An amphiphilic thickened oil viscosity-reducing catalyst based on a defect-regulated MOF, a preparation method and application thereof

Abstract

This invention discloses an amphiphilic heavy oil viscosity-reducing catalyst based on defect-regulated MOFs, its preparation method, and its application. The amphiphilic MOF-based catalyst is composed of MOF-NH4+ with oxygen vacancy defects. 2 The substrate and the grafted MOF-NH through chemical bonds 2 The substrate surface is composed of amphiphilic polymers; the amphiphilic polymers include hydrophilic and hydrophobic structural units, and the mass composition of the amphiphilic MOF-based catalyst is as follows: MOF-NH 2 The substrate comprises 50%-75%, and the amphiphilic polymer comprises 15%-35%. The catalyst provided by this invention significantly improves the pyrolysis efficiency of heavy oil, optimizes the distribution of pyrolysis products, and promotes the deep pyrolysis reaction of heavy oil heavy components, thereby improving the quality of pyrolysis products.

Description

An amphiphilic heavy oil viscosity-reducing catalyst based on defect-regulated MOF, its preparation method and application Technical Field

[0001] This invention relates to an amphiphilic heavy oil viscosity-reducing catalyst based on defect-regulated MOF, its preparation method and application, belonging to the field of catalytic pyrolysis technology. Background Technology

[0002] As a crucial pillar of the global energy system, oil holds irreplaceable strategic value in ensuring national energy security and economic development. However, with the gradual decline of conventional crude oil reserves, heavy oil, with its enormous reserve potential (accounting for over 70% of global remaining oil reserves), is gradually becoming a key target for the oil industry. my country possesses abundant and widely distributed heavy oil resources, but over 80% of these are medium-deep, extra-heavy oil reservoirs buried at depths exceeding 800 meters. The crude oil in these reservoirs generally has a viscosity exceeding 50,000 mPa·s (50℃), with gum and asphaltenes content often exceeding 40%, resulting in extremely poor fluidity and posing severe challenges to efficient extraction and resource utilization. Under traditional technologies, heavy oil extraction faces problems such as high energy consumption, low efficiency, and significant environmental pressure, urgently requiring the development of new green and efficient extraction technologies.

[0003] Currently, heavy oil extraction technologies are mainly divided into two categories: cold recovery and thermal recovery. Cold recovery technologies primarily improve heavy oil recovery through non-heating methods, such as waterflooding, chemical flooding, carbon dioxide flooding, and microbial flooding. However, these cold recovery technologies are difficult to implement significantly for deep-buried, poorly mobile heavy oil reservoirs. Thermal recovery technologies are currently the mainstream approach for heavy oil development. Commonly used methods include steam huff and puff (CSS), steam flooding, steam-assisted gravity drainage (SAGD), and fire flooding. These methods reduce the viscosity and improve the fluidity of heavy oil by heating it, thereby increasing the recovery rate. However, traditional thermal recovery technologies face problems such as high energy consumption and operating costs, severe environmental pollution, and limited reservoir applicability, especially in the development of complex medium-deep heavy oil reservoirs. At present, developing heavy oil extraction methods with low energy consumption, high efficiency, and strong adaptability has become an inevitable trend.

[0004] Compared to traditional technologies, chemical catalytic viscosity reduction technology is a heavy oil extraction technology with both potential application value and environmental friendliness. It introduces a catalyst into the formation to decompose the complex organic molecular structure (such as CC, CS, CN, and CO bonds) in heavy oil under catalytic action, thereby breaking down heavy molecules, reducing viscosity, and improving fluidity. Currently, researchers both domestically and internationally have developed various catalysts, mainly including: ① water-soluble catalysts; ② oil-soluble catalysts; ③ amphiphilic catalysts; ④ solid catalysts; ⑤ ultradispersed nanocatalysts; and ⑥ ionic liquid catalysts. These catalysts promote the recombination and decomposition of heavy oil molecules through different mechanisms and have shown good results under laboratory conditions. However, these studies are mostly focused on the preliminary technology exploration stage, and their practical applicability under in-situ reservoir conditions still needs further verification. In particular, existing technologies still have significant problems in terms of strong temperature dependence, insufficient engineering adaptability, and high operating costs, limiting their potential for large-scale industrial application.

[0005] Chinese patent application (CN118308081A) proposes an emulsion viscosity reduction technology based on a high-entropy oxide catalyst. This system promotes the breaking and cleavage of complex chemical bonds (such as CS and CN) in heavy oil through the synergistic effect of multiple transition metals, combined with oxidants and surfactants, and further reduces the viscosity of heavy oil through emulsification. This method exhibits advantages such as strong initial activity and significant viscosity reduction efficiency under heavy oil formation conditions (50–180℃). Furthermore, the proportion of catalyst metal components can be adjusted and optimized according to specific reservoir compositions, demonstrating strong customization capabilities. However, the long-term chemical stability of high-entropy oxide catalysts is poor, especially in complex formation conditions; whether their catalytic performance can remain effective is still one of the bottlenecks of this technology.

[0006] Chinese invention application (CN113444511A) discloses a heavy oil modifier based on nano-copper. Nano-copper forms a homogeneous oil-soluble catalytic system with a hydrogen donor through a suspending dispersant, enabling rapid pyrolysis of gums and asphaltenes in heavy oil. The resulting small-molecule compounds significantly improve the viscosity of heavy oil and exhibit good reservoir compatibility. However, this catalyst is highly dependent on the amount of hydrogen donor used and requires a high reaction temperature, resulting in high costs for industrialization and limiting its widespread application.

[0007] Although some progress has been made in the research of catalytic viscosity reduction technology for heavy oil, problems still exist, such as insufficient universality of the technology, complexity of the catalytic system, and low engineering adaptability. Existing catalytic technologies generally rely on high-temperature environments to activate catalytic performance, and also suffer from poor adaptability to the dynamic and static characteristics of oil reservoirs. Furthermore, some catalysts are difficult to meet the needs of large-scale industrial application due to high raw material costs and poor recyclability. Summary of the Invention

[0008] The purpose of this invention is to provide an amphiphilic heavy oil viscosity-reducing catalyst based on a defect-regulated MOF, its preparation method, and its application. By constructing a metal-organic framework material with defect structures, the catalytic viscosity-reducing effect of heavy oil is significantly improved. Furthermore, the catalyst surface is modified to enhance its reactivity and contact area. This catalyst exhibits good dispersibility and injection properties in heavy oil formations, providing a reliable theoretical basis and technical support for catalytic viscosity-reducing technology in heavy oil formations, demonstrating broad application prospects and practical value.

[0009] The amphiphilic MOF-based catalyst for in-situ catalytic viscosity reduction in heavy oil formations provided by the present invention is composed of a MOF-NH2 substrate with oxygen vacancy defects and an amphiphilic polymer grafted onto the surface of the MOF-NH2 substrate by chemical bonds.

[0010] The amphiphilic polymer includes hydrophilic structural units and hydrophobic structural units. The hydrophilic structural units include at least one characteristic functional group selected from sulfonic acid groups, amide groups and carboxylic acid groups. The hydrophobic structural units contain alkyl segments with ≥6 carbon atoms or aromatic hydrophobic groups.

[0011] The mass composition of the amphiphilic MOF-based catalyst is as follows:

[0012] 50%-75% MOF-NH2 matrix, 15%-35% amphiphilic polymer.

[0013] Preferably, the central metal salt of the MOF in the MOF-NH2 substrate is selected from one or more of molybdenum salt, iron salt, copper salt, nickel salt, manganese salt, and cobalt salt.

[0014] Preferably, the hydrophilic structural unit is derived from at least one of the following hydrophilic monomers: acrylic acid, methacrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, ethoxylated acryloyloxyethyl sulfonate, and methacryloyloxyethyl trimethylammonium chloride; the hydrophobic structural unit is derived from at least one of the following hydrophobic monomers: Span 80, sodium α-olefin sulfonate, and sodium octenyl succinate.

[0015] Preferably, the oxygen vacancy defects in the MOF-NH2 substrate are controlled by the following conditions: the pH of the hydrothermal reaction solution is 1.5-4.5, the reaction temperature is 90-160℃, and the reaction time is 6-14 hours.

[0016] Preferably, the amphiphilic polymer is grafted onto the MOF-NH2 substrate by click chemistry under nitrogen protection at a temperature of 50-70°C for 6-12 hours.

[0017] The present invention also provides a method for preparing the amphiphilic MOF-based catalyst, comprising the following steps:

[0018] S1. Synthesis of defective MOF-NH2 substrate: Metal salt and 2-aminoterephthalic acid were dissolved in a water-ethanol mixed solvent and subjected to a hydrothermal reaction to obtain MOF-NH2 substrate;

[0019] S2. Amphiphilic polymer grafting: The MOF-NH2 substrate is dispersed in an organic solvent (such as DMF), hydrophilic monomers and hydrophobic monomers are added, and the grafting reaction is carried out under Cu(I) catalyst and nitrogen protection.

[0020] S3. Post-processing: After the reaction is complete, centrifuge to remove ungrafted polymer, wash and vacuum dry to obtain the finished catalyst.

[0021] Specifically, the conditions for the hydrothermal reaction are as follows:

[0022] pH 1.5-4.5, temperature 90-160℃, time 6-14 hours;

[0023] The grafting reaction conditions are: temperature 50-70℃, time 6-12 hours.

[0024] The amphiphilic MOF-based catalyst of this invention can be used for in-situ viscosity reduction in heavy oil formations. Under low temperature (120-150℃) and micro-disturbance conditions, the amphiphilic MOF-based catalyst triggers asphaltene topological depolymerization through π-π interactions and hydrogen bonding synergistic effects, thereby reducing the viscosity of heavy oil. The amphiphilic structure of the amphiphilic MOF-based catalyst reduces the interfacial tension between oil and water, and the catalyst exists stably in both phases, which is significantly better than traditional catalysts.

[0025] When applied, the amphiphilic MOF-based catalyst is combined with a hydrogen donor and injected into the formation, which can simultaneously improve viscosity reduction efficiency and oil quality.

[0026] This invention is the first to combine defect engineering with interface mass transfer enhancement, breaking through the technical bottleneck of low-temperature catalytic viscosity reduction, and establishing a laboratory microfluidic testing system to simulate real formation conditions, promoting the transformation of catalytic evaluation from "ideal stirring" to "engineering adaptation", and providing an innovative solution for green and efficient heavy oil extraction.

[0027] The present invention also provides a method for evaluating the viscosity-reducing effect of the amphiphilic MOF-based catalyst, comprising the following steps:

[0028] 1) Heavy oil, water, hydrogen donor and the amphiphilic MOF-based catalyst are injected into a high-temperature and high-pressure reactor;

[0029] 2) Nitrogen gas is continuously introduced into the high-temperature and high-pressure reactor, and the reaction is carried out under stirring conditions;

[0030] 3) Measure and evaluate the properties of the heavy oil after the reaction.

[0031] The hydrogen donor is one or more of tetrahydronaphthalene and its derivatives, and its amount is 0.5-1.5% of the mass of the heavy oil.

[0032] The amphiphilic MOF-based catalyst comprises 0.1-1.5% of the heavy oil by mass;

[0033] Formation shear conditions were simulated using a microfluidic device, with shear rates ranging from 1 to 100 s⁻¹. -1 ;

[0034] The reaction temperature is 120-150℃.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) Existing metal oxide catalysts can only be activated at temperatures above 180°C. This invention achieves the viscosity of heavy oil at low temperatures through the synergistic effect of defect engineering and dynamic regulation technology of amphiphilic interface, reducing energy consumption and breaking through the technical bottleneck in the field of low-temperature catalytic viscosity reduction.

[0037] (2) Traditional catalysts are prone to formation blockage due to excessive particle size and surface charge mismatch. However, this invention significantly reduces catalyst agglomeration and improves its dispersibility in heavy oil through polymer grafting optimization, effectively overcoming the limitations of the prior art.

[0038] (3) The catalyst provided by the present invention significantly improves the pyrolysis reaction efficiency of heavy oil, optimizes the distribution of pyrolysis products, promotes the deep pyrolysis reaction of heavy oil components, and thus improves the quality of pyrolysis products.

[0039] (4) In response to the problem that laboratory stirring conditions are disconnected from the real micro-permeability environment in the formation, this invention has for the first time constructed a microfluidic simulation test system, which verifies that the catalyst still has high catalytic efficiency under slight disturbance conditions, which is closer to the needs of actual working conditions and provides a scientific basis for the practical application of heavy oil viscosity reduction catalysis technology. Attached Figure Description

[0040] Figure 1 is a SEM image of the heavy oil pyrolysis catalyst of Example 1.

[0041] Figure 2 is the XRD pattern of the heavy oil pyrolysis catalyst of Example 1.

[0042] Figure 3 is a diagram showing the separation and recovery effect of the heavy oil pyrolysis catalyst in Example 6. Detailed Implementation

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0044] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0045] In the MOF-NH2 substrate with oxygen vacancy defects of the present invention, MOF refers to metal-organic framework compound, and oxygen vacancy defect refers to a point defect in the crystal structure in which the position where oxygen atoms should be formed is vacant due to various reasons, thereby causing changes in the material properties.

[0046] Example 1: Preparation of Amphiphilic MOF-based Catalysts

[0047] The catalyst in this embodiment is prepared from the following raw materials in the indicated weight percentages: 68.5% MOF-NH2 substrate and 31.5% amphiphilic polymer; the MOF-NH2 substrate has oxygen vacancy defects, wherein the central metal salt of the MOF is an iron salt; the amphiphilic polymer, comprising hydrophilic and hydrophobic segments, is chemically grafted onto the surface of the MOF-NH2 substrate, wherein the monomers of the polymer are acrylic acid (AA), Span 80, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS). The specific preparation method is as follows:

[0048] A) Synthesis of defective MOF-NH2: Iron nitrate and 2-aminoterephthalic acid were dissolved in a water-ethanol mixed solvent, the pH was adjusted to 2, and the reaction was carried out hydrothermally at 140℃ for 6 hours. After centrifugation, washing, and drying, the product was dried.

[0049] B) Amphiphilic polymer grafting: The MOF-NH2 obtained in step A) was dispersed in DMF, and an equal proportion of acrylic acid and 1% of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) were added. The mixture was reacted at 60°C for 6 hours under stirring. Subsequently, an equal proportion of deionized water, 2.5% of Span 80 and 7% of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) were added to the system, and the mixture was stirred until homogeneous. The mixture was then reacted at 60°C for 8 hours under the action of Cu(I) catalyst.

[0050] C) Post-processing: After the reaction is complete, centrifuge to remove ungrafted polymer, wash sequentially, and vacuum dry to obtain the finished catalyst.

[0051] The scanning electron microscope (SEM) and X-ray diffraction (XRD) results of the heavy oil pyrolysis catalyst prepared in this embodiment are shown in Figures 1 and 2. It can be seen that the amphiphilic MOF-based catalyst was successfully prepared. The characteristic diffraction peaks of the MOF-NH2 catalyst appeared in the XRD pattern, indicating that its crystal structure was formed. The SEM images show that the prepared catalyst has a nanosphere morphology and its surface is coated with polymer.

[0052] Amphiphilic MOF-based catalysts with copper, cobalt, nickel, and manganese salts as the central metal salt were obtained sequentially according to the above method, and were denoted as Cu-MOF, Co-MOF, Ni-MOF, and Mn-MOF.

[0053] Example 2: Evaluation of the catalyst's catalytic viscosity-reducing performance on heavy oil using a high-temperature, high-pressure reactor.

[0054] 70g of heavy oil, 30g of water, 0.5wt% tetrahydronaphthalene, and 0.5wt% catalyst were sequentially added to a high-temperature, high-pressure reactor. To eliminate the interference of residual oxygen on the experimental results, the reactor was purged three times with nitrogen (N2) before the reaction began. Nitrogen was continuously introduced during the reaction until the reactor pressure reached 2MPa. Subsequently, the reaction temperature was gradually increased to 140℃, and the slight agitation of heavy oil under formation conditions was simulated by different stirring speeds. The reaction was maintained at this temperature for 24 hours. After the reaction, the system was allowed to cool naturally to room temperature. Finally, the catalytic viscosity reduction effect was evaluated by measuring the viscosity of the dehydrated heavy oil at 50℃. The experimental results are shown in Table 1.

[0055] Table 1. Viscosity reduction parameters of heavy oil before and after catalysis (50℃)

[0056]

[0057]

[0058] As shown in Table 1, under the same experimental conditions, the defective MOF catalyst exhibits significantly higher catalytic viscosity reduction performance than the defect-free MOF. At high shear rates (100 s⁻¹), the defective MOF catalyst demonstrates this superior performance. -1 Under the given conditions, both MOF-NH2 and polymer-modified catalysts exhibited excellent catalytic viscosity reduction effects, with viscosity reduction rates exceeding 85%. However, with decreasing shear rate, the catalytic performance of MOF-NH2 decreased significantly, while the polymer-modified catalyst maintained high catalytic activity under low shear conditions. Under shear-free conditions, the viscosity reduction rate of the polymer-modified catalyst still reached 73.21%, an improvement of over 50% compared to MOF-NH2.

[0059] Example 3: Catalytic viscosity reduction performance of MOF catalysts with different metal active centers on heavy oil

[0060] 70g of heavy oil, 30g of water, 0.5wt% tetrahydronaphthalene, and 0.5wt% catalyst were sequentially added to a high-temperature, high-pressure reactor. To avoid interference from residual oxygen, the reactor was purged three times with nitrogen (N2) before the reaction began. Nitrogen was continuously introduced during the reaction until the pressure of the reaction system reached 2MPa. Subsequently, the reaction temperature was gradually increased to 140℃, and the reaction was carried out over 100 seconds. -1The reaction was carried out at this temperature for 24 hours with stirring. After the reaction was completed, the system was allowed to cool naturally to room temperature. The catalytic viscosity reduction effect was evaluated by measuring the viscosity of the heavy oil (dehydrated) at 50°C. The experimental results are shown in Table 2.

[0061] Table 2. Viscosity reduction parameters of heavy oil before and after catalysis (50℃)

[0062] -η / mPa·s Viscosity Reduction Rate / % -η / mPa·s Viscosity Reduction Rate / % No Catalyst 3000 1.2 7.87 Co-MOF 865 3.47 3.43 Cu-MOF 953 6.27 0.71 Ni-MOF 458 6.38 5.91 Fe-MOF 300 5.39 0.80 Mn-MOF 1000 0.26 9.29 surface

[0063] As shown in Table 2, MOF catalysts with different metal active centers exhibit significant differences in their catalytic viscosity reduction effects on heavy oil. Ni-MOF and Fe-MOF catalysts show the most pronounced viscosity reduction effects, especially Fe-MOF, which can significantly reduce the viscosity of heavy oil from 30001.2 mPa·s to 3005.3 mPa·s, with a viscosity reduction rate as high as 90.80%. Co-MOF, Cu-MOF, and Mn-MOF catalysts show the next best performance, with viscosity reduction rates of approximately 70%.

[0064] Example 4

[0065] Thin-layer chromatography (TLC) was used to analyze the group composition of the heavy oil before and after the reaction, including asphaltenes, gums, aromatics and saturated hydrocarbons. The specific data are shown in Table 3.

[0066] Experimental results show that the catalytic effect is significantly enhanced with increasing shear rate, and more heavy components are converted into light components during pyrolysis, thereby effectively reducing the viscosity of heavy oil. Furthermore, it exhibits a certain catalytic effect even under shear-free conditions. Compared with hydrothermal pyrolysis, the contents of asphaltenes and resins decreased by 6.58% and 2.24%, respectively, while the contents of aromatic hydrocarbons and saturated hydrocarbons increased by 2.45% and 6.55%, respectively. Moreover, the difference in catalytic effect between low and high shear rate conditions is not significant. This indicates that the catalyst of this invention can fully interact with heavy oil, maintaining high catalytic efficiency even under low shear rate conditions, making it more suitable for the actual working conditions of heavy oil formations and showing good prospects for field application.

[0067] Table 3. Analysis of the group composition of heavy oil before and after catalysis.

[0068] - Asphaltene, resin, aromatic hydrocarbons, saturated hydrocarbons, crude oil 32.88 21.65 24.56 20.99 No catalyst 31.59 21.35 24.56 22.50 Catalyst (0s) -1)25.0119.1127.0129.05 catalyst (10s) -1 )24.1118.6526.0131.48 catalyst (50s) -1 )23.4518.5627.5630.48 Catalyst (100s) -1 )21.8817.6528.5631.91 surface

[0069] Example 5

[0070] In this embodiment, a stability analyzer was used to test the stability of the heavy oil catalyst of the present invention in the oil phase (Table 4) and the aqueous phase (Table 5) to simulate the distribution of the catalyst in the formation heavy oil and the feasibility of its injection through the aqueous phase.

[0071] Experimental results show that, compared with the unmodified catalyst (MOF-NH2), the catalyst of this invention exhibits significantly lower TSI values ​​in both the oil and aqueous phases. This indicates that the unmodified catalyst has poor stability in both oil and aqueous phases and is prone to aggregation and deposition. In contrast, the catalyst of this invention demonstrates good stability in both oil and aqueous phases, indicating its ability to achieve uniform distribution in heavy oil formations and its feasibility for injection into the aqueous phase. This provides technical support for the widespread application of heavy oil formation catalysis technology.

[0072] Table 4. Stability of heavy oil catalysts in the oil phase

[0073] Top / Middle / Bottom of TSI / TSIMOF-NH2 120.2289.62102.35 Catalyst 9.513.216.32 surface

[0074] Table 5. Stability of heavy oil catalysts in the aqueous phase

[0075]

[0076]

[0077] Example 6

[0078] This embodiment demonstrates the feasibility of separating and recovering the catalyst from heavy oil pyrolysis, as shown in Figure 3. It can be seen that the heavy oil, aqueous phase, and catalyst are uniformly dispersed together after catalytic pyrolysis. High-speed centrifugation can separate the oil and aqueous phases, and the catalyst will precipitate in the aqueous phase. The catalyst can then be separated and recovered through filtration and drying.

[0079] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Obviously, those skilled in the art, after thoroughly understanding the content and principles of the present invention, can make various improvements and adjustments to its form or details without departing from the core ideas and technical structure of the present invention. Any simple modifications or equivalent substitutions made to the above embodiments based on the technical essence of the present invention should be considered to fall within the protection scope of the present invention.

Claims

1. An amphiphilic MOF-based catalyst for in-situ catalytic viscosity reduction in heavy oil formations, comprising a MOF-NH2 substrate with oxygen vacancy defects and an amphiphilic polymer grafted onto the surface of the MOF-NH2 substrate via chemical bonds; the amphiphilic polymer comprises hydrophilic and hydrophobic structural units, wherein the hydrophilic structural unit comprises at least one characteristic functional group selected from sulfonic acid groups, amide groups, and carboxylic acid groups, and the hydrophobic structural unit comprises an alkyl segment with ≥6 carbon atoms or an aromatic hydrophobic group; the mass composition of the amphiphilic MOF-based catalyst is as follows: MOF-NH2 substrate 50%-75%, amphiphilic polymer 15%-35%; the central metal salt of the MOF in the MOF-NH2 substrate is selected from one of molybdenum salt, iron salt, copper salt, nickel salt, manganese salt, and cobalt salt. Or several; the hydrophilic structural unit is derived from at least one of the following hydrophilic monomers: acrylic acid, methacrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, ethoxylated acryloyloxyethyl sulfonate, and methacryloyloxyethyl trimethylammonium chloride; the hydrophobic structural unit is derived from at least one of the following hydrophobic monomers: Span 80, sodium α-olefin sulfonate, and sodium octenyl succinate; the oxygen vacancy defects of the MOF-NH2 substrate are controlled by the following conditions: pH of the hydrothermal reaction solution is 1.5-4.5, reaction temperature is 90-160℃, and reaction time is 6-14 hours; the amphiphilic polymer is grafted onto the MOF-NH2 substrate by click chemistry under nitrogen protection at a reaction temperature of 50-70℃ for 6-12 hours.

2. The preparation method of the amphiphilic MOF-based catalyst according to claim 1, comprising the following steps: S1, synthesis of defective MOF-NH2 substrate: dissolving metal salt and 2-aminoterephthalic acid in a water-ethanol mixed solvent and performing a hydrothermal reaction to obtain MOF-NH2 substrate; S2, amphiphilic polymer grafting: dispersing the MOF-NH2 substrate in an organic solvent, adding hydrophilic monomers and hydrophobic monomers, and performing a grafting reaction under Cu(I) catalyst and nitrogen protection; S3, post-treatment: centrifuging to remove ungrafted polymer after the reaction, washing and vacuum drying to obtain the finished catalyst.

3. The preparation method according to claim 2, characterized in that: The conditions for the hydrothermal reaction are as follows: pH 1.5-4.5, temperature 90-160℃, and time 6-14 hours; the conditions for the grafting reaction are: temperature 50-70℃ and time 6-12 hours.

4. The application of the amphiphilic MOF-based catalyst of claim 1 in in-situ viscosity reduction of heavy oil formations.

5. A method for evaluating the viscosity-reducing effect of the amphiphilic MOF-based catalyst of claim 1, comprising the following steps: 1) injecting heavy oil, water, a hydrogen donor and the amphiphilic MOF-based catalyst into a high-temperature and high-pressure reactor; 2) continuously introducing nitrogen gas into the high-temperature and high-pressure reactor and carrying out the reaction under stirring conditions; 3) measuring and evaluating the properties of the heavy oil after the reaction.

6. The method according to claim 5, characterized in that: The hydrogen donor is one or more of tetrahydronaphthalene and its derivatives, and its amount is 0.5-1.5% of the heavy oil mass; the amphiphilic MOF-based catalyst is 0.1-1.5% of the heavy oil mass; formation shear conditions are simulated using a microfluidic device, with a shear rate of 1-100 s⁻¹. -1 The reaction temperature is 120-150℃.

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