Recyclable clamp ligand Pincer catalyst based on self-contained microporous polymer as well as preparation method and application of recyclable clamp ligand Pincer catalyst

Abstract

The invention discloses a recyclable pincer ligand Pincer catalyst based on an intrinsic microporous polymer as well as a preparation method and application of the recyclable pincer ligand Pincer catalyst. In the invention, the catalyst ligand is a modified polymer with own micropores, has outstanding chemical controllability compared with other polymers, and can form a PN3P type Pincer structure on a skeleton through precise chemical modification. The structure endows the ligand with strong coordination ability with metal ruthenium, and meanwhile, the PIM material can be dissolved or semi-dissolved in dimethyl sulfoxide (DMSO), so that the reaction is a quasi-homogeneous system, which is beneficial to full contact of active sites and a substrate. According to the present invention, the Pincer structure is formed on the PIM polymer skeleton through chemical modification by combining the high specific surface area, the dissolvability and the recoverability of the intrinsic microporous polymer (PIM) and the high activity and the high stability of the pincer ligand Pincer structure, and the Pincer structure is coordinated with the active metal, such that the comprehensive advantages of high activity, high stability and excellent recoverability are represented, and the good industrial application prospect is provided.

Description

Technical Field

[0001] This invention belongs to the field of energy catalytic materials technology, specifically a recyclable pincer catalyst based on a self-porous polymer, its preparation method, and its application. Background Technology

[0002] With the continuous growth of global energy demand and increasing emphasis on environmental protection, the importance of hydrogen as a clean energy source is becoming increasingly prominent. Hydrogen possesses advantages such as high energy density and pollution-free combustion products, and is considered key to the future energy transition. However, the challenges of hydrogen storage and transportation have always been a major bottleneck restricting its large-scale application. Traditional compressed hydrogen storage and liquid hydrogen storage technologies suffer from high costs and poor safety. Therefore, safe and efficient chemical hydrogen storage has become a research hotspot.

[0003] Formic acid (HCOOH) is considered one of the most promising liquid hydrogen storage media due to its high hydrogen storage capacity (4.4 wt%), room-temperature liquid stability, and low toxicity (Energy Fuels, 2023, 37, 1441-1450). Its catalytic decomposition can efficiently release hydrogen through the dehydrogenation pathway (HCOOH → H2 + CO2), but this reaction is highly dependent on the performance of the catalyst. Developing highly selective, highly stable, and recyclable catalysts is the core of promoting the industrialization of formic acid hydrogen production technology.

[0004] In recent years, Pincer ligands (tridentate chelate ligands) have been widely used in catalyst design due to their precise control over the electronic structure of metal centers and their superior structural stability, exhibiting unique advantages such as high activity and good selectivity in the formic acid dehydrogenation reaction. However, existing Pincer catalysts are mostly small-molecule homogeneous systems (such as the PXN2P type ruthenium catalyst in patent CN 104014372 A), which suffer from difficulties in recovery and poor reusability, limiting their industrial applications. On the other hand, conventional supported heterogeneous catalysts suffer from poor selectivity and low activity, making it difficult to covalently bond with Pincer ligands to form a monolithic structure, resulting in low stability. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems by providing a recyclable pincer catalyst based on a self-porous polymer, its preparation method, and its applications.

[0006] The technical solution adopted in this invention is as follows: a recyclable pincer catalyst based on a microporous polymer, wherein the catalyst is a phosphine-grafted 2,4-diamino-1,3,5-triazine-functionalized microporous polymer based on a pincer ligand support PN3P-PIM, and its chemical structure is as follows: .

[0007] In a preferred embodiment, the metal Ru in the catalyst coordinates with the PN3P-PIM ligand at the PN3P structure to form PN 3 P-type recyclable Pincer ruthenium metal catalyst PN 3 The chemical structure diagram of P-PIM-Ru is shown below: .

[0008] In a preferred embodiment, the mass fraction of ruthenium is 0.01% to 5%, preferably 1.5%, and a portion of the 2,4-diamino-1,3,5-triazine may not participate in metal chelation.

[0009] In a preferred embodiment, a method for preparing a recyclable pincer ligand Pincer catalyst based on a self-porous polymer includes: using PIM-1 as an initial raw material, reacting it with polycyanamide to generate 2,4-diamino-1,3,5-triazine-functionalized DATPIM, and then reacting it with di-tert-butylphosphine chloride to generate PN. 3 P-PIM ligands; PN 3 The P-PIM ligand reacts with ruthenium tris(triphenylphosphine)carbonyl hydrochloride, followed by treatment with a strong base. Preferably, the reaction solvent is dimethyl sulfoxide (DMSO).

[0010] In a preferred embodiment, the strong base is potassium tert-butoxide.

[0011] In a preferred embodiment, the application of a recyclable pincer ligand Pincer catalyst based on a self-porous polymer as described in claim 1, the application comprising catalyzing the release of hydrogen from formic acid in the range of 333 K to 423 K.

[0012] In a preferred embodiment, the reaction conditions are: temperature 393K, atmospheric pressure, solvent is dimethyl sulfoxide, and additive is cesium formate.

[0013] In a preferred embodiment, the formic acid comprises formic acid with a high water content of 85%.

[0014] In a preferred embodiment, a method for recovering Pincer catalyst based on a self-porous polymer and recyclable pincer ligand involves adding a poor solvent to the system after the reaction, shaking to precipitate the solid, centrifuging to separate it, dissolving the separated solid with DMSO, adding the poor solvent again to precipitate it, and repeating this process twice. After washing, filtering, and drying, the recovered PN is obtained. 3 P-PIM-Ru.

[0015] In a preferred embodiment, the undesirable solvent includes dichloromethane, trichloromethane, water, etc., and is preferably deionized water.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In this invention, the catalyst ligand is a modified microporous polymer (PIM), which exhibits superior chemical tunability compared to other polymers. A PN3P-type pincer structure can be formed on the framework through precise chemical modification. This structure endows the ligand with a strong coordination ability with ruthenium. Simultaneously, the PIM material is soluble or semi-soluble in dimethyl sulfoxide (DMSO), making the reaction a quasi-homogeneous system, which facilitates sufficient contact between the active sites and the substrate. In practical applications, this catalyst can efficiently catalyze the decomposition of formic acid to produce hydrogen within a temperature range of 333K–423K. When the reaction temperature is 393K (120℃), the maximum time-of-flight (TOF) can reach 9781 h⁻. 1 It exhibits extremely high catalytic activity; and by adjusting the reaction temperature, the type of additives (such as preferably cesium formate), and other conditions, the catalytic performance can be flexibly controlled to meet the needs of different scenarios.

[0017] 2. In this invention, the PN3P tridentate pincer structure in the catalyst ligand forms a strong coordination bond with metallic ruthenium, significantly improving the structural stability of the catalyst and effectively preventing the loss of metal active centers. Compared with the difficulty in recovering traditional small-molecule Pincer catalysts, this catalyst, based on a self-contained microporous polymer support, can be recovered through a simple "dissolution and desorption" method: after the reaction, adding a poor solvent such as deionized water to the system allows the catalyst to precipitate and be separated by centrifugation. After two dissolution and desorption cycles, washing, and drying, it can be reused. Experiments show that in 10 catalytic cycles, the hydrogen yield of this catalyst remains above 94%, the total conversion number (TON) exceeds 60,000, and the activity does not show a significant decrease, perfectly solving the problem of small-molecule catalyst recovery and significantly reducing long-term operating costs.

[0018] 3. In this invention, the catalyst preparation process is clear and easy to operate: PN3P-PIM ligand is prepared by reacting 2,4-diamino-1,3,5-triazine-functionalized PIM (DATPIM) with di-tert-butylphosphine chloride, then coordinated with ruthenium salt in DMSO and treated with a strong alkali to obtain the target catalyst. No complex equipment is required throughout the process. The recovery process only requires adding a poor solvent (such as deionized water) to the reaction system to precipitate the catalyst, which can then be reused after centrifugation, dissolution, and drying. The process involves few steps and is time-efficient. This simple preparation and recovery process has low equipment requirements, is suitable for large-scale production and industrial application, and provides a feasible path for the practical application of formic acid hydrogen storage technology. Attached Figure Description

[0019] Figure 1This is the synthetic route for the catalyst PN3P-PIM-Ru in this invention; Figure 2 This is the infrared spectrum of the PN3P-PIM synthesized in Example 1 of this invention; Figure 3 This is a scanning electron microscope (SEM) image of the catalyst PN3P-PIM-Ru in Example 1 of this invention; Figure 4 The graph shows the gas production of 0.25 ml formic acid under different conditions using PN3P-PIM-Ru catalytic decomposition in Examples 2-6. Figure 5 This is a graph showing the yield of formic acid catalyzed by PN3P-PIM-Ru in the first 10 cycles of a cyclic catalytic experiment using PN3P-PIM-Ru. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] Example: Refer to Figure 1-5 A recyclable pincer ligand Pincer catalyst based on a self-porous polymer, wherein the catalyst is a phosphine-grafted 2,4-diamino-1,3,5-triazine-functionalized self-porous polymer based on a pincer ligand support PN3P-PIM, and its chemical structure is as follows: .

[0022] In the catalyst, metallic Ru coordinates with the PN3P-PIM ligand at the PN3P structure to form PN 3 P-type recyclable Pincer ruthenium metal catalyst PN 3 The chemical structure diagram of P-PIM-Ru is shown below: .

[0023] A PN 3 The preparation method of P-PIM-Ru catalyst includes the following steps: (1) Preparation of PN 3P-PIM carrier: 689 mg (1.00 mmol) of DATPIM (prepared according to the method described in Adv. Mater. 2017, 29, 1605826) was dissolved in 10 mL of DMSO, and the solution was cooled to 0°C. 4.40 mmol of n-butyllithium (5.5 mL, 1.6 M hexane solution) was added to the reaction mixture, and the mixture was stirred at room temperature for 1 hour. The mixture was cooled to 0°C, and 0.83 mL (4.4 mmol) of di-tert-butylphosphine chloride was added. The mixture was refluxed for 48 hours. After the reaction mixture cooled, pure water was added to precipitate the solid. The precipitate was filtered, and the resulting solid was dried under vacuum at 100°C to obtain PN. 3 P-PIM ligand.

[0024] (2) Preparation of PN 3 P-PIM-Ru: 100 mg PN 3 P-PIM ligand was dissolved in DMSO with 7.5 mg of tris(triphenylphosphine)carbonyl ruthenium chloride, stirred at 65°C for 12 h, cooled to room temperature, and then 0.9 mg of potassium tert-butoxide was added and stirred at room temperature for 2 h to obtain PN dissolved in DMSO solution. 3 P-PIM-Ru catalyst.

[0025] (3) Add deionized water to the above mixture solution to dissolve PN 3 The P-PIM-Ru catalyst was precipitated, centrifuged, washed, and dried for later use.

[0026] Example 2: Using PN 3 The P-PIM-Ru catalyst, used for the catalytic hydrogen production from formic acid at 100°C, includes the following steps: (1) Dissolve 80g of sodium bicarbonate in 700ml of water to prepare a saturated sodium bicarbonate solution for later use. (2) Dissolve 589 mg of cesium formate in 1 mL of 99% formic acid to form a formic acid / cesium formate mixed solution for later use; (3) Weigh 30 mg of the PN obtained in Example 1 3 The P-PIM-Ru catalyst was dissolved in 5 ml of DMSO solution, and the stirring speed was set to 700 rpm until homogeneous.

[0027] (4) Place the system in an oil bath and heat it to 100°C. After stabilizing for 15 minutes, add 0.25 ml of the formic acid / cesium formate mixed solution prepared in step (2) into the system using a syringe. Collect the generated gas by water displacement and record the change in gas production over time.

[0028] (5) After gas production is completed, calculate the catalyst conversion frequency (TOF) and hydrogen yield.

[0029] Example 3: Using PN 3 The P-PIM-Ru catalyst is used for the catalytic hydrogen production of formic acid at 110°C. The process includes the following steps: the heating to 100°C in step (4) of Example 2 is changed to 110°C, and the other steps are the same as in Example 2.

[0030] Example 4: Using PN 3 The P-PIM-Ru catalyst is used for the catalytic hydrogen production of formic acid at 120°C. The process includes the following steps: the heating temperature in step (4) of Example 2 is changed from 100°C to 120°C, and the other steps are the same as in Example 2.

[0031] Example 5: Using PN 3 The P-PIM-Ru catalyst is used for the catalytic hydrogen production of formic acid at 130°C. The following steps are included: the heating to 100°C in step (4) of Example 2 is changed to 130°C, and the other steps are the same as in Example 2.

[0032] Example 6: Using PN 3 Formic acid hydrogen production experiments were conducted using P-PIM-coordinated tris(triphenylphosphine)carbonyl ruthenium chloride as a control, including the following steps: (1) Dissolve 80g of sodium bicarbonate in 700ml of water to prepare a saturated sodium bicarbonate solution for later use. (2) Dissolve 589 g of cesium formate in 1 mL of 99% formic acid to form a formic acid / cesium formate mixed solution for later use; (3) Weigh 2.5 mg of tris(triphenylphosphine)carbonyl ruthenium chloride and dissolve it in 5 ml of DMSO solution. Set the stirring speed to 700 rpm and stir until homogeneous.

[0033] Steps (4) and (5) are the same as in Example 2. Table 1. PN prepared in Examples 2-6 3 A summary table of the formic acid hydrogen production effects of P-PIM-Ru catalyst Group catalyst Temperature (°C) Yield (%) <![CDATA[TOFmax(h -1 )]]> Example 2 <![CDATA[PN 3 P-PIM-Ru]]> 100 90 2261 Example 3 <![CDATA[PN 3 P-PIM-Ru]]> 110 95 6102 Example 4 <![CDATA[PN 3 P-PIM-Ru]]> 120 98 9781 Example 5 <![CDATA[PN 3 P-PIM-Ru]]> 130 98 10127 Example 6 <![CDATA[RuH(CO)(PPh3)3]]> 120 23 306 Table 1 shows that the reaction temperature has a significant effect on PN 3 The P-PIM-Ru catalyst has a significant impact on the rate of hydrogen production from formic acid; when the reaction temperature is above 120℃, the TOFmax can reach 9000 h⁻¹. -1 The above demonstrates high activity. Compared to not adding PN... 3 Small molecule RuH(CO)(PPh3) of p-PIM ligand 3， PN 3The catalytic activity of the P-PIM-Ru catalyst was significantly improved.

[0034] Example 7: PN 3 The recycling of P-PIM-Ru catalysts includes the following steps: (1) Add 6 ml of deionized water to the catalytic system for the production of hydrogen from formic acid in Example 4 to allow the catalyst to precipitate, and then centrifuge to separate the catalyst. (2) The separated PN 3 P-PIM-Ru was dissolved in a small amount of dimethyl sulfoxide solution, and then 8 ml of deionized water was added to precipitate the solid, which was then separated by centrifugation.

[0035] (3) The obtained solid is dried to obtain the recovered PN. 3 P-PIM-Ru catalyst (4) Add 5 ml of DMSO solution to the recovered catalyst, sonicate and stir to dissolve, and repeat the formic acid hydrogen production experiment according to Example 4. Calculate the hydrogen yield and the conversion number TON value to determine the stability of the catalyst.

[0036] Table 2. PN recycled in Example 7 3 P-PIM-Ru catalyst performance table Loop count Yield TON 0 98% 5980 1 98% 12980 2 99% 17012 3 97% 23950 4 98% 30980 5 98% 35890 6 98% 41790 7 96% 47987 8 95% 53980 9 96% 60210 10 94% 63850 As shown in Table 2, PN 3 The P-PIM-Ru catalyst showed no significant decrease in activity during ten cycles, with hydrogen yields consistently above 95% and total TON exceeding 60,000, demonstrating the effectiveness of this P-PIM-Ru catalyst. 3 The P-PIM-Ru catalyst exhibits recyclability and good stability.

[0037] From the above, we can conclude that: 1. In this invention, the catalyst ligand is a modified microporous polymer (PIM), which exhibits superior chemical tunability compared to other polymers. A PN3P-type pincer structure can be formed on the framework through precise chemical modification. This structure endows the ligand with a strong coordination ability with ruthenium. Simultaneously, the PIM material is soluble or semi-soluble in dimethyl sulfoxide (DMSO), making the reaction a quasi-homogeneous system, which facilitates sufficient contact between the active sites and the substrate. In practical applications, this catalyst can efficiently catalyze the decomposition of formic acid to produce hydrogen within a temperature range of 333K–423K. When the reaction temperature is 393K (120℃), the maximum time-of-flight (TOF) can reach 9781 h⁻. 1 It exhibits extremely high catalytic activity; and by adjusting the reaction temperature, the type of additives (such as preferably cesium formate), and other conditions, the catalytic performance can be flexibly controlled to meet the needs of different scenarios.

[0038] In this invention, the PN3P tridentate pincer structure in the catalyst ligand forms a strong coordination bond with metallic ruthenium, significantly improving the structural stability of the catalyst and effectively preventing the loss of metal active centers. Compared with the difficulty in recovering traditional small-molecule Pincer catalysts, this catalyst, based on a self-porous polymer support, can be recovered through a simple "dissolution and desorption" method: after the reaction, adding a poor solvent such as deionized water to the system allows the catalyst to precipitate and be separated by centrifugation. After two dissolution and desorption cycles, washing, and drying, it can be reused. Experiments show that in 10 catalytic cycles, the hydrogen yield of this catalyst remains above 94%, the total conversion number (TON) exceeds 60,000, and the activity does not show a significant decrease, perfectly solving the problem of small-molecule catalyst recovery and significantly reducing long-term operating costs.

[0039] In this invention, the catalyst preparation process is clear and easy to operate: PN3P-PIM ligand is prepared by reacting 2,4-diamino-1,3,5-triazine-functionalized PIM (DATPIM) with di-tert-butylphosphine chloride, then coordinated with ruthenium salt in DMSO and treated with a strong alkali to obtain the target catalyst. The entire process requires no complex equipment. The recovery process only requires adding a poor solvent (such as deionized water) to the reaction system to precipitate the catalyst, which can then be reused after centrifugation, dissolution, and drying. The process involves few steps and is time-efficient. This simple preparation and recovery process has low equipment requirements, is suitable for large-scale production and industrial application, and provides a feasible path for the practical application of formic acid hydrogen storage technology.

[0040] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the term "comprising" or any other variations thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A recoverable pincer catalyst based on a self-porous polymer, characterized in that: The catalyst is a phosphine-grafted 2,4-diamino-1,3,5-triazine-functionalized microporous polymer based on a self-microporous polymer-based clamp ligand support PN3P-PIM, with the following chemical structure: 。 2. The Pincer catalyst based on a self-porous polymer and a recyclable pincer ligand as described in claim 1, characterized in that: In the catalyst, metallic Ru coordinates with the PN3P-PIM ligand at the PN3P structure to form PN 3 P-type recyclable Pincer ruthenium metal catalyst PN 3 The chemical structure diagram of P-PIM-Ru is shown below: 。 3. The Pincer catalyst based on a self-contained microporous polymer and its recyclable pincer ligand, as described in claim 1, and its preparation method thereof, characterized in that: The mass fraction of ruthenium is 0.01% to 5%, preferably 1.5%, and some 2,4-diamino-1,3,5-triazine may not participate in metal chelation.

4. The method for preparing a recyclable pincer catalyst based on a self-porous polymer as described in claim 1, characterized in that: include: Using PIM-1 as the starting material, it reacts with polycyanamide to generate 2,4-diamino-1,3,5-triazine-functionalized DATPIM, which then reacts with di-tert-butylphosphine chloride to generate PN. 3 P-PIM ligands; PN 3 The P-PIM ligand reacts with tris(triphenylphosphine)carbonyl ruthenium chloride, followed by treatment with a strong base, in dimethyl sulfoxide (DMSO) as the reaction solvent.

5. The Pincer catalyst based on a self-contained microporous polymer and its preparation method as described in claim 4, characterized in that: The strong base is potassium tert-butoxide.

6. An application of the Pincer catalyst based on a self-porous polymer and a recyclable pincer ligand as described in claim 1, characterized in that: The application involves catalyzing the release of hydrogen from formic acid in the range of 333K to 423K.

7. The application of the Pincer catalyst based on a self-porous polymer and a recyclable pincer ligand as described in claim 6, characterized in that: The reaction conditions were: temperature 393K, atmospheric pressure, solvent dimethyl sulfoxide, and additive cesium formate.

8. The application of the Pincer catalyst based on a self-porous polymer and a recyclable pincer ligand as described in claim 6, characterized in that: The formic acid includes formic acid with a high water content of 85%.

9. The method for recovering the Pincer catalyst based on a self-porous polymer and recyclable pincer ligand as described in claim 1, characterized in that: include: After the reaction is complete, a poor solvent is added to the system, the mixture is shaken to precipitate the solid, and then centrifuged. The separated solid is then dissolved in DMSO, and the poor solvent is added again to precipitate the solid. After two dissolutions and precipitates, the solid is washed, filtered, and dried to obtain the recovered PN. 3 P-PIM-Ru.

10. The Pincer catalyst based on a self-contained microporous polymer and its recyclable pincer ligand, as described in claim 9, and its preparation method and application, characterized in that: The unsuitable solvents include dichloromethane, trichloromethane, or deionized water.

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