Preparation methods and applications of microporous SiO2-modified MOF-derived cobalt-iron composites

Abstract

The application discloses a preparation method and application of a microporous SiO2 modified MOF derived cobalt-iron composite material, and the application is characterized in that: a precursor Fe-ZIF 67 is coated with mesoporous SiO2, and after calcination, a CoFeCMs@mSiO2 with a core-shell structure is formed. 2 The catalyst has a large specific surface area and excellent catalytic performance, and the specific surface area can reach 274.82 m 2 / g. This makes the catalyst produce more exposed active sites, can efficiently activate PMS, and makes the CoFeCMs@mSiO2 / PMS system can effectively degrade 91.7% of OFX with a concentration of 20 mg / L within 20 min. The application provides more choices for the application of MOF derived bimetallic composite materials as AOPs to degrade organic pollutants.

Description

Technical Field

[0001] This invention relates to the field of organic pollutant antibiotic treatment technology, specifically to a method for preparing and applying a microporous SiO2-modified MOF-derived cobalt-iron composite material. Background Technology

[0002] Over the past few decades, antibiotics have played a vital role in treating human and animal diseases and promoting livestock growth and development. However, only a portion of antibiotics are metabolized and absorbed by humans or animals; the remainder is excreted into the aquatic environment through feces or urine. Their persistent presence in the aquatic environment leads to strong antibiotic resistance in bacteria, seriously threatening the aquatic environment and human health.

[0003] Traditional AOPs technologies based on ·OH exhibit non-selective mineralization pathways for organic matter and generally require highly acidic environments. SR-AOPs processes, on the other hand, are universally applicable and highly efficient in disinfection and removal of emerging pollutants. Through AOPs technology, environmental pollutants are mineralized into smaller molecules, ultimately existing as CO2 and H2O. SR-AOPs technology has gradually replaced traditional ·OH-based AOPs technologies to some extent, primarily due to ①SO4 ·- The redox potential of SO4 is 2.5-3.1V, which is higher than that of ·OH (1.8-2.7V); ·- ③ High stability and long half-life; ④ Highly effective removal of numerous pollutants; ⑤ SO42- resistant over a wide pH range. ·- It can effectively remove pollutants; ⑤ It is economical, efficient, and environmentally friendly.

[0004] MOF-derived materials retain the advantages of MOF materials, such as three-dimensional porous structure, large specific surface area, abundant active sites, tunable metal elements, and pore structure, making them promising SR-AOPs catalysts. Cobalt is considered the most effective transition metal for the removal of organic pollutants in SR-AOPs; however, MOF-derived cobalt-based metal materials have limited catalytic performance, exhibiting problems such as easy aggregation and poor stability. MOF-derived cobalt-iron bimetallic materials promote the catalytic activity of Co... 3+ / Co 2+ Fe 3+ / Fe 2+ The redox cycle enhances catalytic performance.

[0005] Eggshell structures have attracted considerable interest due to their unique structure and wide range of applications across various fields. In particular, eggshell catalysts exhibit the following significant advantages: they stabilize active nanoparticles through encapsulation; the microenvironment created by the eggshell structure provides the driving force for adsorption and degradation reactions; and active sites can be designed into the core or embedded in the voids to improve stability while preserving the entire surface of the active sites. SiO2, acting as an outer shell, can enhance material stability and also provides protection during calcination.

[0006] In summary, the microporous SiO2-modified MOF-derived cobalt-iron composite material shows great potential in activating PMS to degrade antibiotics in water. As a highly efficient catalyst in advanced oxidation technologies, the microporous SiO2-modified MOF-derived cobalt-iron composite material will undoubtedly have significant application value in wastewater treatment in the future. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing and applying a microporous SiO2-modified MOF-derived cobalt-iron composite material. This is achieved by coating the surface of a precursor Fe-ZIF 67 with mesoporous SiO2, followed by water etching and calcination to form a microporous SiO2-modified MOF-derived cobalt-iron bimetallic composite catalyst, CoFeCMs@mSiO2. The MOF-derived cobalt-iron bimetallic catalyst exhibits synergistic effects, enhancing both catalytic activity and structural stability, while SiO2 acts as a shell to improve material stability.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing a microporous SiO2-modified MOF-derived cobalt-iron composite material includes the following steps:

[0010] Step 1: Prepare the precursor Fe-ZIF 67 using the co-precipitation method:

[0011] Take 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, mix them thoroughly, and sonicate the mixture for 10 min. The resulting solution is referred to as solution A.

[0012] 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 with water to 12 mL, and sonicate for 10 min to obtain solution B.

[0013] Under stirring conditions, solution B was slowly added dropwise to solution A. After the addition was completed, stirring was continued at room temperature for 24 hours. The mixture was centrifuged and the solid was collected. The solid was then washed repeatedly with water and methanol alternately several times and dried at 60°C to obtain the precursor Fe-ZIF 67. The molar ratio of Co to Fe in the precursor Fe-ZIF 67 was 1:1.5.

[0014] Step 2: Preparation of Fe-ZIF 67@mSiO2:

[0015] The precursor Fe-ZIF 67 prepared in step one was dispersed in water to prepare an aqueous solution with a concentration of 1 mg / mL. 100 mL of the Fe-ZIF 67 aqueous solution was mixed with 20 mL of a 62.5 mg / mL cetyltrimethylammonium bromide ethanol solution and stirred for 1 h. The mixture was heated to 50 °C, and 0.5 mL of ammonia water was added. 583 mg of tetraethyl silicate was mixed with 10 mL of ethanol and then added dropwise to the above mixed solution in several portions. The mixture was stirred vigorously at 50 °C for 6 h. After the reaction was completed, the solution was centrifuged, the solid was collected, washed three times with ethanol, and dried at 60 °C to obtain Fe-ZIF 67@mSiO2.

[0016] Step 3: Preparation of Fe-ZIF 67@mSiO2 after removal of hexadecyltrimethylammonium bromide and water etching.

[0017] The Fe-ZIF 67@mSiO2 prepared in step two was extracted with an ethanol solution of ammonium nitrate at 80°C to remove hexadecyltrimethylammonium bromide from the shell structure of Fe-ZIF 67@mSiO2.

[0018] Fe-ZIF 67@mSiO2 after removing hexadecyltrimethylammonium bromide was dispersed in water at a concentration of 2 mg / mL. 70 mL of the dispersion was loaded into a 100 mL reactor and kept at 100 °C for 24 h.

[0019] After centrifuging the dispersion, the solid was collected, washed with ethanol, and dried at 60°C to obtain Fe-ZIF 67@mSiO2 after removing hexadecyltrimethylammonium bromide and water etching.

[0020] Step 4: Calcination in air atmosphere to prepare CoFeCMs@mSiO2

[0021] The Fe-ZIF 67@mSiO2 prepared in step 3 after removing hexadecyltrimethylammonium bromide and water etching was ground into powder, placed in a tube furnace at 500-600℃, and calcined in air atmosphere for 2 hours to obtain the microporous SiO2 modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2.

[0022] Preferably, in step two, tetraethyl silicate is added to the mixture in five separate drops.

[0023] Preferably, the centrifugation rate of the solution in steps one and two is 8000 rpm.

[0024] Preferably, the heating rate of the tubular furnace in step four is 5°C / min.

[0025] Application of a microporous SiO2-modified MOF-derived cobalt-iron composite material: The microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 is used to activate peroxymonosulfate to degrade ofloxacin.

[0026] Preferably, the degradation method is as follows: 100 mL of ofloxacin solution with a concentration of 20-30 mg / L is placed in a 1000 mL beaker, and the beaker is placed on a shaker for shaking. 0.04-0.05 g of microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 and 0.03-0.04 g of peroxymonosulfate are added to the beaker. The peroxymonosulfate is activated to degrade ofloxacin under the synergistic effect of the cobalt-iron bimetallic compound CoFeCMs@mSiO2. The degradation time is 20 min. 2-3 mL of the solution is taken out with a syringe during the degradation process. The solution is filtered through a 0.22 μm polyethersulfone (PES) filter membrane and placed in a quartz cuvette. The concentration of ofloxacin is analyzed using UV-Vis at a wavelength of 294 nm. The degradation rate of ofloxacin is 88.9%-91.7%.

[0027] Characterization of the microporous SiO2-modified MOF-derived cobalt-iron composite catalyst CoFeCMs@mSiO2:

[0028] 1. Characterization of microscopic morphology

[0029] like Figure 2 As shown in (a), the synthesized precursor Fe-ZIF 67 has a relatively smooth surface and a dodecahedral structure of ZIF. Figure 2 (b) Mesoporous SiO2 was coated on the surface of Fe-ZIF 67 to form spherical nanoparticles with a particle size of about 300-600 nm. Figure 2 (c) is a SEM image of uncoated mesoporous SiO2-treated CoFeCMs after calcination. It shows severe structural collapse, with cobalt-iron bimetallic oxide deposits on the surface causing roughness. Figure 2 The TEM image in (d) shows the core-shell structure formed by mesoporous SiO2 coating, which still has a complete core-shell structure after calcination; Figure 2In (e), HRTEM measured a lattice spacing of 0.254 nm, corresponding to the (311) plane of CoFe2O4.

[0030] 2. XRD Analysis

[0031] Figure 3 (a) shows the XRD patterns of Fe-ZIF 67, Fe-ZIF 67@mSiO2, CoFeCMs@mSiO2, and CoFeCMs. The characteristic peaks of SiO2 at 22.0° and 36.4° correspond to the (101) and (112) crystal planes of SiO2, respectively, and the characteristic peak at 33.1° corresponds to the (104) crystal plane of Fe2O3. The characteristic diffraction peaks of CoFeCMs@mSiO2 and CoFeCMs at 35.7° and 53.8° correspond to the (311) and (422) crystal planes of SiO2, respectively, which are consistent with the characteristic peaks of spinel structure CoFe2O4. In addition, two other characteristic peaks of CoFe2O4 appear in CoFeCMs, located at 37.3° and 62.7°, corresponding to the (222) and (440) crystal planes. The weakening of the SiO2 characteristic peaks at 22.0° and 36.4° in Fe-ZIF 67@mSiO2 and CoFeCMs@mSiO2 is due to the partial decomposition of silicon dioxide after calcination. Figure 3 (b) shows that the higher the calcination temperature, the stronger the characteristic peak of CoFe2O4, indicating that the content of CoFe2O4 formed is greater. Based on the above analysis, it is confirmed that there are SiO2 and CoFe2O4 components in CoFeCMs@mSiO2. Combined with SEM analysis, it shows that SiO2 is successfully coated.

[0032] 3. XPS Analysis

[0033] The chemical state and surface elemental composition of CoFeCMs@mSiO2 were analyzed using XPS spectroscopy. Figure 4 (a) It can be seen that the prepared material contains C, O, Si, Fe, and Co elements; Figure 4 The binding energies of the three peaks appearing in (b) are 284.8 eV, 286.6 eV and 288.1 eV, respectively, which correspond to -CC, -CO and OCO. Before the catalytic reaction, the proportions of -CC, -CO and OCO are 74.39%, 19.65% and 5.96%, respectively, and after the reaction they are 72.72%, 21.44% and 5.94%, respectively. Figure 4The three peaks in (c) are at 532.4 eV, 533.0 eV, and 533.8 eV, respectively, belonging to lattice oxygen, adsorbed oxygen, and surface adsorbed water. The binding energy of 532.4 eV is attributed to Fe-O / Co-O, while the peak at 533.0 eV originates from the CO peak, corresponding to 286.6 eV in the C1s spectrum. This may be due to partial oxidation of the carbon skeleton of the MOF. Before the catalytic reaction, the contents of lattice oxygen, adsorbed oxygen, and surface adsorbed water were 51.21%, 29.70%, and 19.09%, respectively, and after the reaction, they were 50.48%, 23.55%, and 25.97%, respectively, indicating that O participated in the redox process of iron and cobalt ions. Figure 4 The peak at 103.6 eV in (d) originates from SiO2; Figure 4 In (e), the peak values ​​of 711.1 eV / 724.0 eV in the Fe 2p spectrum belong to Fe 2+ (2p 3 / 2 / 2p 1 / 2 ), 714.1 eV / 726.6 eV belongs to Fe 3+ (2p 3 / 2 / 2p 1 / 2 ), 718.6 eV is a satellite peak, Fe 2+ / Fe 3+ The increase from 1.27 to 2.07 indicates that Fe 2+ / Fe 3+ It participated in the degradation process; Figure 4 In (f), the peaks at 782.1 eV / 797.8 and 785.5 eV / 800.0 eV in the Co 2p spectrum are respectively those of 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 eV are satellite peaks; Co 2+ / Co 3+ The decrease from 2.37 to 2.23 indicates that Co 2+ / Co 3+ It participated in the degradation process. Combined with the above SEM, TEM, and XRD analysis results, it can be concluded that CoFeCMs@mSiO2 with a core-shell structure was successfully prepared.

[0034] 4. Raman analysis

[0035] In Raman spectroscopy, the D band and G band represent the presence of defects in the carbon framework and the presence of sp, respectively. 2 Hybridized carbon atoms. For example... Figure 5 As shown, CoFeCMs@mSiO2 and CoFeCMs at 1580 cm⁻¹ -1The lower G-band peaks nearby may be due to less pronounced stretching vibrations of the in-plane bonds of carbon atoms; at 1310 cm⁻¹... -1 The D-band peaks in the vicinity are significantly stronger for CoFeCMs than for CoFeCMs@mSiO2, indicating that the density of disordered carbon and carbon defects in CoFeCMs is higher than that in CoFeCMs@mSiO2. Based on the above analysis, it can be concluded that the carbon defect density of Fe-ZIF 67 coated with mesoporous SiO2 after calcination is lower than that of Fe-ZIF 67 directly calcined, and the mesoporous SiO2 plays a protective role during the calcination process.

[0036] 5. N2 adsorption curve and BET analysis

[0037] Table 1 shows the BET test data for FeZIF-67, CoFeCMs, and CoFeCMs@mSiO2. Figure 6 (a) and as shown in Table 1, the specific surface area of ​​Fe-ZIF 67 is 820.35 m². 2 / g, the specific surface area of ​​CoFeCMs@mSiO2 coated with mesoporous SiO2 after calcination is 274.82m². 2 / g, the specific surface area of ​​CoFeCMs formed by direct calcination is only 22.97m². 2 / g; After calcination, the specific surface area of ​​Fe-ZIF 67 will decrease due to the loss of the carbon skeleton of Fe-ZIF 67 during the calcination process. However, the specific surface area of ​​CoFeCMs@mSiO2 is much higher than that of CoFeCMs. Figure 6 In (a), the N2 adsorption-desorption isotherms of Fe-ZIF 67, CoFeCMs@mSiO2 and CoFeCMs are the IV isotherms of the H3 hysteresis loop, indicating that there are mesopores inside. The pore size distribution of Fe-ZIF 67 and CoFeCMs@mSiO2 is about 2-10 nm, mainly concentrated at about 5 nm. The pore size of CoFeCMs is relatively large, basically concentrated at 10-30 nm, but the pore volume is small.

[0038] Table 1

[0039]

[0040] The microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 prepared by this method catalytically degrades ofloxacin:

[0041] The target pollutant is calculated using the following formula:

[0042] Among them, R t The degradation rates at time t are represented by C0 and C2. t These represent the concentration of the pollutant and the concentration of the pollutant at time t, respectively.

[0043] 1. Effect of calcination temperature on the degradation of ofloxacin (OFX)

[0044] During the formation of MOF-derived materials, the calcination temperature has a significant impact on the material's structure and catalytic performance. Therefore, this experiment investigated the effect of CoFeCMs@mSiO2 calcined at 300℃, 400℃, 500℃, 600℃, and 700℃ on OFX degradation. Figure 7 As shown, the removal rate of OFX by CoFeCMs@mSiO2 at 300-600℃ remained around 90% within 20 min, but the removal rate varied significantly within 1 min, with a faster removal rate at 500℃. The removal efficiency at 700℃ was 85.6%, but the degradation rate was slower. This may be because the high temperature during calcination severely damaged the carbon skeleton of the ZIF structure, resulting in fewer active sites and a limited number of active species, thus leading to a slower degradation rate of OFX.

[0045] 2. Effects of different catalyst systems on OFX degradation

[0046] To investigate the effects of coating mSiO2 to form core-shell structured CoFeCMs@mSiO2, which, with its protective mSiO2 shell, minimizes carbon skeleton loss during calcination and provides more active sites, the degradation performance of CoFeCMs@mSiO2 and CoFeCMs on OFX was compared. Figure 8 As shown in (a), without PMS, the degradation rates of OFX by CoFeCMs@mSiO2 and CoFeCMs were 54.9% and 11.3%, respectively, indicating that the degradation rate of the composite catalyst was significantly improved after coating and calcination. After adding 0.3 g / L PMS, the CoFeCMs@mSiO2 / PMS and CoFeCMs / PMS systems removed 91.7% and 35.6% of OFX, respectively, within 20 min. Notably, CoFeCMs@mSiO2 / PMS efficiently degraded 88.7% of OFX within 3 min. Figure 8 As shown in (b), the reaction kinetic constants of the CoFeCMs@mSiO2 / PMS and CoFeCMs / PMS systems were calculated, and were 0.255 min⁻¹. -1 and 0.55min -1 The rate constant of the CoFeCMs@mSiO2 / PMS system is approximately the same as that of the CoFeCMs / PMS system. Based on the above analysis, it is confirmed that the material coated with mSiO2 has superior catalytic degradation performance.

[0047] 3. Effect of different initial pH on OFX degradation

[0048] The initial pH of the solution has a certain influence on the generation of free radicals and the changes in the form of organic matter. Therefore, the effect of initial pH on the removal of OFX in the CoFeCMs@mSiO2 / PMS system was studied. Figure 9 It can be seen that the removal rate of OFX increases continuously as the pH gradually increases from 3 to 7, with degradation rates of 84.6%, 88.2%, and 91.7% at pH 3, 5, and 7, respectively. Under lower pH conditions, SO4... ·- ·OH will react with H + The reaction produces less reactive HSO4 - Alternatively, it can be directly removed (3-1—3-3). As the pH gradually increases from 7 to 11, the degradation efficiency of OFX significantly decreases, from 91.7% to 34.7%. Under higher pH conditions, M(III) is reduced to M(II), inhibiting the production of active species (3-4, 3-5), leading to a significant decrease in the removal rate of OFX. Based on the above analysis, the degradation effect of OFX is optimal under neutral or weakly acidic conditions; therefore, pH = 7 was selected as the optimal pH for this experiment.

[0049] M(Ⅱ) + H2O → MOH + + H + (3-1)

[0050]

[0051] ·OH + H + + e + → H2O (3-3)

[0052]

[0053] 4. Effect of PMS peroxymonosulfate dosage on OFX degradation

[0054] CoFeCMs@mSiO2 generates active species by activating peroxymonosulfate PMS, thereby mineralizing and removing OFX. Therefore, the dosage of PMS plays a crucial role in the degradation of OFX in the system. Figure 10 As shown, when the PMS dosage increased from 0.1 g / L to 0.3 g / L, the degradation efficiency of OFX gradually increased. The removal rate remained around 90% within 20 minutes, but gradually increased within 3 minutes. At a PMS dosage of 0.3 g / L, the removal rate of OFX within 20 minutes was 91.7%. With increasing PMS dosage, the number of active species generated in the system relatively increased, accelerating the removal of OFX. When the PMS dosage continued to increase from 0.3 g / L, the degradation efficiency within 20 minutes did not change significantly, but the degradation efficiency within 3 minutes decreased slightly. This indicates that when the amount of PMS and the amount of catalyst reach equilibrium, SO42-20% of the total oxygen content decreases.·- Free radicals undergo self-quenching reactions. Based on the above analysis, this experiment determined the optimal dosage of PMS to be 0.3 g / L.

[0055] 5. Effect of catalyst dosage on OFX degradation

[0056] To investigate the effect of catalyst dosage on PMS activation, different amounts of CoFeCMs@mSiO2 were used; such as Figure 11 As shown, the removal rate of OFX gradually increased within 20 minutes when the catalyst concentration was increased from 0.2 g / L to 0.4 g / L. At 0.4 g / L, the degradation efficiency of OFX was 91.7%. Further increases in catalyst concentration did not significantly increase the removal rate of OFX. Considering both catalytic degradation efficiency and operating costs, 0.4 g / L was selected as the optimal catalyst concentration in this experiment.

[0057] 6. Effect of initial OFX concentration on OFX degradation

[0058] The experiment investigated the effect of the concentration of the target pollutant OFX solution on the degradation performance of the catalyst CoFeCMs@mSiO2. Figure 12 As shown, when the initial concentrations of OFX were 10 mg / L, 20 mg / L, and 30 mg / L, the removal rates of OFX within 20 min were 92.0%, 91.7%, and 88.9%, respectively. This indicates that the degradation efficiency decreases with increasing initial OFX concentration. This is because the amount of PMS and catalyst in the system is limited, resulting in a limited number of active sites. In solutions with higher OFX concentrations, OFX molecules compete for active species, thus reducing the reaction rate.

[0059] 7. The impact of actual water bodies on OFX degradation

[0060] To investigate the impact of actual water bodies on OFX degradation, this experiment compared OFX solutions prepared from ultrapure water, Yellow River water, and tap water. Figure 13 As shown, the OFX degradation efficiencies of ultrapure water, Yellow River water, and tap water were 91.7%, 81.4%, and 79.7%, respectively. Yellow River water and tap water have a certain impact on OFX degradation. Considering the influence of different ions on OFX degradation, the decrease in OFX degradation efficiency may be due to HCO3-. - and HPO4 2- The effects of plasma.

[0061] 8. Cyclic stability analysis

[0062] To investigate the cyclic stability of the CoFeCMs@mSiO2 / PMS and CoFeCMs / PMS systems, five cycles were performed. Figure 14As shown in (a), after 5 cycles, the degradation efficiency of OFX by CoFeCMs@mSiO2 / PMS decreased from 91.7% to 69.1% within 20 min. Figure 14 As shown in (b), the degradation efficiency of OFX in the CoFeCMs / PMS system decreased from 35.6% to 9.5%. The CoFeCMs@mSiO2 / PMS system achieved an OFX removal rate of 84.6% after the first three cycles. The degradation rate of OFX decreased rapidly in the fourth and fifth cycles, possibly due to partial blockage of mSiO2 channels, which reduced the diffusion rate of OFX into CoFeCMs@mSiO2. However, the OFX removal rate was still higher than that of bare CoFeCMs material. Figure 14 (c) shows the XRD patterns of CoFeCMs@mSiO2 and CoFeCMs before and after 5 cycles. It was found that the main diffraction peaks did not change before and after the reaction, remaining consistent with the main diffraction peaks of spinel-structured CoFe2O4, indicating that the crystal structure of the material did not change. Furthermore, from... Figure 14 (d) and (e) show that the microstructure of the material did not change significantly after 5 cycles. Based on the above analysis, the degradation efficiency and degradation rate of CoFeCMs@mSiO2 after 5 cycles are significantly higher than those of CoFeCMs. However, the degradation efficiency of CoFeCMs@mSiO2 after 5 cycles is lower, which may be due to the blockage of the pores of mSiO2, which slows down the transfer rate between active oxygen components and OFX.

[0063] 9. Degradation mechanism

[0064] (1) Determination of free radicals

[0065] To further identify the active species in the reaction system, radical quenching experiments and EPR tests of the CoFeCMs@mSiO2 / PMS system using DMPO and TEMP spin traps were conducted. Figure 15 (a) Radical quenching experiments were conducted on the CoFeCMs@mSiO2 / PMS system to determine the contribution of different active species to the catalytic activity. This was achieved by adding methanol (Methanol, SO42-) to the system. ·- Quenching agents), tert-butanol (TBA, ·OH quenching agent), p-benzoquinone (p-BQ, O2) ·- Quenching agents) and furfuryl alcohol (FFA, 1 (O2 quencher). After adding 10 mM FFA to the system, the degradation efficiency of OFX decreased to 31.3% after 20 min. After adding methanol, the removal rate of OFX decreased to 68.2%, and after adding p-BQ and TBA, the removal rates of OFX decreased to 75.7% and 87.4%, respectively. The order of contribution rates of the four active species to the catalytic activity is as follows: 1O2 > SO4 ·- >O2 ·- >·OH, the active species that play a major role in degradation of CoFeCMs@mSiO2 / PMS are 1 O2 and SO4 ·- .

[0066] like Figure 15 As shown in (b), (c), and (d), active species in the detection system were captured using DMPO and TEMP at 1 min and 5 min. Figure 15 (b) The signal peaks with peak intensity ratios of 1:2:2:1 and 1:1:1:1:1:1 in the above-intensity ratios correspond to DMPO-·OH and DMPO-SO4, respectively. ·- . Figure 15 The sextet in (c) is DMPO-O2 ·- The signal. Figure 15 In (d), the signal peak with a peak intensity of 1:1:1 is TEMP- 1 The signal of O2. Combined Figure 15 (b), (c), and (d) indicate that SO4 is present in the CoFeCMs / PMS system. ·- ·OH, O2 ·- , 1 O2 consists of four types of reactive oxygen species.

[0067] like Figure 16 As shown, chronoamperometry demonstrated the electron transfer from OFX to PMS. Using CoFeCMs@mSiO2 and CoFeCMs as working electrodes, chronoamperometry (itC) curves were performed. When PMS and OFX were added at 100s and 200s respectively, significant current changes were observed, indicating that CoFeCMs@mSiO2 and CoFeCMs, as dielectrics, can transfer electrons from OFX to PMS via a non-radical pathway. Furthermore, CoFeCMs@mSiO2 showed significant current changes at 100s and 200s, indicating substantial electron transfer, while the current peak intensity of CoFeCMs was weaker, suggesting that CoFeCMs@mSiO2 has a stronger electron transfer capability.

[0068] (2) Degradation pathways of OFX

[0069] The intermediate substances in the degradation of OFX by the CoFeCMs@mSiO2 / PMS system were determined by HPLC-MS, and the possible degradation pathways of OFX were analyzed. Figure 17As shown, the cleavage of the CN or CC bond of the piperazine ring in OFX produces products P1 (m / z, 364), P2 (m / z, 336), P3 (m / z, 279), and P4 (m / z, 228). P3 undergoes further decarboxylation and demorpholine ring removal to generate P5 (m / z, 116). OFX first undergoes decarboxylation to generate P6 (m / z, 334), P6 undergoes hydroxyl addition and dealkylation to generate P7 (m / z, 336), and then alkylation of the piperazine ring to generate P8 (m / z, 274). P8 then undergoes further... 1 O2, SO4 ·- Oxidation by reactive free radicals gradually generates P9 (m / z, 175) and P10 (m / z, 149). In general, the degradation pathway of OFX mainly involves several processes such as decarboxylation, hydroxylation, alkylation, and hydroxy oxidation.

[0070] (3) Mechanism of OFX degradation by CoFeCMs@mSiO2 / PMS system

[0071] The degradation mechanism of OFX by the CoFeCMs@mSiO2 / PMS system is as follows: Figure 18 As shown, Co in the system 3+ / Fe 3+ The reaction with PMS generates sulfate radicals SO5. ·- SO5 ·- The two react to produce SO4 ·- Co 2+ / Fe 2+ SO4 is generated by reaction with PMS. ·- O2 ·- It is made of SO5 ·- The O2 produced in the reaction gains an electron to form SO4. ·- ·OH is generated in the diffusion solution, and ·OH reacts with O2. ·- The reaction can produce 1 O2. Produced during the reaction. 1 O2, SO4 ·- O2 ·- The attack of ·OH disrupts the structure of OFX, further mineralizing pollutants into smaller molecules, CO2, and H2O. The entire reaction process is illustrated in equations 3-6 to 3-12. Furthermore, the non-radical mechanism of CoFeCMs@mSiO2 effectively promotes the transfer of electrons from OFX to PMS.

[0072]

[0073] In summary, this invention forms a core-shell structure CoFeCMs@mSiO2 by coating the precursor Fe-ZIF 67 with mesoporous SiO2 and then calcining it. This catalyst exhibits a large specific surface area and excellent catalytic performance, with a specific surface area reaching 251.86 m². 2 / g. This results in more exposed active sites on the catalyst, enabling efficient activation of PMS. Consequently, the CoFeCMs@mSiO2 / PMS system can effectively degrade 91.7% of OFX at a concentration of 20 mg / L within 20 min. This invention provides more options for the application of MOF-derived bimetallic matrix composites in the degradation of organic pollutants by AOPs. Attached Figure Description

[0074] Figure 1 This is a synthesis route diagram for CoFeCMs@mSiO2;

[0075] Figure 2 (a) is a SEM image of Fe-ZIF 67; (b) is a SEM image of CoFeCMs@mSiO2; (c) is a SEM image of CoFeCMs; (d) is a TEM image of CoFeCMs@mSiO2; and (e) is a HRTEM image.

[0076] Figure 3 (a) shows the XRD patterns of Fe-ZIF 67, Fe-ZIF 67@mSiO2, CoFeCMs@mSiO2, and CoFeCMs; (b) shows the XRD patterns of CoFeCMs@mSiO2 at different calcination temperatures.

[0077] Figure 4 These are the fine XPS spectra of CoFeCMs@mSiO2 before and after the reaction: (a) full spectrum; (b) C 1s; (c) O 1s; (d) Si 2p; (e) Fe 2p; (f) Co 2p;

[0078] Figure 5 These are the Raman spectra of CoFeCMs@mSiO2 and CoFeCMs;

[0079] Figure 6 (a) N2 adsorption-desorption curves of Fe-ZIF 67, CoFeCMs@mSiO2 and CoFeCMs; (b) pore size distribution of Fe-ZIF 67, CoFeCMs@mSiO2 and CoFeCMs;

[0080] Figure 7 The effect of different calcination temperatures on the degradation of OFX (experimental parameters: [OFX] = 20 mg / L, [catalyst] = 0.4 g / L, [PMS] = 0.5 g / L);

[0081] Figure 8 The effect of different catalytic systems on the degradation of OFX (experimental parameters: [OFX] = 20 mg / L, [catalyst] = 0.4 g / L, [PMS] = 0.3 g / L);

[0082] Figure 9 The effect of different initial pH values ​​on the degradation of OFX (experimental parameters: [OFX] = 20 mg / L, [catalyst] = 0.4 g / L, [PMS] = 0.3 g / L);

[0083] Figure 10 The effect of PMS dosage on the degradation of OFX (experimental parameters: [OFX] = 20 mg / L, [catalyst] = 0.4 g / L, [pH] = 7);

[0084] Figure 11 The effect of catalyst dosage on the degradation of OFX (experimental parameters: [OFX] = 20 mg / L, [PMS] = 0.3 g / L, [pH] = 7);

[0085] Figure 12 The effect of initial OFX concentration on OFX degradation (experimental parameters: [catalyst] = 0.4 g / L, [PMS] = 0.3 g / L, [pH] = 7);

[0086] Figure 13 The effect of different water bodies on OFX degradation (experimental parameters: [OFX] = 20 mg / L, [catalyst] = 0.4 g / L, [PMS] = 0.3 g / L, [pH] = 7);

[0087] Figure 14 The results are as follows: (a) Stability test of the CoFeCMs@mSiO2 / PMS system after 5 cycles (experimental parameters: [OFX] = 20 mg / L, [catalyst] = 0.4 g / L, [PMS] = 0.3 g / L, [pH] = 7); (b) Stability test of the CoFeCMs / PMS system after 5 cycles (experimental parameters: [OFX] = 20 mg / L, [catalyst] = 0.4 g / L, [PMS] = 0.3 g / L, [pH] = 7); (c) XRD comparison of CoFeCMs@mSiO2 and CoFeCMs before and after 5 cycles; (d) SEM image of CoFeCMs@mSiO2 after 5 cycles; (e) SEM image of CoFeCMs after 5 cycles.

[0088] Figure 15(a) Free radical quenching experiment (experimental parameters: [OFX] = 20 mg / L, [PMS] = 0.3 g / L, [catalyst] = 0.4 g / L, [pH] = 7), EPR spectrum of CoFeCMs@mSiO2 / PMS system; (b) DMPO-·OH and DMPO-SO4 ·- (c)DMPO-O2 ·- (d)TEMP- 1 O2;

[0089] Figure 16 These are the chronoamperometric curves of CoFeCMs@mSiO2 and CoFeCMs;

[0090] Figure 17 This describes the degradation pathway of OFX by the CoFeCMs@mSiO2 / PMS system.

[0091] Figure 18 This is a diagram illustrating the reaction mechanism of OFX in the CoFeCMs@mSiO2 / PMS system. Detailed Implementation

[0092] The present invention will now be described in further detail with reference to the accompanying drawings.

[0093] Example 1

[0094] A method for preparing a microporous SiO2-modified MOF-derived cobalt-iron composite material includes the following steps:

[0095] Step 1: Prepare the precursor Fe-ZIF 67 using the co-precipitation method:

[0096] Take 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, mix them thoroughly, and sonicate the mixture for 10 min. The resulting solution is referred to as solution A.

[0097] 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 with water to 12 mL, and sonicate for 10 min to obtain solution B.

[0098] Under stirring conditions, solution B was slowly added dropwise to solution A. After the addition was complete, stirring was continued at room temperature for 24 hours. The mixture was then centrifuged at 8000 rpm to collect the solid. The solid was then washed repeatedly with water and methanol alternately several times and dried at 60°C to obtain the precursor Fe-ZIF 67. The molar ratio of Co to Fe in the precursor Fe-ZIF 67 was 1:1.5.

[0099] Step 2: Preparation of Fe-ZIF 67@mSiO2:

[0100] The precursor Fe-ZIF 67 prepared in step one was dispersed in water to prepare an aqueous solution with a concentration of 1 mg / mL. 100 mL of the Fe-ZIF 67 aqueous solution was mixed with 20 mL of a 62.5 mg / mL cetyltrimethylammonium bromide ethanol solution and stirred for 1 h. The mixture was heated to 50 °C, and 0.5 mL of ammonia water was added. 583 mg of tetraethyl silicate was mixed with 10 mL of ethanol and then added dropwise to the above mixed solution in 5 portions. The mixture was stirred vigorously at 50 °C for 6 h. After the reaction was completed, the solution was centrifuged at a speed of 8000 rpm. The solid was collected, washed three times with ethanol, and dried at 60 °C to obtain Fe-ZIF67@mSiO2.

[0101] Step 3: Preparation of Fe-ZIF 67@mSiO2 after removal of hexadecyltrimethylammonium bromide and water etching.

[0102] The Fe-ZIF 67@mSiO2 prepared in step two was extracted with an ethanol solution of ammonium nitrate at 80°C to remove hexadecyltrimethylammonium bromide from the shell structure of Fe-ZIF 67@mSiO2.

[0103] Fe-ZIF 67@mSiO2 after removing hexadecyltrimethylammonium bromide was dispersed in water at a concentration of 2 mg / mL. 70 mL of the dispersion was loaded into a 100 mL reactor and kept at 100 °C for 24 h.

[0104] After centrifuging the dispersion, the solid was collected, washed with ethanol, and dried at 60°C to obtain Fe-ZIF 67@mSiO2 after removing hexadecyltrimethylammonium bromide and water etching.

[0105] Step 4: Calcination in air atmosphere to prepare CoFeCMs@mSiO2

[0106] The Fe-ZIF 67@mSiO2 prepared in step 3 after removing hexadecyltrimethylammonium bromide and water etching was ground into powder and placed in a tube furnace at 500℃ with a heating rate of 5℃ / min. It was then calcined in air for 2 hours to obtain the microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2.

[0107] Application of a microporous SiO2-modified MOF-derived cobalt-iron composite material: The microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 is used to activate peroxymonosulfate to degrade ofloxacin.

[0108] The degradation method was as follows: 100 mL of ofloxacin solution with a concentration of 20 mg / L was placed in a 1000 mL beaker. 0.04 g of microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 and 0.03 g of peroxymonosulfate were added to the beaker. The beaker was placed on a shaker and shaken for 20 min. The synergistic effect of the cobalt-iron bimetallic compound CoFeCMs@mSiO2 activated the peroxymonosulfate to degrade ofloxacin. 2-3 mL of the degraded solution was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) filter membrane, and placed in a quartz cuvette. The ofloxacin concentration was analyzed using UV-Vis at a wavelength of 294 nm. The degradation rate of ofloxacin was 91.7%.

[0109] XRD patterns of CoFeCMs@mSiO2 catalysis before and after are shown below. Figure 16 ,Depend on Figure 16 It can be seen that the characteristic peaks of CoFeCMs@mSiO2 did not change before and after the catalytic reaction, indicating that the structure of CoFeCMs@mSiO2 did not change, thus proving the stability of the catalyst.

[0110] The CoFeCMs@mSiO2 in the solution after the above degradation reaction was collected by centrifugation and used again in the ofloxacin degradation experiment. The degradation experiment described in Example 1 was repeated 5 times. After each treatment of the contaminant, the recovered CoFeCMs@mSiO2 was washed and dried. The degradation rate of ofloxacin was 89.4% in the second degradation experiment, 84.6% in the third, 79.0% in the fourth, and 69.1% in the fifth.

[0111] Plotting the degradation data from each degradation experiment on the x-axis (sampling time) and the degradation rate of ofloxacin on the y-axis, the resulting degradation graph of ofloxacin by CoFeCMs@mSiO2 is shown below. Figure 16 .Depend on Figure 16 It can be seen that CoFeCMs@mSiO2 can still rapidly degrade ofloxacin in a short time within 3 cycles of the experiment, and maintain the degradation rate of ofloxacin at over 84%.

[0112] Fe-ZIF 67 with a Co to Fe molar ratio of 1:1.5 was prepared using step one. The Fe-ZIF 67 was then calcined at 500℃ to prepare CoFeCMs. SEM images of the prepared CoFeCMs are shown below. Figure 2 (c) It can be seen that the CoFeCMs structure collapses very severely, and the cobalt-iron bimetallic oxide deposits on the surface make the surface rough.

[0113] The SEM image of CoFeCMs@mSiO2 prepared in Example 1 is shown below. Figure 2 (b). By Figure 2 (b) It can be seen that the Fe-ZIF 67 surface coated with mesoporous SiO2 forms spherical nanoparticles with a particle size of about 300-600 nm.

[0114] Example 2

[0115] The preparation method of the microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 in this embodiment is the same as in Example 1.

[0116] Microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 was used to activate peroxymonosulfate to degrade ofloxacin.

[0117] The degradation method was as follows: 100 mL of ofloxacin solution with a concentration of 20 mg / L was placed in a 1000 mL beaker and shaken on a shaker. 0.04 g of microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 and 0.04 g of peroxymonosulfate were added to the beaker. The synergistic effect of the cobalt-iron bimetallic compound CoFeCMs@mSiO2 activated the peroxymonosulfate to degrade ofloxacin. The degradation time was 20 min. 2-3 mL of the solution was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) membrane, and placed in a quartz cuvette. The ofloxacin concentration was analyzed using UV-Vis at a wavelength of 294 nm. The degradation rate of ofloxacin was 90.9%.

[0118] Example 3

[0119] The preparation method of the microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 in this embodiment is the same as in Example 1.

[0120] Microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 was used to activate peroxymonosulfate to degrade ofloxacin.

[0121] The degradation method was as follows: 100 mL of ofloxacin solution with a concentration of 20 mg / L was placed in a 1000 mL beaker and shaken on a shaker. 0.05 g of microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 and 0.03 g of peroxymonosulfate were added to the beaker. The synergistic effect of the cobalt-iron bimetallic compound in CoFeCMs@mSiO2 activated the peroxymonosulfate to degrade ofloxacin. The degradation time was 20 min. 2-3 mL of the solution was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) membrane, and placed in a quartz cuvette. The ofloxacin concentration was analyzed using UV-Vis at a wavelength of 294 nm. The degradation rate of ofloxacin was 91.6%.

[0122] Example 4

[0123] A method for preparing a microporous SiO2-modified MOF-derived cobalt-iron composite material includes the following steps:

[0124] Step 1: Prepare the precursor Fe-ZIF 67 using the co-precipitation method:

[0125] Take 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, mix them thoroughly, and sonicate the mixture for 10 min. The resulting solution is referred to as solution A.

[0126] 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 with water to 12 mL, and sonicate for 10 min to obtain solution B.

[0127] Under stirring conditions, solution B was slowly added dropwise to solution A. After the addition was complete, stirring was continued at room temperature for 24 hours. The mixture was then centrifuged at 8000 rpm to collect the solid. The solid was then washed repeatedly with water and methanol alternately several times and dried at 60°C to obtain the precursor Fe-ZIF 67. The molar ratio of Co to Fe in the precursor Fe-ZIF 67 was 1:1.5.

[0128] Step 2: Preparation of Fe-ZIF 67@mSiO2:

[0129] The precursor Fe-ZIF 67 prepared in step one was dispersed in water to prepare an aqueous solution with a concentration of 1 mg / mL. 100 mL of the Fe-ZIF 67 aqueous solution was mixed with 20 mL of a 62.5 mg / mL cetyltrimethylammonium bromide ethanol solution and stirred for 1 h. The mixture was heated to 50 °C, and 0.5 mL of ammonia water was added. 583 mg of tetraethyl silicate was mixed with 10 mL of ethanol and then added dropwise to the above mixed solution in 5 portions. The mixture was stirred vigorously at 50 °C for 6 h. After the reaction was completed, the solution was centrifuged at a speed of 8000 rpm. The solid was collected, washed three times with ethanol, and dried at 60 °C to obtain Fe-ZIF67@mSiO2.

[0130] Step 3: Preparation of Fe-ZIF 67@mSiO2 after removal of hexadecyltrimethylammonium bromide and water etching.

[0131] The Fe-ZIF 67@mSiO2 prepared in step two was extracted with an ethanol solution of ammonium nitrate at 80°C to remove hexadecyltrimethylammonium bromide from the shell structure of Fe-ZIF 67@mSiO2.

[0132] Fe-ZIF 67@mSiO2 after removing hexadecyltrimethylammonium bromide was dispersed in water at a concentration of 2 mg / mL. 70 mL of the dispersion was loaded into a 100 mL reactor and kept at 100 °C for 24 h.

[0133] After centrifuging the dispersion, the solid was collected, washed with ethanol, and dried at 60°C to obtain Fe-ZIF 67@mSiO2 after removing hexadecyltrimethylammonium bromide and water etching.

[0134] Step 4: Calcination in air atmosphere to prepare CoFeCMs@mSiO2

[0135] The Fe-ZIF 67@mSiO2 prepared in step 3 after removing hexadecyltrimethylammonium bromide and water etching was ground into powder and placed in a tube furnace at 600℃ with a heating rate of 5℃ / min. It was then calcined in air for 2 hours to obtain the microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2.

[0136] Application of a microporous SiO2-modified MOF-derived cobalt-iron composite material: The microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 is used to activate peroxymonosulfate to degrade ofloxacin.

[0137] The degradation method was as follows: 100 mL of ofloxacin solution with a concentration of 20 mg / L was placed in a 1000 mL beaker. 0.04 g of microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 and 0.03 g of peroxymonosulfate were added to the beaker. The beaker was placed on a shaker and shaken for 20 min. The synergistic effect of the cobalt-iron bimetallic compound CoFeCMs@mSiO2 activated the peroxymonosulfate to degrade ofloxacin. 2-3 mL of the degraded solution was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) filter membrane, and placed in a quartz cuvette. The ofloxacin concentration was analyzed using UV-Vis at a wavelength of 294 nm. The degradation rate of ofloxacin was 90.4%.

[0138] Example 5

[0139] The preparation method of the microporous SiO2-modified MOF-derived cobalt-iron composite material in this embodiment is the same as in Example 1.

[0140] Application of a microporous SiO2-modified MOF-derived cobalt-iron composite material: The microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 is used to activate peroxymonosulfate to degrade ofloxacin.

[0141] The degradation method was as follows: 100 mL of ofloxacin solution with a concentration of 30 mg / L was placed in a 1000 mL beaker and shaken on a shaker. 0.04 g of microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 and 0.03 g of peroxymonosulfate were added to the beaker. The synergistic effect of the cobalt-iron bimetallic compound in CoFeCMs@mSiO2 activated the peroxymonosulfate to degrade ofloxacin. The degradation time was 20 min. 2-3 mL of the solution was taken out with a syringe, filtered through a 0.22 μm polyethersulfone (PES) membrane, and placed in a quartz cuvette. The ofloxacin concentration was analyzed using UV-Vis at a wavelength of 294 nm. The degradation rate of ofloxacin was 88.9%.

[0142] The above are merely preferred embodiments of the present invention. It should be noted that, for those skilled in the art, other equivalent modifications and improvements can be made based on the technical teachings provided by the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a microporous SiO2-modified MOF-derived cobalt-iron composite material, characterized in that: Includes the following steps: Step 1: Prepare the precursor Fe-ZIF-67 using the co-precipitation method: Take 10 mL of 1 mol / L NaOH and 10 mL of 3.36 mol / L 2-methylimidazole solution, mix them thoroughly, and sonicate the mixture for 10 min. The resulting solution is referred to as solution A. 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 with water to 12 mL, and sonicate for 10 min to obtain solution B; Under stirring conditions, solution B was slowly added dropwise to solution A. After the addition was completed, stirring was continued at room temperature for 24 h. The mixture was centrifuged and the solid was collected. The solid was then washed repeatedly with water and methanol alternately several times and dried at 60 °C to obtain the precursor Fe-ZIF-67. The molar ratio of Co to Fe in the precursor Fe-ZIF-67 was 1:1.

5. Step 2: Preparation of Fe-ZIF-67@mSiO2: The precursor Fe-ZIF-67 prepared in step one was dispersed in water to prepare an aqueous solution with a concentration of 1 mg / mL. 100 mL of the Fe-ZIF-67 aqueous solution was mixed with 20 mL of a 62.5 mg / mL cetyltrimethylammonium bromide ethanol solution and stirred for 1 h. The mixture was heated to 50 °C, and 0.5 mL of ammonia water was added. 583 mg of tetraethyl silicate was mixed with 10 mL of ethanol and then added dropwise to the above mixed solution in several portions. The mixture was stirred vigorously at 50 °C for 6 h. After the reaction was completed, the solution was centrifuged, the solid was collected, washed three times with ethanol, and dried at 60 °C to obtain Fe-ZIF-67@mSiO2. Step 3: Preparation of Fe-ZIF-67@mSiO2 after removal of hexadecyltrimethylammonium bromide and water etching. The Fe-ZIF-67@mSiO2 prepared in step two was extracted with an ethanol solution of ammonium nitrate at 80 °C to remove hexadecyltrimethylammonium bromide from the shell structure of Fe-ZIF-67@mSiO2. Fe-ZIF-67@mSiO2 after removing hexadecyltrimethylammonium bromide was dispersed in water at a concentration of 2 mg / mL. 70 mL of the dispersion was loaded into a 100 mL reactor and kept at 100 °C for 24 h. After centrifuging the dispersion, the solid was collected, washed with ethanol, and dried at 60 °C to obtain Fe-ZIF-67@mSiO2 after removing hexadecyltrimethylammonium bromide and water etching. Step 4: Calcination in air atmosphere to prepare CoFeCMs@mSiO2 The Fe-ZIF-67@mSiO2 prepared in step 3 after removing hexadecyltrimethylammonium bromide and water etching was ground into powder and placed in a tube furnace at 300-700 °C and calcined in air atmosphere for 2 h to obtain the microporous SiO2 modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2.

2. The method for preparing the microporous SiO2-modified MOF-derived cobalt-iron composite material according to claim 1, characterized in that: In step two, tetraethyl silicate is added to the mixture in five separate drops.

3. The method for preparing the microporous SiO2-modified MOF-derived cobalt-iron composite material according to claim 1, characterized in that: The centrifugation rate of the solution in steps one and two is 8000 rpm.

4. The method for preparing the microporous SiO2-modified MOF-derived cobalt-iron composite material according to claim 1, characterized in that: The heating rate of the tubular furnace in step four is 5°C / min.

5. An application of a microporous SiO2-modified MOF-derived cobalt-iron composite material, characterized in that: The microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 prepared by the method of any one of claims 1 to 4 is used to activate peroxymonosulfate to degrade ofloxacin.

6. The application of the microporous SiO2-modified MOF-derived cobalt-iron composite material according to claim 5, characterized in that: The degradation method was as follows: 100 mL of ofloxacin solution with a concentration of 10-30 mg / L was placed in a 1000 mL beaker and shaken on a shaker. 0.02-0.06 g of microporous SiO2-modified MOF-derived cobalt-iron composite material CoFeCMs@mSiO2 and 0.01-0.05 g of peroxymonosulfate were added to the beaker. The peroxymonosulfate was activated to degrade ofloxacin under the synergistic effect of the cobalt-iron bimetallic compound CoFeCMs@mSiO2. The degradation time was 20 min. 2-3 mL of the solution 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 ofloxacin was analyzed using UV-Vis at a wavelength of 294 nm.

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