Preparation Method and Application of a MIL-100(Fe) Material

Abstract

The invention provides a preparation method and application of a MIL-100(Fe) material. Ferric chloride hexahydrate, an organic ligand, sodium acetate and deionized water are added into a dry polytetrafluoroethylene-lined autoclave and fully mixed, wherein the molar ratio of the sodium acetate to the organic ligand is 1:8-5:8, and the heating temperature is 130°C for 3 days to obtain a solid product; after cooling to room temperature, the product is purified with deionized water at 60-80°C for 5-20 hours, and after centrifugation, the product is purified with anhydrous ethanol at 60-80°C for 5-20 hours; after centrifugation, the solid product is dried under vacuum at 50-70°C, and the prepared surface hydroxyl-rich MIL-100(Fe) can enhance the activation of H2O2 to incrementally generate highly oxidizing active species such as •OH, thereby enhancing the photocatalytic Fenton degradation and mineralization of target organic matter.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation and water treatment, and relates to a preparation method and application of a MIL-100 (Fe) material. Background Art

[0002] Metal organic framework (MOFs) has been widely used in gas adsorption, material separation, catalysis and drug carriers due to its huge specific surface area and adjustable structural functions. It is a new type of multifunctional material. Among them, MIL-100 (Fe) is a type of MOFs material that has been studied more. Compared with other organic framework materials synthesized with toxic and harmful metals such as Cr, Cu, and Co, MIL-100 (Fe) has the characteristics of low toxicity and green environmental protection. In addition, compared with MOFs such as UiO, ZIF, and MIL-53, MIL-100 (Fe) type materials have higher water stability. Therefore, many researchers are committed to studying its removal process and mechanism of pollutants in the water environment. In order to overcome the shortcomings of traditional homogeneous Fenton technology, such as severe iron loss, narrow pH range, and Fe in practice. 2+ In order to overcome the challenges of regeneration, people tend to focus on the design and development of heterogeneous Fenton-like catalysts and pay more attention to the reactions occurring at the interface. Heterogeneous photocatalytic Fenton technology has emerged, which accelerates the iron-catalyzed hydrogen peroxide (H 2 O 2 ) decomposes, usually by producing hydroxyl radicals (•OH) to remove pollutants, and has been widely studied and applied in wastewater treatment. However, although •OH is highly oxidizing, its life span (<10 -6 ns) limits the diffusion distance and makes it difficult to migrate into the solution to degrade the target pollutant molecules with weak mineralization polarity. 2 O 2The number of •OH produced, researchers are also committed to analyzing and improving the various processes of the photo-Fenton heterogeneous reaction, or by realizing the conversion between different active species, in order to make up for this deficiency of •OH. By adjusting the electronic and geometric structure changes caused by the functional groups of the catalyst, the state and quantity of the active substance (•OH) may be changed. In recent years, researchers have used surface engineering methods to achieve the regulation of the surface hydroxyl groups of the catalyst, appropriately raising the valence band of the catalyst to narrow the band gap and enhance the light absorption ability. At the same time, it acts as a hole trap to effectively capture photogenerated holes to enhance the charge separation efficiency, thereby achieving the purpose of strengthening the efficient generation of hydroxyl radicals and ultimately improving the removal efficiency of pollutants. In addition, the characteristics of the surface hydroxyl groups themselves are also conducive to the photocatalytic Fenton reaction system, such as the surface hydroxyl groups can enhance the hydrophilicity of the material surface. Better hydrophilicity means that the water medium can be better adsorbed on the catalyst surface, so that the reaction activation site has a closer contact with the target molecule. Some studies have even shown that the surface hydroxyl groups can be directly used as adsorption sites to adsorb pollutants, thereby enhancing the degradation and mineralization of the target organic matter produced at the phase interface. Summary of the invention

[0003] The purpose of the present invention is to provide a MIL-100 (Fe) material, which uses MIL-100 (Fe) as a template to carry out surface hydroxyl-rich modified MIL-100 (Fe) to broaden the application range of surface hydroxyl modification.

[0004] The purpose of the present invention is specifically achieved through the following technical solutions:

[0005] A method for preparing a MIL-100 (Fe) material comprises the following steps:

[0006] First, an iron source, an organic ligand, sodium acetate and water are added to a dry polytetrafluoroethylene-lined autoclave and mixed thoroughly, wherein the molar ratio of the sodium acetate to the organic ligand is 1:8-5:8, and the heating temperature is 130°C for 3 days to obtain a solid product;

[0007] Then, the solid product was cooled to room temperature and purified with deionized water at 60-80°C for 5-20 h, centrifuged and purified with anhydrous ethanol at 60-80°C for 5-20 h; the solid product was orange after centrifugation.

[0008] Finally, the orange solid product was dried under vacuum conditions at 50-70 °C for 12-24 h to obtain MIL-100(Fe) material.

[0009] As a more optimal technical solution of the present invention: the iron source is ferric chloride hexahydrate or ferric nitrate.

[0010] As a more optimal technical solution of the present invention: the organic ligand is benzene 1,3,5-tricarboxylic acid.

[0011] As a more optimal technical solution of the present invention: the mass ratio of the ferric chloride hexahydrate to benzene 1,3,5-tricarboxylic acid is 1:0.66.

[0012] As a more optimal technical solution of the present invention: the molar ratio of the sodium acetate to benzene 1,3,5-tricarboxylic acid is 1:2.

[0013] As a more optimal technical solution of the present invention: the obtained solid product is purified with deionized water at 70°C for 15 hours, and then purified with anhydrous ethanol at 70°C for 6 hours after centrifugation.

[0014] As a more optimal technical solution of the present invention: the orange solid product is dried under vacuum conditions at 60° C. and maintained for 12 h.

[0015] Another object of the present invention is to provide a use of surface hydroxyl-rich modified MIL-100(Fe) as a photocatalyst.

[0016] The beneficial effects are as follows:

[0017] The present invention adds a specific amount of sodium acetate during the preparation of the MIL-100 (Fe) material, so that the surface hydroxyl groups in the MIL-100 (Fe) material can not only reduce the band gap and increase the light absorption range of the material, but also enhance the electron transfer ability and improve the separation efficiency of photogenerated charges and holes, so as to accelerate the iron cycle in the Fenton reaction, thereby strengthening the H 2 O 2 The activation of the photocatalyst can generate highly oxidative active species such as •OH in increments, thereby enhancing the effect of photocatalytic Fenton degradation and mineralization of target organic matter.

[0018] The present invention is simple and effective to operate, has low cost and is green and pollution-free. Without changing the overall structure of the crystal, the unsaturated coordinated metal ions and H 2 The coordination process of O molecules is accelerated by base regulation to accelerate the deprotonation reaction, forming a hydroxyl-rich reaction, which enhances the surface polarity of MIL-100(Fe) and improves the surface hydrophilicity, thereby enhancing the mass transfer process with the target organic matter at the heterogeneous interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The main flow chart of the method for preparing MIL-100 (Fe) material in each embodiment of the present invention;

[0020] Figure 2 The XRD patterns of the MIL-100 (Fe) materials before and after treatment in various embodiments of the present invention are shown in FIG.

[0021] Figure 3FTIR spectra of the MIL-100 (Fe) material before and after each embodiment of the present invention;

[0022] Figure 4 The XPS spectrum of O1s of the MIL-100 (Fe) material before and after each embodiment of the present invention;

[0023] Figure 5 The UV / Vis diffuse reflectance spectra of the MIL-100(Fe) material before and after each embodiment of the present invention (the inset shows the band gap energy (Eg));

[0024] Figure 6 The following are (a) EIS electrochemical impedance spectroscopy, (b) Tafel curve, (c) CV curve and (d) transient photocurrent response spectrum of the MIL-100 (Fe) material before and after each embodiment of the present invention;

[0025] Figure 7 The (a) degradation performance and the corresponding (b) apparent rate constant of the MIL-100 (Fe) material before and after the photo-Fenton reaction of tetracycline hydrochloride (TCH) in each embodiment of the present invention; and the (c) adsorption performance, (d) adsorption capacity and the corresponding (e) pseudo-first-order and (f) pseudo-second-order rate constants at different times;

[0026] Figure 8 It is a comparison chart of the contact angle test results of the original MIL-100 (Fe) of Example 1 of the present invention and the Fe-MOFs-4 modified with the best sodium acetate equivalent and rich surface hydroxyl groups of Example 4;

[0027] Fig. 9 The original MIL-100 (Fe) in Example 1 of the present invention, the Fe-MOFs-4 modified with the best sodium acetate equivalent and rich surface hydroxyl groups in Example 4, and the KHCO modified with other alkaline substances potassium bicarbonate in Examples 6-8 3 -MOFs, and other alkaline substances of Examples 9-11, DEA-MOFs modified with diethanolamine, for degradation of tetracycline hydrochloride (TCH) in the photo-Fenton reaction;

[0028] Fig.10 (a) ROS scavenger experiment in the photo-Fenton degradation of TCH by the original MIL-100(Fe) of Example 1 of the present invention and the Fe-MOFs-4 modified with the best sodium acetate equivalent surface hydroxyl group of Example 4; (b) quantitative determination of •OH content; (c) comparison of ESR spectra of •OH under DMPO of MIL-100(Fe) and Fe-MOFs-4; (d) •O 2 − In DMPO and (e) 1 O2 ESR spectrum under TEMP. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below by specific examples. However, it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of protection of the present invention. In addition, those who do not indicate specific technical operation steps or conditions in the examples are all carried out according to the general techniques or conditions described in the literature in this area or according to the product instructions. Those who do not indicate the manufacturer of reagents or instruments used are all conventional products that can be obtained by commercial purchase.

[0030] Example 1

[0031] The preparation method of the MIL-100 (Fe) material used for comparison is as follows:

[0032] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC, 2.64 mmol) was placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0033] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0034] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0035] Step 4: The orange-red product was placed in a 60 °C drying oven and vacuum dried for 12 h to obtain the original MIL-100 (Fe).

[0036] The original MIL-100(Fe) prepared in Example 1 is not modified with sodium acetate to enrich the surface hydroxyl groups, which is denoted as MIL-100(Fe) in the figure.

[0037] Example 2

[0038] A preparation method of MIL-100 (Fe) material has the following steps:

[0039] Step 1: Weigh ferric chloride hexahydrate (FeCl 3•6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC, 2.64 mmol) and sodium acetate (NaAc, 0.33 mmol) were placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0040] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0041] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0042] Step 4: The orange-red product was placed in a 60 °C drying oven and vacuum dried for 12 h to obtain 1 / 8 equivalent sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand) modified surface hydroxyl-rich MIL-100 (Fe).

[0043] The preparation method of the MIL-100(Fe) material provided in this embodiment prepares a surface hydroxyl-rich MIL-100(Fe) modified with 1 / 8 equivalent sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand), which is denoted as Fe-MOFs-1.

[0044] Example 3

[0045] A preparation method of MIL-100 (Fe) material has the following steps:

[0046] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC (2.64 mmol) and sodium acetate (NaAc, 0.99 mmol) were placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0047] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0048] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0049] Step 4: The orange-red product was placed in a 60 °C drying oven and vacuum dried for 12 h to obtain 3 / 8 equivalent sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand) modified surface hydroxyl-rich MIL-100 (Fe).

[0050] The preparation method of the MIL-100(Fe) material provided in this embodiment prepares a surface hydroxyl-rich MIL-100(Fe) modified with 3 / 8 equivalent sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand), which is denoted as Fe-MOFs-3.

[0051] Example 4

[0052] A preparation method of MIL-100 (Fe) material has the following steps:

[0053] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC (2.64 mmol) and sodium acetate (NaAc, 1.32 mmol) were placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0054] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0055] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0056] Step 4: The orange-red product was placed in a 60 °C drying oven and vacuum dried for 12 h to obtain surface hydroxyl-rich MIL-100(Fe) modified with 1 / 2 equivalent of sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand).

[0057] The preparation method of the MIL-100(Fe) material provided in this embodiment prepares a surface hydroxyl-rich MIL-100(Fe) modified with 1 / 2 equivalent sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand), which is denoted as Fe-MOFs-4.

[0058] Example 5

[0059] A preparation method of MIL-100 (Fe) material has the following steps:

[0060] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC, 2.64 mmol) and sodium acetate (NaAc, 1.65 mmol) were placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0061] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0062] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0063] Step 4: The orange-red product was placed in a 60 °C drying oven and vacuum dried for 12 h to obtain 5 / 8 equivalent sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand) modified surface hydroxyl-rich MIL-100 (Fe).

[0064] The preparation method of the MIL-100(Fe) material provided in this embodiment prepares a 5 / 8 equivalent sodium acetate (relative to benzene 1,3,5-tricarboxylic acid ligand) modified surface hydroxyl-rich MIL-100(Fe), which is denoted as Fe-MOFs-5.

[0065] Example 6

[0066] A preparation method for modifying MIL-100 (Fe) using other alkaline substances potassium bicarbonate is as follows:

[0067] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H3 BDC, 2.64 mmol) and potassium bicarbonate (KHCO 3 , 0.33 mmol,) was placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0068] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0069] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0070] Step 4: The orange-red product was placed in a 60 °C drying oven under vacuum for 12 h to obtain MIL-100(Fe) modified with 1 / 8 equivalent potassium bicarbonate (relative to benzene 1,3,5-tricarboxylic acid ligand).

[0071] The method for preparing potassium bicarbonate-modified MIL-100(Fe) provided in this embodiment is a method for preparing a MIL-100(Fe) modified with 1 / 8 equivalent potassium bicarbonate (relative to benzene 1,3,5-tricarboxylic acid ligand), denoted as 1 / 8 KHCO 3 -MOFs were compared with the above-mentioned surface hydroxyl-rich MIL-100(Fe) modified with sodium acetate.

[0072] Example 7

[0073] A preparation method for modifying MIL-100 (Fe) using other alkaline substances potassium bicarbonate is as follows:

[0074] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC, 2.64 mmol) and potassium bicarbonate (KHCO 3 , 0.99 mmol,) was placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0075] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0076] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0077] Step 4: The orange-red product was placed in a 60 °C drying oven under vacuum for 12 h to obtain MIL-100(Fe) modified with 3 / 8 equivalent potassium bicarbonate (relative to benzene 1,3,5-tricarboxylic acid ligand).

[0078] The method for preparing potassium bicarbonate-modified MIL-100(Fe) provided in this embodiment is a MIL-100(Fe) modified with 3 / 8 equivalent potassium bicarbonate (relative to benzene 1,3,5-tricarboxylic acid ligand), denoted as 3 / 8 KHCO 3 -MOFs were used to compare the effects with the surface hydroxyl-rich MIL-100(Fe) modified with sodium acetate.

[0079] Example 8

[0080] A preparation method for modifying MIL-100 (Fe) using other alkaline substances potassium bicarbonate is as follows:

[0081] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC, 2.64 mmol) and potassium bicarbonate (KHCO 3 , 1.32 mmol,) was placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0082] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0083] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0084] Step 4: The orange-red product was placed in a 60 °C drying oven under vacuum for 12 h to obtain MIL-100(Fe) modified with 1 / 2 equivalent of potassium bicarbonate (relative to benzene 1,3,5-tricarboxylic acid ligand).

[0085] The method for preparing potassium bicarbonate-modified MIL-100(Fe) provided in this embodiment is a MIL-100(Fe) modified with 1 / 2 equivalent potassium bicarbonate (relative to benzene 1,3,5-tricarboxylic acid ligand), denoted as 1 / 2 KHCO 3 -MOFs were used to compare the effects with the surface hydroxyl-rich MIL-100(Fe) modified with sodium acetate.

[0086] Example 9

[0087] A preparation method for modifying MIL-100 (Fe) using other alkaline substances diethanolamine is as follows:

[0088] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC (2.64 mmol) and diethanolamine (DEA, 0.33 mmol) were placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0089] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0090] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0091] Step 4: The orange-red product was placed in a drying oven at 60 °C and vacuum dried for 12 h to obtain MIL-100(Fe) modified with 1 / 8 equivalent of diethanolamine (relative to benzene 1,3,5-tricarboxylic acid ligand).

[0092] The preparation method of diethanolamine-modified MIL-100(Fe) provided in this embodiment prepares a MIL-100(Fe) modified with 1 / 8 equivalent diethanolamine (relative to benzene 1,3,5-tricarboxylic acid ligand), denoted as 1 / 8 DEA-MOFs, to compare the effect with the surface hydroxyl-rich MIL-100(Fe) modified with sodium acetate mentioned above.

[0093] Example 10

[0094] A preparation method for modifying MIL-100 (Fe) using other alkaline substances diethanolamine is as follows:

[0095] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC (2.64 mmol) and diethanolamine (DEA, 0.99 mmol) were placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0096] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0097] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0098] Step 4: The orange-red product was placed in a drying oven at 60 °C and vacuum dried for 12 h to obtain MIL-100(Fe) modified with 3 / 8 equivalent of diethanolamine (relative to benzene 1,3,5-tricarboxylic acid ligand).

[0099] The preparation method of diethanolamine-modified MIL-100(Fe) provided in this embodiment prepares a MIL-100(Fe) modified with 3 / 8 equivalent diethanolamine (relative to benzene 1,3,5-tricarboxylic acid ligand), denoted as 3 / 8 DEA-MOFs, to compare the effect with the surface hydroxyl-rich MIL-100(Fe) modified with sodium acetate mentioned above.

[0100] Embodiment 11

[0101] A preparation method for modifying MIL-100 (Fe) using other alkaline substances diethanolamine is as follows:

[0102] Step 1: Weigh ferric chloride hexahydrate (FeCl 3 •6H 2 O, 4.0 mmol), benzene 1,3,5-tricarboxylic acid (H 3 BDC (2.64 mmol) and diethanolamine (DEA, 1.32 mmol) were placed in a 50 mL dry polytetrafluoroethylene-lined autoclave, deionized water (20 mL) was added and mixed thoroughly for 20 min, and then placed in a 130 °C oven for 3 d;

[0103] Step 2: After the product obtained in step 1 is naturally cooled to room temperature, it is transferred to a 500 mL beaker, 350 mL of deionized water is added, and it is placed in a 70 °C constant temperature water bath and stirred for purification for 15 h, and then centrifuged to achieve solid-liquid separation;

[0104] Step 3: Transfer the product obtained in step 2 to a 500 mL beaker, add 350 mL of anhydrous ethanol, place in a 70 °C constant temperature water bath, stir and purify for 6 h, and then centrifuge to achieve solid-liquid separation;

[0105] Step 4: The orange-red product was placed in a drying oven at 60 °C and vacuum dried for 12 h to obtain MIL-100(Fe) modified with 1 / 2 equivalent of diethanolamine (relative to benzene 1,3,5-tricarboxylic acid ligand).

[0106] The preparation method of diethanolamine-modified MIL-100(Fe) provided in this embodiment prepares a MIL-100(Fe) modified with 1 / 2 equivalent diethanolamine (relative to benzene 1,3,5-tricarboxylic acid ligand), denoted as 1 / 2 DEA-MOFs, to compare the effect with the surface hydroxyl-rich MIL-100(Fe) modified with a specific amount of sodium acetate.

[0107] The sample materials prepared before and after the different equivalents of MIL-100 (Fe) materials in Examples 1 to 5 were subjected to the following test characterizations:

[0108] The XRD patterns of different equivalent MIL-100 (Fe) materials before and after treatment in each embodiment are as follows: Figure 2 As shown, after adding different equivalents of sodium acetate for alkali adjustment during the synthesis process, the modified sample Fe-MOFs-X maintained the same diffraction peak pattern as the original MIL-100(Fe), indicating that the incremental introduction of surface hydroxyl groups still well retained the original structure of MIL-100(Fe), and also proved the successful synthesis of each sample before and after different equivalents of MIL-100(Fe) materials.

[0109] The FTIR spectra of different equivalent MIL-100 (Fe) materials before and after the treatment of Examples 1 to 5 are as follows: Figure 3 As shown, compared with the original MIL-100(Fe), the characteristic vibration peak intensity of MIL-100(Fe) modified with different equivalents of sodium acetate about surface O–H is enhanced to varying degrees, proving the successful incremental introduction of surface hydroxyl groups, among which Fe-MOFs-4 has the strongest peak intensity, that is, the surface hydroxyl-rich modification effect of 1 / 2 equivalent sodium acetate is the best.

[0110] The XPS spectra of O 1s before and after the different equivalents of MIL-100 (Fe) materials in Examples 1 to 5 are as follows: Figure 4 As shown in the figure, the O 1s peak of the best modified equivalent Fe-MOFs-4 can be specifically fitted into three peaks located at 531.47, 531.98 and 533.49 eV, which are respectively attributed to the O atoms of the surface hydroxyl groups, the O-Fe components in the Fe-O atomic clusters and the O=C groups of the ligand BDC. It can be seen that compared with the original MIL-100 (Fe), the binding energy of O 1s has a tendency to shift to high binding energy, indicating that the electron cloud density around oxygen decreases. And there is a certain regularity in the proportion of the OH peak area of ​​the modified samples with different base adjustment gradients, among which Fe-MOFs-4 has the largest proportion. The overall trend is roughly consistent with the FTIR results, providing auxiliary evidence for the incremental introduction of surface hydroxyl groups.

[0111] UV / Vis diffuse reflectance spectra of different equivalent MIL-100(Fe) materials before and after in Examples 1 to 5 (the inset shows the band gap energy (Eg)) are shown in Figure 2. Figure 5 As shown, the optimal sodium acetate modified equivalent Fe-MOFs-4 has the strongest light absorption ability, proving that increasing the surface hydroxyl content has the effect of improving the light absorption range of the photocatalyst; it exhibits the narrowest band gap, which also means that it has the potential to absorb more visible light to generate photoinduced charge carriers, which is conducive to the photocatalytic reaction.

[0112] The electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), Tafel curve test and photocurrent (It) measurement results of different equivalent MIL-100 (Fe) materials before and after the experiment are shown in Figure 1. Figure 6 As shown in the figure, the above electrochemical characterization tests all used the ITO plate coated with catalyst as the working electrode, Pt foil as the counter electrode, and Ag / AgCl as the reference electrode, using a standard three-electrode system. The above electrochemical characterizations, except for the Tafel curve, were conducted in 0.2 M sodium sulfate electrolyte (Na 2 SO 4 , 100 mL). In particular, the Tafel curve, which is in potassium ferrocyanide (K 4 [Fe(CN) 6 ], 5 M), potassium ferrocyanide (K 3 [Fe(CN)6 ], 3 M) and potassium chloride (KCl, 0.1 M). Comparing the EIS, CV, Tafel and It curve test results, compared with the original MIL-100(Fe), the Fe-MOFs-4 modified with 1 / 2 equivalent sodium acetate has the best improvement in electron generation and transfer ability, that is, the charge separation efficiency is improved, thereby improving the photocatalytic degradation efficiency.

[0113] The (a) degradation performance and the corresponding (b) apparent rate constants of tetracycline hydrochloride (TCH) before and after the photo-Fenton reaction of different equivalents of MIL-100(Fe) materials in Examples 1 to 5 are shown in FIG. Figure 7 As shown; as well as (c) adsorption performance, (d) adsorption capacity and the corresponding (e) pseudo-first-order and (f) pseudo-second-order rate constants at different times. Figure 8 The contact angle test results of MIL-100 (Fe) before and after modification with sodium acetate-rich surface hydroxyl groups in Examples 1 and 4 of the present invention are compared. 2 mg of the catalyst materials prepared in each example before and after modification with sodium acetate-rich surface hydroxyl groups were weighed and added to a beaker containing 20 mL of 50 mg / L tetracycline hydrochloride (TCH). After being fully stirred for 30 min in the dark to reach adsorption-desorption equilibrium, 20 μL of H was added to the suspension. 2 O 2 , keep stirring and use a 300 W xenon lamp equipped with a 420 nm cutoff filter as the light source; within the predetermined 5 min irradiation interval, extract 1 mL of the suspension, filter it with a 0.22 μm membrane filter, and determine its concentration using a high performance liquid chromatograph. Figure 7 As shown in the figure, under dark conditions, the prepared samples all reached adsorption-desorption equilibrium within 30 min. There are slight differences in the adsorption capacity and adsorption rate constant of catalyst samples modified with different equivalents of sodium acetate, which has an important influence on the mass transfer process between active substances and target pollutants TCH in the photocatalytic degradation reaction. The original MIL-100 (Fe) and the best modified equivalent Fe-MOFs-4 were selected for contact angle test comparison ( Figure 8 ), the improvement of the hydrophilicity of the material also verifies the successful incremental introduction of surface hydroxyl groups, which is conducive to the effective degradation of mineralized target organic matter by short-lived and highly active species generated on the surface of the material. In the process of photocatalytic degradation, the degradation performance of TCH by materials modified with different equivalents of sodium acetate and rich surface hydroxyl groups was different. Among them, Fe-MOFs-4 showed the best catalytic degradation activity, with a rate constant (0.1012 min −1 ) is about MIL-100(Fe) (0.0606 min −1) is 1.67 times that of the samples modified with sodium acetate (the rate constants of the other equivalent sodium acetate surface hydroxyl-rich samples are shown in Table 1). The increase in degradation rate is mainly due to the fact that the increased surface hydroxyl groups promote a more intimate mass transfer process and more efficient carrier separation to produce more abundant •OH surface This can be further confirmed by the following active species identification: OH quantitative determination and ESR test.

[0114] The reaction rate constants and fitting coefficients obtained by pseudo first-order kinetic fitting of the MIL-100 (Fe) materials prepared in Examples 1 to 5 are shown in Table 1.

[0115] Table 1

[0116]

[0117] The original MIL-100(Fe) of Example 1, the Fe-MOFs-4 of Example 4, and the KHCO 3 The degradation performance of DEA-MOFs and DEA-MOFs of Examples 9-11 on tetracycline hydrochloride (TCH) in the photo-Fenton reaction is shown in FIG. Fig. 9 As shown. The specific operation steps of the degradation experiment of Examples 6-11 are the same as those described above. The photo-Fenton degradation effect of TCH on Fe-MOFs-4 and even the original MIL-100(Fe) was far inferior to that of Fe-MOFs-4, and even inferior to that of the original MIL-100(Fe), which shows the particularity of using a specific amount of sodium acetate for alkali adjustment to achieve surface hydroxyl-rich modified MIL-100(Fe).

[0118] The ROS scavenger experiment in the photo-Fenton degradation of TCH by the original MIL-100 (Fe) of Example 1 and Fe-MOFs-4 of Example 4 is as follows Fig.10 The original MIL-100(Fe) of Example 1 and the best Fe-MOFs-4 of Example 4 were selected for active species identification test. The experimental process was similar to photocatalytic degradation except that a certain amount of quencher was added after dark balance. 2 , 40 min), furfuryl alcohol (FFA, 10 mM), tert-butyl alcohol (TBA, 300 mM), sodium dihydrogen phosphate (NaH 2 PO 4 , 2 mM) and formic acid (HCOOH, 10 mM) were used to identify superoxide radicals (•O 2 − )、Singlet oxygen( 1 O 2 ), surface hydroxyl radicals (•OH surface ), free hydroxyl radicals (•OHfree ) and photogenerated holes (h + ) effect. When adding excess TBA, NaH 2 PO 4 and FFA to capture •OH free ,•OH surf and 1 O 2 In the case of , the degradation rate of TCH decreased significantly by 48.04%, 73.12% and 56.82% within 30 min, indicating that •OH (especially •OH surf )and 1 O 2 It is the main reaction free radical that causes TCH degradation.

[0119] The results of the •OH concentration determination of the original MIL-100(Fe) of Example 1 and the Fe-MOFs-4 of Example 4 are as follows: Fig.10 As shown in (b). The original MIL-100(Fe) of Example 1 and the optimal Fe-MOFs-4 of Example 4 were selected for the determination of •OH concentration. Under the same reaction conditions and system as the above-mentioned degradation experiment, benzoic acid (BA, 10 mM) was used as a molecular probe to determine the •OH concentration, where the •OH concentration was analyzed by the p-HBA concentration according to the equation: [•OH]=[p-HBA]×5.87. The p-HBA concentration was measured by high performance liquid chromatography. The test conditions were: the detection wavelength was 270 nm, the mobile phase was water / acetonitrile (85 / 15, v / v), and the flow rate was 0.2 mL / min. In order to further refine and prove the enhancing effect of surface hydroxyl groups on the generation of •OH, sodium fluoride (NaF, 10 mM) was also added to desorb •OH surf , using BA to quantitatively measure •OH free and •OH surf The results show that the concentration of •OH measured by Fe-MOFs-4 surf The concentration is 1.57 times that of the original sample.

[0120] ESR spectra of •OH, •O of MIL-100(Fe) and the best Fe-MOFs-4 under DMPO 2 − The ESR spectra of DMPO and 1 O 2 The ESR spectrum under TEMP is as follows Fig.10As shown in (c)-(e), the original MIL-100 (Fe) of Example 1 and Fe-MOFs-4 of Example 4 were selected to detect the electron spin resonance (ESR) spectra of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) or 2,2,6,6-tetramethyl-4-piperidine (TEMP) capturing reactive oxidizing species in water and methanol. The ESR test results correspond to the changing trends of various active species in the active species identification test and •OH concentration determination results, directly revealing the direct reason why the modified Fe-MOFs-4 improves the photocatalytic Fenton degradation reaction rate.

[0121] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a MIL-100 (Fe) material, characterized in that: The steps include: The iron source, organic ligand, sodium acetate and deionized water are added into a dry polytetrafluoroethylene-lined autoclave and mixed thoroughly, wherein the molar ratio of the sodium acetate to the organic ligand is 3:8-1:2, and the heating temperature is 130° C. for 3 days to obtain a solid product; The obtained solid product was cooled to room temperature and purified with deionized water at 60-80°C for 5-20 h, centrifuged and then purified with anhydrous ethanol at 60-80°C for 5-20 h; the solid product was orange after further centrifugation. The orange solid product is dried under vacuum conditions at 50-70° C. and maintained for 12-24 h to obtain a sodium acetate surface hydroxyl-rich modified product; The iron source is ferric chloride hexahydrate; The organic ligand is benzene 1,3,5-tricarboxylic acid; The mass ratio of the ferric chloride hexahydrate to benzene 1,3,5-tricarboxylic acid is 1:0.

66.

2. The method for preparing the MIL-100 (Fe) material according to claim 1, characterized in that: The molar ratio of the sodium acetate to benzene 1,3,5-tricarboxylic acid is 1:

2.

3. The method for preparing the MIL-100 (Fe) material according to claim 1, characterized in that: The solid product was purified with deionized water at 70°C for 15 h, and then purified with anhydrous ethanol at 70°C for 6 h after centrifugation.

4. The method for preparing the MIL-100 (Fe) material according to claim 1, characterized in that: The orange solid product was dried under vacuum at 60 °C for 12 h.

5. The method for preparing the MIL-100 (Fe) material according to claim 1 is used as a photocatalyst.

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