃ for 3 days, and keeping the temperature at 5 ℃ h ^-1 And cooling to room temperature at a speed rate to obtain pink blocky crystals, namely the Dawson type polyacid-BBPTZ organic framework material.

The Dawson type polyacid-based metal-BBPTZ organic framework material is used as a heterogeneous desulfurization catalyst in oxidative desulfurization of fuel.

Through detection, the prepared Dawson type polyacid-based metal-BBPTZ organic framework material shows good catalytic activity in a catalytic reaction of DBT oxidation desulfurization. After 8h of reaction, the DBT conversion rate can reach 94.59%, the DBT conversion rate is further measured along with the increase of time, the DBT conversion rate is found to be very slow after 8h, the DBT conversion rate is only 95.05% after 12h, the DBT conversion rate is basically consistent with that of 8h, and therefore the catalytic activity of the compound as a catalyst is completely embodied at 8 h. The conversion rate of the polyacid and the metal to DBT is improved in the same time, but the catalytic activity of the polyacid raw material is obviously higher than that of the metal raw material, so that the polyacid unit is an active species for catalyzing the compound. The combination of metal and polyacid produces synergistic effect to increase its catalytic activity, but the simple mixing of two raw materials still makes the polyacid not well monodispersed on molecular level, so that the active site of polyacid can not be well exposed, so that its catalytic activity is still high without that of the prepared compound.

The compound as a catalyst is insoluble in a solvent, and the catalyst can be well separated by simple centrifugal separation, and then recovered and recycled. Experiments prove that the catalytic activity of the catalyst is slightly reduced after the catalyst is recycled for 6 times (as shown in figure 14), which is probably caused by slight loss of the catalyst when the catalyst is centrifugally separated, but the catalytic effect can still reach 93.56%, and the catalyst still has high catalytic activity. The infrared spectrum data, XRD and other data confirm that the compound as a catalyst is unchanged before and after reaction, and the collapse of the structure before and after the reaction is proved to be avoided.

The Dawson type polyacid intervenes in the metal-BBPTZ organic framework, can well improve the specific surface area of the Dawson type polyacid, and enables the Dawson type polyacid to be highly uniformly dispersed on a molecular level; the combination of Dawson type polyacid and metal-BBPTZ organic framework realizes the synergistic catalysis, and the composite functional catalyst of '1 +1> 2' is obtained; the stable frame can effectively prevent the loss of the Dawson type polyacid molecular catalyst and improve the service life and efficiency of the catalyst.

Compared with the prior art, the synthesis method has the advantages of simple process, easy acquisition of high-quality single crystals, simple and feasible structural analysis, easy repetition of materials, high yield and the like. The Dawson type polyacid-BBPTZ organic framework material prepared by the method has a stable crystal structure, and enables the Dawson type polyacid homogeneous catalyst to be a heterogeneous catalyst through the loading of a metal organic framework, so that the specific surface area of the Dawson type polyacid is increased, and the Dawson type polyacid can be highly uniformly dispersed on a molecular level; the combination of Dawson type polyacid and metal-BBPTZ organic framework realizes the synergistic catalysis, and the composite functional catalyst of '1 +1> 2' is obtained; the stable frame can effectively prevent the loss of the Dawson type polyacid molecular catalyst and improve the service life and efficiency of the catalyst.

The compound synthesized by the invention provides a high-efficiency catalyst for a fuel oxidation desulfurization method, and further improves the environmental problems of air pollution and the like. The invention shows that the metal-organic framework is used as an ideal carrying agent of polyacid, and can more perfectly express the excellent catalytic performance of the polyacid. In addition, the bridging ligand and the metal ions for constructing the metal organic framework have wide design selection space, various synthetic strategies and directional designs can be developed, novel and various structures can be obtained, various carrying agents are provided for polyacid, and therefore the high-efficiency catalyst for the fuel oxidation desulfurization reaction can be found.

Drawings

FIG. 1 shows the prepared compound [ H ] ₂ BBPTZ] ₂ Co(BBPTZ) ₂ [P ₂ W ₁₈ O ₆₂ ]·3H ₂ The basic structural unit of the O pink blocky crystal, all hydrogen atoms and cations Bmim are ignored in the figure;

FIG. 2 shows Cu and L in the prepared compound ² The ligands are connected to form a 1-D chain structure with buckled rings;

FIG. 3 shows a 2-D layered structure formed by the 1-D chain and the polyacid in the prepared compound;

FIG. 4 shows the 2-D layer and free ligand L in the prepared compound ² Forming a 2-D layer structure of the winding knot;

FIG. 5 is a 3-D supramolecular network structure of entanglements in the prepared compound;

FIG. 6 is an infrared spectrum of the prepared compound;

FIG. 7 is a thermogravimetric plot of the compounds prepared;

FIG. 8 is an analytical plot of XRD data for the prepared compounds, in which: the curve at the bottom represents the fitted curve and the curve at the top represents the measured curve;

FIG. 9 is a schematic diagram of the reaction of DBT converted to sulfoxide and sulfone by oxidation;

FIG. 10 is a graph of DBT conversion versus reaction time for different catalysts;

FIG. 11 shows DBT and the oxidation products DBTO, DBTO ₂ The top curve represents DBT and the bottom represents the oxidized product;

FIG. 12 shows the results of gas chromatographic detection of DBT oxidation products;

FIG. 13 is a mass spectrum of DBT oxidation product and un-oxidized DBT;

FIG. 14 is a graph showing the number of cycles of the prepared compound as an oxidation catalyst;

FIG. 15 is an infrared spectrum of a compound prepared before and after catalysis, with the top curve representing before catalysis and the bottom representing after catalysis;

FIG. 16 is an analysis of XRD data for the prepared compound with the bottom curve representing fitted, the middle curve representing pre-catalytic measurement and the top curve representing post-catalytic measurement;

FIG. 17 shows DBT conversion in model oils with the prepared compound as catalyst;

FIG. 18 shows the number of cycles of the prepared compound as a model oil oxidation catalyst.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1: a Dawson type polyacid-BBPTZ organic framework material has a molecular formula as follows: [ H ] ₂ BBPTZ] ₂ Co(BBPTZ) ₂ [P ₂ W ₁₈ O ₆₂ ]·3H ₂ O; namely: i.e. C ₇₂ H ₇₄ N ₂₄ O ₆₅ P ₂ W ₁₈ Co, a monoclinic system,C2/cspace group, the basic unit includes one [ P ₂ W ₁₈ O ₆₂ ] ^6- A polyanion, one co (ii) cation, two BBPTZ ligands, two protonated BBPTZ ligands, and three crystalline water molecules; the unit cell parameters are as follows:a＝26.675(2)Å，b＝16.1311(12)Å，c＝30.321(2)Å，α＝90°，β＝104.396(8)°，γ＝90°，V＝12637.4(16)Å ³ ，Z＝4，μ＝16.557mm ^-1 ，F(000)= 10332。

(1) synthesis of 4, 4' -bis (1,2, 4-triazole-1-methylene) biphenyl, BBPTZ: weighing 1.38g (20 mmol) of 1,2, 4-triazole, dissolving the 1,2, 4-triazole in 50ml of acetone, then sequentially adding 4g of PEG-400, 5g of anhydrous potassium carbonate and 0.5g of potassium iodide, stirring for 30min at normal temperature, after stirring uniformly, adding 2.51g (10 mmol) of biphenyl dichlorobenzyl into the mixture, stirring uniformly, refluxing for 12h, filtering after cooling, distilling the filtrate to obtain white residue, and recrystallizing with water for 2-3 times to obtain the pure organic ligand BBPTZ.

(2) Synthesis of K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ The method of O comprises the following steps: adding 100g of Na ₂ WO ₄ ·2H ₂ O (0.31 mol) was dissolved in 200ml of water, 84ml of 85% phosphoric acid (1.24 mol) was added, the solution was heated to 100 ℃ under reflux for 8 hours, and H was added to the solution ₂ O ₂ The greenish color of the solution can be removed. And after the solution is cooled, adding 40g of ammonium chloride, stirring the solution for 10-15min to obtain a large amount of precipitate, performing suction filtration to obtain light yellow powder, dissolving the light yellow powder in 240ml of water, adding 40g of ammonium chloride, stirring the solution for 10-15min to obtain precipitate, performing suction filtration, and drying. Dissolving the precipitate in 100ml water, adding 20g KCl (0.27 mol) to obtain large amount of precipitate, filtering, and drying to obtain light yellow K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ O。

(3) Synthesis of Dawson type polyacid-BBPTZ organic framework materials: mixing Co (NO) ₃ ) ₂ ·3H ₂ O (0.075 g, 0.25 mmol), K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ A mixture of O (0.69g, 0.15 mmol) and BBPTZ (0.05 g, 0.16 mmol) was added to a beaker containing 12mL of distilled water, then stirred for 15min under a stirrer, then adjusted to pH 2.5 with NaOH (1M), continued stirring at room temperature for 0.5h, and finally the well-stirred suspension was transferred to a 25mL Teflon lined reactorAnd the reaction kettle is put into an oven, kept at a high temperature of 130 ℃ for 3 days and then kept at 5 ℃ per hour ^-1 And (5) cooling at a speed rate to slowly cool the temperature of the reaction kettle to room temperature to obtain pink blocky crystals.

Prepared [ H ] ₂ BBPTZ] ₂ Co(BBPTZ) ₂ [P ₂ W ₁₈ O ₆₂ ]·3H ₂ The O yellow bulk crystals were rinsed with distilled water and dried to obtain a pure Dawson-type polyacid-based metal organic framework material with a yield of 65% calculated as W.

In the above synthesis, Co (NO) as a raw material is used ₃ ) ₂ ·3H ₂ O is an analytically pure starting material purchased directly on the market without further purification.

Example 2: analysis of the crystal structure of the prepared Dawson type polyacid-based metal-BBPTZ organic framework material compound: the structure of the prepared yellow bulk crystal compound was acquired by single crystal X-ray diffraction data of the prepared compound using Bruker D8 Aventura photon 100CMOS diffractometer at 298K temperature with Mo ka radiation (λ =0.71073 ĩ), then solved using ShelXT structure solver (using intrinsic phase method), and solved using least squares F ² Fine trimming by the method. All non-hydrogen atoms in the compound are anisotropic, hydrogen atoms on organic carbon atoms are fixed in calculated positions, and hydrogen atoms on water molecules, protonated BBPTZ and polyoxoanions cannot be assigned by weak reflection peaks but are directly included in the final formula.

Finally, the molecular formula of the crystal material is determined to be [ H ₂ BBPTZ] ₂ Co(BBPTZ) ₂ [P ₂ W ₁₈ O ₆₂ ]·3H ₂ And O. C, H and N elements were also determined by a Perkin-Elmer 2400 CHN analyzer and the metal elements were determined by an ICP plasma chromatograph analyzer, further demonstrating the accuracy of molecular formula determination for this compound. The results are as follows: c ₇₂ H ₇₄ N ₂₄ O ₆₅ P ₂ W ₁₈ Theoretical value (%) of Co element analysis: c15.03, H1.29, N5.85, P1.07, Co 1.11, W57.40; experimental values (%): c15.25, H1.38, N5.56, P1.18, Co 1.18,w57.30. Crystal data and structural refinements of the prepared compounds are shown in table 1.

Table 1 crystal data and structure refinement of the prepared compounds

Note: ^a R ₁ = Σ||F _o | – |F _c ||/Σ|F _o |; ^b wR ₂ = Σ[w(F _o ² – F _c ² ) ² ]/Σ[w(F _o ² ) ² ] ^1/2 。

The structures of the compounds prepared are described below: the test is carried out under an X-ray single crystal diffractometer, and the data are analyzed by SHELX software, so that the prepared compound is monoclinic system, C2/C space group. As shown in FIG. 1, the compound is a 1-D chain consisting of 1 Co-BBPTZ, 2 protonated BBPTZ organic ligands, and 1 Dawson-type polyacid anion [ P ₂ W ₁₈ O ₆₂ ] ^6- The components are as follows.

From a crystallographic point of view, this compound presents only one Co center, the coordination mode of which is hexacoordinated (as shown in fig. 1 and 2), i.e. coordinated to the terminal nitrogen atoms of the triazole of the four cis ligands BBPTZ, the terminal oxygen atoms of the two polyacids, the valence of which is +2, the Co-N bond lengths are 2.235(15) and 2.273(19), the Co-O bond length is 2.178 (13) a, the N-Co-N bond angle range is from 83.4(7) to 180.0(1), the N-Co-O bond angle range is from 86.1(7) to 93.8(8), and the bond angle of O-Co-O is 180 °.

As shown in figure 2, two adjacent Co centers of the prepared compound are connected by two cis ligands BBPTZ to form a ring, a 1-D chain formed by buckling of the ring is further expanded, and adjacent 1-D are connected by polyacid anions to form a 2-D layered structure with holes as shown in figure 3.

As shown in fig. 4, there are also free protonated ligands BBPTZ in this compound, which run through the Co center in the rings with the BBPTZ ligand, and are crossed by two free ligands BBPTZ in each ring, and there is a certain misalignment of the positions of these two free ligands BBPTZ.

These intertwined 2-D layers, as shown in figure 5, are further stacked to form a 3-D supramolecular network, and the layers are parallel to each other and have no forces.

Example 3: infrared spectroscopy (IR) analysis of the prepared compound crystals: the compound is tabletted by using KBr at 400-4000cm ^-1 In the wavenumber range, measurements were performed using an Alpha Centauri FT-IR infrared spectrometer.

The infrared spectrum of the compound is shown in FIG. 6, which shows four characteristic peaks in the range of 1100-700cm-1, about 1089cm ^-1 , 968cm ^-1 , 914cm ^-1 And 785cm ^-1 And assign them as { P }respectively ₂ W ₁₈ O ₆₂ } ⁶⁻ V (P-O), v (W = Od) and v (W-Ob/c-W). Furthermore, it is approximately 3122cm ^-1 With the peak being ascribed to the benzene and pyridine rings of the BBPTZ ligandv(C-H) shaking, of the benzene and triazole rings of the BBPTZ ligandv(C=C), v(C = N) andvthe peak of vibration (C = N) is represented at 1610-1435 cm ^-1 In the context of the above range of (a) and (b),v(H ₂ o) is approximately 3567cm ^-1 Is shown.

Example 4: thermogravimetric (TG) analysis of the prepared compound crystals: the temperature range and percent weight loss of the compound was determined using a Perkin-Elmer TGA7 analyzer and was measured at N ₂ Protection, the heating rate is 10 ℃ min ^-1 Under the conditions of (1).

The test results are shown in fig. 7, and analysis of the measured data revealed that the TG curve of the compound showed weight loss in two steps. In the temperature range of 70-125 ℃, the compound loses 1.01% in the first step, the weight loss can be attributed to the loss of 3 crystal water molecules, and the weight loss of 3 water molecules is 0.94% theoretically and is basically consistent with the actual weight loss in the first step; in the temperature range of 300 ℃ to 600 ℃, the second step weight loss of the compound is 22.06 percent, and the weight loss can be attributed to two ligands BBPTZ and two qualitiesProtonated ligand H ₂ The decomposition of BBPTZ, its decomposition weightlessness is 22.07% theoretically, it is basically consistent with the actual second step weightlessness; the actual total weight loss of the compound was 23.07%, which was substantially consistent with its theoretical weight loss value of 23.01%.

Example 5: powder diffraction (XRD) analysis of the prepared compound crystal: to demonstrate the purity of the compounds prepared, measurements were made at room temperature using a Rigaku D/MAX-3 powder diffractometer.

As shown in fig. 8, the experimentally determined data for the compound were consistent with the position of the peak fitted from the data of X-ray single crystal diffraction, indicating that the compound was of good purity and that the difference in peak intensity could be due to the different orientation of the powder sample.

Example 6: research on oxidative desulfurization catalytic activity of the prepared compound:

in the present society, a great deal of smoke, acid rain, PM2.5 air pollution and other problems are closely related to the generation of sulfides by human combustion fuel, so that the reduction of the sulfur content in the fuel is urgently needed to be solved and is a great problem closely related to the livelihood and the environment. The refractory organic sulfides in fuels can be removed by Oxidative Desulfurization (ODS) process, usually the sulfides are oxidized to the corresponding sulfones, which is one of the important ways to reduce the sulfur pollutant emissions. In the process of oxidative desulfurization, the catalyst is an important condition for determining the good and bad desulfurization effect, so that the research of the efficient oxidative desulfurization catalyst is a research hotspot in the research field. At present, polyacids have been found as a highly efficient catalyst in oxidative desulfurization reaction in oxidative desulfurization process, but they are easily dissolved in catalytic reaction system and thus difficult to reuse, and they are easily aggregated in solution, thereby reducing catalytic efficiency, so that their application is limited, and thus introduction of polyacids into metal framework materials is a new way to obtain heterogeneous catalysts.

Considering the structure of the prepared compound, Dawson type polyacid was well supported on the cationic frame formed by Co and BBPTZ, so we used Dibenzothiophene (DBT), a typical sulfur-containing compound in fuel, as a catalytic reaction model to evaluate the catalytic activity of the prepared compound as a heterogeneous catalyst.

Experimental method for catalytic reaction: as shown in FIG. 9, 0.5mmol of DBT and 2mmol of t-butyl hydroperoxide (TBHP) were added to 3ml of dichloromethane, 0.06mmol of catalyst (prepared compound) was further added thereto, and the mixture was heated to 50 ℃ to conduct a reaction, sampling was conducted every 1h using a pipette, and each sampled was detected by High Performance Liquid Chromatography (HPLC) for about 8h, and the reaction was substantially completed. The final product was determined by Infrared (IR) and mass on-line (GC-MS) characterization.

As shown in table 2 and fig. 10, the prepared compounds exhibited good catalytic activity in the catalytic reaction of DBT oxidative desulfurization. After 8h of reaction, the DBT conversion rate can reach 94.59%, and the DBT conversion rate is further measured along with the increase of time, and the DBT conversion rate is found to be very slow in 8h, and the DBT conversion rate is only 95.05% when reaching 12h, which is basically consistent with that in 8h, so that the catalytic activity of the compound as a catalyst is completely embodied in 8 h. In order to explore the catalytic active species in the compound, raw material Co (NO) is used ₃ ) ₂ ·3H ₂ O，K ₆ P ₂ W ₁₈ O ₆₂ ·n H ₂ The catalytic activity of O is studied, and K is found at 8h ₆ P ₂ W ₁₈ O ₆₂ ·n H ₂ The conversion rate of DBT can reach 49.06% under the catalysis of O raw material, and Co (NO) can be obtained ₃ ) ₂ ·3H ₂ In the presence of O raw material, the conversion rate is 26.2%, and in the same time, the conversion rate of DBT of the catalyst-free reaction system is only 13.12%, so the result shows that the conversion rate of DBT is improved when polyacid and metal exist, but the catalytic activity of polyacid raw material is obviously higher than that of metal raw material, and the polyacid unit is an active species catalyzed by the compound. In addition, when K is ₆ P ₂ W ₁₈ O ₆₂ ·n H ₂ O，Co(NO ₃ ) ₂ ·3H ₂ O, is added into a catalytic reaction system at the same time, the conversion rate of DBT can reach 63.84 percent at 8h and is higher than the catalytic activity of any single raw material, and the result proves that the combination of metal and polyacid generatesThe synergistic effect can increase the catalytic activity of the compound, but the polyacid can not be well monodispersed on the molecular level due to the simple mixing of the two raw materials, so that the active site of the polyacid can not be well exposed, and the catalytic activity of the compound is still high without the catalytic activity of the prepared compound.

TABLE 2 catalysis of DBT to DBTO as oxidants of TBHP by various catalysts ₂ Oxidation reaction of

The final DBT oxidation products were also analyzed and infrared indicated sulfone by FTIR (as shown in FIG. 11) and GC-MS (as shown in FIGS. 12 and 13)v _as(O=S=O) Andv _s(O=S=O) of sulfoxidesv _S=O Peak of (2) appears at 1282 cm ^-1 ，1167cm ^-1 And 1020 cm ^-1 In the vicinity, GC-MS further demonstrated the presence of both products. In addition, the compound as a catalyst is insoluble in a solvent, and the catalyst can be well separated by simple centrifugation and then recovered and recycled. Experiments prove that the catalytic activity of the catalyst is slightly reduced after the catalyst is recycled for 6 times (as shown in figure 14), which is probably caused by slight loss of the catalyst when the catalyst is centrifugally separated, but the catalytic effect can still reach 93.56%, and the catalyst still has high catalytic activity. The infrared spectrum data, XRD data and the like confirm that the compound is used as a catalyst and is not changed before and after the reaction, and the structural collapse is not proved before and after the reaction (as shown in figures 15 and 16).

In order to further confirm the oxidative desulfurization effect of the compound as a catalyst in fuel oil, model oils containing DBT were selected for investigation. First, a model oil containing 500ppm of DBT was prepared: 4.4040g of n-tetradecane (internal standard substance) and 2.9318g of DBT are weighed and respectively added into a volumetric flask of 1000ml, n-octane is used for fixing the volume to the scale, and the mixture is shaken up to prepare the model oil containing 4000ppm of the n-tetradecane and 500ppm of sulfur content. Then, oxidative desulfurization is carried out by using the catalytic experiment method under the same conditions, and the research result shows that the DBT conversion rate can reach 93.07% in 8h (as shown in figure 17), and the compound is further researched, wherein after six times of circulation, the activity of the catalyst is slightly reduced, but the conversion rate can reach 91.95% (as shown in figure 18), and the compound still has high catalytic activity. Therefore, the prepared compound proved to have high efficiency as a heterogeneous catalyst for the oxidative desulfurization effect of fuel.

Through research on the oxidative desulfurization activity of the prepared compound, a Dawson type polyacid intervened metal-BBPTZ organic framework can be found, the specific surface area of the Dawson type polyacid can be well increased, and the Dawson type polyacid can be highly uniformly dispersed on a molecular level; the combination of Dawson type polyacid and a metal-BBPTZ organic framework realizes the concerted catalysis, and a composite functional catalyst with 1+1>2 is obtained; the stable frame can effectively prevent the loss of the Dawson type polyacid molecular catalyst and improve the service life and the efficiency of the catalyst.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Dawson type polyacid-based-BBPTZ organic framework material is characterized in that: the molecular formula of the Dawson type polyacid-BBPTZ organic framework material is as follows: [ H ] ₂ BBPTZ] ₂ Co(BBPTZ) ₂ [P ₂ W ₁₈ O ₆₂ ]·3H ₂ O; namely: i.e. C ₇₂ H ₇₄ N ₂₄ O ₆₅ P ₂ W ₁₈ Co, a monoclinic system,C2/cspace group, the basic unit includes one [ P ₂ W ₁₈ O ₆₂ ] ^6- Polyanion, one Co (II) cation, two BBPTZ ligands, two protonated BBPTZ ligands and three crystalsA water molecule; the unit cell parameters are as follows:a＝26.675(2)Å，b＝16.1311(12)Å，c＝30.321(2)Å，α＝90°，β＝104.396(8)°，γ＝90°，V＝12637.4(16)Å ³ ，Z＝4，μ＝16.557mm ^-1 ，F(000)= 10332。

2. a method for preparing the Dawson-type polyacid-based metal-BBPTZ organic framework material of claim 1, characterized in that: the method comprises the following specific steps:

(1) synthesis of 1, 4-bis (1,2, 4-triazole-1-methylene) biphenyl, BBPTZ: dissolving 20mmol of 1,2, 4-triazole in 50ml of acetone, then sequentially adding 4g of PEG-400, 5g of anhydrous potassium carbonate and 0.5g of potassium iodide, stirring for 30min at normal temperature, after stirring uniformly, adding 10mmol of biphenyl dichlorobenzyl, stirring uniformly, refluxing for 12h, cooling, filtering, distilling the filtrate to obtain white residue, and recrystallizing for 2-3 times with water to obtain pure organic ligand BBPTZ;

(2) synthesis of K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ O: 0.31mol of Na ₂ WO ₄ ·2H ₂ Dissolving O in 200ml water, adding 84ml phosphoric acid 1.24mol with mass concentration of 85%, heating the solution to 100 deg.C, refluxing, maintaining for 8 hr, adding H ₂ O ₂ Removing the pale green color of the solution; cooling, adding 40g ammonium chloride, stirring for 10-15min to obtain precipitate, vacuum filtering to obtain light yellow powder, dissolving the light yellow powder in 240ml water, adding 40g ammonium chloride, stirring for 10-15min to obtain precipitate, vacuum filtering, and drying; dissolving the dried precipitate in 100ml water, adding 0.27mol KCl to obtain precipitate, filtering, and drying to obtain light yellow K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ O；

(3) Synthesis of Dawson-type polyacid-based metal-BBPTZ organic framework material: 0.25 mmol of Co (NO) ₃ ) ₂ ·3H ₂ O, 0.15 mmol of K ₆ P ₂ W ₁₈ O ₆₂ ·nH ₂ O and 0.16 mmol of BBPTZ, adding 12mL of distilled water to the mixture, stirring for 15min, adjusting pH to 2.5 with 1M NaOH, stirring at room temperature for 0.5h, and stirring to obtain a uniform suspensionTransferring the solution to a 25ml reaction kettle with a polytetrafluoroethylene lining, keeping the temperature at 130 ℃ for 3 days, and then keeping the temperature at 5 ℃ for h ^-1 And (3) cooling to room temperature at a high speed to obtain pink blocky crystals, namely the Dawson type polyacid-based metal-BBPTZ organic framework material.

3. Use of the Dawson-type polyacid-based metal-BBPTZ organic framework material of claim 1 as a catalyst, characterized in that: the Dawson type polyacid-based metal-BBPTZ organic framework material is used as a heterogeneous desulfurization catalyst in oxidative desulfurization of fuel.