A titanium carbide-based nanocomposite material capable of accelerating enzyme-catalyzed conversion of carbon dioxide into formic acid and its preparation method

Abstract

This invention relates to a titanium carbide-based nanocomposite material and its preparation method, which can significantly accelerate the enzyme-catalyzed conversion of carbon dioxide to formic acid. It belongs to the fields of nanocomposite materials and enzyme catalysis. The purpose of this invention is to overcome the shortcomings of existing best-performing reinforcing materials, mesoporous silica (mSiO2), whose structural parameters are easily affected by the preparation process and external environment, making structural control difficult and leading to unstable performance. This invention further improves the reinforcing effect. The composite material of this invention is based on Ti3C2T... x Ti3C2T was prepared by a one-step sintering method using nano-SiO2 and organic carbon and nitrogen compounds as raw materials. x / SiO2 / carbon nitride (CN), abbreviated as TSCN, is a simple preparation method with easily controllable material structure and stable performance. Since all three components adsorb carbon dioxide, this composite material is used to accelerate the enzyme-catalyzed conversion of carbon dioxide to formic acid, surpassing the best-performing existing technology, mSiO2. After amino modification, its reinforcing effect surpasses that of polydopamine / polyethyleneimine modified mSiO2.

Description

Technical Field

[0001] This invention relates to a titanium carbide-based nanocomposite material that can accelerate the enzyme-catalyzed conversion of carbon dioxide into formic acid and its preparation method, belonging to the fields of nanocomposite materials and enzyme catalytic reactions. Background Technology

[0002] To address the greenhouse effect and meet humanity's long-term fuel needs, converting CO2 into renewable fuels and high-value chemicals is of great significance. Formate dehydrogenase (FDH) as a biocatalyst and nicotinamide adenine dinucleotide (NADH) as a cofactor can reversibly catalyze the conversion of CO2 into formic acid. However, the low solubility of CO2 at room temperature and pressure results in a low conversion rate for the enzyme-catalyzed system. In recent years, it has been discovered that adding materials with CO2 adsorption properties to the system can accelerate the reaction rate and improve the yield by increasing the local CO2 concentration.

[0003] Existing technology utilizes polydopamine (PDA) / polyethyleneimine (PEI) to modify micron-sized SiO2. Adding 200 mg of the prepared PDA / PEI-SiO2 to 2 mL of an enzyme-catalyzed CO2 to formic acid system can increase the initial reaction rate to 21.7 times the rate before addition (defined as the enhancement factor), with an average enhancement factor of 2.17 per 20 mg of PDA / PEI-SiO2. However, due to the relatively large particle size (>1 μm) and low specific surface area of ​​the SiO2 used, the adsorption of CO2 is limited, thus the enhancement effect is limited. To overcome the shortcomings of the above technology, one approach is to immobilize carbonic anhydrase (CA) onto the surface of PDA / PEI-SiO2. CA can catalyze the hydration reaction of CO2, thereby accelerating the conversion of CO2 to formic acid. In a 2 mL enzyme reaction system, adding 200 mg of PDA / PEI-SiO2 with surface-loaded CA resulted in an enhancement factor of 47, with an average enhancement factor of 4.7 per 20 mg of material. However, this technology uses expensive CA, increasing costs. Another approach is to use mesoporous SiO2 (mSiO2) with smaller particle size and higher specific surface area instead of micron-sized SiO2. In a 2 mL enzyme reaction system, adding 50 mg of mSiO2 and PDA / PEI-mSiO2 resulted in enhancement factors of 14.2 and 30.8, respectively. On average, the enhancement factors per 20 mg of material were 5.6 and 12.4, respectively, representing a significant improvement over previous methods. However, the structural parameters (such as particle size and pore structure) of mSiO2 and PDA / PEI-mSiO2 are easily affected by the preparation process and external environment, making structural control difficult and leading to unstable performance.

[0004] Titanium carbide (Ti3C2T) xTi3C2T is a typical MXene two-dimensional material, obtained by etching away the intermediate Al or Si atomic layers from precursors such as Ti3AlC2 or Ti3SiC2 with strong acid. T represents the end groups on the etched surface, and x represents the number of end groups. x It possesses a two-dimensional layered structure resembling an accordion, which can be used for gas adsorption and enzyme immobilization. Current techniques utilize hydrofluoric acid (HF) to etch Ti3AlC2, followed by intercalation with a mixture of ammonia and KCl to obtain intercalated Ti3C2T. x (hereinafter referred to as Ti3C2T) x Then, PEI is adsorbed onto Ti3C2T using electrostatic attraction. x PEI-Ti3C2T was obtained on the surface. x 20 mg of Ti3C2T was added to a 2 mL enzyme-catalyzed CO2 to formic acid conversion system. x and PEI-Ti3C2T x The enhancement factors were 5.3 and 9.2, respectively.

[0005] In summary, all existing reinforcing materials that accelerate the enzyme-catalyzed conversion of CO2 to formic acid employ amino modification (either PDA / PEI modification or PEI modification). The accelerating effect of reinforcing materials depends on two aspects: the bulk material and the amino modification. Given similar modification methods, the type of bulk material plays a decisive role; therefore, developing bulk materials with good reinforcing effects is of great value. Among the disclosed bulk materials, mSiO2 exhibits the best reinforcing effect, with an average reinforcing factor of 5.6 per 20 mg of mSiO2. However, the structural parameters of this material are easily affected by the preparation process and external environment, making its structure difficult to control and leading to unstable performance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing reinforcing materials, such as mSiO2, whose structural parameters are easily affected by the preparation process and external environment, making structural control difficult and leading to unstable performance. This invention aims to further improve the reinforcing effect by providing a titanium carbide-based nanocomposite material that can accelerate the enzyme-catalyzed conversion of carbon dioxide to formic acid, and its preparation method. This composite material is based on Ti3C2T… x Ti3C2T was prepared by a one-step sintering method using nano-SiO2 and organic carbon and nitrogen compounds as raw materials. x / SiO2 / carbon nitride (CN), abbreviated as TSCN, is a simple preparation method with easily controllable material structure and stable performance. Since all three components adsorb CO2, this composite material is used to accelerate the enzyme-catalyzed conversion of CO2 to formic acid, surpassing the best-performing existing technology, mSiO2; after amino modification, its reinforcing effect surpasses that of PDA / PEI-mSiO2.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing titanium carbide-based nanocomposite materials that can accelerate the enzyme-catalyzed conversion of carbon dioxide to formic acid, using Ti3C2T x TSCN is prepared by a one-step sintering method using nano-SiO2 and carbon-nitrogen organic compounds as raw materials.

[0009] The preparation steps are as follows: Weigh a certain mass of Ti3C2T x SiO2 powder and other ingredients were added separately to deionized water and ultrasonically dispersed. Then, they were mixed with organic carbon and nitrogen compounds and stirred in a water bath until all the water was evaporated. The resulting black solid was transferred to a covered crucible and heated to the sintering temperature at a certain heating rate in a tube furnace under an inert atmosphere and held for a period of time. After naturally cooling to room temperature, the resulting solid was ground and sieved through a sieve of a certain mesh size to remove large particles, thus obtaining TSCN.

[0010] The carbon-nitrogen organic compound is cyanamide, but it can also be dicyandiamide or melamine.

[0011] The mass ratio of the carbon-nitrogen organic compound to SiO2 is 0.1 to 10, preferably 0.5 to 5.

[0012] The Ti3C2T x The mass ratio of SiO2 to SiO2 is 0.1 to 10, preferably 0.5 to 5.

[0013] The particle size of the SiO2 is 1-100 nm, preferably 2-50 nm.

[0014] The mass of the deionized water is Ti3C2T x The mass of SiO2 is 5 to 250 times that of SiO2, preferably 20 to 200 times.

[0015] The ultrasound duration is 0.01 to 2 hours, preferably 0.05 to 0.5 hours.

[0016] The water bath temperature is 40–90°C, preferably 60–80°C.

[0017] The stirring speed is 40-400 rpm, preferably 80-200 rpm.

[0018] The inert gas can be either nitrogen or argon.

[0019] The flow rate of the inert gas is 20–80 mL / min, preferably 40–60 mL / min.

[0020] The heating rate is 0.5–10 °C / min, preferably 1–5 °C / min.

[0021] The sintering temperature is 400–600℃, preferably 500–580℃.

[0022] The heat preservation time is 1 to 10 hours, preferably 2 to 6 hours.

[0023] The sieve mesh size is 10 to 500 mesh, preferably 100 to 300 mesh.

[0024] The Ti3C2T x The preparation method is as follows: first, the precursor is etched by chemical method, and then intercalated with an intercalating agent to obtain the product.

[0025] The etching steps are as follows: A certain amount of precursor is weighed and dispersed in an etchant solution of a certain concentration. After stirring and etching at room temperature for a period of time, the mixture is centrifuged. The resulting precipitate is washed several times with deionized water until the supernatant is neutral. Then, it is sonicated in an ice-water mixture and freeze-dried. The resulting black powder is sieved through a sieve of a certain mesh size to remove large particles, yielding Ti3C2T before intercalation. x .

[0026] The precursor is Ti3AlC2, or it can be Ti3SiC2.

[0027] The etching agent is HF, or it can be NH4HF2, or a mixture of dilute hydrochloric acid and LiF.

[0028] The concentration of the etchant is 10-55 wt%, preferably 20-50 wt%.

[0029] The concentration of the precursor in the etchant solution is 10–100 g / L, preferably 30–70 g / L.

[0030] The etching time is 4 to 72 hours, preferably 10 to 36 hours.

[0031] The stirring speed is 50-500 rpm, preferably 100-250 rpm.

[0032] The ultrasound duration is 0.1 to 6 hours, preferably 0.5 to 4 hours.

[0033] The centrifugal speed is 5000-16000 r / min, preferably 8000-14000 r / min.

[0034] The centrifugation time is 3 to 40 minutes, preferably 5 to 25 minutes.

[0035] The freeze-drying time is 2 to 48 hours, preferably 4 to 24 hours.

[0036] The sieve mesh size is 10 to 500 mesh, preferably 100 to 300 mesh.

[0037] The intercalation process is as follows: A certain mass of Ti3C2T before intercalation is applied... x Add the intercalating agent to the solution, stir at room temperature for a period of time for intercalation, then centrifuge. Wash the resulting precipitate several times with deionized water until the supernatant is neutral. Then sonicate in an ice-water mixture, freeze-dry, and sieve the resulting black powder through a sieve of a certain mesh to remove large particles, obtaining the intercalated Ti3C2T. x .

[0038] The Ti3C2T before intercalation x The concentration of the intercalating agent in the solution is 50–200 g / L, preferably 80–150 g / L.

[0039] The intercalating agent is a mixture of ammonia and KCl, or it can be ammonia or KOH.

[0040] In the mixture of ammonia and KCl, the commercially available concentration of ammonia is 25-28 wt%, and the concentration of KCl in the ammonia is 0.5-3 mol / L.

[0041] The concentration of the KOH aqueous solution is 2–15 mol / L.

[0042] The intercalation time is 4 to 72 hours, preferably 10 to 36 hours.

[0043] The stirring speed is 50-500 rpm, preferably 100-250 rpm.

[0044] The ultrasound duration is 0.1 to 6 hours, preferably 0.5 to 4 hours.

[0045] The centrifugal speed is 5000-16000 r / min, preferably 8000-14000 r / min.

[0046] The centrifugation time is 3 to 40 minutes, preferably 5 to 25 minutes.

[0047] The freeze-drying time is 2 to 48 hours, preferably 4 to 24 hours.

[0048] The sieve mesh size is 10 to 500 mesh, preferably 100 to 300 mesh.

[0049] The method for accelerating the conversion of carbon dioxide into formic acid by enzyme catalysis is as follows: TSCN or amino-modified TSCN is added to a buffer solution containing FDH and NADH, and then CO2 gas is introduced and a certain pressure is maintained, and the reaction is carried out in a constant temperature oscillator.

[0050] The concentration of the TSCN or amino-modified TSCN in the buffer solution is 1–100 g / L, preferably 5–60 g / L.

[0051] The amino-modified TSCN can be PDA / PEI-modified TSCN or PEI-modified TSCN.

[0052] The concentration of FDH in the buffer solution is 0.1–10 g / L, preferably 0.5–6 g / L.

[0053] The concentration of NADH in the buffer solution is 0.01–0.1 mol / L, preferably 0.02–0.06 mol / L.

[0054] The buffer solution is either phosphate buffer or Tris-HCl buffer.

[0055] The buffer solution has a pH value of 5 to 8, preferably 5.5 to 7.0.

[0056] The buffer solution has a concentration of 0.01–1.0 mol / L, preferably 0.02–0.2 mol / L.

[0057] The pressure is 0.1 to 5 MPa, preferably 0.2 to 2 MPa.

[0058] The oscillator has a rotational speed of 50-250 rpm, preferably 100-200 rpm.

[0059] The reaction temperature is 15–45°C, preferably 25–40°C.

[0060] The reaction time is 2 to 120 minutes, preferably 10 to 60 minutes.

[0061] Beneficial effects

[0062] 1. This invention uses Ti3C2T x TSCN composite materials are prepared by a one-step sintering method using nano-SiO2 and organic carbon and nitrogen compounds as raw materials. The preparation method is simple, the structural parameters of the material are not easily affected by the preparation process and the external environment, the structure is easy to control, and the performance is stable.

[0063] 2. This invention utilizes the high specific surface area of ​​nano-SiO2 and the multiple adsorption sites of CN for CO2, loading both onto Ti3C2T, which has a two-dimensional large planar structure and a multilayer structure. x On the surface, a ternary composite material TSCN was prepared. This structural design can weaken the Ti3C2T x The interlayer stacking increases the specific surface area, inhibits the aggregation of SiO2 and the agglomeration of CN during thermal polymerization, exposes more adsorption sites for SiO2 and CN, and enhances the adsorption of CO2 by the material. This composite material is used to accelerate the enzyme-catalyzed conversion of CO2 to formic acid, surpassing existing technologies.

[0064] 3. The TSCN prepared in this invention is used to accelerate the enzyme-catalyzed conversion of carbon dioxide into formic acid. The enhancement factor of TSCN per 20 mg is greater than 10. After further modification with PEI, the enhancement factor of PEI-TSCN with an addition amount of 20 mg can reach more than 20, which is higher than the best-performing mSiO2 and PDA / PEI-mSiO2 in the prior art (the enhancement factors per 20 mg are 5.6 and 12.4, respectively). Attached Figure Description

[0065] Figure 1 The reaction mechanism for obtaining CN from cyanamide via a one-step sintering method;

[0066] Figure 2 This is a schematic diagram of the preparation of TSCN and the modification of PEI.

[0067] Figure 3 The TSCN(Ti3C2T) prepared in Example 1 x (The mass ratio of cyanamide to SiO2 is 1.5:1.5:1), Ti3C2T x The X-ray diffraction (XRD) and Fourier transform infrared (FTIR) characterization results of SiO2 and CN are shown in Figure a; Figure b shows the XRD results.

[0068] Figure 4 Figure a shows the SEM images of the samples; where Figure a is the TSCN(Ti3C2T) prepared in Example 1. x Figure 1 shows the SEM image of Ti3C2T (with a mass ratio of cyanamide to SiO2 of 1.5:1.5:1); Figure 2 shows the SEM image of Ti3C2T. x Figure 1 is a SEM image of SiO2; Figure 2c is a SEM image of CN; Figure 3d is a SEM image of CN.

[0069] Figure 5 Different Ti3C2T prepared in Example 1 x A magnified view of the XRD pattern of TSCN with a mass ratio of cyanamide to SiO2;

[0070] Figure 6 Different Ti3C2T prepared in Example 1 x TSCN and PEI-TSCN with a mass ratio of cyanamide to SiO2 were used to accelerate the initial reaction rate of the enzyme-catalyzed conversion of CO2 to formic acid, and compared with the free enzyme system before addition. Detailed Implementation

[0071] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0072] Example 1

[0073] (1) Preparation of Ti3C2T x

[0074] Etching steps: Weigh 1g of precursor Ti3AlC2 and disperse it in 20mL of 40wt% HF solution (the concentration of the precursor in the HF solution is 50g / L). Etch at room temperature with stirring at 150rpm for 24h. Then centrifuge at 10500r / min for 10min. Wash the resulting precipitate repeatedly with deionized water until the supernatant is neutral. Then sonicate in an ice-water mixture for 2h and freeze-dry for 12h. The resulting black powder is sieved through a 200-mesh sieve to remove large particles, obtaining Ti3C2T before intercalation. x .

[0075] Intercalation steps: 1g of Ti3C2T before intercalation x Add to 10 mL of intercalating agent solution (Ti3C2T before intercalation) x The concentration of the intercalating agent solution was 100 g / L, with 10 mL of NH4OH (25-28 wt%) and KCl concentration of 1.34 mol / L. Intercalation was carried out at room temperature with stirring at 150 rpm for 24 hours. The mixture was then centrifuged at 10500 rpm for 20 minutes. The resulting precipitate was washed several times with deionized water until the supernatant was neutral. After sonication in an ice-water mixture for 2 hours, it was freeze-dried for 12 hours. The resulting black powder was sieved through a 200-mesh sieve to remove large particles, yielding the intercalated Ti3C2T. x .

[0076] (2) Preparation of TSCN

[0077] Weigh out 0.2g, 0.4g, or 0.6g of intercalated Ti3C2T x (making Ti3C2T x The mass ratios of cyanamide to SiO2 were 0.5:1.5:1, 1:1.5:1, and 1.5:1.5:1, respectively. 0.4 g of SiO2 powder (particle size 7 nm) was added to 20 mL of deionized water (for dispersing Ti3C2T). x The masses of deionized water were Ti3C2T x The SiO2 was dispersed by ultrasonication for 3 min at 100, 50, and 33.3 times the mass of SiO2 (the mass of deionized water used to disperse SiO2 was 50 times the mass of SiO2), then mixed with 0.6 g of cyanamide and stirred in a water bath at 70 °C (150 rpm) until all the water was evaporated. The resulting black solid was transferred to a covered crucible and heated to 550 °C at a heating rate of 2.3 °C / min in a tube furnace under N2 atmosphere (50 mL / min) and held for 4 h. After naturally cooling to room temperature, the resulting solid was ground and sieved through a 200-mesh sieve to remove large particles, yielding TSCN.

[0078] Figure 1 The reaction mechanism for obtaining CN from cyanamide via a one-step sintering method; the preparation process of TSCN is as follows: Figure 2 As shown.

[0079] Figure 3 a is the TSCN(Ti3C2T) prepared in Example 1. x (The mass ratio of cyanamide to SiO2 is 1.5:1.5:1) and Ti3C2T x The XRD patterns of TSCN were obtained and compared with those of SiO2 and CN. It can be seen that Ti3C2T appears in the TSCN pattern. x The characteristic diffraction peaks of 002 (6.00°), SiO2 (broad peak near 22.7°), and CN (13.0° and 27.4°) prove that TSCN is composed of these three materials.

[0080] Figure 3 b is the TSCN(Ti3C2T) prepared in Example 1. x (The mass ratio of cyanamide to SiO2 is 1.5:1.5:1) and Ti3C2T x The FTIR spectra of TSCN were obtained and compared with those of SiO2 and CN. It can be seen that the TSCN spectra show a higher peak density at 1074 cm⁻¹. -1 Symmetric tensile vibration peaks of Si-O-Si were observed, in the range of 1200–1700 cm⁻¹. -1 A stretching vibration peak appeared in the CN heterocyclic compound at 574 cm⁻¹. -1 Ti3C2T was found nearby. x The characteristic peaks are those of Ti-O tensile vibration; in the range of 3000–3700 cm⁻¹ -1 Nearby are the NH stretching vibration peak of CN and the asymmetric stretching vibration peak of –OH of SiO2, as well as the Ti3C2T peak. x The composite peak of the asymmetric tensile vibration peak of the –OH on the surface further proves that TSCN is composed of these three materials.

[0081] Figure 4 a is the TSCN(Ti3C2T) prepared in Example 1. x SEM images of cyanamide and SiO2 in a mass ratio of 1.5:1.5:1. Figure 4 b is Ti3C2T x SEM image, Figure 4 c is the SEM image of SiO2. Figure 4 d is the SEM image of CN. As shown in the figure, Ti3C2T xThe TSCN composite material has an accordion-like multilayer structure, consisting of a thin layer of CN coating and SiO2 particles. This demonstrates that the TSCN composite material was successfully prepared by a one-step sintering method.

[0082] Figure 5 The Ti3C2T in Example 1 x The image shows a partially magnified XRD pattern of TSCN prepared under conditions where the mass ratio of cyanamide to SiO2 is 0.5:1.5:1, 1:1.5:1, and 1.5:1.5:1, respectively. It can be seen that with the increase of Ti3C2T... x Increased dosage, Ti3C2T x The intensity of the 002 characteristic diffraction peak increases, and the peak position (corresponding to c-LP in Table 1) gradually shifts positively, indicating that Ti3C2T x The interlayer spacing decreased (see Table 1). The specific surface area was measured using the BET method, and the CO2 adsorption capacity of the material was measured using thermogravimetric analysis. It was found that the adsorption capacity decreased with increasing Ti3C2T... x As the dosage increases, the specific surface area decreases accordingly, but the CO2 adsorption capacity increases (see Table 1).

[0083] The Ti3C2T in Example 1 x TSCN prepared under conditions where the mass ratio of cyanamide to SiO2 was 0.5:1.5:1, 1:1.5:1, and 1.5:1.5:1, was used to accelerate the enzyme-catalyzed conversion of CO2 to formic acid. 20 mg of TSCN (TSCN concentration in the buffer solution was 10 g / L) was added to 2 mL of phosphate buffer (pH 6.0, 0.5 mol / L) containing 1 g / L FDH and 50 mmol / L NADH. CO2 gas was then introduced and the reaction was maintained at a pressure of 0.05 MPa in a constant-temperature shaker at 37℃ and 170 rpm for 10 min. After centrifugation, the supernatant was derivatized, and the formic acid concentration (in mmol / L) was analyzed by high-performance liquid chromatography (HPLC). The initial reaction rate (in mmol / (L·h)) was calculated by dividing the formic acid concentration by the reaction time and compared with a free enzyme system using the same amount of enzyme to calculate the enhancement factor. The initial reaction rate of the enzyme-catalyzed conversion of CO2 to formic acid is as follows: Figure 6 As shown, the enhancement factors are shown in Table 1.

[0084] Table 1. Parameters of TSCN prepared in Example 1

[0085]

[0086]

[0087] (3) Amino-modified TSCN

[0088] TSCN was modified with PEI, and the modification process is as follows: Figure 2 As shown. Weigh out TSCN(Ti3C2T) x 1 g of PEI-TSCN powder (with a mass ratio of 1.5:1.5:1) was added to 22.5 mL of an aqueous solution containing 4 g / L PEI, resulting in a TSCN concentration of 44.4 g / L. The mixture was stirred at 28 °C for 12 h, then centrifuged at 12000 r / min for 5 min. The mixture was washed with deionized water until the supernatant was colorless and transparent. After freeze-drying for 12 h, the mixture was ground and sieved through a 200-mesh sieve to remove large particles, yielding PEI-TSCN.

[0089] Table 2 shows a comparison of the performance of PEI-TSCN with that of TSCN, and the initial reaction rate is as follows: Figure 6 As shown, compared to TSCN, the 002 diffraction characteristic peak of PEI-TSCN shifts to the left, indicating an increase in interlayer spacing. Elemental analysis revealed an increase in nitrogen (N) content on the PEI-TSCN surface, indicating successful introduction of amino groups. Thermogravimetric analysis showed a significant increase in CO2 adsorption. Therefore, the addition of 20 mg of PEI-TSCN increases the initial rate of the enzyme-catalyzed CO2-to-formic acid reaction, and the enhancing factor also increases.

[0090] Table 2 Comparison of various parameters of PEI-TSCN and TSCN prepared in Example 1

[0091]

[0092] Example 2

[0093] Weigh 0.6g Ti3C2T x Weigh out 0.2g, 0.4g, or 0.6g of SiO2 powder (particle size 12nm) to make Ti3C2T x The mass ratios of cyanamide to SiO2 were 3:3:1, 1.5:1.5:1, and 1:1:1, respectively. These were added to 30 and 40 mL of deionized water (for dispersing Ti3C2T). x The mass of the deionized water is Ti3C2T x The SiO2 was dispersed ultrasonically for 5 min at a mass of 50 times the mass of SiO2, and the mass of deionized water used for dispersing SiO2 was 200, 100, and 66.7 times the mass of SiO2, respectively. Then it was mixed with 0.6 g of cyanamide and stirred in a water bath at 75 °C (180 rpm) until all the water was evaporated. The resulting black solid was transferred to a covered crucible and heated to 580 °C at a heating rate of 2.5 °C / min in a tube furnace under N2 atmosphere (60 mL / min) and held for 3 h. After naturally cooling to room temperature, the resulting solid was ground and sieved through a 300-mesh sieve to remove large particles, thus obtaining TSCN.

[0094] The properties of the prepared TSCN are shown in Table 3.

[0095] Table 3. Parameters of TSCN prepared in Example 2

[0096]

[0097]

[0098] Example 3

[0099] Weigh 0.6g Ti3C2T x 0.4 g of SiO2 powder (particle size 30 nm) was added to 30 mL of deionized water (the mass of the deionized water was Ti3C2T respectively). x Disperse the mixture ultrasonically for 10 min at 50 and 75 times the mass of SiO2, then mix it with 0.4 g or 0.6 g or 0.8 g of cyanamide (to make Ti3C2T x The mass ratios of cyanamide and SiO2 were 1.5:1:1, 1.5:1.5:1, and 1.5:2:1, respectively. The mixture was stirred in a water bath at 80°C (120 rpm) until all the water was evaporated. The resulting black solid was transferred to a covered crucible and heated to 500°C at a heating rate of 2.0°C / min in a tube furnace under an argon atmosphere (40 mL / min) and held for 6 hours. After naturally cooling to room temperature, the resulting solid was ground and sieved through a 250-mesh sieve to remove large particles, yielding TSCN.

[0100] The properties of the prepared TSCN are shown in Table 4.

[0101] Table 4. Parameters of TSCN prepared in Example 3

[0102]

[0103] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a titanium carbide-based nanocomposite material that can accelerate the enzyme-catalyzed conversion of carbon dioxide into formic acid, characterized in that: With Ti3C2T x TSCN was prepared by a one-step sintering method using nano-SiO2 and organic carbon and nitrogen compounds as raw materials. The specific preparation steps are as follows: Weigh Ti3C2T x SiO2 powder and other ingredients were separately added to deionized water and ultrasonically dispersed. Then, they were mixed with organic carbon and nitrogen compounds and stirred in a water bath until all the water was evaporated. The resulting black solid was transferred to a covered crucible and heated to the sintering temperature at a certain heating rate in a tube furnace under an inert atmosphere and held for a period of time. After naturally cooling to room temperature, the resulting solid was ground and sieved to obtain TSCN. The inert gas flow rate was 20-80 mL / min; the heating rate was 0.5-10 °C / min; the sintering temperature was 400-600 °C; and the holding time was 1-10 h.

2. The method as described in claim 1, characterized in that: The mass ratio of organic carbon and nitrogen compounds to SiO2 is 0.1–10; Ti3C2T x The mass ratio of the compound to SiO2 is 0.1 to 10; the organic carbon-nitrogen compound is cyanamide, dicyandiamide, or melamine; the ultrasonic time is 0.01 to 2 hours.

3. The method as described in claim 1, characterized in that: The Ti3C2T x The preparation method is as follows: first, the precursor is etched by chemical method, and then intercalated with an intercalating agent to obtain the product; The etching steps are as follows: the precursor is dispersed in an etchant solution of a certain concentration, stirred and etched at room temperature for a period of time, then centrifuged, and the resulting precipitate is repeatedly washed with deionized water until the supernatant is neutral. Then, it is sonicated in an ice-water mixture and freeze-dried. The resulting black powder is sieved to obtain Ti3C2T before intercalation. x The concentration of the precursor in the etchant solution is 10–100 g / L. The intercalation steps are as follows: Apply Ti3C2T before intercalation... x A certain concentration of intercalating agent solution was added, and after intercalation at room temperature for a period of time with stirring, the mixture was centrifuged. The resulting precipitate was repeatedly washed with deionized water until the supernatant was neutral. Then, it was sonicated in an ice-water mixture and freeze-dried. The resulting black powder was sieved to obtain the intercalated Ti3C2T. x Ti3C2T before intercalation x The concentration of the intercalating agent in the solution is 50–200 g / L.

4. The method as described in claim 3, characterized in that: The precursor is Ti3AlC2 or Ti3SiC2; the etchant is HF, NH4HF2 or a mixture of dilute hydrochloric acid and LiF; The etchant concentration is 10–55 wt%; the etching time is 4–72 h; The intercalating agent is a mixture of ammonia and KCl, ammonia, or KOH; In the mixture of ammonia and KCl, the concentration of ammonia is 25-28 wt%, and the concentration of KCl in the ammonia is 0.5-3 mol / L. The concentration of KOH is 2–15 mol / L; The intercalation time is 4 to 72 hours.

5. A method for accelerating the enzyme-catalyzed conversion of carbon dioxide to formic acid using the composite material prepared by the method described in claim 1, characterized in that: TSCN or amino-modified TSCN is added to a buffer solution containing FDH and NADH, and then CO2 gas is introduced and a certain pressure is maintained. The reaction is carried out in a constant temperature oscillator. The concentration of TSCN or amino-modified TSCN in the buffer solution is 1-100 g / L. The amino-modified TSCN is either PDA / PEI-modified TSCN or PEI-modified TSCN; the buffer solution is phosphate buffer or Tris-HCl buffer.

6. The method as described in claim 5, characterized in that: The concentration of FDH in the buffer solution is 0.1–10 g / L; the concentration of NADH in the buffer solution is 0.01–0.1 mol / L. The buffer solution has a pH of 5 to 8; The buffer solution has a concentration of 0.01–1.0 mol / L; The pressure is 0.1–5 MPa; the reaction temperature is 15–45 °C.

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