Preparation method and application of MOF-derived cobalt-iron composite material

Abstract

The present invention discloses a preparation method and application of a MOF-derived cobalt-iron composite material. The method synthesizes dodecahedral Fe-ZIF 67 by coprecipitation, followed by a two-step calcination process of carbonization and oxidation to synthesize the cobalt-iron composite material. Under a mild CO2 atmosphere, the ZIF loses little carbon skeleton during oxidation. The MOF-derived cobalt-iron bimetallic composite material, CoFeCMs (CO2), prepared by calcination has a larger specific surface area and a complete carbon skeleton, providing more active sites and exhibiting superior catalytic performance and electron transfer efficiency. The CoFeCMs (CO2) can activate PMS to degrade OFX with an efficiency of 94.2% within 30 minutes.

Description

Technical Field

[0001] The present invention relates to the technical field of antibiotic treatment of organic matter pollution, and in particular to a preparation method and application of a MOF-derived cobalt-iron composite material. Background Art

[0002] Antibiotics are widely used in medicine and veterinary medicine as compounds with antibacterial, antiviral, and antifungal activity. Antibiotics can enter the environment through various pathways, such as the pharmaceutical industry, hospital wastewater, and human and animal waste disposal. Approximately 30-90% of antibiotics remain active and unmetabolized, excreting into the environment through urine and feces. This can lead to the development of antibiotic-resistant pathogens, potentially threatening ecosystems and human health. Traditional biological treatment methods struggle to effectively remove recalcitrant antibiotics from water bodies due to their high toxicity to bacterial communities, which can halt biological processes in wastewater treatment.

[0003] Ofloxacin OFX is a third-generation fluoroquinolone antibiotic that can be frequently detected in water bodies. The concentration of OFX detected in local water bodies in eastern my country was as high as 254.74 ng / L, which is much higher than other antibiotics.

[0004] MOF-derived materials retain the advantages of MOF materials such as three-dimensional pore structure, large specific surface area, abundant active sites, adjustable metal elements and pore structure, and are a promising SR-AOPs catalyst. Advanced oxidation technology SR-AOPs based on sulfate radicals has excellent mineralization rate and applicability for refractory organic matter such as antibiotics. The SR-AOPs method mainly produces SO4 ·- and ·OH strong oxidizing species with reduction potentials (E) of 2.8 V and 2.5~3.1 V, respectively, which can rapidly and non-selectively oxidize antibiotic pollutants in wastewater.

[0005] Cobalt is considered to be the most effective transition metal for SR-AOPs to remove organic pollutants. However, the catalytic performance of MOF-derived cobalt-based metal materials is limited, and they are prone to agglomeration and have poor stability. 3+ / Co 2 + 、Fe 3+ / Fe 2+ However, MOFs-derived cobalt-iron bimetallic materials are limited by the low number of active sites and the easy leaching of metal ions, which restricts their application. Their activity and stability need to be further improved. Summary of the Invention

[0006] The present invention provides a method for preparing and applying a MOF-derived cobalt-iron composite material. The MOF-derived cobalt-iron bimetallic composite material is prepared by calcining it in a mild CO2 oxidizing atmosphere. The resulting MOF-derived cobalt-iron composite material has a relatively complete carbon skeleton and abundant bimetallic active sites, resulting in improved catalytic performance. The composite material can be used to activate peroxymonosulfate to degrade ofloxacin.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for preparing a MOF-derived cobalt-iron composite material comprises the following steps:

[0009] Step 1: Prepare the precursor Fe-ZIF 67 by co-precipitation method:

[0010] Mix 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, stir until evenly distributed, and ultrasonicate the mixture for 10 min. The resulting solution is designated as Solution A.

[0011] Take 0.67-0.8 mL of 0.8 mol / L Co(NO3)2·6H2O and 9.6-10.7 mL of 0.1 mol / L FeCl3·6H2O solution, mix them evenly, dilute to 12 mL with water, and ultrasonicate for 10 min to prepare solution B. The molar ratio of Co to Fe in solution B is 1:1.5-2.

[0012] Solution B was slowly added dropwise to solution A under stirring. After the addition was completed, stirring was continued at room temperature for 24 h. The mixture was centrifuged to collect the solids, which were then washed alternately with water and methanol several times and dried at 60 °C to obtain the precursor Fe-ZIF 67.

[0013] Step 2: Carbonization to prepare CoFe@C:

[0014] The precursor Fe-ZIF 67 prepared in step 1 was ground into powder and placed in a porcelain boat in a tube furnace. The temperature was raised to 500-800 °C and kept in an Ar atmosphere for 2 h to obtain CoFe@C.

[0015] Step 3: Calcination under CO2 atmosphere to synthesize MOF-derived cobalt-iron composite material CoFeCMs (CO2):

[0016] The CoFe@C prepared in step 2 was placed in a tubular furnace, heated to 500 °C, and a continuous flow of CO2 was introduced into the tubular furnace as a gas atmosphere. The temperature was kept for 1 h to obtain the MOF-derived cobalt-iron composite material CoFeCMs (CO2).

[0017] Preferably, the heating rate of the tube furnace in step 2 is 5°C / min.

[0018] Preferably, the heating rate of the tube furnace in step 3 is 5°C / min.

[0019] Preferably, the centrifugal speed of the mixed solution in step 1 is 8000 rpm.

[0020] The invention discloses an application of a MOF-derived cobalt-iron composite material, wherein the MOF-derived cobalt-iron composite material is applied to activate peroxymonosulfate to degrade ofloxacin.

[0021] Preferably, the MOF-derived cobalt-iron composite material is used to activate peroxymonosulfate to degrade ofloxacin. The degradation method is as follows: 100 mL of a 20 mg / L OFX solution is placed in a 1000 mL beaker, the beaker is placed on a shaker for shaking, 0.4 g of a MOF-derived cobalt-iron composite material CoFeCMs (CO2) and 0.5 g of PMS are added to the beaker, and the PMS is activated by the synergistic effect of the cobalt-iron bimetallic in the MOF-derived cobalt-iron composite material CoFeCMs (CO2) to degrade OFX; the degradation time is 30 min, 2-3 mL of the solution in the degradation process is taken out with a syringe, the solution is filtered with a 0.22 μm polyethersulfone PES filter membrane and placed in a quartz cuvette, and the OFX concentration is analyzed by UV-Vis at a wavelength of 294 nm. The degradation rate of OFX is 94.2%.

[0022] Characterization of the MOF-derived cobalt-iron composite material CoFeCMs (CO2) prepared in the present invention:

[0023] 1. Characterization of micromorphology

[0024] The CoFeCMs (CO2) and precursors were characterized by electron microscopy, e.g. Figure 2 As shown in (a), the synthesized Fe-ZIF67 has a dodecahedral structure. Figure 2 (b) is CoFe@C formed by carbonization. It can be seen that the surface of CoFe@C becomes rough, but the morphology is similar to that of Fe-ZIF 67. Figure 2 As can be seen from (c), (e) and (f), the surface of CoFeCMs (CO2) formed by oxidizing CoFe@C in a CO2 atmosphere is rough, but the surface of the dodecahedron is slightly concave. This is because the carbon skeleton of ZIF collapses during the oxidation process, while CoFeCMs (CO2) still retains most of the carbon skeleton. In contrast, Figure 2(d) The dodecahedral structure of CoFeCMs (air) formed by oxidation of CoFe@C in air is destroyed, forming agglomerated nanoparticles; the lattice spacing of 0.254 nm in HRTEM corresponds to the (311) crystal plane of CoFe2O4. Based on the above analysis, it is confirmed that CO2, as a mild oxidizing atmosphere, can not only generate CoFe2O4 but also protect the carbon skeleton from loss.

[0025] 2. XRD analysis

[0026] Figure 3 (a) is the XRD spectrum of ZIF 67 and its precursor Fe-ZIF 67. It can be seen that the characteristic peaks of Fe-ZIF 67 are consistent with those of ZIF 67, indicating that the crystal structures of Fe-ZIF 67 and ZIF 67 are the same; there are two main characteristic diffraction peaks in CoFe@C, located at 44.3° and 44.7° respectively. The diffraction peak at 44.3° belongs to the (111) plane of elemental cobalt, and the diffraction peak at 44.7° belongs to the (110) plane of elemental iron. The precursor Fe-ZIF 67 was calcined in two steps to obtain CoFeCMs (air). The characteristic diffraction peaks appeared at 30.3°, 35.7°, 37.3°, 43.5°, 57.2°, and 62.7°, pointing to the (220), (311), (222), (400), (511), and (440) crystal planes of spinel CoFe2O4 (JCPDS No.01-1121). The XRD pattern of CoFeCMs (CO2) also showed the (220), (311), (222), (400), (511), and (440) crystal planes of spinel CoFe2O4, proving that CoFe2O4 was synthesized by calcination in a CO2 atmosphere. In addition, the XRD spectrum of CoFeCMs (CO2) also showed the characteristic peaks of zero-valent iron and zero-valent cobalt, indicating that iron and cobalt were not completely oxidized.

[0027] 3. XPS analysis

[0028] The chemical state and surface element composition of CoFeCMs (CO2) materials were analyzed using XPS spectroscopy. Figure 4 As shown in (a), the precursor Fe-ZIF 67 was calcined in a CO2 atmosphere to form CoFeCMs (CO2). The coexistence of C, O, Fe, and Co elements was observed in the full spectrum, proving that a composite material containing cobalt iron oxide was successfully formed in a CO2 atmosphere. In order to further study the surface chemical state of the material, the CoFeCMs (CO2) were subjected to XPS fine spectral analysis. Figure 4(b) is the fine XPS pattern of C 1s, with three peaks appearing at 284.8 eV, 285.8 eV, and 289.9 eV, corresponding to the peaks of -CC, -CO, and OCO, respectively; Figure 4 (c) shows that the peaks of CoFeCMs (CO2) at 530.1 eV, 531.9 eV, and 534.0 eV belong to lattice oxygen, adsorbed oxygen, and surface adsorbed water, respectively. The characteristic peak of lattice oxygen at 530.1 eV is related to Fe-O / Co-O, and the peak at 531.9 eV comes from the CO peak, which corresponds to 285.8 eV in the C 1s spectrum. This may be due to partial oxidation of the carbon skeleton of the MOF. Figure 4 (d) The four peaks are located at 706.8 eV, 709.4 eV, 712.9 eV, and 716.83 eV, respectively. The peak at 706.8 eV corresponds to zero-valent iron, and the peaks at 709.4 eV and 712.9 eV are Fe 2+ and Fe 3+ 2p 3 / 2 , the peak at 716.83 eV is a satellite peak; Figure 4 In (e), the peaks at 780.2 eV / 795.3 and 782.8 eV / 797.9 eV of the Co 2p spectrum are Co 2+ (2p 3 / 2 / 2p 1 / 2 ) and Co 3+ (2p 3 / 2 / 2p 1 / 2 ), the peaks at 787.4 eV and 803.7 are satellite peaks. Combined with the results of XRD analysis, it can be seen that the method of the present invention successfully prepared CoFeCMs (CO2).

[0029] 4. Raman analysis

[0030] Figure 5 The Raman spectra of Fe-ZIF 67, CoFe@C, CoFeCMs (air) and CoFeCMs (CO2) show the graphitization degree and carbon hybrid orbital type of Fe-ZIF 67, CoFe@C, CoFeCMs (air) and CoFeCMs (CO2). -1 and 1580 cm -1 The D band related to the carbon atom crystal defect and the sp band related to the carbon atom can be observed at 2 Hybridization-related G band, the ratio between the D band and the G band I D / I GThe intensity relationship between these two peaks can be described. The precursor Fe-ZIF 67 was not carbonized, so no carbon peak appeared. The carbonized CoFe@C showed D band and G band, indicating the presence of graphitic carbon in CoFe@C. No carbon peak was detected in CoFeCMs (air) calcined in air, indicating that carbon was completely decomposed during the calcination process. CoFeCMs (CO2) calcined in carbon dioxide atmosphere retained the carbon peak in CoFe@C. The I D / I G The carbon atoms in the CoFeCMs (CO) were 1.08 and 1.28, respectively, indicating a high degree of graphitization and significant crystal defects in the carbon structure of the CoFeCMs (CO). Combined with XRD analysis, this indicates that CO, a mild oxidizing atmosphere, effectively reduces carbon skeleton loss in Fe-ZIF 67, resulting in CoFeCMs (CO) with a more complete carbon skeleton than CoFeCMs (air).

[0031] 5. N2 adsorption curve and BET analysis

[0032] Table 1 records the BET test data of CoFe@C, CoFeCMs (air) and CoFeCMs (CO2). Figure 6 (a) and Table 1, the BET test showed that the specific surface area of ​​CoFe@C, CoFeCMs (air) and CoFeCMs (CO2) was 46.372m 2 / g, 9.626 m 2 / g, 44.460 m 2 / g, the surface area of ​​CoFeCMs (CO2) is much larger than that of CoFeCMs (air), which indicates that the CoFeCMs (CO2) composite catalyst has more active sites. Figure 3-6 (a) shows that the N2 adsorption-desorption isotherms of CoFe@C, CoFeCMs (air) and CoFeCMs (CO2) exhibit type IV isotherms with H3-type hysteresis loops, indicating the existence of mesoporous structures inside the samples. Figure 6 (b) shows that the pore size of CoFe@C, CoFeCMs (air) and CoFeCMs (CO2) are mainly mesopores with a diameter of 5 nm. The pore volume of CoFeCMs (CO2) is larger than that of CoFeCMs (air), as shown in Table 1, which is more conducive to the transfer and diffusion of pollutants.

[0033] Table 1

[0034]

[0035] Verification of the catalytic degradation of OFX by CoFeCMs (CO2) prepared in the present invention in activated PMS:

[0036] Calculation formula for target pollutants:

[0037] Among them, R t represents the degradation rate at time point t, C0 and C t represent the initial concentration of the pollutant and the pollutant concentration at time point t, respectively.

[0038] The above degradation experiments were repeated three times, and the final experimental results were taken as the mean ± standard deviation.

[0039] 1. Effect of Cobalt-Iron Ratio in CoFeCMs (CO2) on OFX Degradation

[0040] The different ratios of cobalt and iron in CoFeCMs (CO2) materials affect the activation of the redox cycle of PMS, and thus affect the catalytic degradation performance. This experiment studied the degradation performance of OFX materials synthesized with five ratios of cobalt and iron: 2:1, 1.5:1, 1:1, 1:1.5, and 1:2. Figure 7 As shown in the figure, within 0-30 min, the OFX removal rate of CoFeCMs(CO2) with different cobalt and iron ratios reached more than 90%, among which the OFX residual removal rate and removal rate were the best when the cobalt and iron ratio was 1:1.5.

[0041] 2. Effect of calcination temperature on OFX degradation

[0042] This method prepares CoFeCMs (CO2) by two-step calcination. The calcination temperature during the carbonization process affects the specific surface area and pore structure of CoFeCMs (CO2), thereby affecting the catalytic active sites. CoFe@C was prepared at carbonization temperatures of 500 ℃, 600 ℃, 700 ℃, and 800 ℃. After oxidation in a CO2 atmosphere, a series of CoFeCMs (CO2) were synthesized, such as Figure 8 As shown in the figure, the OFX removal rate gradually increases with increasing carbonization temperature. At a carbonization temperature of 700°C, CoFeCMs (CO2) achieves an OFX removal rate of 94.2% within 30 minutes. When the carbonization temperature is further increased to 800°C, the OFX removal rate decreases. This is because the structure of CoFeCMs (CO2) is destroyed at such a high carbonization temperature. Therefore, the optimal carbonization temperature selected in the experiment is 700°C.

[0043] 3. Effects of different catalytic systems on OFX degradation

[0044] The catalytic performance of different systems was investigated, such as Figure 9 As shown in (a), when no PMS is added, the OFX removal rates of Fe-ZIF 67, CoFeCMs (air) and CoFeCMs (CO2) are very limited, only 19.9%, 7% and 18.2% respectively. When PMS is added, the OFX removal effect is significantly improved. The OFX removal rates of Fe-ZIF 67 / PMS, CoFeCMs (air) / PMS and CoFeCMs (CO2) / PMS systems are 40.8%, 71.7% and 94.2% respectively within 30 min. In particular, the OFX removal rate of the CoFeCMs (CO2) / PMS system reached 87.1% within 5 min, which is significantly higher than that of CoFeCMs (air) / PMS, and the OFX removal rate within 30 min is also higher than that of CoFeCMs (air) / PMS. Figure 9 As shown in (b), the reaction kinetic constants of different systems were calculated. The reaction kinetic constant of CoFeCMs (CO2) is 0.526 min -1 The reaction kinetic constant of CoFeCMs (air) is 0.0513 min -1 This also proves that CoFeCMs (CO2) calcined in a mild CO2 atmosphere have a larger specific surface area and a more complete carbon skeleton, providing more active sites.

[0045] 4. Effect of initial pH on OFX degradation

[0046] The initial pH of the solution will react with the free radicals generated in the catalytic system and the electrons generated on the catalyst surface, thus affecting the degradation efficiency of the catalyst on pollutants to varying degrees. Figure 10 As shown in the figure, at pH = 3, 5, 7, 9, and 11, the OFX degradation efficiency reached 81.2%, 87.3%, 94.2%, 85.1%, and 69.6% within 30 min, respectively. It is obvious that the CoFeCMs(CO2) / PMS system has a wide pH range of application. When the initial pH increases from 7 to 11, the OFX degradation efficiency decreases significantly. This is because the hydroxide ion (OH - ) sulfate radicals (SO4 ·- ) into oxygen free radicals (O ·- When the initial pH dropped from 7 to 3, the degradation rate of OFX decreased because the hydrogen ions (H + ) will scavenge sulfate and hydroxyl radicals (·OH), which has a certain impact on the degradation of OFX. Based on this, pH = 7 was selected as the optimal initial pH in this experiment.

[0047] (1)

[0048] (2)

[0049] (3)

[0050] (4)

[0051] 5. Effect of PMS addition on OFX degradation

[0052] CoFeCMs (CO2) degrade OFX by activating PMS, e.g. Figure 11 As shown in the figure, when the amount of PMS added is 0.3 g / L, 83.7% of SO4 can be removed within 30 minutes. When the amount of PMS added is increased to 0.5 g / L, the removal rate reaches 94.2%. This shows that as the amount of PMS added increases, sufficient dose of PMS can produce more SO4 ·- , ·OH and other active species, which accelerate and promote the degradation of OFX. However, when the amount of PMS added continues to increase, the removal rate of OFX decreases. When the amount of PMS added is 0.7 g / L, the degradation rate of OFX is 86.9%. This is because excessive PMS will cause a quenching reaction, converting SO4 ·- Converted into SO5 with lower oxidizing ability ·- Therefore, 0.5 g / L was the optimal dosage of PMS in this experiment.

[0053] (5)

[0054] (6)

[0055] 6. Effect of the addition amount of catalyst CoFeCMs (CO2) on OFX degradation

[0056] The experiment verified the effect of the amount of catalyst CoFeCMs (CO2) added on the degradation of OFX. Figure 12As shown, when the CoFeCMs (CO2) catalyst addition levels were 0.2 g / L, 0.3 g / L, and 0.4 g / L, the OFX removal rates within 30 minutes were 78.5%, 86.9%, and 94.2%, respectively. With increasing CoFeCMs (CO2) catalyst addition levels, the OFX removal rate also increased, as the appropriate increase in CoFeCMs (CO2) catalyst provided more active sites. However, with further increases in CoFeCMs (CO2) catalyst addition levels, the OFX removal rate remained roughly constant at around 92%. Due to the limited PMS content, it was often consumed, hindering pollutant removal. Catalytic degradation performance and operating costs are important considerations in practical applications. In this experiment, 0.4 g / L of CoFeCMs (CO2) catalyst was used as the optimal dosage.

[0057] 7. Effect of OFX initial concentration on OFX degradation

[0058] The experiments verified the catalytic performance of CoFeCMs (CO2) under different OFX initial concentration conditions. Figure 13 As shown in the figure, at initial OFX concentrations of 10 mg / L, 20 mg / L, and 30 mg / L, the OFX removal efficiencies were 95.9%, 94.3%, and 89.9% after 30 minutes. As the initial OFX concentration increased, the degradation efficiency gradually decreased. This is because the increase in the initial OFX concentration led to an increase in the number of OFX molecules in the solution, resulting in competition among OFX molecules and a slowing of the reaction rate.

[0059] 8. Effect of inorganic anions on OFX degradation

[0060] The experiment verified that the four common anions Cl - 、NO3 - 、HCO3 - 、HPO4 2- Effect on the degradation of OFX. Figure 14 As shown, when Cl - When the concentration increased from 0 to 20 mM, the degradation efficiency of OFX decreased from 94.2% to 86.6%, which was due to the fact that Cl - With SO4 ·- , OH reacts to form Cl · , Cl · The catalytic activity is lower than that of Cl - With SO4 ·- , so the degradation efficiency will be reduced. NO3 - Effects on OFX degradation, and Cl - The effects of NO3 are similar. -When the concentration increased from 0 to 20 mM, the degradation efficiency of OFX decreased to 77.3%, which was due to the fact that NO3 - With SO4 ·- , OH reacts to produce NO3 · HCO3 - When the concentration increases, the degradation efficiency of OFX is seriously affected. At 20 mM, the degradation efficiency drops to 12.9%. This is because HCO3 - With SO4 ·- , ·OH reacts to generate HCO3 · and CO3 · , its activity is much lower than SO4 ·- 、·OH. When HPO4 2- When the concentration increased to 20 mM, the degradation efficiency of OFX dropped to 83.6%, which was due to the fact that HPO4 2- It undergoes a quenching reaction with ·OH (Equation 13).

[0061] (7)

[0062] (8)

[0063] (9)

[0064] (10)

[0065] (11)

[0066] (12)

[0067] (13)

[0068] 9. Impact of actual water bodies on OFX degradation

[0069] In order to further explore the effect of actual water on OFX degradation, OFX solutions were prepared using ultrapure water, Yellow River water and tap water under experimental conditions to explore the effects of different water bodies on OFX degradation. Figure 15 As shown, the OFX degradation efficiencies of solutions prepared with ultrapure water, Yellow River water, and tap water were 94.2%, 88.1%, and 88.1%, respectively. Actual water conditions have a certain impact on OFX degradation, slowing the degradation rate. This may be due to the influence of inorganic anions in the water. Overall, however, the OFX removal capability is excellent.

[0070] 10. Cyclic stability analysis of CoFeCMs (CO2) / PMS system

[0071] In practical applications, the stability and reusability of the catalyst are important evaluation indicators of its practicality. Under the same experimental conditions, the catalyst was tested for 5 cycles and XRD characterization was performed on the catalyst after 5 cycles. Figure 16 As shown in (a), after five cycles, the degradation efficiency of OFX reached 85.5%, which still has a high removal efficiency. Figure 16 As shown in (b), the main XRD diffraction peaks of the catalyst after five cycles are essentially the same as before degradation, indicating that the catalyst's crystal structure remains unchanged during the five degradation processes. Furthermore, VSM testing reveals that CoFeCMs(CO2) possesses strong magnetic properties, enabling easy separation of the catalyst from solution. This demonstrates that CoFeCMs(CO2) is a highly stable, high-performance, reusable, and easily separable catalyst.

[0072] 11. Degradation mechanism of MOF-derived CoFeCMs

[0073] (1) Determination of free radicals

[0074] Through free radical quenching experiments, the degradation mechanism of OFX by CoFeCMs (CO2) / PMS system and the types of free radicals that degrade OFX were investigated. Figure 17 As shown in (a), methanol is used as SO4 ·- When 0.2 M inhibitor was added, the degradation efficiency of OFX was 79.54% after 30 min, indicating that SO4 ·- When tert-butyl alcohol TBA was used as the quencher of ·OH, after adding 0.2 M TBA, the degradation efficiency of OFX was 90.39% at 30 min, which was slightly lower than the degradation efficiency of 94.2% without TBA, indicating that there was a small amount of ·OH in the reaction system. In addition, furfuryl alcohol FFA and p-benzoquinone p-BQ were used as O2 ·- and 1 When the O2 quencher was added to the reaction system, the removal rates of OFX were 24.1% and 60.67%, respectively, indicating that the reaction system had O2 ·- and 1 O2 participates in the reaction and plays a major role.

[0075] To further prove the above speculation, EPR technology was used to qualitatively analyze the free radical species that degrade OFX. At 1 min and 5 min, the free radicals were captured using spin traps 5,5-dimethylpyrroline oxide (DMPO) and 4-oxy-2,2,6,6-tetramethylpiperidinium (TEMP). Figure 17As shown in (b), there are four signal peaks with an intensity ratio of 1:2:2:1, which are the signals of DMPO-·OH, and a six-fold signal peak with an intensity ratio of 1:1:1:1:1:1, which is attributed to DMPO-SO4 ·- . Figure 17 The sextet in (c) corresponds to DMPO-O2 ·- . Figure 17 In (d), three signal peaks with an intensity ratio of 1:1:1 appear, which is TEMP- 1 O2 signal. Based on the above analysis, OH, SO4 ·- 、O2 ·- 、 1 Four active components of O2 exist in the process of OFX degradation by CoFeCMs (CO2) / PMS system.

[0076] The electron transfer from OFX to PMS was confirmed by chronoamperometry. Figure 18 As shown in the figure, when CoFeCMs (CO2) was used as the working electrode, the current changed significantly when PMS and OFX were added at 100 s and 200 s, respectively. The negative current peak at 100 s was due to the contact between the added PMS and CoFeCMs (CO2), resulting in significant electron transfer. At 180 s, the addition of OFX resulted in another negative current peak, indicating electron transfer between OFX and CoFeCMs (CO2) / PMS.

[0077] (2) Possible degradation pathways of OFX

[0078] In order to explore the possible degradation pathway of OFX by CoFeCMs (CO2) / PMS system, the intermediate products in the reaction process were identified by HPLC-MS. According to the analysis results and combined with relevant literature, such as Figure 19 As shown, two potential degradation pathways of OFX are described. Pathway one involves complete removal of the piperazine ring in OFX to produce P1 (m / z = 336). Further decarboxylation and removal of the morpholine ring of P1 yield P2 (m / z = 279) and P3 (m / z = 116). The other pathway involves decarboxylation and hydroxylation of the quinolone moiety in OFX to produce P4 (m / z = 334). This is followed by dealkylation and addition of a hydroxyl group to produce P5 (m / z = 336). The piperazine ring of P5 is then destroyed to produce the analogue P6 (m / z = 274). As active species oxidize P6, it gradually transforms into P7 (m / z = 175) and P8 (m / z = 149). Through a series of reactions, the macromolecular intermediates are converted into small molecules, H2O, and CO2.

[0079] (3) Reaction mechanism of OFX degradation by CoFeCMs (CO2) / PMS system

[0080] The degradation mechanism of OFX by CoFeCMs (CO2) / PMS system is as follows Figure 20 As shown in the figure, CoFe2O4 is evenly distributed on the carbon skeleton of ZIF. The CoFeCMs (CO2) formed by calcination in a CO2 atmosphere retain the carbon skeleton as much as possible, giving CoFeCMs (CO2) a larger specific surface area and more active sites, making it easier for active substances to transfer and diffuse. The peroxide bond (-OO-) in PMS accepts an electron transferred by Co (II) or Fe (II) and breaks, and PMS is activated to produce active species. Co (III) or Fe (III) is reacted with HSO5 - is reduced to form Co(Ⅱ) or Fe(Ⅱ), forming a complete redox cycle (Formula 14-21). The active species generated (·OH, SO4 ·- 、O2 ·- ,and 1 O2) will oxidize and destroy the structure of OFX, and further mineralize the pollutants into small molecular substances, H2O, and CO2 (Equation 22).

[0081] (14)

[0082] (15)

[0083] (16)

[0084] (17)

[0085] (18)

[0086] (19)

[0087] (20)

[0088] (twenty one)

[0089] OH, SO4 ·- , , 1 O2 + OFX Intermediate products + H2O + CO2 (22)

[0090] Compared with the prior art, the present invention has the following beneficial effects:

[0091] In summary, the present invention synthesized dodecahedral Fe-ZIF 67 via a coprecipitation method, followed by a two-step carbonization and oxidation calcination to synthesize CoFeCMs (CO2). Under a mild CO2 atmosphere, the oxidation process resulted in minimal loss of the Fe-ZIF 67 carbon skeleton. The resulting MOF-derived cobalt-iron bimetallic composite, CoFeCMs (CO2), exhibited a larger specific surface area and a more intact carbon skeleton, providing more active sites and exhibiting superior catalytic performance and electron transfer efficiency. CoFeCMs (CO2) achieved a 94.2% efficiency in activating PMS to degrade OFX within 30 minutes.

[0092] On the premise of retaining the MOF-derived carbon skeleton, the preparation of MOFs-derived cobalt-iron bimetallic materials can increase the number of active sites and conductivity of the material, thereby improving the catalytic performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 This is the synthesis route of MOF-derived cobalt-iron composites CoFeCMs (CO2);

[0094] Figure 2 Middle: (a) is the SEM image of Fe-ZIF 67;

[0095] (b) is the SEM image of CoFe@C;

[0096] (c) is the SEM image of CoFeCMs (CO2);

[0097] (d) is the SEM image of CoFeCMs (air);

[0098] (e) is the TEM image of CoFeCMs (CO2);

[0099] (f) TEM image of CoFeCMs (CO2);

[0100] (g) is the HRTEM image of CoFeCMs (CO2);

[0101] Figure 3 Middle: (a) is the XRD spectra of ZIF 67 and its precursor Fe-ZIF 67;

[0102] (b) XRD spectra of CoFe@C, CoFeCMs (air), and CoFeCMs (CO2);

[0103] Figure 4This is the XPS fine spectrum of CoFeCMs (CO2), where: (a) full spectrum; (b) C 1s; (c) O 1s; (d) Fe2p; (e) Co 2p;

[0104] Figure 5 are the Raman spectra of Fe-ZIF 67, CoFe@C, CoFeCMs (air), and CoFeCMs (CO2);

[0105] Figure 6 (a) is the N2 adsorption-desorption curves of CoFe@C, CoFeCMs (air), and CoFeCMs (CO2); (b) is the pore size distribution;

[0106] Figure 7 The effect of different cobalt-iron ratios on the degradation of OFX. The experimental parameters shown in the figure are: OFX concentration of 20 mg / L, PMS concentration of 0.5 g / L, and catalyst concentration of 0.4 g / L.

[0107] Figure 8 The effect of calcination temperature on the degradation of OFX. The experimental parameters shown in the figure are: OFX concentration of 20 mg / L, PMS concentration of 0.5 g / L, and catalyst concentration of 0.4 g / L.

[0108] Figure 9 (a) shows the effect of different catalytic systems on the degradation of OFX; (b) shows the reaction rate constants of different catalytic systems. The experimental parameters in the figure are: OFX concentration of 20 mg / L, PMS concentration of 0.5 g / L, and catalyst concentration of 0.4 g / L.

[0109] Figure 10 The effect of initial pH on the degradation of OFX. The experimental parameters in the figure are: OFX concentration of 20 mg / L, PMS concentration of 0.5 g / L, and catalyst concentration of 0.4 g / L.

[0110] Figure 11 This is the effect of PMS addition on OFX degradation. The experimental parameters in the figure are: OFX concentration of 20 mg / L, catalyst concentration of 0.4 g / L, pH=7;

[0111] Figure 12 This is the effect of catalyst addition on OFX degradation. The experimental parameters in the figure are: OFX concentration of 20 mg / L, PMS concentration of 0.5 g / L, pH=7;

[0112] Figure 13 This is the effect of the initial OFX concentration on the degradation of OFX. The experimental parameters in the figure are: PMS concentration of 0.5 g / L, catalyst concentration of 0.4 g / L, pH = 7;

[0113] Figure 14 The effects of inorganic anions on OFX degradation: (a) Cl - , (b) NO3 - , (c) HCO3 - , (d) HPO4 2- ,Experimental parameters in the figure: OFX concentration is 20 mg / L, PMS concentration is 0.5 g / L, catalyst concentration is 0.4 g / L, pH=7;

[0114] Figure 15 This is the effect of different water bodies on the degradation of OFX. The experimental parameters in the figure are: OFX concentration is 20 mg / L, PMS concentration is 0.5 g / L, catalyst concentration is 0.4 g / L, and pH=7;

[0115] Figure 16 (a) Cyclic stability of the CoFeCMs (CO2) / PMS system. Experimental parameters are: OFX concentration of 20 mg / L, PMS concentration of 0.5 g / L, catalyst concentration of 0.4 g / L, pH = 7. (b) XRD comparison of CoFeCMs (CO2) before and after reaction.

[0116] Figure 17 (a) is a free radical quenching experiment. The experimental parameters in the figure are: OFX concentration of 20 mg / L, PMS concentration of 0.5 g / L, catalyst concentration of 0.4 g / L, pH = 7; EPR spectrum of CoFeCMs (CO2) / PMS system: (b) DMPO-·OH and DMPO-SO4 ·- , (c) DMPO-O2 ·- , (d) TEMP- 1 O2;

[0117] Figure 18 is the chronoamperometric curve of CoFeCMs (CO2);

[0118] Figure 19 It is a possible pathway for the degradation of OFX by the CoFeCMs (CO2) / PMS system;

[0119] Figure 20 This is the reaction mechanism diagram of the degradation of OFX by CoFeCMs (CO2) / PMS system. DETAILED DESCRIPTION

[0120] The present invention will be further described in detail below with reference to the accompanying drawings. Example

[0121] A method for preparing a MOF-derived cobalt-iron composite material comprises the following steps:

[0122] Step 1: Prepare the precursor Fe-ZIF 67 by co-precipitation method:

[0123] Mix 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, stir until evenly distributed, and ultrasonicate the mixture for 10 min. The resulting solution is designated as Solution A.

[0124] Take 0.8 mL of 0.8 mol / L Co(NO3)2·6H2O and 9.6 mL of 0.1 mol / L FeCl3·6H2O solution, mix them evenly, dilute them to 12 mL with water, and ultrasonicate them for 10 min to prepare solution B. The molar ratio of Co to Fe in solution B is 1:1.5.

[0125] Solution B was slowly added dropwise to solution A under stirring, and the mixture was stirred at room temperature for 24 h. The mixture was centrifuged at 8000 rpm to collect the solids. The solids were then washed alternately with water and methanol several times and dried at 60°C to obtain the precursor Fe-ZIF 67.

[0126] Step 2: Carbonization to prepare CoFe@C:

[0127] The precursor Fe-ZIF 67 prepared in step 1 was ground into powder and placed in a porcelain boat. The mixture was then placed in a tube furnace and heated to 700 °C at a rate of 5 °C / min. The mixture was kept in an Ar atmosphere for 2 h to obtain CoFe@C.

[0128] Step 3: Calcination under CO2 atmosphere to synthesize MOF-derived cobalt-iron composite material CoFeCMs (CO2)

[0129] The CoFe@C prepared in step 2 was placed in a tubular furnace and heated to 500 °C at a heating rate of 5 °C / min. A continuous flow of CO2 was introduced into the tubular furnace as a gas atmosphere and kept warm for 1 h to obtain the MOF-derived cobalt-iron composite material CoFeCMs(CO2).

[0130] The MOF-derived cobalt-iron composite material was applied to activate peroxymonosulfate to degrade ofloxacin.

[0131] The degradation method is as follows: take 100 mL of OFX solution with a concentration of 20 mg / L and put it into a beaker with a volume of 1000 mL, place the beaker on a shaker and add 0.4 g of MOF-derived cobalt-iron composite material CoFeCMs (CO2) and 0.5 g of PMS into the beaker, and use the synergistic effect of the cobalt-iron bimetallic in the MOF-derived cobalt-iron composite material CoFeCMs (CO2) to activate PMS to degrade OFX.

[0132] The degradation experiment lasted for 30 minutes. 2-3 mL of the solution during the degradation process was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) filter membrane, and placed in a quartz cuvette. The concentration of OFX was analyzed by UV-Vis spectrophotometry at a wavelength of 294 nm, and the degradation rate of OFX was found to be 94.2%. Example

[0133] A method for preparing a MOF-derived cobalt-iron composite material comprises the following steps:

[0134] Step 1: Prepare the precursor Fe-ZIF 67 by co-precipitation method:

[0135] Mix 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, stir until evenly distributed, and ultrasonicate the mixture for 10 min. The resulting solution is designated as Solution A.

[0136] Take 0.67 mL of 0.8 mol / L Co(NO3)2·6H2O and 10.7 mL of 0.1 mol / L FeCl3·6H2O solution, mix them evenly, dilute them to 12 mL with water, and ultrasonicate them for 10 min to prepare solution B. The molar ratio of Co to Fe in solution B is 1:2.

[0137] Solution B was slowly added dropwise to solution A under stirring, and the mixture was stirred at room temperature for 24 h. The mixture was centrifuged at 8000 rpm to collect the solids. The solids were then washed alternately with water and methanol several times and dried at 60°C to obtain the precursor Fe-ZIF 67.

[0138] Step 2: Carbonization to prepare CoFe@C:

[0139] The precursor Fe-ZIF 67 prepared in step 1 was ground into powder and placed in a porcelain boat. The mixture was then placed in a tube furnace and heated to 700 °C at a rate of 5 °C / min. The mixture was kept in an Ar atmosphere for 2 h to obtain CoFe@C.

[0140] Step 3: Calcination under CO2 atmosphere to synthesize MOF-derived cobalt-iron composite material CoFeCMs (CO2)

[0141] The CoFe@C prepared in step 2 was placed in a tubular furnace and heated to 500 °C at a heating rate of 5 °C / min. A continuous flow of CO2 was introduced into the tubular furnace as a gas atmosphere and kept warm for 1 h to obtain the MOF-derived cobalt-iron composite material CoFeCMs(CO2).

[0142] The MOF-derived cobalt-iron composite material was applied to activate peroxymonosulfate to degrade ofloxacin.

[0143] The degradation method is as follows: take 100 mL of OFX solution with a concentration of 20 mg / L and put it into a beaker with a volume of 1000 mL, place the beaker on a shaker and add 0.4 g of MOF-derived cobalt-iron composite material CoFeCMs (CO2) and 0.5 g of PMS into the beaker, and use the synergistic effect of the cobalt-iron bimetallic in the MOF-derived cobalt-iron composite material CoFeCMs (CO2) to activate PMS to degrade OFX.

[0144] The degradation experiment lasted for 30 minutes. 2-3 mL of the solution during the degradation process was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) filter membrane, and placed in a quartz cuvette. The concentration of OFX was analyzed by UV-Vis spectrophotometry at a wavelength of 294 nm, and the degradation rate of OFX was found to be 92.1%. Example

[0145] A method for preparing a MOF-derived cobalt-iron composite material comprises the following steps:

[0146] Step 1: Prepare the precursor Fe-ZIF 67 by co-precipitation method:

[0147] Mix 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, stir until evenly distributed, and ultrasonicate the mixture for 10 min. The resulting solution is designated as Solution A.

[0148] Take 0.8 mL of 0.8 mol / L Co(NO3)2·6H2O and 9.6 mL of 0.1 mol / L FeCl3·6H2O solution, mix them evenly, dilute them to 12 mL with water, and sonicate for 10 min to prepare solution B. The molar ratio of Co:Fe in solution B is 1:1.5.

[0149] Solution B was slowly added dropwise to solution A under stirring, and the mixture was stirred at room temperature for 24 h. The mixture was centrifuged at 8000 rpm to collect the solids. The solids were then washed alternately with water and methanol several times and dried at 60°C to obtain the precursor Fe-ZIF 67.

[0150] Step 2: Carbonization to prepare CoFe@C:

[0151] The precursor Fe-ZIF 67 prepared in step 1 was ground into powder and placed in a porcelain boat. The mixture was then placed in a tube furnace and heated to 500 °C at a rate of 5 °C / min. The mixture was kept in an Ar atmosphere for 2 h to obtain CoFe@C.

[0152] Step 3: Calcination under CO2 atmosphere to synthesize MOF-derived cobalt-iron composite material CoFeCMs (CO2)

[0153] The CoFe@C prepared in step 2 was placed in a tubular furnace and heated to 500 °C at a heating rate of 5 °C / min. A continuous flow of CO2 was introduced into the tubular furnace as a gas atmosphere and kept warm for 1 h to obtain the MOF-derived cobalt-iron composite material CoFeCMs(CO2).

[0154] The MOF-derived cobalt-iron composite material was applied to activate peroxymonosulfate to degrade ofloxacin.

[0155] The degradation method is as follows: take 100 mL of OFX solution with a concentration of 20 mg / L and put it into a beaker with a volume of 1000 mL, place the beaker on a shaker and add 0.4 g of MOF-derived cobalt-iron composite material CoFeCMs (CO2) and 0.5 g of PMS into the beaker, and use the synergistic effect of the cobalt-iron bimetallic in the MOF-derived cobalt-iron composite material CoFeCMs (CO2) to activate PMS to degrade OFX.

[0156] The degradation experiment lasted for 30 minutes. 2-3 mL of the solution during the degradation process was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) filter membrane, and placed in a quartz cuvette. The concentration of OFX was analyzed by UV-Vis spectrophotometry at a wavelength of 294 nm, and the degradation rate of OFX was found to be 88.2%. Example

[0157] A method for preparing a MOF-derived cobalt-iron composite material comprises the following steps:

[0158] Step 1: Prepare the precursor Fe-ZIF 67 by co-precipitation method:

[0159] Mix 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, stir until evenly distributed, and ultrasonicate the mixture for 10 min. The resulting solution is designated as Solution A.

[0160] Take 0.8 mL of 0.8 mol / L Co(NO3)2·6H2O and 9.6 mL of 0.1 mol / L FeCl3·6H2O solution, mix them evenly, dilute them to 12 mL with water, and sonicate for 10 min to prepare solution B. The molar ratio of Co:Fe in solution B is 1:1.5.

[0161] Solution B was slowly added dropwise to solution A under stirring, and the mixture was stirred at room temperature for 24 h. The mixture was centrifuged at 8000 rpm to collect the solids. The solids were then washed alternately with water and methanol several times and dried at 60°C to obtain the precursor Fe-ZIF 67.

[0162] Step 2: Carbonization to prepare CoFe@C:

[0163] The precursor Fe-ZIF 67 prepared in step 1 was ground into powder and placed in a porcelain boat. The mixture was then placed in a tube furnace and heated to 800 °C at a heating rate of 5 °C / min. The mixture was kept in an Ar atmosphere for 2 h to obtain carbonized CoFe@C.

[0164] Step 3: Calcination under CO2 atmosphere to synthesize MOF-derived cobalt-iron composite material CoFeCMs (CO2)

[0165] The CoFe@C prepared in step 2 was placed in a tubular furnace and heated to 500 °C at a heating rate of 5 °C / min. A continuous flow of CO2 was introduced into the tubular furnace as a gas atmosphere and kept warm for 1 h to obtain the MOF-derived cobalt-iron composite material CoFeCMs(CO2).

[0166] The MOF-derived cobalt-iron composite material was applied to activate peroxymonosulfate to degrade ofloxacin.

[0167] The degradation method is as follows: take 100 mL of OFX solution with a concentration of 20 mg / L and put it into a beaker with a volume of 1000 mL, place the beaker on a shaker and add 0.4 g of MOF-derived cobalt-iron composite material CoFeCMs (CO2) and 0.5 g of PMS into the beaker, and use the synergistic effect of the cobalt-iron bimetallic in the MOF-derived cobalt-iron composite material CoFeCMs (CO2) to activate PMS to degrade OFX.

[0168] The degradation experiment lasted for 30 minutes. 2-3 mL of the solution during the degradation process was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) filter membrane, and placed in a quartz cuvette. The concentration of OFX was analyzed by UV-Vis spectrophotometry at a wavelength of 294 nm, and the degradation rate of OFX was found to be 68.8%. Example

[0169] A method for preparing a MOF-derived cobalt-iron composite material comprises the following steps:

[0170] Step 1: Prepare the precursor Fe-ZIF 67 by co-precipitation method:

[0171] Mix 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, stir until evenly distributed, and ultrasonicate the mixture for 10 min. The resulting solution is designated as Solution A.

[0172] Take 0.8 mL of 0.8 mol / L Co(NO3)2·6H2O and 9.6 mL of 0.1 mol / L FeCl3·6H2O solution, mix them evenly, dilute them to 12 mL with water, and ultrasonicate them for 10 min to prepare solution B. The molar ratio of Co to Fe in solution B is 1:1.5.

[0173] Solution B was slowly added dropwise to solution A under stirring, and the mixture was stirred at room temperature for 24 h. The mixture was centrifuged at 8000 rpm to collect the solids. The solids were then washed alternately with water and methanol several times and dried at 60°C to obtain the precursor Fe-ZIF 67.

[0174] Step 2: Carbonization to prepare CoFe@C:

[0175] The precursor Fe-ZIF 67 prepared in step 1 was ground into powder and placed in a porcelain boat. The mixture was then placed in a tube furnace and heated to 700 °C at a rate of 5 °C / min. The mixture was kept in an Ar atmosphere for 2 h to obtain CoFe@C.

[0176] Step 3: Calcination under CO2 atmosphere to synthesize MOF-derived cobalt-iron composite material CoFeCMs (CO2)

[0177] The CoFe@C prepared in step 2 was placed in a tubular furnace and heated to 500 °C at a heating rate of 5 °C / min. A continuous flow of CO2 was introduced into the tubular furnace as a gas atmosphere and kept warm for 1 h to obtain the MOF-derived cobalt-iron composite material CoFeCMs(CO2).

[0178] The MOF-derived cobalt-iron composite material was applied to activate peroxymonosulfate to degrade ofloxacin.

[0179] The degradation method is as follows: take 100 mL of OFX solution with a concentration of 20 mg / L and put it into a beaker with a volume of 1000 mL, place the beaker on a shaker and shake, add 0.6 g of MOF-derived cobalt-iron composite material CoFeCMs (CO2) and 0.5 g of PMS into the beaker, and use the synergistic effect of the cobalt-iron bimetallic in the MOF-derived cobalt-iron composite material CoFeCMs (CO2) to activate PMS to degrade OFX.

[0180] The degradation experiment lasted for 30 minutes. 2-3 mL of the solution during the degradation process was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) filter membrane, and placed in a quartz cuvette. The concentration of OFX was analyzed by UV-Vis spectrophotometry at a wavelength of 294 nm, and the degradation rate of OFX was found to be 91.1%. Example

[0181] The MOF-derived cobalt-iron composite material CoFeCMs (CO2) prepared in Example 1 was used to degrade ofloxacin. The degradation method was the same as in Example 1, with each degradation time of 30 min and repeated 5 times. After each pollutant degradation, the CoFeCMs (CO2) catalyst was recovered and washed with deionized water. The CoFeCMs (CO2) catalyst was repeatedly used. The concentration of OFX in the pollutant after each degradation was analyzed, and the OFX degradation rate after the fifth cycle was 85.5%.

[0182] The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make other equivalent variations and improvements based on the technical enlightenment provided by the present invention, which should also be considered as the scope of protection of the present invention.

Claims

1. A method for preparing a MOF-derived cobalt-iron composite material, characterized in that: The following steps are involved: Step 1: Prepare the precursor Fe-ZIF 67 by co-precipitation method: Mix 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, stir until evenly distributed, and ultrasonicate the mixture for 10 min. The resulting solution is designated as Solution A. Take 0.67-0.8 mL of 0.8 mol / L Co(NO3)2·6H2O and 9.6-10.7 mL of 0.1 mol / L FeCl3·6H2O solution, mix them evenly, dilute them to 12 mL with water, and ultrasonicate them for 10 min to prepare solution B. The molar ratio of Co to Fe in solution B is 1:1.5-2. Solution B was slowly added dropwise to solution A under stirring. After the addition was completed, stirring was continued at room temperature for 24 h. The mixture was centrifuged to collect the solids, which were then washed alternately with water and methanol several times and dried at 60 °C to obtain the precursor Fe-ZIF 67. Step 2: Carbonization to prepare CoFe@C: The precursor Fe-ZIF 67 prepared in step 1 was ground into powder and placed in a porcelain boat in a tube furnace. The temperature was raised to 500-800 °C and kept in an Ar atmosphere for 2 h to obtain CoFe@C. Step 3: Calcination under CO2 atmosphere to synthesize MOF-derived cobalt-iron composite material CoFeCMs: The CoFe@C prepared in step 2 was placed in a tubular furnace, heated to 500 °C, a continuous flow of CO2 was introduced into the tubular furnace as a gas atmosphere, and kept warm for 1 h to obtain the MOF-derived cobalt-iron composite material CoFeCMs.

2. The method for preparing a MOF-derived cobalt-iron composite material according to claim 1, wherein: The heating rate of the tubular furnace in step 2 is 5°C / min.

3. The method for preparing a MOF-derived cobalt-iron composite material according to claim 1, wherein: The heating rate of the tubular furnace in step 3 is 5°C / min.

4. The method for preparing a MOF-derived cobalt-iron composite material according to claim 1, wherein: The centrifugal speed of the mixed solution in step 1 is 8000 rpm.

5. Use of a MOF-derived cobalt-iron composite material prepared by the method according to any one of claims 1 to 4, characterized in that: The MOF-derived cobalt-iron composite material was applied to activate peroxymonosulfate to degrade ofloxacin (OFX).

6. The use of the MOF-derived cobalt-iron composite material according to claim 5, characterized in that: The degradation method is as follows: 100 mL of a 20 mg / L ofloxacin OFX solution is placed in a 1000 mL beaker, the beaker is placed on a shaker, 0.4-0.6 g of a MOF-derived cobalt-iron composite material CoFeCMs and 0.5 g of peroxymonosulfate PMS are added to the beaker, and the peroxymonosulfate PMS is activated by the synergistic effect of the cobalt-iron bimetallic in the MOF-derived cobalt-iron composite material CoFeCMs to degrade ofloxacin OFX; the degradation time is 30 min, 2-3 mL of the solution in the degradation process is taken out with a syringe, the solution is filtered with a 0.22 μm polyethersulfone PES filter membrane and placed in a quartz cuvette, and the ofloxacin OFX concentration is analyzed by UV-Vis at a wavelength of 294 nm. The degradation rate of ofloxacin OFX is 68.8-94.2%.

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