Dawson type polyacid-based metal-TBTZ ligand organic framework material and preparation method and application thereof
阅读说明：本技术 一种Dawson型多酸基金属-TBTZ配体有机框架材料及其制备方法和用途 (Dawson type polyacid-based metal-TBTZ ligand organic framework material and preparation method and application thereof ) 是由 郝秀丽 贾士芳 温艳珍 于 2021-01-18 设计创作，主要内容包括：本发明属金属有机框架材料技术领域,为解决在多酸基金属有机框架材料时,容易发生催化活性降低的问题,提供一种Dawson型多酸基金属-TBTZ配体有机框架材料及其制备方法和用途。分子式为：[(Co-2(TBTZ)-2(H-2O)-4][H-2P-2W-(18)O-(62)]·11H-2O,单斜晶系,P21/m空间群,基本单元包含一个[H-2P-2W-(18)O-(62)]～(6-)多阴离子,两个Co(II)阳离子,两个TBTZ配体,四个配位水和十一个结晶水分子。晶体结构稳定,为非均相催化剂,提高了比表面积,分子水平上高度均匀分散；实现协同催化,获得“1+1>2”的复合型功能催化剂；有效地防止Dawson型多酸分子催化剂的流失,提高催化剂的寿命及效率。(The invention belongs to the technical field of metal organic framework materials, and provides a Dawson type polyacid-based metal-TBTZ ligand organic framework material, a preparation method and application thereof, aiming at solving the problem that the catalytic activity is easy to reduce when the polyacid-based metal organic framework material is used. The molecular formula is: [ (Co) 2 (TBTZ) 2 (H 2 O) 4 ][H 2 P 2 W 18 O 62 ]·11H 2 O, a monoclinic system, P 21/ m space group, the basic unit includes one [ H ] 2 P 2 W 18 O 62 ] 6‑ Polyanion, two co (ii) cations, two TBTZ ligands, four coordinated waters and eleven crystalline water molecules. The crystal structure is stable, the catalyst is a heterogeneous catalyst, the specific surface area is increased, and the molecular level is improvedThe upper height is uniformly dispersed; realize the concerted catalysis to obtain' 1+1>2' of a composite functional catalyst; effectively prevent the loss of the Dawson type polyacid molecular catalyst and improve the service life and efficiency of the catalyst.)
1. A Dawson type polyacid-based metal-TBTZ ligand organic framework material, characterized in that: the molecular formula of the Dawson type polyacid-based metal-TBTZ ligand organic framework material is as follows: [ (Co)2(TBTZ)2(H2O)4][H2P2W18O62]·11H2O is C36H74N18O77P2W18Co2The crystal structure of the monoclinic system,P21/mspace group, the basic unit includes one [ H ]2P2W18O62]6-Polyanion, two co (ii) cations, two TBTZ ligands, four coordinated waters and eleven crystalline water molecules; the unit cell parameters are as follows:a＝14.3743(8)Å，b＝25.6237(7)Å，c＝14.6114(6)Å，α＝90°，β＝97.852(4)°，γ＝90°，V＝5331.3(4)Å3，Z＝2，μ＝17.769mm-1，F(000)= 4896。
2. a method of preparing a Dawson-type polyacid-based metal-TBTZ ligand organic framework material of claim 1, characterized in that: the method comprises the following specific steps:
(1) synthesizing 1,3, 5-tris (1,2, 4-triazole-1-methylene) -2,4, 6-trimethylbenzene, namely TBTZ: dissolving 20mmol of 1,2, 4-triazole in 50ml of acetonitrile, adding 5g of anhydrous potassium carbonate, uniformly stirring at normal temperature, adding 10mmol of 1,3, 5-tri (bromomethyl) -2,4, 6-trimethylbenzene, uniformly stirring, refluxing at 80 ℃ for 16h, cooling, filtering, distilling the filtrate to obtain white residue, and recrystallizing with water for 2-3 times to obtain pure organic ligand TBTZ;
(2) synthesis of K6P2W18O62·nH2O: 0.31mol of Na2WO4·2H2Dissolving O in 200ml water, adding 84ml phosphoric acid with mass concentration of 85% at 1.24mol, heating the solution to 100 deg.C, refluxing, maintaining for 8 hr, adding H2O2Removing the pale green color of the solution; cooling the solution, adding 40g of ammonium chloride, stirring the solution for 10-15min to obtain a precipitate, performing suction filtration to obtain a 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 a precipitate, continuously performing suction filtration, and drying; the precipitate was redissolved in 100ml of water, and 0.27mol of KCl was added thereto to obtain a precipitate, which was then filtered and dried to obtain pale yellow K6P2W18O62·nH2O；
(3) Synthesizing a Dawson type polyacid-based metal-TBTZ ligand organic framework material: 0.25mmol of Co (NO)3)2·3H2O, 0.15mmol of K6P2W18O62·nH2Mixing O and 0.16 mmol TBTZ, adding 10mL distilled water into the mixture, stirring for 15min, adjusting pH to 4.0 with 1M NaOH, continuing stirring at room temperature for 0.5h, transferring the uniformly stirred suspension into 18mL reaction kettle with polytetrafluoroethylene lining, keeping at 130 deg.C for 3 days, and keeping at 5 deg.C. h-1And (3) cooling at a speed rate to reduce the temperature of the reaction kettle to room temperature to obtain pink blocky crystals, namely the Dawson type polyacid-TBTZ ligand organic framework material.
3. Use of a Dawson-type polyacid-based metal-TBTZ ligand organic framework material according to claim 1, characterized in that: the Dawson type polyacid-based metal-TBTZ ligand organic framework material is used as a heterogeneous desulfurization catalyst in oxidative desulfurization of fuel.
Technical Field
The invention belongs to the technical field of metal organic framework materials, and particularly relates to a Dawson type polyacid-based metal-TBTZ ligand organic framework material, a preparation method and application thereof.
Background
Polyacid as a unique oxygen cluster of early transition metals (including Mo, W, V, Nb, Ta and the like) 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 m2·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 to be directed to 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.
Synthesis of metal-organic frameworks (MOFs) based on triazole derivatives, study of crystal structures and catalytic properties thereof, li strictness and the like, abstract collection of 30 th academic annual meeting of the chinese chemical society-sixth division: metal organic framework chemistry, 2016-07-01), which discloses the design and synthesis of ligand 1,3, 5-tris (1,2, 4-triazole-1-methylene) -2,4, 6-trimethylbenzene, the ligand is coordinated with metallic copper, and the complex is characterized by elemental analysis, crystal structure determination, powder diffraction, infrared analysis, thermogravimetric analysis, fluorescence analysis and the like. And finally, the effect of the catalyst on the catalytic degradation is researched through the degradation effect of the catalyst on the dye, and the catalyst is further applied to the actual life. However, the abstract does not disclose a polyacid-based complex formed by introducing a polyacid into the metal-organic framework, and the introduction of the polyacid induces a great difference in the structure formation, and the catalytic effect of the polyacid as a catalyst in the oxidative desulfurization of fuel is not described in detail.
Disclosure of Invention
The invention provides a Dawson type polyacid-based metal-TBTZ ligand 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, 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 metal-TBTZ ligand organic framework material, characterized in that: the molecular formula of the Dawson type polyacid-based metal-TBTZ ligand organic framework material is as follows: [ (Co)2(TBTZ)2(H2O)4][H2P2W18O62]·11H2O is C36H74N18O77P2W18Co2The crystal structure of the monoclinic system,P21/mspace group, the basic unit includes one [ H ]2P2W18O62]6-Polyanion, two co (ii) cations, two TBTZ ligands, four coordinated waters and eleven crystalline water molecules; the unit cell parameters are as follows:a＝14.3743(8)Å，b＝25.6237(7)Å，c＝14.6114(6)Å，α＝90°，β＝97.852(4)°，γ＝90°，V＝5331.3(4)Å3，Z＝2，μ＝17.769mm-1，F(000)= 4896。
a method of preparing a Dawson-type polyacid-based metal-TBTZ ligand organic framework material of claim 1, characterized in that: the method comprises the following specific steps:
(1) synthesizing 1,3, 5-tris (1,2, 4-triazole-1-methylene) -2,4, 6-trimethylbenzene, namely TBTZ: dissolving 20mmol of 1,2, 4-triazole in 50ml of acetonitrile, adding 5g of anhydrous potassium carbonate, uniformly stirring at normal temperature, adding 10mmol of 1,3, 5-tri (bromomethyl) -2,4, 6-trimethylbenzene, uniformly stirring, refluxing at 80 ℃ for 16h, cooling, filtering, distilling the filtrate to obtain white residue, and recrystallizing with water for 2-3 times to obtain pure organic ligand TBTZ;
(2) synthesis of K6P2W18O62·nH2O: 0.31mol of Na2WO4·2H2Dissolving O in 200ml water, adding 84ml phosphoric acid with mass concentration of 85% at 1.24mol, heating the solution to 100 deg.C, refluxing, maintaining for 8 hr, adding H2O2Removing the pale green color of the solution; cooling the solution, adding 40g of ammonium chloride, stirring the solution for 10-15min to obtain a precipitate, performing suction filtration to obtain a 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 a precipitate, continuously performing suction filtration, and drying; the precipitate was redissolved in 100ml of water, and 0.27mol of KCl was added thereto to obtain a precipitate, which was then filtered and dried to obtain pale yellow K6P2W18O62·nH2O；
(3) Synthesizing a Dawson type polyacid-based metal-TBTZ ligand organic framework material: 0.25mmol of Co (NO)3)2·3H2O、0.15mmol of K6P2W18O62·nH2Mixing O and 0.16 mmol TBTZ, adding 10mL distilled water into the mixture, stirring for 15min, adjusting pH to 4.0 with 1M NaOH, continuing stirring at room temperature for 0.5h, transferring the uniformly stirred suspension into 18mL reaction kettle with polytetrafluoroethylene lining, keeping at 130 deg.C for 3 days, and keeping at 5 deg.C. h-1And (3) cooling at a speed rate to reduce the temperature of the reaction kettle to room temperature to obtain pink blocky crystals, namely the Dawson type polyacid-TBTZ ligand organic framework material.
Use of a Dawson-type polyacid-based metal-TBTZ ligand organic framework material according to claim 1, characterized in that: the Dawson type polyacid-based metal-TBTZ ligand organic framework material is used as a heterogeneous desulfurization catalyst in oxidative desulfurization of fuel.
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-based metal-TBTZ ligand organic framework material prepared by the method has a stable crystal structure, so that the Dawson type polyacid homogeneous catalyst is supported by the metal organic framework to form a heterogeneous catalyst, the specific surface area of the Dawson type polyacid is improved, and the Dawson type polyacid homogeneous catalyst can be highly uniformly dispersed on a molecular level; the combination of Dawson type polyacid and metal-TBTZ ligand organic framework realizes the concerted catalysis, and the 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 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 synthesis 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 [ (Co)2(TBTZ)2(H2O)4][H2P2W18O62]·11H2The basic structural unit of the O pink blocky crystal, and all hydrogen atoms are ignored in the figure;
FIG. 2 shows the structure of a ladder-type 1-D chain formed by the connection of Co and TBTZ ligand;
FIG. 3 is a 2-D layered structure of a 1-D chain with a polyacid, wherein: (a) along the direction of the a axis; (b) along the c-axis direction;
fig. 4 is a 3-D supramolecular network structure, in which: (a) along the direction of the a axis; (b) along the c-axis direction;
FIG. 5 is an infrared spectrum of the prepared compound;
FIG. 6 is a thermogravimetric plot of the prepared compound;
FIG. 7 is an analysis of XRD data for the prepared compound, the bottom curve representing fitted and the top curve representing measured;
FIG. 8 is a graph showing the conversion of DBT to sulfoxide and sulfone by an oxidation reaction;
FIG. 9 is a graph of DBT conversion versus reaction time for different catalysts;
FIG. 10 shows DBT and the oxidation products DBTO, DBTO2The top curve represents DBT and the bottom represents the oxidized product;
FIG. 11 shows the results of gas chromatographic detection of DBT oxidation products;
FIG. 12 is a mass spectrum of DBT oxidation product and un-oxidized DBT;
FIG. 13 is a graph showing the number of cycles of the prepared compound as an oxidation catalyst;
FIG. 14 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. 15 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. 16 shows DBT conversion in model oils with the prepared compound as catalyst;
FIG. 17 is a graph showing 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.
The Dawson type polyacid-based metal-organic framework material has a molecular formula of [ (Co)2(TBTZ)2(H2O)4][H2P2W18O62]·11H2O is C36H74N18O77P2W18Co2The crystal structure of the monoclinic system,P21/mspace group, the basic unit includes one [ H ]2P2W18O62]6-Polyanion, two co (ii) cations, two TBTZ ligands, four coordinated waters and eleven crystalline water molecules; the unit cell parameters are as follows:a＝14.3743(8)Å，b＝25.6237(7)Å，c＝14.6114(6)Å，α＝90°，β＝97.852(4)°，γ＝90°，V＝5331.3(4)Å3，Z＝2，μ＝17.769mm-1，F(000)= 4896。
the preparation method comprises the following steps:
(1) synthesizing 1,3, 5-tris (1,2, 4-triazole-1-methylene) -2,4, 6-trimethylbenzene, namely TBTZ: dissolving 20mmol of 1,2, 4-triazole in 50ml of acetonitrile, adding 5g of anhydrous potassium carbonate, uniformly stirring at normal temperature, adding 10mmol of 1,3, 5-tri (bromomethyl) -2,4, 6-trimethylbenzene, uniformly stirring, refluxing at 80 ℃ for 16h, cooling, filtering, distilling the filtrate to obtain white residue, and recrystallizing with water for 2-3 times to obtain pure organic ligand TBTZ;
(2) synthesis of K6P2W18O62·nH2O: 0.31mol of Na2WO4·2H2Dissolving O in 200ml water, adding 84ml phosphoric acid with mass concentration of 85% at 1.24mol, heating the solution to 100 deg.C, refluxing, maintaining for 8 hr, adding H2O2Removing the pale green color of the solution; cooling the solution, adding 40g of ammonium chloride, stirring the solution for 10-15min to obtain a precipitate, performing suction filtration to obtain a 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 a precipitate, continuously performing suction filtration, and drying; the precipitate was redissolved in 100ml of water, and 0.27mol of KCl was added thereto to obtain a precipitate, which was then filtered and dried to obtain pale yellow K6P2W18O62·nH2O；
(3) Synthesizing a Dawson type polyacid-based metal organic framework material: mixing Co (NO)3)2·3H2O (0.075 g, 0.25 mmol), K6P2W18O62·nH2A mixture of O (0.69g, 0.15 mmol) and TBTZ (0.06 g, 0.16 mmol) was added to a beaker containing 10mL of distilled water and then stirred under a stirrer for 15min, followed by pH adjustment to 4.0 with NaOH (1M), continued stirring at room temperature for 0.5h, and finally the well-stirred suspension was transferred to an 18mL Teflon lined reactor and the reactor was placed in an oven, held at a high temperature of 130 ℃ for 3 days and further held at 5 ℃ h-1And (5) cooling at a speed rate to slowly cool the temperature of the reaction kettle to room temperature to obtain pink blocky crystals.
The [ (Co)2(TBTZ)2(H2O)4][H2P2W18O62]·11H2The O pink block crystals were rinsed with distilled water and dried to obtain pure Dawson-type polyacid-based metal organic framework material with a yield of 50% calculated as W.
In the above synthesis, Co (NO) as a raw material is used3)2·3H2O is an analytically pure starting material purchased directly on the market without further purification.
Example 2: preparation ofAnalysis of crystal structure of the compound: the prepared pink bulk crystal compound structure was obtained by collecting 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 F2Fine trimming by the method.
All non-hydrogen atoms in the compound are anisotropic, the hydrogen atoms on the organic carbon atoms are fixed in the calculated positions, the hydrogen atoms on the water molecules 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 [ (Co)2(TBTZ)2(H2O)4][H2P2W18O62]·11H2And 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: c36H74N18O77P2W18Co2Theoretical value (%) of elemental analysis: c7.88, H1.35, N4.60, P1.13, W60.44, Co 2.15; experimental values (%): c7.81, H1.40, N4.68, P1.07, W60.35 and Co 2.24.
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。
Preparation ofThe structure of the compounds is described below: the test is carried out under an X-ray single crystal diffractometer, and the data are analyzed by SHELX software, the structure is shown in figure 1, compound 1 is monoclinic system, P21/m space group. The compound is a 1-D chain consisting of 1 Co-TBTZ and 1 Dawson type polyacid anion [ H2P2W18O62]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 (see fig. 2), i.e. with the terminal triazole nitrogen atoms of the three ligands TBTZ, the terminal oxygen atom of one polyacid, and two water molecules coordinated, the valence of which is +2, the Co-N bond length range being 2.092(14) a-2.134 (13), the Co-O bond length being 2.097 (13) a, the N-Co-N bond angle range being from 87.3(6) ° to 173.4(5) ° and the N-Co-O bond angle range being from 92.6(8) to 175.0(2) ° and the bond angles of O-Co-O being 91.4(9) and 178.3 (7).
The ligand in the prepared compound has three flexible connecting groups-CH2To make the transformation of ligands more flexible, as shown in fig. 2, each TBTZ ligand shows a T-shaped configuration to connect with three Cu centers, so that adjacent TBTZ ligands are connected through the Cu centers to form a closed loop, thereby forming a ladder-type 1-D chain. The 1-D chains parallel to the b-axis are further connected by polyacid anions to form a 2-D layered structure (as shown in FIG. 3), interesting ladder type 1-D chains are perpendicular to the 2-D layer, the Cu centers in the handrails on both sides of the ladder type 1-D chains are just opposite to the direction of connecting the polyacid, and the 2-D layer is constructed by alternately finishing the upper and the lower sides, and the polyacid is staggered in the 2-D layer (as shown in FIG. 3). Along the a-axis direction, 2-D layers are further stacked to form 3-D supramolecular networks (as shown in FIG. 4), and the layers are parallel to each other without any force.
Example 3: infrared spectroscopy (IR) analysis of the prepared compound crystals: the compounds were tableted with KBr and measured using an Alpha Centauri FT-IR infrared spectrometer at a wave number in the range of 400-4000 cm-1.
The infrared spectrum of the compound is shown in FIG. 5, which shows four characteristic peaks in the range of 1100-700cm-1, about 1093cm-1, 960cm-1, 910cm-1And 790cm-1And assign them as { P }respectively2W18O62}6−V (P-O), v (W = Od) and v (W-Ob/c-W). Furthermore, approximately at 3130cm-1With the peak being ascribed to the benzene and pyridine rings of the TBTZ ligandv(C-H) shaking, of the benzene ring and of the triazole ring of the TBTZ ligandv(C=C), v(C = N) andvthe vibration peak of (C = N) is represented in 1620-1446 cm-1In the range of (a) to (b),v(H2o) is about 3430cm-1Is 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 N2Protection, the heating rate is 10 ℃ min-1Under the conditions of (1).
Analysis of the data determined therefrom revealed that the TG curve of the compound showed a weight loss in two steps (see fig. 6). In the temperature range of 50-190 ℃, the compound loses 4.86% in the first step, the weight loss can be attributed to the loss of 4 coordinated water and 11 crystallized water molecules, and the weight loss of 15 water molecules is 4.93% in theory and is basically consistent with the weight loss in the actual first step; in the temperature range of 300 ℃ to 620 ℃, the second step weight loss of 3 compounds is 13.28 percent, the weight loss can be attributed to the decomposition of two ligands TBTZ, the decomposition weight loss is 13.25 percent theoretically, and the second step weight loss is basically consistent with the actual second step weight loss; the actual total weight loss of this compound was 18.14%, which is essentially consistent with its theoretical weight loss value of 18.18%.
Example 5: powder diffraction (XRD) analysis of the prepared compound crystal: to demonstrate the purity of the prepared compound, a Rigaku D/MAX-3 powder diffractometer was used for determination at room temperature.
As shown in fig. 7, the experimentally determined data for the compound are consistent with the position of the peak fitted from the data of X-ray single crystal diffraction, indicating that the compound is of good purity and that the difference in peak intensity may be due to different positional orientations of the powder samples.
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 framework formed by Co and TBTZ, 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: 0.5mmol of DBT and 2mmol of t-butyl hydroperoxide (TBHP) were added to 3ml of dichloromethane, 0.06mmol of catalyst (the prepared compound) was added thereto, and the mixture was heated to 50 ℃ to carry out the reaction (see FIG. 8), and samples were taken every 1h by using a pipette, and each sample 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. 9, 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 98.32%, and the DBT conversion rate is further measured along with the increase of time, and the DBT conversion is found to be very slow to 1 in 8hThe 2h conversion is only 98.60%, which is basically consistent with 8h, so that the catalytic activity of the compound as a catalyst is fully demonstrated at 8 h. In addition, a blank control was performed, and the DBT conversion after 8h was only 13.12% in the absence of catalyst under otherwise identical reaction conditions, confirming that the compound exhibited good catalytic activity in this catalytic model. In order to explore the catalytic active species in the compound, raw material Co (NO) is used3)2·3H2O，K6P2W18O62·n H2The catalytic activity of O is studied, and K is found at 8h6P2W18O62·n H2The conversion rate of DBT can reach 49.06 percent under the catalysis of O raw material, and Co (NO)3)2·3H2The conversion in the presence of the O feedstock was only 26.2%, which indicates that both the polyacid and the metal had improved DBT conversion in the same time period, but the polyacid feedstock had a significantly higher catalytic activity than the metal feedstock, indicating that the polyacid unit is the active species catalyzed by this compound. Furthermore, when K is6P2W18O62·n H2O，Co(NO3)2·3H2And O is simultaneously added into a catalytic reaction system, the conversion rate of DBT can reach 63.84% 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 generates a synergistic effect and can increase the catalytic activity of the polyacid.
TABLE 2 catalysis of DBT to DBTO as oxidants of TBHP by various catalysts2Oxidation reaction of
The oxidation products of DBT were also analyzed and determined by FTIR (as shown in FIG. 10) and GC-MS (as shown in FIGS. 11 and 12) as redOf exo-indicated sulphonesv as(O=S=O)Andv s(O=S=O)of sulfoxidesv S=OThe peak of (A) appears at 1290 cm-1，1155cm-1And 1020 cm-1In the vicinity, GC-MS further demonstrated the presence of both products. Furthermore, the compound is insoluble in a solvent as a catalyst, and the catalyst can be separated well 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 13), which is probably caused by slight loss of the catalyst when the catalyst is centrifugally separated, but the catalytic effect still reaches 97.73 percent and 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 before and after the reaction is proved (as shown in figures 14 and 15).
In order to further confirm the oxidative desulfurization effect of the compound as a catalyst in fuel oil, a model oil containing DBT was 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 research results show that the DBT conversion rate can reach 96.46% within 8h (as shown in figure 16), and further research is carried out on the compound in a cycle experiment, after six times of cycle, the activity of the catalyst is slightly reduced, but the conversion rate can reach 94.02% (as shown in figure 17), and the compound still has high catalytic activity. Therefore, the prepared compound demonstrates high efficiency as a heterogeneous catalyst for the oxidative desulfurization effect of fuel.
Through research on the oxidative desulfurization activity of the prepared compound, the fact that the Dawson type polyacid intervenes in a metal-TBTZ organic framework can be found, the specific surface area of the Dawson type polyacid can be well improved, 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.
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.