A method for catalytic preparation of THFDCA from 5-methylfurfural

Abstract

The present application relates to the technical field of catalyst, and specifically provides a method for preparing tetrahydrofuran dicarboxylic acid (THFDCA) by catalysis from 5-methylfurfural (5-MF) as raw material. A kind of bifunctional catalyst based on MXene is used, and 5-MF is converted into furan dicarboxylic acid (FDCA) by oxidation reaction in water / 1,4-dioxane two-phase system;Then, FDCA is further converted into THFDCA in one step reaction with water as solvent. The present application effectively overcomes many limitations existing in the oxidation and hydrogenation process of biomass-derived compounds (such as 5-MF and FDCA) in the prior art, successfully solves the problems of dependence on alkali, need to use pure oxygen, harsh reaction conditions and low yield of catalytic reaction, and has important application value and popularization prospect.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more specifically to a method for the catalytic preparation of THFDCA using 5-methylfurfural. Background Technology

[0002] Biomass-derived 5-methylfurfural (5-MF) is a stable hydrophobic platform chemical and a promising precursor for the production of 2,5-furandicarboxylic acid (FDCA). However, conventional synthesis of FDCA from 5-MF typically requires harsh conditions, acidic solvents, and a multi-step pathway, resulting in low yields and environmental problems. Similarly, subsequent hydrogenation of FDCA to THFDCA also faces challenges such as inefficient catalysts and undesirable side reactions.

[0003] MXenes are two-dimensional transition metal carbides and nitrides obtained by selectively etching strongly bonded layered solids. MXenes Ti3C2T x Ti3C2T is a novel type of two-dimensional material with significant potential as a catalyst support due to its tunable structure, diverse end groups, and variable interlayer spacing. Its unique properties enable its application in hydrogenation, dehydrogenation, and electrochemical reactions. x It is highly susceptible to oxidation, especially in the presence of strong oxidizing agents, which limits its application in oxidation reactions.

[0004] This invention presents a multifunctional MXene catalyst that combines oxidation stability with hydrogenation capability. In a green solvent, the addition of metals such as Pd, Co, and Mn, as well as functional groups such as N-hydroxy-o-phenylenediamine (NHPI), promotes the oxidation of 5-MF to FDCA and the one-step conversion of FDCA to THFDCA. This strategy provides an efficient and sustainable pathway for biomass value-added and represents a significant advancement towards industrially feasible and renewable FDCA and THFDCA production. Summary of the Invention

[0005] To overcome the limitations of existing technologies in the oxidation and hydrogenation of biomass-derived compounds (such as 5-MF and FDCA), this invention provides a bifunctional catalyst based on MXene, capable of oxidizing 5-MF to FDCA in a water / 1,4-dioxane solvent, and further converting FDCA to THFDCA in water in one step. This invention solves a series of problems in existing technologies, such as dependence on alkali, requirement for pure oxygen, harsh reaction conditions, and low yields.

[0006] This invention uses modified MXene (e.g., Ti3C2T) x As a catalyst support, it is functionalized with amino and carboxyl groups to improve oxidation stability. This support can disperse metals (such as Pd, Co and Mn) combined with activators (such as NHPI).

[0007] The technical solution of the present invention is as follows:

[0008] An MXene-based catalyst comprising an NHPI group and a transition metal, wherein the transition metal is cobalt, manganese, or palladium.

[0009] Furthermore, the method for preparing the MXene-based catalyst includes the following steps:

[0010] S1. Polymer modification of MXene yields P@MX;

[0011] S2. P@MX was modified with cobalt and manganese to obtain CoMn-P@MX;

[0012] S3. Modify CoMn-P@MX with Car-NHPI to obtain NHPI@CoMn-P@MX;

[0013] S4. Pd-NHPI@CoMn-P@MX was obtained by modifying NHPI@CoMn-P@MX with palladium.

[0014] Furthermore, in step S1, the specific process for polymer modification is as follows:

[0015] (1) Wet etching: Ti3AlC2 (MAX phase) powder is etched in hydrofluoric acid solution to obtain Ti3C2T x (MXene);

[0016] (2) Surface functionalization modification: Ammonia solution is added to the product of step (1) to introduce amino-terminal groups into the MXene layer;

[0017] (3) Heat treatment: The mixture from step (2) is heat treated to obtain a dark powder with amine functionalized surface groups;

[0018] (4) Synthesis of polymer P by carbodiimide-assisted amidation: In an acetonitrile solution containing citric acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI) and hydroxybenzotriazole (HOBt) are added and reacted for a period of time, followed by the addition of melamine and a reaction for a period of time to obtain polymer P.

[0019] (5) Preparation of polymer-modified MXene: EDCI and HOBt are dispersed in an acetonitrile solution of polymer P to obtain solution A; MXene is dispersed in acetonitrile to form solution B; solution B is added to solution A and reacted to covalently graft the polymer onto the MXene after heat treatment in step (3) through an amidation reaction to obtain gray powder P@MX of polymer-functionalized MXene.

[0020] MXene is a two-dimensional material derived from the MAX phase. The MAX phase is a layered ceramic with the general formula Mn+1AXn, where M is a transition metal, A is a main group element, and X is carbon. The MAX phase combines the properties of both metals and ceramics and is a precursor to MXene. MXene can be prepared by selectively removing the A layer, typically using hydrofluoric acid or similar etching methods. This material has a two-dimensional structure with functional groups such as -OH, -O, or -F on its surface, enhancing its surface activity and demonstrating high practicality in catalyst applications. The MAX phase is Ti3AlC2, and MXene is Ti3C2T. x (Tx = -OH, -NH2, F).

[0021] Preferably, in step (1), the etching step specifically involves: slowly introducing 1-3g of Ti3AlC2 (MAX phase) powder into a 30-50wt% hydrofluoric acid solution in 50ml of ice bath; magnetically stirring the mixture at 30-50℃ for 12-36h; after etching, collecting the material, centrifuging at 3000-7000 rpm for 3-7min per cycle, and repeatedly washing with deionized water until the suspension reaches a neutral pH.

[0022] Preferably, in step (1), the etching step is as follows: 2g of Ti3AlC2 (MAX phase) powder is slowly introduced into 50ml of 40wt% hydrofluoric acid solution in an ice bath; the mixture is magnetically stirred at 40℃ for 24h; after etching, the collected material is centrifuged at 5000 rpm for 5min per cycle and washed repeatedly with deionized water until the suspension reaches a neutral pH of 6-7.

[0023] Etching the MAX phase with hydrofluoric acid (HF) is a crucial step in MXene synthesis, primarily serving to selectively remove A-layer elements (such as aluminum) from the parent MAX structure. This process transforms the three-dimensionally tightly bound MAX phase into a two-dimensional layered MXene structure, while simultaneously generating surface end groups (such as -OH, -F, and -O), thereby enhancing the material's chemical reactivity and functional properties. A-layer removal not only facilitates the exfoliation into few-layer or monolayer MXenes but also preserves the integrity of the transition metal carbide or nitride (MX) layer, retaining its unique electronic, catalytic, and adsorption properties, making it suitable for applications such as energy storage, catalysis, and sensing.

[0024] To selectively remove the A layer from the MAX phase to prepare MXene, various etching strategies have been developed, with the specific method chosen depending on the reaction conditions and the intended use of the resulting MXene. Among these methods, hydrofluoric acid (HF) etching is the most commonly used and yields the highest. HF is chosen because it introduces predominantly -F and -OH groups as surface end groups on the MXene sheets. These groups serve as ideal anchoring sites for subsequent surface functionalization (such as the introduction of amine groups), significantly improving the efficiency of downstream modification. The concentration of HF, reaction temperature, and reaction time were determined through multiple experiments to ensure reproducibility and optimal MXene quality.

[0025] Preferably, in step (2), the functionalization modification step specifically involves: adding 40 mL of ammonia solution to the slurry from step (1), shaking the mixture for 5-15 min, and ultrasonically treating it at ambient temperature for 40-80 min; centrifuging the mixture at 3000-4000 rpm for 10-30 min to remove unpeeled Ti3C2T. x The particles, and the resulting suspension contained amination of Ti3C2T x The nanosheets are then subjected to ultrasonic treatment again for 40-80 minutes under a nitrogen-protected atmosphere.

[0026] Preferably, in step (2), the functionalization modification step specifically involves: adding 40 mL of ammonia solution (adjusted to pH 9) to the slurry from step (1), shaking the mixture for 10 min, and ultrasonically treating it at ambient temperature for 60 min; centrifuging the mixture at 3500 rpm for 20 min to remove unpeeled Ti3C2T. x The particles, and the resulting suspension contained amination of Ti3C2T x The nanosheets were then subjected to ultrasonic treatment again for 60 minutes under a nitrogen-protected atmosphere.

[0027] The amino-functionalization of the MXene surface using an ammonia solution in step (2) has several important applications. First, it significantly enhances the oxidation resistance of MXene. Studies have shown that MXene oxidation begins at the edges and outer layers and gradually spreads to the inner layers, a process accelerated by the presence of surface hydroxyl groups. Replacing these hydroxyl groups with amino functional groups significantly improves its antioxidant chemical stability. Second, since the purpose of surface modification is to attach polymer layers containing carboxylic acid groups, the presence of amino groups allows for the formation of very stable amide bonds, which are much stronger than ester bonds formed at the hydroxyl end surfaces. This surface modification also affects the interlayer spacing, as evidenced by the shift of the (002) XRD peak to a lower angle, indicating the successful introduction of nitrogen-containing functional groups and an increase in the d-interlayer spacing according to Bragg's law. The increased interlayer spacing facilitates polymer intercalation, with the polymer acting as a binder to connect the MXene sheets, thereby improving the mechanical properties of the catalyst—a key factor in ensuring the reliability of the shielding material.

[0028] Preferably, in step (3), the heat treatment step is as follows: the obtained mixture is transferred to a 100mL Teflon-lined stainless steel autoclave and kept at 60-80℃ for 4-6h; after heat treatment, the product is recovered by centrifugation at 8000-12000rpm, and then repeatedly washed with deionized water until the pH value reaches neutral; the delaminated amination MXene nanosheets are collected and freeze-dried to prevent re-aggregation, resulting in a dark powder with amine functionalized surface groups.

[0029] Preferably, in step (3), the heat treatment step is as follows: the obtained mixture is transferred to a 100 mL Teflon-lined stainless steel autoclave and kept at 70 °C for 5 h; after heat treatment, the product is recovered by centrifugation at 10000 rpm and then repeatedly washed with deionized water until the pH value reaches neutral; the delaminated amination MXene nanosheets are collected and freeze-dried to prevent re-aggregation, resulting in a dark powder with amine functionalized surface groups.

[0030] The purpose of step (3) heat treatment is to promote the amination reaction on the MXene surface and to facilitate the separation of the layered structure of the MXene nanosheets. Heat treatment increases the surface energy and mobility of the amino groups, enabling them to effectively adhere to the MXene surface while maintaining the integrity of the layered structure.

[0031] The selection of heat treatment temperature and time in step (3) aims to balance sufficient surface amination with the prevention of MXene degradation or unnecessary oxidation. Lower temperatures may result in incomplete amination, while higher temperatures may disrupt the layered structure or accelerate oxidation. A heat treatment duration of 4–6 hours ensures sufficient penetration of ammonia into the aqueous solution and stability of the amino functional groups. Choosing the above-mentioned suitable heat treatment temperature and time is beneficial for achieving a uniform and stable amino-functionalized surface, promoting the separation of the MXene layered structure and preventing recombination, maintaining the mechanical and structural properties of MXene, and generating a final powder with high performance and active surface sites suitable for further modification or polymer attachment.

[0032] Preferably, in step (4), the specific steps for obtaining polymer P are as follows: 1.5-2.5g of citric acid is dissolved in 20ml of acetonitrile, and 0.5-1.5g of EDCI and 0.6-1.0g of HOBt are added simultaneously. The mixture is stirred at room temperature for 40-80min until a homogeneous solution is formed. Then, 1.0-1.5g of melamine is added and stirred at ambient temperature for 12-36h to obtain a white precipitate. The precipitate is washed sequentially with water and methanol and dried in an oven at 70-90℃ for 8-16h to obtain polymer P.

[0033] Preferably, in step (4), the specific steps for obtaining polymer P are as follows: 1.92g of citric acid is dissolved in 20ml of acetonitrile, and 0.92g of EDCI and 0.80g of HOBt are added at the same time. The mixture is stirred at room temperature for 60min until a homogeneous solution is formed. Then, 1.26g of melamine is added and stirred at ambient temperature for 24h to obtain a white precipitate. The precipitate is washed with water and methanol in sequence and dried in an oven at 80℃ for 12h to obtain polymer P.

[0034] The reaction involves the formation of an amide bond between the carboxyl group of citric acid and the amino group of melamine, yielding a polymer structure that can subsequently be grafted onto the MXene surface. The amounts of citric acid, EDCI, HOBt, and melamine were selected to ensure optimal stoichiometry between the reactants and to achieve a complete and homogeneous reaction; these amounts represent the best and most optimized choices.

[0035] Preferably, in step (5), the modification step specifically involves: dispersing 0.8-1.2g of polymer P in 20mL of acetonitrile and stirring vigorously; then adding 0.7-1.0g of EDCI and 0.6-0.8g of HOBt and stirring at room temperature for 40-80min to form solution A; dispersing 0.6-1.0g of MXene after heat treatment in step (3) in 10mL of acetonitrile and stirring with a strong magnetic field for 20-40min to form solution B; then adding solution B to solution A and stirring the mixture at room temperature for 6-10h to covalently graft the polymer onto MXene through an amidation reaction; washing multiple times with ethanol and then centrifuging with deionized water to separate the obtained solid; drying at 70-90℃ to obtain a gray powder P@MX of polymer-functionalized MXene.

[0036] Preferably, in step (5), the modification step is as follows: 1.0 g of polymer P is dispersed in 20 mL of acetonitrile and stirred vigorously; then, 0.85 g of EDCI and 0.70 g of HOBt are added and stirred at room temperature for 1 h to form solution A; 0.80 g of MXene after heat treatment in step (3) is dispersed in 10 mL of acetonitrile and stirred with a strong magnetic force for 30 min to form solution B; then solution B is added to solution A and the mixture is stirred at room temperature for 8 h to allow the polymer to be covalently grafted onto MXene through an amidation reaction; the solid is washed multiple times with ethanol and then centrifuged with deionized water; the solid is dried at 80 °C to obtain a gray powder P@MX of polymer-functionalized MXene.

[0037] As a preferred option, a cobalt-manganese modified polymer functionalized MXene composite material CoMn-P@MX is further used. Cobalt and manganese are added to the polymer functionalized MXene matrix, and the synergistic effect of the bimetallic components and the covalently grafted polymer framework is utilized to improve catalytic activity and stability.

[0038] The simultaneous presence of cobalt and manganese ions on the polymer-modified MXene substrate plays a crucial role in enhancing the performance of the NHPI group. These two metals, cobalt and manganese, combine with functional groups in the covalently grafted polymer framework to produce a significant synergistic effect, which promotes electron transfer and provides more active sites for oxidation reactions. Specifically, cobalt functions by providing an efficient electron transfer pathway, while manganese functions by promoting stable redox cycles, thereby simultaneously improving the catalyst's activity and stability. Therefore, the ternary synergistic effect among cobalt, manganese, and the NHPI group not only enhances oxidation activity but also significantly improves the catalyst's structural stability and durability.

[0039] Further, in step S2, P@MX is modified using cobalt and manganese to obtain CoMn-P@MX; the specific preparation method of the cobalt-manganese modified polymer functionalized MXene composite material CoMn-P@MX is as follows:

[0040] (a) Dispersion: Cobalt acetate tetrahydrate and manganese acetate tetrahydrate are added to a solution containing P@MX;

[0041] (b) Hydrothermal treatment: The above mixture is hydrothermally treated for a period of time;

[0042] (c) Washing and drying.

[0043] Preferably, in step (a), 1.0 g of P@MX is added to a beaker containing a mixture of 30 mL of water and ethanol (where the volume ratio of water to ethanol is 1:1); the mixture is sonicated for 20-40 min (preferably 30 min) to achieve uniform dispersion; subsequently, under continuous stirring, 0.10-0.14 g of cobalt acetate tetrahydrate Co(OAc)2·4H2O and 0.10-0.14 g of manganese acetate tetrahydrate Mn(OAc)2·4H2O are added; more preferably, 0.124 g of cobalt acetate tetrahydrate Co(OAc)2·4H2O and 0.125 g of manganese acetate tetrahydrate Mn(OAc)2·4H2O are added.

[0044] In step (a), the ratio of cobalt to manganese is adjusted to be approximately equal. Choosing a higher ratio would impair the catalytic activity in the hydrogenation reaction, as the primary catalytic action under these conditions is performed by palladium nanoparticles. Conversely, using a lower ratio may result in reduced catalytic activity.

[0045] Preferably, in step (b), the mixture obtained in step (a) is transferred to a 75 mL Teflon-lined stainless steel autoclave and heated at 70-90°C for 12-36 h, more preferably at 80°C for 24 h.

[0046] In step (b), mild thermal conditions (relatively low temperature and long reaction time) are chosen to effectively capture and stabilize the metals at the active sites of the catalyst. Since cobalt acetate and manganese acetate cannot be effectively reduced to metal nanoparticles by sodium hydride (NaBH4), these metals are introduced in their divalent forms, cobalt(II) and manganese(II), rather than in their nanoparticle form. The reaction conditions are carefully designed to prevent catalyst structure degradation while ensuring the stable and uniform incorporation of these metal ions within the catalyst support.

[0047] Preferably, in step (c), the precipitate obtained in step (b) is repeatedly washed with ethanol and deionized water to remove unreacted substances and byproducts, thereby obtaining the cobalt-manganese polymer-functionalized MXene composite material CoMn-P@MX; the washed product is a black solid, which is collected and freeze-dried to prevent aggregation, preferably for 24 hours.

[0048] Further, Car-NHPI (4-carboxy-N-hydroxyphthalimide) was prepared by adding excess hydroxylamine hydrochloride to a pyridine solution of tricarboxylic acid to react and obtain the hydroxylamine-modified product Car-NHPI, which was then used to modify CoMn-P@MX.

[0049] Specifically, 1.0 g of tricarboxylic acid (TMA) was thoroughly ground into a fine powder using ceramic slurry and transferred to a reaction flask. Then, 40 mL of pyridine was added as a solvent, followed by the addition of excess hydroxylamine hydrochloride (NH2OH·HCl) to the solution. The reaction mixture was placed under reflux for 12 h. After the reaction was completed, the mixture was acidified to form a white solid precipitate. The precipitate was collected and dried under vacuum at 70 °C for 12 h to obtain Car-NHPI.

[0050] To introduce NHPI carboxyl groups onto the catalyst surface and achieve its heterogeneity, tricarboxylic acid TMA was used. Because this compound contains a carboxylic acid group, it can readily bind to the amine groups present on the catalyst surface via an amidation reaction. However, the conversion of the anhydride group requires the participation of pyridine and hydroxyammonium chloride to generate the NHPI carboxyl group.

[0051] Further, in step S3, CoMn-P@MX is modified with Car-NHPI to obtain NHPI@CoMn-P@MX. The ethanol solution containing CoMn-P@MX is mixed with the ethanol solution containing Car-NHPI, EDCI, and HOBt, and the mixture is stirred to obtain the modified product NHPI@CoMn-P@MX.

[0052] As a preferred method, the specific modification method is as follows: 0.8-1.2g of CoMn-P@MX is dispersed in 10mL of ethanol and ultrasonically treated for 0.5-1.5h to obtain a uniform suspension C; 0.8-1.2g of Car-NHPI, 0.6-1.0g of EDCI, and 0.8-1.0g of HOBt are dissolved in 15mL of ethanol respectively, and stirred continuously at room temperature for 20-40min to form a mixture D; then C and D are mixed and reacted under stirring for 9-15h, resulting in the formation of a precipitate; the solid product is collected by centrifugation and dried at 40-80℃.

[0053] As a preferred option, the amount of CoMn-P@MX was 1g, the ultrasonic treatment time was 1h, the amount of Car-NHPI was 1.0g, the amount of EDCI was 0.80g, the amount of HOBt was 0.90g, the continuous stirring time at room temperature was 30min, and the reaction of C and D was carried out under stirring for 12h. The solid product was dried at 60℃.

[0054] The raw material consumption and process parameters of the above process are the best and most optimized selections after multiple experiments.

[0055] In this modification reaction, the carboxyl group of Car-NHPI undergoes amidation with the amine functional group present in polymer P, resulting in the covalent anchoring of the NHPI-based functional group on the surface of the CoMn-P@MX catalyst. This modification enhances the catalytic surface chemistry and provides active oxygen transfer groups suitable for oxidation reactions.

[0056] Further, in step S4, NHPI@CoMn-P@MX is modified with palladium to obtain Pd-NHPI@CoMn-P@MX.

[0057] Palladium was chosen for several key reasons: it exhibits excellent selectivity in the hydrogenation of furan compounds and carbon-carbon double bonds, and can readily reduce double bonds within the furan ring. Furthermore, this patent study revealed that the presence of palladium nanoparticles plays a crucial role in the activation of NHPI groups during radical oxidation reactions.

[0058] Preferably, 0.8-1.2 g of NHPI@CoMn-P@MX powder and 0.2-0.4 g of sodium chloropalladium(II) were dissolved in 25 mL of deionized water, and then sonicated for 20-40 min to ensure uniform dispersion. Subsequently, under ice bath conditions, 10 mL of freshly prepared NaBH4 solution (0.1 M) was added dropwise to the suspension to promote in-situ reduction of palladium. The reaction mixture was then stirred at room temperature for 8-12 h. After completion, the obtained solid product was collected and thoroughly washed several times with deionized water to remove residual salts. Finally, the material was dried at 70-90 °C to obtain a dark-colored Pd-NHPI@CoMn-P@MX powder.

[0059] Preferably, 1.0 g of NHPI@CoMn-P@MX powder and 0.3 g of sodium chloropalladium(II) were dissolved in 25 mL of deionized water and then sonicated for 30 min to ensure uniform dispersion. Subsequently, 10 mL of freshly prepared NaBH4 solution (0.1 M) was added dropwise to the suspension under ice bath conditions to promote in-situ reduction of palladium. The reaction mixture was then stirred at room temperature for 10 h. After completion, the obtained solid product was collected and thoroughly washed several times with deionized water to remove residual salts. Finally, the material was dried at 80 °C to obtain a dark-colored Pd-NHPI@CoMn-P@MX powder, under which the highest yield was achieved.

[0060] This invention also protects the application of the above-mentioned catalyst Pd-NHPI@CoMn-P@MX for the catalytic preparation of THFDCA from 5-methylfurfural.

[0061] The catalytic reaction is as follows:

[0062] (1) Preparation of 2,5-furandicarboxylic acid (FDCA): In the presence of 5-MF, Pd-NHPI@CoMn-P@MX catalyst and solvent (water / 1,4-dioxane mixed solvent), the reactor was sealed and oxygen was used as the oxidant to react and obtain FDCA; reaction pressure range: 2-4MPa, reaction temperature range: 120-140℃, reaction time: 0-6 hours, reactant ratio (5-MF : catalyst : solvent): 1mmol : 0.1-0.2g : 10mL.

[0063] (2) Hydrogenation to prepare THFDCA adipic acid: FDCA, Pd-NHPI@CoMn-P@MX catalyst and water (as solvent) were added to the reactor, the reactor was sealed and the hydrogenation reaction was carried out to obtain THFDCA. The reaction pressure was 2-4 MPa, the reaction temperature was 60-140 ℃, and the reaction time was 0-3.5 h. The ratio of FDCA, Pd-NHPI@CoMn-P@MX catalyst and water was 1 mmol : 0.1-0.3 g : 5 mL.

[0064] Preferably, in step (1), the reaction pressure is 3 MPa, the temperature is 130 ℃, the reaction time is 5 h, the ratio of 5-MF to catalyst is 1 mmol: 0.15 g, and the reaction solvent is a mixture of water and 1,4-dioxane with a volume ratio (H2O:DX) of 9:1.

[0065] Preferably, in step (2), the reaction pressure is 3 MPa, the temperature range is 130 °C, the reaction time is 3 h, and the ratio of FDCA, Pd-NHPI@CoMn-P@MX catalyst, and water is 1 mmol: 0.10 g: 5 mL.

[0066] In both of the above reaction steps, water plays a crucial role in improving the efficiency of the catalytic system. The addition of water is significant in both oxidation and hydrogenation reactions, as it increases the yields of both products.

[0067] In the oxidation step, adding water can accelerate the free radical reaction and enhance the dispersibility of the catalyst, thereby reducing the formation of byproducts.

[0068] In the hydrogenation step, water plays a key role as a solvent in improving the solubility of FDCA, while also contributing to good catalyst dispersion and increasing reaction yield.

[0069] The beneficial technical effects of the present invention are as follows: The present invention provides a bifunctional catalyst based on MXene for oxidizing 5-MF to FDCA in a water / 1,4-dioxane mixed solvent, and for converting FDCA to THFDCA in water in one step, thereby overcoming the limitations of existing technologies in the oxidation and hydrogenation processes of biomass-derived compounds (such as 5-MF and FDCA). Attached Figure Description

[0070] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0071] Figure 1 FTIR spectra of pristine MXene, MAX phase, and Pd-NHPI@MnCo-P@MX;

[0072] Figure 2 MAX phase (Ti3AlC2), original MXene (Ti3C2T) x (T) x XRD patterns of (-OH, -NH2, F), MX and Pd-NHPI@MnCo-P@MX;

[0073] Figure 3 TGA curves of MX, P-NHPI and Pd-NHPI@MnCo-P@MX;

[0074] Figure 4 Schematic diagram of the path by which 5-MF generates THFDCA. Figure 5 Optimized reaction for the oxidation of 5-MF to FDCA

[0075] Figure 6 Optimized reaction for hydrogenating FDCA to THFDCA Detailed Implementation

[0076] To more clearly illustrate the purpose, technical solution, and advantages of this invention, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments. The drawings illustrate only exemplary embodiments of the invention and are not intended to limit its implementation. This invention can be implemented in various forms, and its design concept and core technology are not limited to the embodiments shown in the drawings. These embodiments are provided to facilitate understanding of the principles, structure, and function of this invention by those skilled in the art, thereby enabling them to better master and apply its technical solutions. The terminology used in this specification is only for describing specific embodiments and does not constitute a limitation of the invention.

[0077] Example 1

[0078] Preparation of Pd-NHPI@CoMn-P@MX catalyst:

[0079] (1) Preparation of Ti3C2NH2 (aminated MXene)

[0080] 2g of Ti3AlC2 (MAX phase) powder was slowly introduced into 50 mL of 40wt% hydrofluoric acid solution in an ice bath; the mixture was magnetically stirred at 40°C for 24 h; after etching, the collected material was centrifuged at 5000 rpm for 5 min per cycle and washed repeatedly with deionized water until the suspension reached a neutral pH of 6-7.

[0081] Add 40 mL of ammonia solution (adjusted to pH 9) to the above slurry, shake the mixture well for 10 min, and sonicate at ambient temperature for 60 min; centrifuge the mixture at 3500 rpm for 20 min to remove unpeeled Ti3C2T. x The particles, and the resulting suspension contained amination of Ti3C2T x The nanosheets were then subjected to ultrasonic treatment again for 60 minutes under a nitrogen-protected atmosphere.

[0082] The obtained mixture was transferred to a 100 mL Teflon-lined stainless steel autoclave and kept at 70 °C for 5 h. After heat treatment, the product was recovered by centrifugation at 10,000 rpm and then repeatedly washed with deionized water until the pH value reached neutral. The delaminated amination MXene nanosheets were collected and freeze-dried to prevent re-aggregation, resulting in a dark powder Ti3C2NH2 with amine functionalized surface groups.

[0083] (2) Preparation of P@MX (polymer-modified MXene)

[0084] The specific steps to obtain polymer P are as follows: 1.92 g of citric acid was dissolved in 20 mL of acetonitrile, and 0.92 g of EDCI and 0.80 g of HOBt were added simultaneously. The mixture was stirred at room temperature for 60 min until a homogeneous solution was formed. Then, 1.26 g of melamine was added, and the mixture was stirred at ambient temperature for 24 h to obtain a white precipitate. The precipitate was washed successively with water and methanol, and dried in an oven at 80 °C for 12 h to obtain polymer P.

[0085] 1.0 g of polymer P was dispersed in 20 mL of acetonitrile and stirred vigorously. Then, 0.85 g of EDCI and 0.70 g of HOBt were added, and the mixture was stirred at room temperature for 1 h to form solution A. 0.80 g of Ti3C2NH2 was dispersed in 10 mL of acetonitrile and stirred with a strong magnetic field for 30 min to form solution B. Solution B was then added to solution A, and the mixture was stirred at room temperature for 8 h to allow the polymer to be covalently grafted onto MXene via an amidation reaction. The mixture was washed several times with ethanol and then centrifuged with deionized water to separate the solid. The solid was dried at 80 °C to obtain a gray powder, P@MX, of polymer-functionalized MXene.

[0086] (3) Preparation of CoMn-P@MX

[0087] Add 1.0 g P@MX to a beaker containing 30 mL of a mixed solvent of water and ethanol (the volume ratio of water to ethanol is 1:1); sonicate the mixture for 30 min to achieve uniform dispersion; then, under continuous stirring, add 0.124 g cobalt acetate tetrahydrate Co(OAc)2·4H2O and 0.125 g manganese acetate tetrahydrate Mn(OAc)2·4H2O.

[0088] The resulting mixture was transferred to a 75 mL Teflon-lined stainless steel autoclave and heated at 80 °C for 24 h.

[0089] The precipitate was repeatedly washed with ethanol and deionized water to remove unreacted substances and byproducts, thus obtaining the cobalt-manganese polymer-functionalized MXene composite material CoMn-P@MX. The washed product was a black solid and was collected and freeze-dried for 24 hours to prevent aggregation.

[0090] (4) Preparation of 4-carboxy-N-hydroxyphthalimide (Car-NHPI)

[0091] 1.0 g of tricarboxylic acid TMA was thoroughly ground into a fine powder using ceramic slurry and transferred to a reaction flask. Then, 40 mL of pyridine was added as a solvent, followed by the addition of excess hydroxylamine hydrochloride (NH2OH·HCl). The reaction mixture was placed under reflux for 12 h. After the reaction was completed, the mixture was acidified to form a white solid precipitate. The precipitate was collected and dried under vacuum at 70 °C for 12 h to obtain Car-NHPI.

[0092] (5) Preparation of NHPI@CoMn-P@MX

[0093] 1 g of CoMn-P@MX was dispersed in 10 mL of ethanol and sonicated for 1 h to obtain a homogeneous suspension C; 1.0 g of Car-NHPI, 0.80 g of EDCI, and 0.90 g of HOBt were dissolved in 15 mL of ethanol respectively and stirred continuously at room temperature for 30 min to form mixture D; then C and D were mixed and reacted with stirring for 12 h, resulting in the formation of a precipitate; the solid product was collected by centrifugation and dried at 60 °C.

[0094] (6) Preparation of Pd-NHPI@CoMn-P@MX

[0095] 1.0 g of NHPI@CoMn-P@MX powder and 0.3 g of sodium chloropalladium(II) were dissolved in 25 mL of deionized water and then sonicated for 30 min to ensure uniform dispersion. Subsequently, 10 mL of freshly prepared NaBH4 solution (0.1 M) was added dropwise to the suspension under ice bath conditions to promote in-situ reduction of palladium. The reaction mixture was then stirred at room temperature for 10 h. After completion, the obtained solid product was collected and thoroughly washed several times with deionized water to remove residual salts. Finally, the material was dried at 80 °C to obtain a dark-colored Pd-NHPI@CoMn-P@MX powder.

[0096] The performance of the prepared catalyst was measured, such as... Figure 1-3 ,in Figure 1 This is an FTIR spectrum; Figure 2 XRD pattern; Figure 3 This is the TGA curve.

[0097] from Figure 1 It can be seen that in the Fourier transform infrared spectrum of the Pd-NHPI@CoMn-P@MX catalyst (red), the 1700-1750 cm⁻¹... -1 The band at 1632 cm⁻¹ indicates the presence of C=O stretching vibration, which is attributed to the carbonyl group in NH₂PI and citric acid. -1 The peak at 3200-3600 cm⁻¹ is attributed to the CN stretching vibration, indicating the presence of melamine and NHPI groups in the catalyst structure. -1The changes in the regions indicate hydrogen interactions between the OH and NH groups and the polymer structure, leading to the preliminary conclusion that the citric acid and melamine polymers have been appropriately immobilized on the MXene surface. These results suggest that the functionalization of MXene has been successfully completed.

[0098] XRD was used to study catalysts and the MAX-to-MXene and re-MX transformation processes. Figure 2 This demonstrates that most of the aluminum in the MAX phase is removed during the etching process, while the diffraction peaks corresponding to the (002) plane are observed in Ti3C2T. x The angle shifted from 9.62° to a lower angle (9.02°). This peak is the original MXene (Ti3C2T). x The characteristic index peak of MXene, shifting to a lower angle (8.62°), indicates the presence of amine (MX) groups on the MXene surface. The catalyst also contains various NH groups, which causes the diffraction peak to shift to 7.34°. These results demonstrate the structural stability of the catalyst support and the effectiveness of its modification.

[0099] Thermogravimetric analysis (TGA) was performed to confirm the growth of the polymer on the MX layer. Furthermore, this analysis demonstrated the thermal stability of the MX, P, and Pd-NHPI@MnCo-P@MX catalysts at temperatures related to the reaction conditions. Figure 3 MX exhibits excellent thermal stability, showing almost no weight loss up to 800 °C, confirming its stability as a catalyst support. P experienced more significant weight loss between 200 and 500 °C, which is related to the degradation of the organic structure and polymer. Furthermore, Pd-NHPI@CoMn-P@MX showed a gradual weight loss, indicating the decomposition of the organic components and polymer structure, while the significant residue indicates the presence of a stable inorganic phase.

[0100] In the following embodiments, by means of Figure 4 The reaction pathway diagram shows the preparation of THFDCA starting from 5-MF.

[0101] Example 2

[0102] To determine the optimal oxidation conditions for 5-methylfurfural, the reaction was carried out using 1 mmol of 5-MF. The reaction was conducted at oxygen pressures of 2, 3, and 4 MPa in the presence of 0.1, 0.15, and 0.2 g of catalyst (Pd-NHPI@CoMn-P@MX catalyst prepared in Example 1). Water and 1,4-dioxane were used as solvents in volume ratios of 10:0, 0:10, 1:9, 9:1, 5:5, and 3:7, with reaction times of 4, 5, and 6 hours. The effect of temperature on the reaction was also investigated at 120, 130, and 140 °C.

[0103] These conditions were designed to evaluate and optimize the catalyst performance and oxidation rate. The relevant results are shown in Table 1 and Figure 5.

[0104] Table 1. Optimization of reaction conditions for the production of FDCA from 5-MF

[0105] ;

[0106] The data in Table 1 was used to determine the optimal conditions.

[0107] The results showed that increasing the temperature (from 100 °C to 140 °C) increased the conversion of 5-MF from 57.1% to 94.2%, but did not significantly improve the yield of FDCA (Table 1, entries 1-5). At temperatures below 130 °C, although the conversion of 5-MF was high (88.6%), the formation of FDCA remained limited. This indicates that the activation energy was insufficient to drive the oxidation reaction to completion. When the temperature was increased to 140 °C, the yield of FDCA did not increase. This trend may be attributed to the occurrence of parallel side reactions, over-oxidation, or thermal decomposition of FDCA at high temperatures, all of which collectively reduced the selectivity of the target product. At 130 °C, increasing the catalyst dosage from 0.10 g to 0.15 g improved the conversion of 5-MF (Table 1, entry 6). This improvement can be attributed to the increased number of active sites available for catalysis, thereby promoting the sequential oxidation steps of aldehyde and alcohol functional groups.

[0108] Under similar conditions, extending the reaction time from 4 hours to 5 hours yielded FDCA yields of 13.4% and 19.7%, respectively, corresponding to conversions of 95.0% and 96.3% (Table 1, Items 6 and 7). This indicates that extending the reaction time is necessary to achieve complete oxidation of these intermediates to FDCA. Given the very limited solubility of 5-MF in the aqueous phase, while almost all reaction intermediates (MFA, HMF, THFDCA, DFF, and FFCA) are soluble in water, the role of the solvent becomes one of the key factors affecting the reaction process. A suitable solvent system should be able to effectively dissolve 5-MF, intermediates, and FDCA, while also contributing to improved catalyst dispersibility and ultimately enhancing catalytic performance. In this regard, the binary H2O / DX solvent system can simultaneously meet all these requirements. Therefore, using only H2O or DX as a solvent will result in insufficient dissolution of reactants, leading to incomplete reaction pathways (Table 1, Items 7-10).

[0109] Optimize oxidation reaction conditions, such as Figure 5 As shown, the effect of different reaction parameters on the yield of FDCA.

[0110] in Figure 5 The reaction conditions are as follows:

[0111] (a) Effect of reaction time (reaction conditions: 5-MF (1 mmol), solvent (10 mL), catalyst (0.15 g), oxygen (3 MPa), 130 °C);

[0112] (b) Effect of temperature (reaction conditions: 5-MF (1 mmol), solvent (10 mL), catalyst (0.15 g), oxygen (3 MPa), reaction time 5 hours);

[0113] (c) Effect of solvent ratio (reaction conditions: 5-MF (1 mmol), catalyst (0.15 g), oxygen (3 MPa), reaction time 5 h, temperature 130 °C);

[0114] (d) Effect of catalyst dosage (reaction conditions: 5-MF (1 mmol), solvent (10 mL), oxygen (3 MPa), reaction time 5 h, temperature 130 °C);

[0115] (e) Effect of oxygen pressure (reaction conditions: 5-MF (1 mmol), solvent (10 mL), catalyst (0.15 g), reaction time 5 h, temperature 130 °C);

[0116] Once the optimal reaction conditions are determined, the reaction pathway needs to be clarified to understand the reaction mechanism and its intermediates. First, the effect of reaction time on the oxidation of 5-MF was investigated. Figure 5 a) In the initial stage of the reaction, the inherent reactivity differences of different functional groups in the 5-MF molecule determine the order of oxidation. Due to the higher reactivity of the -CHO group, its oxidation is preferential over that of the -CH3 group. This observation is consistent with theoretical predictions and is verified by the formation of the main oxidation products MFA (25.0%) and HMFCA (3.0%) at 30 minutes, indicating that the oxidation of the -CHO group is preferential. In the subsequent 90-minute reaction follow-up, MFA (14.0%), HMFCA (19.2%), FFCA (17.0%), and FDCA (5.0%) were obtained, further revealing the main reaction pathway. If the reaction proceeds mainly through the HMF pathway, HMF accumulation and the corresponding large amount of DFF formation should be observed. However, the experimental data do not conform to this; the concentration of HMFCA is significantly higher in the 90-150 minute time interval. This difference strongly suggests that HMF formation is a secondary and non-dominant pathway, not the main reaction route, a conclusion further supported by the absence of detected DFF products during the reaction.

[0117] Therefore, analysis of the product distribution over 180 minutes allows for more accurate prediction of the dominant reaction pathway. Extending the reaction time favors further oxidation of the intermediates, ultimately increasing the yield of FDCA. This observation indicates that the oxidation reaction proceeds via two possible pathways, ultimately converging to form FDCA. Notably, extending the reaction time to 300 minutes yields the highest FDCA yield (80.0%).

[0118] Subsequently, the effect of temperature on the oxidation of 5-MF was investigated in the temperature ranges of 120, 130, and 140 °C. Figure 5 b). High temperatures favor the generation of numerous free radicals, thereby increasing the oxidation rate of the -CH3 group. Simultaneously, increased temperature significantly accelerates side reactions, such as ring cleavage, decarboxylation, and decarbonylation, exceeding the rate of the main reaction. The composition of the solvent system has a profound impact on the selectivity of the oxidation reaction. A binary H2O:DX mixed solvent, especially at a volume ratio of 9:1, yields the highest FDCA yield, while using pure DX or pure water alone results in lower FDCA yields of 20.2% and 3.0%, respectively. The synergistic effect between these two solvents significantly enhances the selectivity of FDCA. Other effective factors affecting reaction performance include the amount of catalyst and the applied O2 pressure (…). Figure 5 (d, 5e). Experimental results show that when the catalyst dosage and O2 pressure exceed the optimal values, the FDCA yield or catalytic performance does not significantly improve, indicating that the reaction is close to completion under these conditions.

[0119] Example 3

[0120] In the hydrogenation reaction of FDCA in an aqueous solvent, 1 mmol of FDCA was reacted with different amounts of catalyst (0.1, 0.2, 0.3 g), and the mass ratio of FDCA (as substrate) to catalyst was determined to be 1:1, 5:1, and 10:1.

[0121] The reaction temperatures were 60, 80, 100, 120, 130, and 140 °C, the hydrogen pressures were 2, 3, and 4 MPa, and the catalyst dosages were 0.1, 0.2, and 0.3 g. The effects of reaction time (0–3.5 h) on catalyst performance and hydrogenation efficiency were investigated. The relevant results are shown in Table 2 and Figure 6.

[0122] Table 2. Optimization of reaction conditions for the production of THFDCA from FDCA

[0123] ;

[0124] The data in Table 2 were used to determine the optimal conditions.

[0125] This table illustrates the effect of different reaction conditions on the conversion and yield of FDCA to THFDCA hydrogenation. As shown in the table, extending the reaction time significantly improved the conversion of FDCA and the yield of THFDCA. For example, at 100°C, a hydrogen pressure of 2 MPa, and a catalyst dosage of 0.1 g, extending the reaction time from 2 hours to 4 hours increased the FDCA conversion from 30% to 49% and the yield from 5% to 15%, indicating that a longer reaction time provides more opportunities for the hydrogenation reaction to complete. Meanwhile, increasing the reaction temperature significantly improved the product yield. Comparing 100°C and 130°C, at a hydrogen pressure of 2 MPa and a catalyst dosage of 0.1 g, the THFDCA yield increased from 10% to 52%. However, excessively high temperatures (such as 140°C) could cause the product yield to decrease to 47%, although the conversion was close to complete, suggesting that side reactions may increase significantly at high temperatures.

[0126] On the other hand, hydrogen pressure and catalyst dosage also significantly affect the efficiency of the hydrogenation reaction. At 130°C and with a catalyst dosage of 0.1 g, increasing the hydrogen pressure from 2 MPa to 3 and 4 MPa resulted in THFDCA yields of 52%, 84%, and 80%, respectively, with near-complete conversion. Furthermore, increasing the catalyst dosage from 0.1 g to 0.2 g increased the conversion to 99%, but the yield slightly decreased to 73%, possibly due to increased side reactions. Overall, these data indicate that the optimal conditions for THFDCA production are 130°C, a hydrogen pressure of 3 MPa, a catalyst dosage of 0.1 g, and a reaction time of 3 hours, under which the highest yield is achieved.

[0127] Combination Figure 6 ,in Figure 6 The reaction parameters for (a)-(e) are as follows:

[0128] (a) Effect of reaction temperature on the reaction (reaction conditions: FDCA (1 mmol), H2O (5 mL), catalyst (0.1 g), H2 (3 MPa), reaction time 3 h);

[0129] (b) Effect of reaction time on the reaction (reaction conditions: FDCA (1 mmol), H2O (5 mL), catalyst (0.1 g), H2 (3 MPa), 130 °C);

[0130] (c) Effect of catalyst dosage on the reaction (reaction conditions: FDCA (1 mmol), H2O (5 mL), H2 (3 MPa), 130 °C, reaction time 3 h);

[0131] (d) Effect of hydrogen pressure on the reaction (reaction conditions: FDCA (1 mmol), H2O (5 mL), catalyst (0.1), reaction time 3 h, 130 ℃).

[0132] (e) Effect of FDCA to catalyst mass ratio on the reaction (reaction conditions: H2O (5 mL), H2 (3 MPa), catalyst (0.1 g), reaction time 3 h, 130 °C).

[0133] The effects of operating parameters on the catalytic hydrogenation of FDCA to THFDCA were investigated. With increasing reaction temperature, the conversion of FDCA gradually increased, reaching near-complete conversion in the range of 130-140 °C. The yield of THFDCA showed a non-linear dependence on temperature, reaching a maximum at 130 °C, indicating that this temperature is the optimal condition for the selective hydrogenation of FDCA. Figure 6 a).

[0134] Extending the reaction time significantly improves the conversion rate of FDCA, achieving complete consumption of FDCA after approximately 3-3.5 h at 130 ℃. Under these conditions, the selectivity of THFDCA reaches its highest value, and the carbon balance is good, indicating that side reactions are effectively suppressed. Figure 6 b).

[0135] Both catalyst dosage and hydrogen pressure exhibit nonlinear effects on reaction performance, with the optimal conditions being a catalyst dosage of 0.1 g and a hydrogen pressure of 3 MPa, respectively. Excessive catalyst or excessively high hydrogen pressure leads to a decrease in selectivity and yield. Figure 6 c, d). Furthermore, studies on the substrate-to-catalyst ratio show that, due to the high palladium loading of the Pd-NHPI@CoMn-P@MX catalyst, the system maintains high conversion efficiency and catalytic activity even with increased FDCA feed. Figure 6 e).

[0136] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. An MXene-based catalyst, characterized in that: The catalyst contains NHPI groups and transition metals, wherein the transition metals are cobalt, manganese and palladium.

2. The method for preparing the catalyst according to claim 1, characterized in that: Includes the following steps: S1. Polymer modification of MXene yields P@MX; S2. P@MX was modified with cobalt and manganese to obtain CoMn-P@MX; S3. Modify CoMn-P@MX with Car-NHPI to obtain NHPI@CoMn-P@MX; S4. Pd-NHPI@CoMn-P@MX was obtained by modifying NHPI@CoMn-P@MX with palladium.

3. The preparation method according to claim 2, characterized in that: In step S1, the specific process for polymer modification is as follows: (1) Wet etching: Ti3AlC2 (MAX phase) powder was etched in hydrofluoric acid solution to obtain Ti3C2T x (MXene); (2) Surface functionalization modification: Ammonia solution is added to the product of step (1) to introduce amino-terminal groups into the MXene layer; (3) Heat treatment: The mixture from step (2) is heat treated to obtain a dark powder Ti3C2NH2(MX) with amine functionalized surface groups; (4) Synthesis of polymer P by carbodiimide-assisted amidation: In an acetonitrile solution containing citric acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCI) and hydroxybenzotriazole (HOBt) are added and reacted, followed by the addition of melamine to obtain polymer P. (5) Preparation of polymer-modified MX: EDCI and HOBt are dispersed in an acetonitrile solution of polymer P to obtain solution A; MX is dispersed in acetonitrile to form solution B; solution B is added to solution A and reacted to allow the polymer to be covalently grafted onto the MX after heat treatment in step (3) through an amidation reaction, resulting in gray powder P@MX of polymer-functionalized MX.

4. The preparation method according to claim 2, characterized in that: In step S2, the specific process for modification is as follows: (a) Dispersion: Cobalt acetate tetrahydrate and manganese acetate tetrahydrate are added to a solution containing P@MX; (b) Hydrothermal treatment: The above mixture is hydrothermally treated for a period of time; (c) Washing and drying.

5. The preparation method according to claim 2, characterized in that: In step S3, the specific modification process is as follows: the ethanol solution containing CoMn-P@MX is mixed with the ethanol solution containing Car-NHPI, EDCI, and HOBt, and the mixture is stirred and reacted to obtain the modified product NHPI@CoMn-P@MX, wherein Car-NHPI is obtained by reacting trimellitic anhydride with excess hydroxylamine hydrochloride.

6. The preparation method according to claim 2, characterized in that: In step S4, the specific process for modification is as follows: NHPI@CoMn-P@MX powder and sodium chloropalladium(II) were dissolved in deionized water and ultrasonically dispersed. Subsequently, under ice bath conditions, NaBH4 solution was added dropwise to promote the in-situ reduction reaction of palladium; then the mixture was washed and dried.

7. The application of the catalyst of claim 1 and the catalyst prepared by any one of the preparation methods of claims 2 to 6, characterized in that, Used to catalyze the preparation of THFDCA from 5-methylfurfural.

8. A method for the catalytic preparation of tetrahydrofuran dicarboxylic acid (THFDCA) using 5-methylfurfural, characterized in that: The catalyst described in claim 1, or the catalyst prepared by any of the preparation methods of claims 2 to 6, is used, wherein the oxidation reaction is carried out in a mixed solvent system consisting of water and 1,4-dioxane, and the hydrogenation reaction is carried out under conditions where water is used as the solvent.

9. The method as described in claim 8, characterized in that: The specific process of the reaction is as follows: (1) Preparation of 2,5-furandicarboxylic acid (FDCA): In the water / 1,4-dioxane binary system, the catalyst Pd-NHPI@CoMn-P@MX is added to 5-methylfurfural (5-MF), the reactor is sealed, and oxygen is used as the oxidant to obtain FDCA; (2) Preparation of THFDCA by hydrogenation: Hydrogen is introduced into FDCA, water and Pd-NHPI@CoMn-P@MX catalyst, the reactor is sealed, and hydrogenation reaction is carried out to obtain THFDCA.

10. The method as described in claim 9, characterized in that: In step (1), the reaction pressure range is 2-4 MPa, the reaction temperature range is 120-140℃, and the reaction time is 0-6 hours; the ratio of 5-MF to catalyst is 1 mmol : 0.1-0.2 g. In step (2), the reaction pressure range is 2-4 MPa, the temperature range is 60-140℃, the reaction time is 0-3.5 h, and the ratio of FDCA to catalyst to water (as solvent) is 1 mmol : 0.1-0.3 g : 5 mL. In a preferred embodiment, in step (1), the reaction pressure is 3 MPa, the reaction temperature is 130 °C, and the reaction time is 5 hours; the ratio of 5-MF: catalyst: solvent (water / 1,4-dioxane) is 1 mmol: 0.15 g: 10 mL. In step (2), the reaction pressure is 3 MPa, the temperature range is 130 °C, and the reaction time is 3 hours. The ratio of FDCA: Pd-NHPI@CoMn-P@MX catalyst to water (as solvent) is 1 mmol : 0.1 g : 5 mL.

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