Monatomic iron nanoszyme with axial coordination of chlorine atom and preparation method thereof

Abstract

The application discloses a kind of single-atom iron nanoscale enzyme of chlorine atom axial coordination and preparation method thereof.The main steps of the method are as follows: first, metal-organic framework ZIF-8 is synthesized at room temperature, then calcined at high temperature under inert gas atmosphere to obtain Zn-NCSAzyme, finally, Zn-NCSAzyme is dissolved in polar solvent at low temperature, and FeCl3 solution is added for ion exchange, and single-atom iron nanoscale enzyme (Fe-NC SAzyme) of chlorine atom axial coordination can be obtained.The method of the application is simple in process, mild in condition and high in repeatability;Fe single atom obtained by replacement is exposed on the surface of carrier, which improves the utilization rate of atoms;the axial coordination of chlorine atom breaks the symmetry of iron atom electronic structure, and improves the catalytic activity of single-atom iron nanoscale enzyme.

Description

Technical Field

[0001] This invention belongs to the field of single-atom nanozymes and their preparation technology. Specifically, it relates to a single-atom iron nanozyme with chlorine atoms axially coordinated and its preparation method. Background Technology

[0002] Nanozymes are nanomaterials with enzyme-like catalytic activity. They are low-cost, highly stable, structurally tunable, and easy to mass-produce, showing broad application prospects in fields such as biosensing, tissue engineering, disease treatment, and environmental protection. Single-atom nanozymes (SAzymes) are nanozymes with isolated single-atom metal active sites. Compared with traditional nanozymes, SAzymes have tunable coordination structures, high atom utilization, and higher enzyme-like catalytic activity and specificity, attracting widespread attention.

[0003] The coordination environment of SAzymes plays a crucial role in catalysis, but precise control at the atomic level remains a significant challenge. Currently, nitrogen-doped carbon-supported single metal atoms (MNCs) are the most studied SAzymes, typically possessing porphyrin-like M-N4 planar structures, such as Zn-N4 (Angewandte Chemie, 2019, 131(15):4965-4970), Fe-N4 (Applied Catalysis B: Environmental, 2022, 310:121327), and Ni-N4 (Journal of Catalysis, 2021, 402:264-274). However, the high electronic / structural symmetry of the M-N4 sites is unfavorable for charge transfer during catalysis, hindering further improvements in the catalytic performance of SAzymes. To break this symmetrical electronic structure, researchers have developed a series of coordination environment regulation strategies, such as changing the coordination number (Nano Energy, 2021, 89:106365) and replacing some coordinating nitrogen atoms with other heteroatoms (Nano Research, 2022:1-6), which have greatly improved the catalytic performance of MNC nanozymes. However, these regulations are all limited to the carbon plane and inevitably alter the properties of the carbon support. Axial coordination environment regulation can be performed outside the carbon support plane, making it an ideal method to optimize the catalytic performance of SAzymes without affecting the performance of the carbon support. Highly electronegative axial halogen atoms can break the symmetrical charge distribution of the planar M-N4 sites, regulate the electronic state of the central metal atom, and thus improve the catalytic activity of SAzymes.

[0004] For the reasons stated above, this invention is proposed. Summary of the Invention

[0005] One of the objectives of this invention is to provide a single-atom iron nanozyme with chlorine atoms axially coordinated.

[0006] The second objective of this invention is to provide a method for preparing single-atom iron nanozymes with chlorine atoms axially coordinated.

[0007] The coordination structure of the axially coordinated chlorine atom single-atom iron nanozyme of the present invention is Fe-N4Cl, where Fe and N4 are in the same plane, and Cl and Fe are coordinated with Fe through the axial direction.

[0008] In the chlorine-atom-coordinated single-atom iron nanozyme of the present invention, the Fe single atom is completely exposed on the surface of the N-modified carbon support.

[0009] The Fe content in the axially coordinated chlorine atom single-atom iron nanozyme of the present invention is 0.13–15.6 wt%.

[0010] The preparation method of the chlorine atom axially coordinated single-atom iron nanozyme of the present invention includes the following steps:

[0011] (1) Dissolve Zn(NO3)2·6H2O and 2-methylimidazole in anhydrous methanol respectively. While stirring, pour the methanol solution containing 2-methylimidazole into the methanol solution containing Zn(NO3)2·6H2O and continue stirring the reaction. After the reaction is completed, centrifuge and wash with methanol three times to obtain ZIF-8 solid.

[0012] (2) The ZIF-8 prepared in step (1) is placed in a tube furnace and calcined at 600-850°C under an inert atmosphere to obtain Zn-NC SAzyme.

[0013] (3) The Zn-NCSAzyme obtained in step (2) was ultrasonically dispersed in polar solvents such as water, methanol, ethanol, N'N-dimethylformamide, and dimethyl sulfoxide. FeCl3 solution was added under stirring to carry out the reaction. After the reaction was completed, the mixture was centrifuged, washed, dried, and ground to obtain Fe-NCSAzyme with chlorine atoms axially coordinated.

[0014] Preferably, the amount of Zn(NO3)2·6H2O used in step (1) is 1.29 to 3.58 g.

[0015] Preferably, the amount of 2-methylimidazole used in step (1) is 1.35 to 3.67 g.

[0016] Preferably, the total amount of anhydrous methanol used in step (1) is 200 mL.

[0017] Preferably, the stirring reaction time in step (1) is 1-10 h.

[0018] Preferably, the calcination procedure in step (2) is as follows: first, the temperature is increased to 600-850℃ at a rate of 5-15℃ / min, maintained for 1-5 hours, and finally cooled to room temperature at a rate of 2-20℃ / min.

[0019] Preferably, the flow rate of the inert gas atmosphere in step (2) is 20 to 100 mL / min.

[0020] Preferably, the Fe content in the FeCl3 solution in step (3) is in a mass ratio of 0.1 to 5:1 to Zn-NCSAzyme.

[0021] Preferably, the temperature in step (3) is between 0 and 60°C.

[0022] Preferably, the stirring time in step (3) is 0.5 to 72 hours.

[0023] The beneficial effects of this invention are as follows: This invention utilizes calcined Zn-NCSAzyme as a precursor material to prepare axially coordinated single-atom iron nanozymes using ion exchange technology under low-temperature stirring conditions. Since FeCl3 has one more Cl atom than ZnCl2, the Cl atom coordinates with Fe axially after the substitution. This method is simple, mild, and highly reproducible. The axial coordination of chlorine atoms breaks the electronic structure symmetry, and this method can only substitute zinc on the outer surface of the support, exposing all the resulting iron single atoms on the material surface, thus improving the catalytic activity of the single-atom iron nanozyme. Attached Figure Description

[0024] Figure 1 TEM image of the axially coordinated chlorine atom single-atom iron nanozyme described in Example 1 of this invention.

[0025] Figure 2 HAADF-STEM image of the axially coordinated chlorine atom single-atom iron nanozyme described in Example 1 of this invention.

[0026] Figure 3 XRD pattern of the axially coordinated chlorine atom single-atom iron nanozyme described in Example 1 of this invention.

[0027] Figure 4 XPS image of the axially coordinated chlorine atom single-atom iron nanozyme described in Example 1 of this invention.

[0028] Figure 5 The peroxidase activity of the Fe-N4 single-atom nanozyme described in Example 6 of this invention is compared with that of the chlorine-atom axially coordinated single-atom iron nanozyme described in Example 1. Detailed Implementation

[0029] Example 1

[0030] (1) Dissolve 2.38g of Zn(NO3)2·6H2O in 100mL of anhydrous methanol, and dissolve 2.77g of 2-methylimidazole in another 100mL of anhydrous methanol. Sonicate to disperse the 2-methylimidazole evenly. While stirring, pour the methanol solution containing 2-methylimidazole into the methanol solution containing Zn(NO3)2·6H2O. Continue stirring at 300rpm for 2h. After the reaction is complete, centrifuge and wash three times with methanol to obtain ZIF-8 solid.

[0031] (2) Spread 100g of ZIF-8 prepared in step (1) in a quartz boat, place it in a tube furnace, and calcine it under an argon atmosphere. The calcine procedure is as follows: first, heat the temperature from 20℃ to 800℃ at a rate of 10℃ / min, hold for 2h, and finally cool it down to room temperature at a rate of 5℃ / min to obtain Zn-NCSAzyme.

[0032] (3) Weigh 30 mg of Zn-NCSAzyme obtained in step (2) and ultrasonically disperse it in 10 mL of anhydrous ethanol. Prepare an aqueous solution of FeCl3 with a Fe ion concentration of 10 mg / mL, and add 1.5 mL (Fe to Zn-NC mass ratio of 0.5:1) to the Zn-NCSAzyme ethanol solution under stirring. Continue stirring at 500 rpm for 12 h at 20 °C. After the reaction, wash three times with deionized water by centrifugation, dry under vacuum at 60 °C, and grind to obtain Fe-NCSAzyme with chlorine atoms axially coordinated. The Fe content determined by ICP is 9.33 wt%. TEM and HAADF-STEM results are shown in the figures. Figure 1 and Figure 2 , Figure 1 It can be seen that the material dimensions are uniform. Figure 2 The small bright spots in the image represent Fe in an atomically dispersed state. Figure 3 The XRD pattern shows only a broad peak for amorphous graphite, indicating that the material is in an amorphous state. Figure 4 The XPS spectrum shows that Fe has divalent and trivalent valence states in the material, and there is a very obvious characteristic peak of Cl element at around 200 eV, which proves that there are axial coordination of Cl atoms in Fe-NCSAzyme.

[0033] (4) Disperse 30 μg of Fe-NCSAzyme prepared in step (3) in 3 mL of buffer solution (pH 5.0) using ultrasound, add 0.6 mg of 3,3',5,5'-tetramethylbenzidine and 3 μL of hydrogen peroxide stock solution (10 mol / L), react for 1 min, and then measure the optical absorption of the oxidation product of 3,3',5,5'-tetramethylbenzidine using a UV-Vis spectrophotometer. The spectrum is shown in [reference needed]. Figure 5 .Depend on Figure 5It can be seen that the characteristic peaks of the oxidation products of 3,3',5,5'-tetramethylbenzidine are very high, indicating that the peroxidase-like activity of Fe-NCSAzyme is much higher than that of Fe-N4SAzyme under these conditions (Reference: Advanced Materials, 2022, 34(15): 2107088). This proves that the axial coordination of chlorine atoms and the large number of Fe atom sites exposed on the surface improve the catalytic activity of the material.

[0034] Example 2

[0035] (1) Dissolve 2.38g of Zn(NO3)2·6H2O in 100mL of anhydrous methanol, and dissolve 2.77g of 2-methylimidazole in another 100mL of anhydrous methanol. Sonicate to disperse the 2-methylimidazole evenly. While stirring, pour the methanol solution containing 2-methylimidazole into the methanol solution containing Zn(NO3)2·6H2O. Continue stirring at 300rpm for 2h. After the reaction is complete, centrifuge and wash three times with methanol to obtain ZIF-8 solid.

[0036] (2) Spread 100g of ZIF-8 prepared in step (1) in a quartz boat and place it in a tube furnace for calcination under an argon atmosphere. The calcination procedure is as follows: first, heat from 20℃ to 800℃ at a rate of 10℃ / min and hold for 2h, and finally cool down to room temperature at a rate of 5℃ / min to obtain Zn-NCSAzyme.

[0037] (3) Weigh 30 mg of Zn-NCSAzyme obtained in step (2) and ultrasonically disperse it in 10 mL of anhydrous ethanol. Prepare FeCl3 into an aqueous solution with a Fe ion concentration of 10 mg / mL. Add 0.3 mL (Fe to Zn-NC mass ratio of 0.1:1) to the ethanol solution of Zn-NCSAzyme under stirring. Continue stirring at 500 rpm for 12 h at 20 °C. After the reaction is completed, wash three times with deionized water by centrifugation, dry under vacuum at 60 °C, and grind to obtain Fe-NCSAzyme with chlorine atoms axially coordinated. The Fe content measured by ICP is 0.13 wt%.

[0038] Example 3

[0039] (1) Dissolve 2.38g of Zn(NO3)2·6H2O in 100mL of anhydrous methanol, and dissolve 2.77g of 2-methylimidazole in another 100mL of anhydrous methanol. Sonicate to disperse the 2-methylimidazole evenly. While stirring, pour the methanol solution containing 2-methylimidazole into the methanol solution containing Zn(NO3)2·6H2O. Continue stirring at 300rpm for 2h. After the reaction is complete, centrifuge and wash three times with methanol to obtain ZIF-8 solid.

[0040] (2) Spread 100g of ZIF-8 prepared in step (1) in a quartz boat and place it in a tube furnace for calcination under an argon atmosphere. The calcination procedure is as follows: first, heat from 20℃ to 800℃ at a rate of 10℃ / min and hold for 2h, and finally cool down to room temperature at a rate of 5℃ / min to obtain Zn-NCSAzyme.

[0041] (3) Weigh 30 mg of Zn-NCSAzyme obtained in step (2) and ultrasonically disperse it in 10 mL of anhydrous ethanol. Prepare an aqueous solution of FeCl3 with a Fe ion concentration of 10 mg / mL. Add 1.5 mL (Fe to Zn-NC mass ratio of 0.5:1) to the ethanol solution of Zn-NCSAzyme while stirring. Continue stirring at 500 rpm for 12 h at 60 °C. After the reaction, wash three times with deionized water by centrifugation, dry under vacuum at 60 °C, and grind to obtain Fe-NCSAzyme with chlorine atoms axially coordinated. The Fe content determined by ICP is 5.26 wt%.

[0042] Example 4

[0043] (1) Dissolve 2.38g of Zn(NO3)2·6H2O in 100mL of anhydrous methanol, and dissolve 2.77g of 2-methylimidazole in another 100mL of anhydrous methanol. Sonicate to disperse the 2-methylimidazole evenly. While stirring, pour the methanol solution containing 2-methylimidazole into the methanol solution containing Zn(NO3)2·6H2O. Continue stirring at 300rpm for 2h. After the reaction is complete, centrifuge and wash three times with methanol to obtain ZIF-8 solid.

[0044] (2) Spread 100g of ZIF-8 prepared in step (1) in a quartz boat and place it in a tube furnace for calcination under an argon atmosphere. The calcination procedure is as follows: first, heat from 20℃ to 800℃ at a rate of 10℃ / min and hold for 2h, and finally cool down to room temperature at a rate of 5℃ / min to obtain Zn-NCSAzyme.

[0045] (3) Weigh 30 mg of Zn-NCSAzyme obtained in step (2) and ultrasonically disperse it in 10 mL of anhydrous ethanol. Prepare FeCl3 into an aqueous solution with a Fe ion concentration of 10 mg / mL. Add 1.5 mL (Fe to Zn-NC mass ratio of 0.5:1) to the ethanol solution of Zn-NCSAzyme under stirring. Continue stirring at 500 rpm for 12 h at 0 °C. After the reaction is completed, wash three times with deionized water by centrifugation, dry under vacuum at 60 °C, and grind to obtain Fe-NCSAzyme with chlorine atoms axially coordinated. The Fe content measured by ICP is 7.49 wt%.

[0046] Example 5

[0047] (1) Dissolve 2.38g of Zn(NO3)2·6H2O in 100mL of anhydrous methanol, and dissolve 2.77g of 2-methylimidazole in another 100mL of anhydrous methanol. Sonicate to disperse the 2-methylimidazole evenly. While stirring, pour the methanol solution containing 2-methylimidazole into the methanol solution containing Zn(NO3)2·6H2O. Continue stirring at 300rpm for 2h. After the reaction is complete, centrifuge and wash three times with methanol to obtain ZIF-8 solid.

[0048] (2) Spread 100g of ZIF-8 prepared in step (1) in a quartz boat and place it in a tube furnace for calcination under an argon atmosphere. The calcination procedure is as follows: first, heat from 20℃ to 800℃ at a rate of 10℃ / min and hold for 2h, and finally cool down to room temperature at a rate of 5℃ / min to obtain Zn-NCSAzyme.

[0049] (3) Weigh 30 mg of Zn-NCSAzyme obtained in step (2) and ultrasonically disperse it in 10 mL of anhydrous ethanol. Prepare FeCl3 into an aqueous solution with a Fe ion concentration of 10 mg / mL. Add 15 mL (Fe to Zn-NC mass ratio of 5:1) to the ethanol solution of Zn-NCSAzyme under stirring. Continue stirring at 20 °C and 500 rpm for 2 days. After the reaction is completed, wash three times with deionized water by centrifugation, dry under vacuum at 60 °C, and grind to obtain Fe-NCSAzyme with chlorine atoms axially coordinated. The Fe content measured by ICP is 15.6 wt%.

Claims

1. A single-atom iron nanozyme with chlorine atoms axially coordinated, characterized in that, The coordination structure of the chlorine-atom-coordinated single-atom iron nanozyme is Fe-N4Cl, with Fe and N4 in the same plane, and Cl and Fe coordinated axially with Fe; the Fe single atom is completely exposed on the surface of the N-modified carbon support; the Fe content is 5.26~15.6 wt%; the preparation method of the chlorine-atom-coordinated single-atom iron nanozyme includes the following steps: (1) Dissolve Zn(NO3)2·6H2O and 2-methylimidazole in anhydrous methanol respectively. Pour the methanol solution containing 2-methylimidazole into the methanol solution containing Zn(NO3)2·6H2O while stirring. Continue stirring and react. After the reaction is complete, centrifuge and wash with methanol three times to obtain ZIF-8 solid. (2) The ZIF-8 prepared in step (1) is placed in a tube furnace and calcined at 600~850 °C under an inert atmosphere to obtain Zn-NCSAzyme; (3) The Zn-NCSAzyme obtained in step (2) is ultrasonically dispersed in water, methanol, ethanol, N'N-dimethylformamide or dimethyl sulfoxide, and FeCl3 solution is added under stirring and reacted at 0~60℃ for 0.5~72h. After the reaction is completed, the mixture is centrifuged, washed, dried and ground to obtain Fe-NCSAzyme with chlorine atoms axially coordinated. The mass ratio of Fe to Zn-NCSAzyme in FeCl3 solution is 50%~500%.

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