MOFs nanoscale enzyme and its preparation and application, cement-based materials and carbon sequestration maintenance

Abstract

The application discloses MOFs nanoscale enzyme, preparation and application thereof, cement-based material and carbon sequestration curing. The MOFs nanoscale enzyme is loaded into organic metal framework MOFs. A cement-based material based on the MOFs nanoscale enzyme is prepared by mixing the MOFs nanoscale enzyme into standard cement paste or standard cement mortar. The cement-based material based on the MOFs nanoscale enzyme is cured by carbon sequestration, the MOFs and the nanoscale enzyme jointly catalyze the hydration reaction of CO2, promote the formation of calcium carbonate in the cement-based material, improve the carbon sequestration capacity of the cement-based material, and obtain higher strength by plugging pores through the formation of a large amount of calcium carbonate, improve the curing efficiency, play a role in carbon sequestration and emission reduction, and obtain a cement-based material enhanced based on the MOFs nanoscale enzyme. The carbon sequestration curing is curing for 1-7 days in an environment with a temperature of 20±2 DEG C and a CO2 pressure of 0.1-0.4 MPa.

Description

Technical Field

[0001] This invention relates to the field of building material preparation technology, specifically to MOF nanozymes and their preparation and application, cement-based materials and carbon fixation curing. Background Technology

[0002] Cement, as the world's most widely used building material, emits a significant amount of CO2 during its production and use, placing immense pressure on carbon sequestration efforts. Current cement carbon reduction technologies effectively reduce CO2 emissions during cement production and use, showing significant progress towards achieving peak carbon emissions, but achieving true carbon neutrality remains a long and arduous task. Reabsorbing and utilizing emitted CO2 is a crucial means of achieving carbon neutrality. The alkaline environment of cement-based materials has good compatibility with CO2, making it an excellent medium for CO2 sequestration. Therefore, utilizing cement-based materials for CO2 sequestration is a vital means of steadily advancing carbon sequestration efforts. Carbon sequestration curing of cement-based materials can effectively promote carbon sequestration.

[0003] Carbon sequestration curing of cement-based materials involves introducing CO2 into the curing stage, subjecting the cement to a CO2 atmosphere under pressure to achieve rapid hardening while simultaneously absorbing and solidifying CO2. As a mineral sequestration technology, carbon sequestration curing can absorb and solidify CO2 during the cement's use phase, offsetting CO2 emissions from the production phase and thus reducing carbon emissions throughout the cement product's lifecycle. This represents a new approach to low-carbon cement applications.

[0004] Currently, atmospheric pressure carbon fixation curing of ordinary cement-based materials faces the following technical challenges: slow carbon fixation rate and limited carbon fixation amount. To improve carbon fixation efficiency, high-purity, high-pressure CO2 atmospheres are typically used for curing cement-based materials, requiring stringent carbonation conditions. Furthermore, the amount of carbon fixation products formed is limited, resulting in limited improvement and enhancement of the microstructure and mechanical properties of cement-based materials. Summary of the Invention

[0005] To address the above technical problems, this invention discloses a MOFs nanozyme for catalyzing CO2 hydration reactions, its preparation method and application, as well as a method for preparing and carbon-fixing curing a high-carbon-fixing cement-based material based on this MOFs nanozyme. Both MOFs materials and nanozymes possess high CO2 hydration catalytic capabilities. The MOFs nanozyme is a composite catalyst formed by combining MOFs materials and nanozymes, exhibiting extremely strong CO2 hydration catalytic capabilities under the combined action of the MOFs materials and nanozymes. Cement-based materials based on this MOFs nanozyme can rapidly absorb and fix CO2 during the carbon-fixing curing stage, achieving rapid hardening. The CaCO3 generated from the reaction of cement hydration products with CO2 improves the mechanical properties and durability of the cement-based material, further aligning with the concept of low-carbon green building materials.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] A method for preparing MOF-based nanoenzyme cement-based materials includes the following steps:

[0008] (1) Add the zinc-containing compound and 2-methylimidazole to water respectively, stir until dissolved, mix them together, and then add Triton X-100 to obtain the pretreatment solution;

[0009] (2) Add zinc salt and histidine to preheated glycerol to obtain nanozyme;

[0010] (3) After mixing the pre-solution with the nanozyme, the reaction was carried out in the dark, aged, ultrasonically dispersed, centrifuged and freeze-dried to obtain MOF nanozymes with different particle sizes.

[0011] Further, in step (1), the zinc-containing compound is one or more of zinc acetate dihydrate or zinc nitrate hexahydrate, the amount of the zinc-containing compound is 0.1-0.5M, and the amount of 2-methylimidazole is 1-3M.

[0012] Furthermore, in step (1), the dosage of Triton X-100 is 0.5mM-4mM.

[0013] Further, in step (2), the nanozyme is artificially synthesized carbonic anhydrase; the glycerol is preheated to 60-80℃; the molar ratio of zinc salt, histidine, and glycerol is 1:3-6:18-24; the zinc salt is one or more of anhydrous zinc chloride or anhydrous zinc sulfate; and the amount of nanozyme used is 3ml-10ml.

[0014] Further, in step (3), the light-protected reaction time is 24-48h; the ultrasonic dispersion time is 30-60min; the centrifugation speed is 5000-12000r / min and the centrifugation time is 30min; the product obtained after freeze-drying is carefully ground into powder.

[0015] The MOF nanozyme prepared by any of the above methods is an effective component of the MOF nanozyme, which is ZIF-8 and nanozyme, the active center of the MOF nanozyme is divalent zinc, and the particle size of the MOF nanozyme is 100-2000 nm.

[0016] The aforementioned MOF nanozyme is used to accelerate the strength development of cement-based materials and to convert carbon dioxide gas into solid for storage.

[0017] A method for preparing MOF-based nanoenzyme cement-based materials includes the following steps:

[0018] The above-mentioned MOF nanozymes are incorporated into standard cement paste or standard cement mortar to form a cement-based material based on MOF nanozymes.

[0019] Furthermore, the amount of MOFs nanozymes incorporated into the MOFs-based cementitious material is 0.01-0.1% of the mass of the cement clinker.

[0020] A MOFs nanoenzyme-based cementitious material comprising the aforementioned MOFs nanoenzyme and standard cement paste or standard cement mortar.

[0021] Further, in step (4), the amount of MOFs nanozymes incorporated into the MOFs nanozyme-based cementitious material is 0.01-0.1% of the mass of the cement clinker.

[0022] Furthermore, the MOFs nanozyme can enhance the ability of a MOFs nanozyme-based cement-based material to absorb and fix CO2.

[0023] Due to the incorporation of MOF nanozymes, a MOF nanozyme-based cementitious material possesses self-healing capabilities. When cracks appear on the surface of this MOF nanozyme-based cementitious material, it can self-repair. The mechanism involves MOF nanozymes catalyzing the hydration of carbon dioxide in the air to produce carbonate ions; these carbonate ions react with calcium hydroxide in the cementitious material, combining to form calcium carbonate precipitate, thus achieving the self-healing process of the MOF nanozyme-based cementitious material.

[0024] A carbon fixation curing method for MOFs nanoenzyme-based cementitious materials includes the following steps: carbon fixation curing is performed on the above-mentioned MOFs nanoenzyme-based cementitious materials to obtain MOFs nanoenzyme-reinforced cementitious materials; the carbon fixation curing is performed by placing the cementitious materials in a CO2 atmosphere for curing.

[0025] Furthermore, the CO2 atmosphere pressure is 0.1-0.4 MPa, the carbon fixation curing temperature is 20±2℃, and the carbon fixation curing time is 1-7 days.

[0026] The present invention also provides a MOFs nanoenzyme-reinforced cement-based material obtained by any of the carbon fixation curing methods described above.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] MOFs, as organometallic frameworks, possess porosity and a large specific surface area, which endow them with excellent adsorption capabilities. Nanozymes and MOFs also possess Zn-N active sites, where Zn is an unsaturated metal site capable of combining with CO2 and H2O to form Zn-HCO3. - This invention enhances the CO2 adsorption capacity of MOFs by loading nanozymes into MOFs materials. Furthermore, incorporating this material into cement-based materials not only improves their CO2 absorption capacity, but the alkaline environment of the cement-based materials also ensures the preservation of their rich Ca content. 2+ With Zn-HCO3 - It combines to form a large amount of CaCO3, which helps to reduce porosity and increase strength. Attached Figure Description

[0029] Figure 1 This is a diagram of the carbon fixation and curing apparatus of the present invention.

[0030] Figure 2 (a) in the figure is the compressive strength diagram of cement paste specimens prepared in Example 1 of the present invention after standard curing and carbon fixation curing for 3 days and 7 days. Figure 2 (b) is a graph showing the calcium carbonate content on the surface of cement paste test blocks prepared in Example 1 of the present invention after conventional curing and carbon fixation curing for 3 days and 7 days.

[0031] Figure 3 (a) is the compressive strength of the cement paste test blocks prepared in Example 2 of the present invention after conventional curing and carbon fixation curing for 3 days and 7 days. Figure 3(b) represents the surface calcium carbonate content of the cement paste test blocks prepared in Example 2 of this invention after conventional curing and carbon fixation curing for 3 days and 7 days. (RN represents standard curing of standard cement paste; RC represents carbon fixation curing of standard cement paste; MOFs-N represents conventional curing of cement paste test blocks based on MOFs nanozymes; MOFs-C represents carbon fixation curing of cement paste test blocks based on MOFs nanozymes).

[0032] Figure 4 (a) is the compressive strength of the cement paste test blocks prepared in Example 3 of the present invention after conventional curing and carbon fixation curing for 3 days and 7 days. Figure 4 (b) represents the surface calcium carbonate content of the cement paste test blocks prepared in Example 3 of this invention after conventional curing and carbon fixation curing for 3 days and 7 days. (RN represents standard curing of standard cement paste; RC represents carbon fixation curing of standard cement paste; MOFs-N represents conventional curing of cement paste test blocks based on MOFs nanozymes; MOFs-C represents carbon fixation curing of cement paste test blocks based on MOFs nanozymes).

[0033] Figure 5 (a) is the CO2 hydration catalytic activity of the MOFs nanozymes synthesized in Examples 1, 2 and 3 in Example 4 of the present invention (R is p-nitrophenyl acetate solution, and Examples 1, 2 and 3 respectively added p-nitrophenyl acetate solution of MOFs nanozymes synthesized in Examples 1, 2 and 3). Figure 5 (b) is the pH change of CO2 absorption after the MOFs nanozymes synthesized in Examples 1, 2 and 3 are incorporated into the buffer solution in Example 4 of the present invention (R is HEPES buffer, and Examples 1, 2 and 3 respectively correspond to the HEPES buffer solution in which the MOFs nanozymes synthesized in Examples 1, 2 and 3 were added). Detailed Implementation

[0034] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the scope of protection and implementation of the present invention are not limited thereto.

[0035] In specific embodiments of the present invention, the zinc acetate dihydrate used is analytical grade with a purity of 99.9%; the zinc nitrate hexahydrate used is analytical grade with a purity of 99.9%; the 2-methylimidazole used is analytical grade with a purity of 99.8%; the Triton X-100 used is analytical grade; the anhydrous zinc chloride used is analytical grade with a purity of 99%; the zinc sulfate used is analytical grade with a purity of 99%; the L-histidine used is analytical grade with a purity of 99%; the L-arginine used is analytical grade with a purity of 99%; the glycerol used is analytical grade with a purity of 99%; the p-nitrobenzene acetate used is analytical grade with a purity of 99%; and the HEPES buffer solution used has a concentration of 1.0 M and a pH of 7.8.

[0036] Figure 1 This is a diagram of the carbon fixation and curing apparatus of the present invention. Figure 1 In the diagram, 1 represents the CO2 reactor, and 2 represents the CO2 outlet. Figure 1 The number 3 in the figure represents a CO2 pressure gauge. Figure 1 The number 4 in the diagram represents the CO2 intake. Figure 1 The number 5 in the text refers to a CO2 gas cylinder.

[0037] Example 1

[0038] A cement-based material based on MOF nanozymes, the specific preparation steps are as follows:

[0039] Weigh out 5g of anhydrous zinc chloride and 17g of L-histidine and mix them evenly. Weigh out 61g of glycerol and preheat it in an oil bath at 70℃ (the molar ratio of the three substances is 1:3:18). Add the anhydrous zinc chloride and L-histidine to the preheated glycerol and stir continuously until completely dissolved to obtain a light yellow uniform liquid, which is nanozyme. 2.20 g of zinc acetate dihydrate and 8.21 g of 2-methylimidazole were weighed and dissolved in 100 ml of ultrapure water and stirred until dissolved to obtain 0.1 M zinc acetate dihydrate solution and 1 M 2-methylimidazole solution. After mixing, 0.5 mM Triton X-100 and 3 ml of nanozyme were added dropwise. The mixture was stirred in the dark for 24 h. After the reaction was completed, the mixture was aged for 2 h and then ultrasonically dispersed for 30 min. The mixture was then centrifuged at 5000 r / min for 30 min. The mixture was washed twice with ultrapure water, freeze-dried for 48 h, and then carefully ground to obtain MOF nanozyme. The average particle size of the MOF nanozyme was about 2000 nm.

[0040] (2) Weigh out cement clinker and water according to a water-cement ratio of 0.4. Mix the cement clinker and water, and use a cement paste mixer to slowly mix for 120 seconds, let it stand for 15 seconds, and then quickly mix for 120 seconds. Pour the mixture into molds of 40mm×40mm×160mm and 40mm×40mm×40mm. After standard curing the molds containing the cement paste for 24 hours, demold them, and then seal and cure them at 20±1℃ for 3 days and 7 days to obtain standard cement paste test blocks RN after standard curing. Alternatively, place the molds containing the cement paste into... Figure 1 After curing in a pressure vessel with a CO2 pressure of 0.4 MPa and a temperature of (20±2)℃ for 1 day, the specimen was demolded and then placed back into the vessel for curing under the same conditions for 3 days and 7 days before being removed to obtain standard cement paste specimens (RC) after carbon fixation curing.

[0041] (3) Weigh cement clinker and water according to a water-cement ratio of 0.4. Weigh MOFs nanozyme at 0.01% of the cement clinker mass and mix with water. Then mix the cement clinker and water, and use a cement paste mixer to slowly mix for 120s, let stand for 15s, and then quickly mix for 120s. Pour the mixture into molds of 40mm×40mm×160mm and 40mm×40mm×40mm. After standard curing of the molds containing the paste for 24 hours, demold them. Then, seal and cure them at room temperature of 20±1℃ for 3 days and 7 days to obtain MOFs-N cement paste test blocks based on MOFs nanozyme after conventional curing. Alternatively, place the molds containing the paste into... Figure 1 After curing in a pressure vessel with a CO2 pressure of 0.4 MPa and a temperature of (20±2)℃ for 1 day, the mold was removed, and the test blocks were placed back into the vessel for curing for 3 days and 7 days before being taken out, thus obtaining MOFs-C test blocks based on MOFs nanoenzymes after carbon fixation curing.

[0042] Figure 2 The values ​​represent the compressive strengths of cement paste specimens prepared in Example 1 after standard curing and carbon fixation curing for 3 and 7 days, respectively. Here, RN represents standard cement paste under standard curing; RC represents standard cement paste under carbon fixation curing; MOFs-N represents standard-cured cement paste based on MOFs nanozymes; and MOFs-C represents carbon fixation-cured cement paste based on MOFs nanozymes. (Combined with...) Figure 2 As shown in (a) and (b), the strength of the standard cement paste specimen decreased relatively quickly under carbon fixation curing with CO2 pressure of 0.4 MPa. However, the strength of the specimen increased after incorporating MOF nanozymes. This is because the calcium carbonate content on the surface of the cement specimen increased, which played a role in plugging the pores.

[0043] Example 2

[0044] (1) Weigh 5g of anhydrous zinc chloride and 34g of L-histidine and mix them evenly. Weigh 81g of glycerol and preheat it in an oil bath at 70℃ (the molar ratio of the three substances is 1:6:24). Add anhydrous zinc chloride and L-histidine to the preheated glycerol and stir continuously until completely dissolved to obtain a light yellow uniform liquid, i.e. nanozyme. 10.98 g of zinc acetate dihydrate and 24.62 g of 2-methylimidazole were weighed and dissolved in 100 ml of ultrapure water to obtain 0.5 M zinc acetate dihydrate solution and 3 M 2-methylimidazole solution. After mixing, 4 m M Triton X-100 and 10 ml of nanozyme were added dropwise. The mixture was stirred in the dark for 24 h. After the reaction was completed, the mixture was aged for 2 h and then centrifuged at 12000 r / min for 30 min. The mixture was washed twice with ultrapure water, freeze-dried for 48 h, and then carefully ground to obtain MOF nanozyme. The average particle size of the MOF nanozyme was about 100 nm.

[0045] (2) Weigh cement clinker and water according to a water-cement ratio of 0.4. Mix the cement clinker and water, and use a cement paste mixer to slowly mix for 120 seconds, let it stand for 15 seconds, and then quickly mix for 120 seconds. Pour the mixture into molds of 40mm×40mm×160mm and 40mm×40mm×40mm. After standard curing for 24 hours, demold the mixture, and then seal and cure it at 20±1℃ for 3 days and 7 days to obtain standard cement paste test blocks RN after standard curing. Alternatively, place the molds containing the cement paste into... Figure 1 After curing in a pressure vessel with a CO2 pressure of 0.1 MPa and a temperature of (20±2)℃ for 1 day, the specimen was demolded and then placed back into the vessel for curing under the same conditions for 3 days and 7 days before being removed to obtain standard cement paste specimens (RC) after carbon fixation curing.

[0046] (3) Weigh cement clinker and water according to a water-cement ratio of 0.4. Weigh MOFs nanozyme at 0.1% of the cement clinker mass and mix it with water. Then mix the cement clinker and water, and use a cement paste mixer to slowly mix for 120s, let it stand for 15s, and then quickly mix for 120s. Pour the mixture into molds of 40mm×40mm×160mm and 40mm×40mm×40mm, and demold after standard curing for 24 hours. Then, seal and cure at room temperature of 20±1℃ for 3d and 7d to obtain MOFs-N cement paste test blocks based on MOFs nanozyme after conventional curing. Alternatively, place the molds containing the paste into... Figure 1 After curing in a pressure vessel with a CO2 pressure of 0.1 MPa and a temperature of (20±2)℃ for 1 day, the mold was removed, and the test blocks were placed back into the vessel for curing for 3 days and 7 days before being taken out, thus obtaining MOFs-C test blocks based on MOFs nanoenzymes after carbon fixation curing.

[0047] Figure 3 The values ​​represent the compressive strengths of cement paste specimens prepared in Example 2 after standard curing and carbon fixation curing for 3 and 7 days, respectively. Here, RN represents standard cement paste under standard curing; RC represents standard cement paste under carbon fixation curing; MOFs-N represents standard-cured cement paste based on MOFs nanozymes; and MOFs-C represents carbon fixation-cured cement paste based on MOFs nanozymes. (Combined with...) Figure 3 As shown in (a)(b), the strength of the standard cement paste specimen increased after 3 days under carbon fixation curing with CO2 pressure of 0.1 MPa, but decreased after 7 days, which is consistent with the carbonization law. After incorporating MOF nanoenzymes, the cement specimen under carbon fixation curing generated more CaCO3 to block the pores, thereby increasing the strength.

[0048] Example 3

[0049] (1) Weigh 5g of anhydrous zinc sulfate and 24.3g of L-arginine and mix them evenly. Weigh 59.9g of glycerol and preheat it in an oil bath at 70℃ (the molar ratio of the three substances is 1:4.5:21). Add anhydrous zinc chloride and L-arginine to the preheated glycerol and stir continuously until completely dissolved to obtain a light yellow uniform liquid, which is nanozyme. Weigh 9.22g of zinc nitrate hexahydrate and 10.26g of 2-methylimidazole and dissolve them in 100ml of ultrapure water to obtain 0.31M zinc acetate dihydrate solution and 1.25M 2-methylimidazole solution. After mixing, add 6ml of nanozyme and stir in the dark for 24h. After the reaction is complete, age for 2h and centrifuge at 8000r / min for 30min. Wash twice with ultrapure water, freeze dry for 48h and grind carefully to obtain MOF nanozyme. The average particle size of the MOF nanozyme is about 500nm.

[0050] (2) Weigh cement clinker and water according to a water-cement ratio of 0.4. Mix the cement clinker and water, and use a cement paste mixer to slowly mix for 120 seconds, let it stand for 15 seconds, and then quickly mix for 120 seconds. Pour the mixture into molds of 40mm×40mm×160mm and 40mm×40mm×40mm. After standard curing for 24 hours, demold the mixture, and then seal and cure it at 20±1℃ for 3 days and 7 days to obtain standard cement paste test blocks RN after standard curing. Alternatively, place the molds containing the cement paste into... Figure 1 After curing in a pressure vessel with a CO2 pressure of 0.3 MPa and a temperature of (20±2)℃ for 1 day, the mold was removed. The test blocks were then placed back into the vessel and cured under the same conditions for 3 days and 7 days, and then removed to obtain standard cement paste test blocks RC after carbon fixation curing.

[0051] (3) Weigh cement clinker and water according to a water-cement ratio of 0.4. Weigh MOFs nanozyme at 0.05% of the cement clinker mass and mix with water. Then mix the cement clinker and water, and use a cement paste mixer to slowly mix for 120s, let stand for 15s, and then quickly mix for 120s. Pour the mixture into molds of 40mm×40mm×160mm and 40mm×40mm×40mm. After standard curing for 24 hours, demold the mixture, and then seal and cure it at room temperature of 20±1℃ for 3d and 7d to obtain MOFs-N cement paste test blocks based on MOFs nanozyme after conventional curing. Alternatively, place the mold containing the paste into... Figure 1 After curing in a pressure vessel with a CO2 pressure of 0.3 MPa and a temperature of (20±2)℃ for 1 day, the mold was removed, and the test blocks were placed back into the vessel for curing for 3 days and 7 days before being taken out, thus obtaining MOFs-C test blocks based on MOFs nanoenzymes after carbon fixation curing.

[0052] Figure 4The values ​​represent the compressive strengths of cement paste specimens prepared in Example 3 after standard curing and carbon fixation curing for 3 and 7 days, respectively. Here, RN represents standard cement paste under standard curing; RC represents standard cement paste under carbon fixation curing; MOFs-N represents standard-cured cement paste based on MOFs nanozymes; and MOFs-C represents carbon fixation-cured cement paste based on MOFs nanozymes. (Combined with...) Figure 4 (a)(b) shows that the strength of the standard cement paste specimen increased after 3 days under carbon fixation curing with CO2 pressure of 0.3 MPa, but decreased after 7 days, which is consistent with the carbonation law. The strength of MOF nanoenzymes without Triton X-100 decreased after carbon fixation curing. This is because the large increase in calcium carbonate will cause cement expansion, leading to the appearance of cracks.

[0053] Example 4

[0054] 0.9 g of p-nitrobenzene acetate was dissolved in 10 ml of ultrapure water to prepare a 0.5 M p-nitrobenzene acetate solution. 0.1 g of the MOF nanozymes synthesized in Examples 1, 2 and 3 were weighed and added to 10 ml of p-nitrobenzene acetate solution, and the ultraviolet absorbance of the solution was measured using an ultraviolet spectrophotometer.

[0055] Measure 10 ml of HEPES buffer and mix it with 90 ml of ultrapure water to obtain a 10-fold diluted HEPES buffer with a concentration of 0.1 M. The pH of this buffer is still 7.8. Weigh 0.1 g of the MOF nanozyme synthesized in Examples 1, 2, and 3 and add it to the 0.1 M HEPES buffer. After mixing thoroughly, CO2 is bubbled through the buffer at a rate of 50 ml / min for 30 min. The pH of the buffer is continuously read using a pH meter.

[0056] Figure 5 (a) is the UV absorbance of the p-nitrobenzene acetate solution. Catalysts with CO2 hydration catalysis properties specifically catalyze the hydrolysis of p-nitrobenzene acetate. The hydrolyzed p-nitrobenzene acetate exhibits a UV absorption peak at 402 nm. The higher the degree of hydrolysis, the higher the CO2 hydration catalytic activity of the MOF nanozyme, and the higher the absorption peak at 402 nm. Figure 5 (a) It can be seen that the p-nitrophenyl acetate solution doped with the three MOF nanozymes all have ultraviolet absorption peaks at 402 nm, and the MOF nanozyme of Example 1 has the highest absorption peak and the greatest activity. Correspondingly, the performance improvement of the cement-based material based on MOF nanozyme in Example 1 is also the most obvious. Figure 5 (b) shows the pH change during the introduction of CO2 into the buffer solution, caused by... Figure 5(b) It can be seen that the pH decrease rate of HEPES buffer incorporating the three MOF nanozymes was accelerated when CO2 was continuously introduced. This is because the three MOF nanozymes promoted the conversion of CO2 to HCO3. - This accelerated the decrease in pH, with the MOF nanozyme in Example 1 showing the most significant effect.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing MOF nanozymes, characterized in that, The steps include: (1) adding the zinc-containing compound and 2-methylimidazole to water, stirring until dissolved to obtain a 0.1-0.5M zinc-containing compound solution and a 1-3M 2-methylimidazole solution, mixing the zinc-containing compound solution and the 2-methylimidazole solution, and then adding 0.5mM-4mM Triton X-100 to obtain a pretreatment solution; the zinc-containing compound is one or more of zinc acetate dihydrate or zinc nitrate hexahydrate; (2) Add zinc salt and histidine to preheated glycerol to obtain nanozyme, wherein the nanozyme is artificially synthesized carbonic anhydrase; the molar ratio of zinc salt, histidine and glycerol is 1:3-6:18-24; the glycerol is preheated to 60-80℃; the zinc salt is one or more of anhydrous zinc chloride and anhydrous zinc sulfate; (3) After mixing the pre-solution with the nanozyme, react in the dark, age, disperse by ultrasound, centrifuge and freeze dry to obtain MOFs nanozymes with different particle sizes; the MOFs nanozymes are suitable for the alkaline environment of cement-based materials; the effective components of the MOFs nanozymes are ZIF-8 and nanozymes, the active center of the MOFs nanozymes is divalent zinc, and the particle size of the MOFs nanozymes is 100-2000 nm.

2. The method for preparing MOF nanozymes according to claim 1, characterized in that, In step (3), the light-protected reaction time is 24-48h; the ultrasonic dispersion time is 30-60min; the centrifugation speed is 5000-12000r / min, and the centrifugation time is 30min.

3. A MOF nanozyme, characterized in that, It is prepared by the preparation method according to any one of claims 1-2.

4. A MOF-based nanoenzyme cement-based material, characterized in that, The mixture includes the MOFs nanozyme as described in claim 3 and standard cement paste or standard cement mortar, wherein the amount of MOFs nanozyme incorporated is 0.01-0.1% of the mass of cement clinker.

5. A carbon fixation curing method based on MOF nanoenzyme cement-based materials, characterized in that, The method includes the following steps: placing the MOFs nanoenzyme-based cementitious material as described in claim 4 in a CO2 atmosphere for curing to obtain MOFs nanoenzyme-reinforced cementitious material; the pressure of the CO2 atmosphere is 0.1-0.4 MPa, the curing temperature is 20±2℃, and the curing time is 1-7 days.

6. A cement-based material reinforced with MOF nanozymes, characterized in that, It is prepared by the carbon fixation and curing method described in claim 5.

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