Zirconium-nitrogen coordination polymer catalysts, methods of preparation, and use in selective reduction of biomass-based aldehyde ketone compounds

Abstract

The application discloses a novel zirconium-nitrogen coordination polymer catalyst, which has a porous structure and is prepared by a coordination self-assembly method at normal temperature from zirconium ions and non-cyclic nitrogen-containing organic ligands, only introduces Lewis acid-base sites, and does not introduce Brønsted acid sites. The presence of the Lewis acid-base sites can efficiently catalyze MPV transfer hydrogenation reaction of biomass-based aldehyde ketone compounds, the absence of the Brønsted acid sites can avoid side reactions such as etherification and acetalization, and the porous structure can greatly promote the mass and heat transfer processes during the reaction, and the synergistic effect between them further improves the yield and selectivity of the target product.

Description

Technical Field

[0001] This invention belongs to the field of new material preparation and application technology, specifically involving zirconium nitrogen coordination polymer catalysts, preparation methods, and their application in the selective reduction of biomass-based aldehyde and ketone compounds. Background Technology

[0002] As is well known, biomass, as a rich, widely distributed, and renewable green carbon resource in nature, plays a crucial role in the sustainable development of the chemical industry through its transformation into high-value-added fine chemicals. This transformation has also become a focal point of global scientific and technological competition and academic research. Biomass-based aldehydes and ketones occupy an important position in the entire biomass-based high-value-added chemical system. Their selective reduction products can be widely used in many fields such as pharmaceuticals, food, fragrances, energy, and materials. Therefore, conducting research on the selective reduction of biomass-based aldehydes and ketones has significant scientific value and practical implications. Typical biomass-based aldehydes and ketones, such as 5-hydroxymethylfurfural, furfural, benzaldehyde, cinnamaldehyde, cyclopentanone, cyclohexanone, and levulinic acid, often contain multiple active groups in their molecules, such as carbon-oxygen double bonds, carbon-carbon double bonds, ether bonds, and carboxyl groups. During the hydrogenation reduction of carbon-oxygen double bonds, competitive side reactions such as hydrogenolysis, decarbonylation, rearrangement, and ring opening often occur. Therefore, developing suitable catalytic strategies that prioritize the hydrogenation of carbon-oxygen double bonds while effectively suppressing further hydrogenation of carbon-carbon double bonds, ether bonds, and carboxyl groups is the core challenge for achieving efficient and selective reduction of biomass-based aldehydes and ketones.

[0003] Currently, the selective reduction pathways for biomass-based aldehydes and ketones mainly include traditional catalytic hydrogenation, electrocatalytic hydrogenation, photocatalytic hydrogenation, and biocatalytic hydrogenation. Compared with these methods, MPV catalytic transfer hydrogenation is a special selective reduction pathway. It often uses lower alcohols as hydrogen donors, does not rely on exogenous hydrogen, and exhibits excellent hydrogenation specificity for carbon-oxygen double bonds, thus demonstrating unique advantages in the selective reduction of biomass-based aldehydes and ketones. It should be noted that the key to this method lies in designing highly efficient and highly selective catalysts. In recent years, scientists have focused their research on zirconium metal-organic coordination polymer catalysts, such as Zr-PA (Angewandte Chemie International Edition, 2016, 54: 9399-9403), Zr-FDCA (ChemSusChem, 2017, 18: 1761-1770), Zr-CA (Chemical Engineering Journal, 2018, 352: 110-119), Zr-AIER (Chemical Communications, 2022, 58: 4067-4070), UIO-SO3H (Journal Energy Chemistry, 2022, 71: 411-417), Zr-PDAE (Fuel, 2023, 331: 125786), and Zr-PDDA (Fuel, 2025, 382: 133745). It should be noted that these catalysts all use organic acids as ligands and belong to the zirconium-oxygen coordination catalysts. Although they can achieve selective reduction of biomass-based aldehydes and ketones, their structures often contain not only Lewis acid-base sites but also certain uncoordinated Brønsted acidic sites. The presence of Brønsted acidic sites can significantly induce side reactions such as acetalization and etherification, thereby reducing the yield and selectivity of the target product. In addition, the synthesis of these catalysts generally requires expensive N,N-dimethylformamide as a deprotonating solvent, and the coordination reaction requires high reaction temperatures and long reaction times, which also increases the production cost and safety risks of the catalysts. Therefore, designing and constructing a zirconium metal-organic coordination polymer catalyst with higher activity, higher selectivity, and safety and economy remains very important. Summary of the Invention

[0004] The technical problem this invention aims to solve is that traditional zirconium-oxygen coordination polymer catalysts require harsh synthesis conditions and are prone to side reactions during the selective reduction of biomass-based aldehydes and ketones due to the presence of Brønsted acidic sites, leading to low yield, selectivity, and safety of the target product. This invention provides a novel zirconium-nitrogen coordination polymer catalyst synthesized under green and mild conditions. It contains only Lewis acid-base sites and no Brønsted acidic sites, enabling the selective reduction of biomass-based aldehydes and ketones via MPV catalytic transfer hydrogenation, while avoiding side reactions such as etherification and acetal formation.

[0005] The catalyst is formed by the self-assembly of zirconium salt and acyclic nitrogen-containing organic ligands through Zr-N coordination bonds to form a coordination network structure. The catalyst contains only Lewis acid-base sites and no Brønsted acid sites. The Zr in the zirconium salt... 4+ The ion coordinates with the nitrogen atom in the acyclic nitrogen-containing organic ligand, wherein the acyclic nitrogen-containing organic ligand does not contain carboxyl, phenolic hydroxyl, phosphonic acid, or sulfonic acid acidic functional groups.

[0006] The acyclic nitrogen-containing organic ligand is selected from one or more of hexamethylenetetramine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, N,N,N',N'-tetramethylethylenediamine, N,N-dimethylethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,6-hexanediamine, tris(2-aminoethyl)amine, and tris(2-dimethylaminoethyl)amine.

[0007] The zirconium salt is selected from one or more of zirconium tetrachloride, zirconium oxychloride, zirconium nitrate, zirconium sulfate, zirconium acetate, and zirconium isopropoxide.

[0008] The molar ratio of zirconium to nitrogen in the catalyst is 1:5-5:1, preferably 1:2-1:4.

[0009] The Lewis acid sites and Lewis base sites of the catalyst work synergistically in the catalytic reaction, and the amount of Brønsted acid in the catalyst is below the detection limit.

[0010] The catalyst exhibits characteristic absorption peaks at 1448 cm⁻¹, 1492 cm⁻¹, and 1610 cm⁻¹ in the pyridine infrared spectrum, and has no absorption peak at 1540 cm⁻¹.

[0011] The preparation method of the zirconium-nitrogen coordination polymer catalyst includes the following steps:

[0012] (1) Dissolve zirconium salt in ethanol solvent to prepare a zirconium salt solution with a concentration of 30-150 mmol / L;

[0013] (2) Dissolve the non-cyclic nitrogen-containing organic ligand in ethanol solvent to prepare a ligand solution with a concentration of 30-150 mmol / L;

[0014] (3) At room temperature, the zirconium salt solution and the ligand solution are mixed, and the molar ratio of zirconium salt to ligand is controlled to be 1:5~5:1. The mixture is stirred for 1-8 hours.

[0015] (4) Aging the reaction mixture at room temperature for 0.5-2 hours;

[0016] (5) Filter, wash, vacuum dry at 60-100°C for 6-24 hours, and pulverize to obtain the catalyst.

[0017] The ethanol solvent is anhydrous ethanol or 95% ethanol, and the preparation method does not use N,N-dimethylformamide, N,N-dimethylacetamide, triethylamine or dimethyl sulfoxide organic solvents.

[0018] The reaction temperature in step (3) is 15-30°C and the reaction time is 2-4 hours.

[0019] The vacuum drying temperature in step (5) is 80°C and the drying time is 12 hours.

[0020] In step (3), the molar ratio of zirconium salt to ligand is 1:2.

[0021] The preparation method further includes an activation step after step (5) of the catalyst, wherein the activation is carried out under vacuum at 100-200°C for 2-6 hours.

[0022] The zirconium-nitrogen coordination polymer catalyst is used in the Meerwein-Ponndorf-Verley transfer hydrogenation reaction of biomass-based aldehyde and ketone compounds. The catalyst selectively reduces the carbonyl group in the aldehyde and ketone compounds to an aldehyde or ketone group without catalyzing etherification or acetal side reactions.

[0023] The biomass-based aldehyde and ketone compounds are selected from one or more of 5-hydroxymethylfurfural, furfural, benzaldehyde, terephthalaldehyde, acetophenone, cyclohexanone, 2-cyclohexenone, acetopropionic acid, ethyl acetopropionate, vanillin, and 4-hydroxybenzaldehyde.

[0024] The hydrogen donor for the transfer hydrogenation reaction is a C2-C4 alcohol, preferably ethanol, n-propanol, isopropanol, n-butanol, or sec-butanol.

[0025] The conditions for the transfer hydrogenation reaction are: reaction temperature 110-180°C, reaction time 1-10 hours, catalyst dosage 10-60 wt% of substrate, and molar ratio of hydrogen donor to substrate 20:1-100:1.

[0026] The reaction is carried out in a closed reactor without the need for external hydrogen pressure.

[0027] The catalyst can be recovered by centrifugation or filtration after the reaction and can be recycled at least 5 times while retaining more than 95% of its catalytic activity.

[0028] The target product selectivity of the transfer hydrogenation reaction is greater than 95%, preferably greater than 98%.

[0029] The beneficial effects of this invention are:

[0030] 1) Zirconium-nitrogen coordination polymer catalysts have solved the side reaction problem caused by Brønsted acid sites in traditional zirconium-oxygen coordination catalysts through improved ligand design. In the zirconium-oxygen coordination system, organic ligands containing carboxyl, phenolic hydroxyl, phosphonic acid, or sulfonic acid groups react with Zr. 4 During coordination, acidic ligands are difficult to fully participate in coordination, resulting in residual acidic groups at the Zr coordination center that have not participated in coordination. These groups can catalyze side reactions such as etherification and acetal formation in the MPV reaction. In contrast, Zr-N coordination networks constructed using acyclic nitrogen-containing ligands such as hexamethylenetetramine do not contain dissociable protons, and the coordination process does not involve deprotonation, thus maintaining the absence of Brønsted acidic sites on the surface.

[0031] 2) The production process is simple and controllable, can be carried out at room temperature, is green and safe, and is easy to scale up and synthesize.

[0032] 3) Zirconium-nitrogen coordination polymer catalysts have excellent catalytic versatility, enabling various biomass-based aldehyde and ketone compounds such as 5-hydroxymethylfurfural and furfural to undergo MPV catalytic transfer hydrogenation reactions, while avoiding side reactions such as etherification and acetalization, thereby achieving the directional and selective preparation of the corresponding target products.

[0033] 4) The endogenous hydrogen system used does not require additional exogenous hydrogen donors or other reaction solvents. The reaction system has a simple composition, the reaction process is safe and stable, the yield and selectivity of the target product are high, and it is easy to separate and apply in subsequent processes. Attached Figure Description

[0034] Figure 1 The image shows the FT-IR spectrum of Zr-MHT (1:2) prepared in Example 1.

[0035] Figure 2 The image shows the Py-IR spectrum of Zr-MHT (1:2) prepared in Example 1.

[0036] Figure 3 This is the SEM image of Zr-MHT(1:2) prepared in Example 1.

[0037] Figure 4The image shows the TEM spectrum of Zr-MHT(1:2) prepared in Example 1.

[0038] Figure 5 This is the GC chromatogram of the selective reduction of 5-hydroxymethylfurfural to 2,5-furandiethanol catalyzed by Zr-MHT (1:2) in Example 4. Detailed Implementation

[0039] The technical concept of this invention is to use readily available and inexpensive ethanol as a medium to construct a zirconium-nitrogen coordination polymer catalyst with a porous structure by coordinating and self-assembling zirconium ions and acyclic nitrogen-containing ligands at room temperature through a coordination self-assembly reaction. The presence of Lewis acid-base sites catalyzes the MPV transfer hydrogenation reaction, while the absence of Brønsted acid sites avoids side reactions such as etherification and acetal formation. The porous structure significantly promotes mass and heat transfer during the reaction. The synergistic effect among these factors ensures the selective reduction of biomass-based aldehydes and ketones into corresponding high-value-added products.

[0040] In some specific embodiments of the present invention, the following technical solutions are included:

[0041] Zirconium-nitrogen coordination polymer catalysts use Zr as the active metal and acyclic nitrogen-containing ligands as organic ligands, and have a porous structure. The active metal and organic ligands are connected through a Zr-N coordination network, and electrons are transferred from Zr to N. The Zr-N coordination network does not contain Brønsted acidic sites.

[0042] The preparation method of zirconium-nitrogen coordination polymer catalyst includes the following steps:

[0043] A non-cyclic nitrogen-containing organic ligand is mixed with an organic solvent to obtain a first mixed solution; a zirconium salt is mixed with an organic solvent to obtain a second mixed solution; the first mixed solution is slowly added to the second mixed solution, and after reaction, the mixture is aged. The resulting precipitate is washed, dried, and pulverized to obtain the zirconium-nitrogen coordination polymer catalyst.

[0044] The aforementioned acyclic nitrogen-containing organic ligands do not contain organic acid groups;

[0045] The organic acidic groups include carboxyl groups, phenolic hydroxyl groups, phosphonic acid groups, or sulfonic acid groups.

[0046] The organic solvent is ethanol; the zircon salt is zirconium tetrachloride or zirconium nitrate, preferably zirconium nitrate; the nitrogen-containing ligand is hexamethylenetetramine, hexamethylenediamine, tetraethylenepentamine or bis(hexamethylene)triamine, preferably hexamethylenetetramine.

[0047] The concentration of the zirconium salt in the organic solvent is 30-150 mmol / L; the molar ratio of the zirconium salt to the acyclic nitrogen-containing organic ligand is 1:5 to 5:1; the reaction conditions are stirring at room temperature for 1-8 h, the aging conditions are standing at room temperature for 0.5-2 h, and the drying conditions are vacuum drying at 80°C for 8-24 h.

[0048] Application of zirconium-nitrogen coordination polymer catalysts in the selective reduction of biomass-based aldehydes and ketones.

[0049] The biomass-based aldehyde and ketone compounds are 5-hydroxymethylfurfural, furfural, 5-methylfurfural, benzaldehyde, p-methylbenzaldehyde, terephthalaldehyde, cinnamaldehyde, cyclopentanone, cyclohexanone, levulinic acid or methyl levulinate, and their target products are 2,5-furandiethanol, furfuryl alcohol, 5-methylfurfural alcohol, benzyl alcohol, p-methylbenzyl alcohol, terephthalaldehyde, cinnamyl alcohol, cyclopentanol, cyclohexanol, γ-valerolactone and γ-valerolactone.

[0050] The application includes the following steps: adding zirconium nitrogen coordination polymer catalyst, biomass-based aldehyde and ketone compound and alcohol in-situ hydrogen donor into a reaction vessel and heating and stirring to react.

[0051] The hydrogen donor is one of ethanol, n-propanol, isopropanol, n-butanol, or sec-butanol, preferably isopropanol; the amount of the biomass-based aldehyde-ketone compound is 1-5 wt% of the amount of the hydrogen donor, the amount of the zirconium-nitrogen coordination polymer catalyst is 10-60 wt% of the amount of the biomass-based aldehyde-ketone compound, the reaction temperature is 110-180°C, and the reaction time is 1-10 h.

[0052] Example 1

[0053] 10 mmol of hexamethylenetetramine was added to 150 mL of ethanol solvent, and 20 mmol of zirconium nitrate was added to 150 mL of ethanol solvent. The mixtures were stirred separately for 10 min under ultrasonic assistance. The hexamethylenetetramine solution was slowly added to the zirconium nitrate solution, and the mixture was stirred vigorously at room temperature for 6 h, followed by aging for 1 h. The solid precipitate was filtered and washed repeatedly with ethanol 6 times. The washed solid precipitate was vacuum dried at 80°C for 12 h and then ground to approximately 200 mesh to obtain zirconium-nitrogen coordination polymer 1, abbreviated as Zr-MHT(1:2). FT-IR characterization analysis showed that… Figure 1 ), 473cm -1 The peak at this location is attributed to the stretching vibration of the Zr-N bond, indicating that Zr and N ions successfully coordinated in Zr-MHT (1:2), and Lewis acid-base sites were introduced. Meanwhile, Py-IR characterization analysis shows that... Figure 2 ), 1448cm -11492cm -1 and 1610cm -1 The peaks at the specified locations are all attributed to the interaction between Lewis acidic sites and pyridine, indicating that Zr-MHT(1:2) does not contain Brønsted acidic sites. Additionally, SEM ( Figure 3 ) and TEM ( Figure 4 Characterization analysis revealed that Zr-MHT(1:2) possesses a distinct porous structure. Next, 0.2 g of 5-hydroxymethylfurfural, 19.8 g of isopropanol, and 0.08 g of Zr-MHT(1:2) were added to a 50 mL reactor. After sealing, the reactor was purged with nitrogen five times consecutively. The temperature was raised to 140°C at 600 rpm, and after 2 h of reaction, the conversion rate of 5-hydroxymethylfurfural was 97.1%, the yield of 2,5-furandiethanol was 92.6%, and the selectivity of 2,5-furandiethanol was 95.4%. This indicates that the Lewis acid-base sites in Zr-MHT(1:2) can effectively catalyze the MPV transfer hydrogenation reaction, and the absence of Brønsted acidic sites largely prevents side reactions. Simultaneously, the porous structure of the catalyst promotes mass and heat transfer. Their synergistic effect successfully and selectively reduces 5-hydroxymethylfurfural to 2,5-furandiethanol.

[0054] Example 2

[0055] 5 mmol of hexamethylenetetramine was added to 150 mL of ethanol solvent, and 20 mmol of zirconium nitrate was added to 150 mL of ethanol solvent. The mixture was stirred for 10 min under ultrasonic assistance. The hexamethylenetetramine solution was slowly added to the zirconium nitrate solution, and the mixture was stirred vigorously at room temperature for 6 h. Then it was allowed to stand for 1 h. The solid precipitate was separated by filtration and washed repeatedly with ethanol 6 times. The washed solid precipitate was dried under vacuum at 80°C for 12 h and then ground to about 200 mesh to obtain zirconium nitrogen coordination polymer 2, abbreviated as Zr-MHT(1:4). Next, 0.2 g of 5-hydroxymethylfurfural, 19.8 g of isopropanol and 0.08 g of Zr-MHT (1:4) were added to a 50 mL reactor. After sealing, the air in the reactor was continuously purged with nitrogen five times. The temperature was raised to 140°C at a stirring speed of 600 rpm. After reacting for 2 h, the conversion rate of 5-hydroxymethylfurfural was 98.3%, the yield of 2,5-furandiethanol was 93.5%, and the selectivity of 2,5-furandiethanol was 95.1%.

[0056] Example 3

[0057] 20 mmol of hexamethylenetetramine was added to 150 mL of ethanol solvent, and 20 mmol of zirconium nitrate was added to 150 mL of ethanol solvent. The mixtures were stirred separately for 10 min with ultrasonic assistance. The hexamethylenetetramine solution was slowly added to the zirconium nitrate solution, and the mixture was stirred vigorously at room temperature for 6 h. The mixture was then allowed to stand for 1 h. The solid precipitate was separated by filtration and washed repeatedly with ethanol 6 times. The washed solid precipitate was dried under vacuum at 80°C for 12 h and then ground to about 200 mesh to obtain zirconium nitrogen coordination polymer 3, abbreviated as Zr-MHT(1:1). Next, 0.2 g of 5-hydroxymethylfurfural, 19.8 g of isopropanol, and 0.08 g of Zr-MHT (1:1) were added to a 50 mL reactor. After sealing, the air in the reactor was continuously purged with nitrogen five times. The temperature was raised to 140°C at a stirring speed of 600 rpm. After reacting for 2 h, the conversion rate of 5-hydroxymethylfurfural was 92.4%, the yield of 2,5-furandiethanol was 86.7%, and the selectivity of 2,5-furandiethanol was 93.8%. This indicates that changing the ratio of zirconium metal and acyclic nitrogen-containing organic ligands significantly affects the catalytic activity of the zirconium-nitrogen coordination polymer catalyst.

[0058] Example 4

[0059] 0.2 g of 5-hydroxymethylfurfural, 19.8 g of isopropanol, and 0.1 g of Zr-MHT (1:2) were added to a 50 mL reactor. After sealing, the reactor was purged with nitrogen five times consecutively. The temperature was raised to 140°C with stirring at 600 rpm. After reacting for 2 h, the conversion rate of 5-hydroxymethylfurfural was 100%, the yield of 2,5-furandiethanol was 98.7%, and the selectivity of 2,5-furandiethanol was 98.7%. Figure 5 This indicates that optimizing reaction conditions and increasing the amount of catalyst can increase Lewis acid-base sites, further promoting the formation of the target product. More importantly, after separating Zr-MHT (1:2) from the reaction solution, washing and drying it, and then carrying out the next MPV transfer hydrogenation reaction under the above reaction conditions, the results showed that after five cycles of Zr-MHT (1:2), the conversion rate of HMF and the yield of BHMF could still reach 99.2% and 96.3%, respectively, demonstrating good catalytic stability.

[0060] To better demonstrate the superiority of zirconium-nitrogen coordination polymer catalysts in improving the yield and selectivity of 2,5-furandiethanol, the catalytic results of Example 4 were compared with those of catalysts in the literature, as shown in Table 1. Table 1 and related literature show that, since the comparative catalysts such as Zr-MOF, UiO-66, DUT-69, Zr-FDCA, Zr-PDAF, Zr-LS, Zr-DTPA, Zr-GAF, Zr-ATMP, and Zr-AZN all use organic acids containing carboxyl, phenolic hydroxyl, phosphonic acid, or sulfonic acid groups as ligands, Zr and the organic acidic groups are coordinated through Zr-O bonds. The uncoordinated organic acidic groups result in a certain amount of Brønsted acidic sites on the catalyst. Their presence can promote side reactions such as etherification and acetalization to some extent, thereby reducing the yield and selectivity of 2,5-furandiethanol. Furthermore, the Zr-MHT(1:2) provided by this invention uses acyclic nitrogen-containing ligands and does not contain Brønsted acidic sites. This avoids the problems associated with zirconium-oxygen coordination catalysts and is beneficial for improving the yield and selectivity of 2,5-furandiethanol. It is also worth noting that the catalytic activity of Zr-MHT(1:2) is significantly higher than that of Zr-MM prepared using cyclic ligand melamine. This is likely because the catalyst prepared with acyclic ligands does not exhibit intracyclic conjugation effects, which can further optimize the electron cloud density and electron transfer rate at Lewis acid-base sites, reduce the reaction energy barrier in the MPV transfer hydrogenation process, and thus significantly enhance the catalytic activity of Zr-MHT(1:2).

[0061] Table 1

[0062]

[0063] Examples 5-14

[0064] The following examples demonstrate the catalytic effect of Zr-HMT(1:2) prepared in Example 1 on the selective reduction and conversion of other biomass-based aldehydes and ketones, such as furfural, 5-methylfurfural, benzaldehyde, p-methylbenzaldehyde, terephthalaldehyde, cinnamaldehyde, cyclopentanone, cyclohexanone, levulinic acid, or methyl levulinate. The specific results are shown in Table 2. As can be seen from Table 2, in addition to catalyzing the conversion of 5-hydroxymethylfurfural to 2,5-furandiethanol, Zr-HMT(1:2) can also efficiently catalyze the conversion of other biomass-based aldehydes and ketones, such as furfural, 5-methylfurfural, benzaldehyde, p-methylbenzaldehyde, terephthalaldehyde, cinnamaldehyde, cyclopentanone, cyclohexanone, levulinic acid, or methyl levulinate, into corresponding high-value-added products. This further illustrates the excellent catalytic activity of Zr-HMT(1:2).

[0065] Table 2

[0066]

[0067] References:

[0068] [1] Chem. Eng. J., 2025, 526: 171169.

[0069] [2] Appl. Catal. A: Gen., 2020, 602: 117719.

[0070] [3] Catal. Lett., 2019, 149: 1845 - 1855.

[0071] [4] ChemSusChem, 2017, 18: 1761 - 1770.

[0072] [5] Fuel, 2023, 331: 125786.

[0073] [6] Appl. Catal. B: Environ., 2019, 248: 31 - 43.

[0074] [7] Waste Biomass Valori., 2020, 11: 3485 - 3499.

[0075] [8] Fuel, 2022, 328: 125233.

[0076] [9] Mol. Catal., 2022, 524: 112253.

[0077]

[10] Sustain. Energy Fuels, 2021, 5: 4069 - 4079.

[0078]

[11] Chem. Eng. J., 2023, 474: 145656。

Claims

1. A zirconium-nitrogen coordination polymer catalyst, characterized in that, The catalyst is formed by the self-assembly of zirconium salt and acyclic nitrogen-containing organic ligands through Zr-N coordination bonds to form a coordination network structure. The catalyst contains only Lewis acid-base sites and no Brønsted acid sites. The Zr in the zirconium salt... 4+ The ion coordinates with the nitrogen atom in the acyclic nitrogen-containing organic ligand, wherein the acyclic nitrogen-containing organic ligand does not contain carboxyl, phenolic hydroxyl, phosphonic acid, or sulfonic acid acidic functional groups.

2. The catalyst according to claim 1, characterized in that, The acyclic nitrogen-containing organic ligand is selected from one or more of hexamethylenetetramine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, N,N,N',N'-tetramethylethylenediamine, N,N-dimethylethylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,6-hexanediamine, tris(2-aminoethyl)amine, and tris(2-dimethylaminoethyl)amine.

3. The catalyst according to claim 1 or 2, characterized in that, The zirconium salt is selected from one or more of zirconium tetrachloride, zirconium oxychloride, zirconium nitrate, zirconium sulfate, zirconium acetate, and zirconium isopropoxide; the molar ratio of zirconium to nitrogen in the catalyst is 1:5-5:1, preferably 1:2-1:

4.

4. A method for preparing the zirconium-nitrogen coordination polymer catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Dissolve zirconium salt in ethanol solvent to prepare a zirconium salt solution with a concentration of 30-150 mmol / L; (2) Dissolve the non-cyclic nitrogen-containing organic ligand in ethanol solvent to prepare a ligand solution with a concentration of 30-150 mmol / L; (3) At room temperature, the zirconium salt solution and the ligand solution are mixed, and the molar ratio of zirconium salt to ligand is controlled to be 1:5~5:

1. The mixture is stirred for 1-8 hours. (4) Aging the reaction mixture at room temperature for 0.5-2 hours; (5) Filter, wash, vacuum dry at 60-100℃ for 6-24h, and pulverize to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that, The ethanol solvent is anhydrous ethanol or 95% ethanol, and the preparation method does not use N,N-dimethylformamide, N,N-dimethylacetamide, triethylamine or dimethyl sulfoxide organic solvents.

6. The preparation method according to claim 4, characterized in that, The reaction temperature in step (3) is 15-30℃ and the reaction time is 2-4h; the molar ratio of zirconium salt to ligand is 1:1-3.

7. The preparation method according to any one of claims 4, characterized in that, The preparation method further includes an activation step after step (5) of the catalyst, wherein the activation is carried out under vacuum conditions at 100-200°C for 2-6 hours.

8. The use of the zirconium-nitrogen coordination polymer catalyst according to any one of claims 1-7 in the Meerwein-Ponndorf-Verley transfer hydrogenation reaction of biomass-based aldehydes and ketones, characterized in that, The catalyst selectively reduces the carbonyl group in the aldehyde-ketone compound to an aldehyde or ketone group, without catalyzing etherification or acetal side reactions.

9. The application according to claim 8, characterized in that, The biomass-based aldehyde and ketone compounds are selected from one or more of 5-hydroxymethylfurfural, furfural, benzaldehyde, terephthalaldehyde, acetophenone, cyclohexanone, 2-cyclohexenone, levulinic acid, ethyl levulinate, vanillin, and 4-hydroxybenzaldehyde; The hydrogen donor for the transfer hydrogenation reaction is a C2-C4 alcohol, preferably ethanol, n-propanol, isopropanol, n-butanol, or sec-butanol.

10. The application according to claim 8, characterized in that, The conditions for the transfer hydrogenation reaction are: reaction temperature 110-180℃, reaction time 1-10h, catalyst dosage 10-60 wt% of substrate, and molar ratio of hydrogen donor to substrate 20:1~100:1.

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