A Multilayer Special Wettability MOF-Derived Composite Membrane and Its Preparation Method and Bifunctional Application

Abstract

The present invention discloses a multi-layer special wetting MOF-derived composite membrane, its preparation method and bifunctional application. The present invention uses an in-situ growth method to form a dense and continuous MOF membrane on an inorganic substrate, and then introduces metal activity on the surface and inside the pores of the MOF membrane through vapor deposition and heat treatment means, forming a multi-level hydrophilic directional permeation multifunctional surface composite metal membrane material composed of hydrophilic active protrusions and superhydrophobic separation layers; the preparation method of this material is simple and practical, and has bifunctional application value, can realize oil-water separation and catalytic degradation of soluble organic pollutants, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of multifunctional composite membrane materials, and particularly to a multilayer special wetting MOF-derived composite membrane and a preparation method thereof, as well as applications in oil-water separation and photocatalytic Fenton degradation of water-soluble organic pollutants. Background Art

[0002] With the continuous development of industrialization and the rapid growth of the population, water resources are deteriorating continuously, and mankind is facing a crisis of water shortage. Environmental governance is urgent. Among them, the pollution of oily wastewater has also had a serious impact on the ecological environment. From the perspective of green chemistry, if oils or macromolecules in water can be recycled, the recovery rate of raw materials can be greatly improved, and the proposed catalytic membrane provides a feasible idea for the above research.

[0003] In recent years, the use of catalytic membranes for oil-water separation and catalytic degradation of pollutants in water has become a new development field and research direction in water treatment. In the field of catalysis, metal-organic frameworks (MOFs), as a kind of porous framework material, can be used to load metal nanoparticles (MNPs) in their pores, which has great advantages in improving catalytic performance. With the continuous in-depth study of MOFs, scholars have integrated them into membrane structures, which can not only overcome the inherent fragility and rigidity characteristics in practical applications, but also be a promising alternative method, attracting more attention in the field of molecular sieving, and significant progress has been made in the technology of growing MOFs on different porous supports. In the field of oil-water separation, MOFs can utilize the hydrophobicity of organic groups on their structures or ligands to separate oil-water mixtures, but there are few literatures reporting a catalytic membrane reaction device that can both separate oil-water mixtures and catalytically degrade organic molecules to remove pollutants by using the special structure of MOF, integrating catalysis and separation.

[0004] Due to the large surface area and uniform pores of MOF catalytic membranes, they have great superiority in the fields of catalysis and efficient separation. Although great progress has been made in the research of catalytic membranes, there are still many problems in the preparation process, such as the coordination of the thickness and continuity of the MOF layer, the compatibility between the MOF layer and the substrate, the dispersion of the catalyst, and the inability to precisely and effectively control the hierarchical structure of the catalytic membrane.

[0005] Therefore, it is particularly important to design a composite catalytic membrane material with good stability, which can not only separate oil-water mixtures but also catalytically degrade water-soluble pollutants in the same unit when treating oily wastewater loaded. Summary of the Invention

[0006] The object of the present invention is to provide a multi-layer special wettability MOF-derived composite membrane, its preparation method and bifunctional applications. During the preparation process of the composite membrane material, the organometal diffuses on or inside the MOF-based surface through multi-scale deposition and thermal conversion to generate a steep energy gradient, thereby forming a bifunctional surface with multi-level hydrophilic directional permeability composed of hydrophilic active protrusions and superhydrophobic separation layers.

[0007] The technical solution of the present invention is as follows:

[0008] A preparation method of a multi-layer special wettability MOF-derived composite membrane, comprising the following steps:

[0009] (1) A dense and continuous MOF membrane is grown on an inorganic framework by an in-situ growth method;

[0010] The inorganic framework can be a metal mesh, such as: copper mesh, nickel mesh, copper foam, nickel foam, etc., with a specification of 100 mesh to 400 mesh; preferably copper mesh;

[0011] The MOF can be Cu-BTC, Cu-BDC or NH2-UiO-66, preferably Cu-BTC; the specific in-situ growth method of the Cu-BTC membrane is as follows: the copper mesh is vertically placed in an ethanol solution containing copper nitrate trihydrate and trimesic acid, and hydrothermal reaction is carried out at 80 °C for 12 h to obtain the copper mesh grown with the Cu-BTC membrane; preferably, the molar ratio of copper nitrate trihydrate to trimesic acid is 1:1;

[0012] (2) The inorganic framework grown with the MOF membrane obtained in step (1) and the metal precursor are put into a reaction kettle, and a vapor deposition reaction is carried out at 80-150 °C (preferably 110 °C) for 2 h, and then cooled to room temperature to obtain a nano-metal particle-MOF membrane;

[0013] The metal precursor is an organometallic salt, such as: organic iron salt, organic nickel salt, organic cobalt salt, etc.; preferably organic iron salt, and particularly preferably ferrocene;

[0014] The loading amount of the metal precursor based on the contained metal is 1-20% of the mass of the MOF membrane, preferably 5%;

[0015] (3) The nano-metal particle-MOF membrane obtained in step (2) is calcined at 150-220 °C (preferably 180 °C) for 2-6 h (preferably 2 h) to obtain the multi-layer special wettability MOF-derived composite membrane.

[0016] The present invention relates to a multi-layer special wettability MOF-derived composite membrane prepared by the above preparation method.

[0017] The multi-layer special wettability MOF-derived composite membrane of the present invention can be used for oil-water separation and photocatalytic Fenton degradation of water-soluble organic pollutants.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention provides a preparation method of a multi-layer special wettability MOF-derived composite membrane. By a multi-scale CVD chemical vapor deposition method, sublimable metal-organic molecules are connected to the functional groups on the surface and pores of the MOF-based membrane. Finally, after thermal conversion, the metal-organic molecules on the membrane surface are calcined into nano-metal oxide clusters, while the metal-organic molecules loaded in the pores that are not completely calcined are converted into a form connected with organic functional groups and exist in the membrane fault structure, generating a steep surface energy gradient, making the surface hydrophilic but not permeable to water while permeable to oil.

[0020] (2) The present invention provides a multi-layer special wettability MOF-derived composite membrane, which shows excellent bifunctionality in treating aqueous organic oily wastewater, and simultaneously realizes oil-water separation and photo-Fenton degradation of water-soluble organic pollutants.

[0021] (3) The bifunctional composite membrane material prepared by the present invention, compared with the traditional super-hydrophilic and super-hydrophobic surface, is beneficial to increasing the contact time and area between pollutants and catalytic sites on the material surface, and also has excellent solvent-resistant chemical stability, simple preparation, easy operation, and no pollution. Description of the Drawings

[0022] Figure 1 : SEM images of the multi-layer special wettability MOF-derived composite membrane in Example 1; a - surface structure, b - cross-section structure.

[0023] Figure 2 : TEM image of the multi-layer special wettability MOF-derived composite membrane in Example 1. Detailed Embodiments

[0024] The technical solutions of the present invention will be clearly and completely described below in conjunction with the detailed embodiments. However, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0025] Example 1:

[0026] Preparation of FcCT@C-C membrane:

[0027] Take a piece of brass mesh (2 cm × 3 cm) with a brass color on the surface and not oxidized. The brass mesh is ultrasonically cleaned and dried in hydrochloric acid and ethanol respectively, and the cleaned brass mesh is vertically fixed on a bracket (supporting the brass mesh).

[0028] Weigh 0.362 g (1.5 mmol) of copper nitrate trihydrate and 0.315 g (1.5 mmol) of trimesic acid, dissolve them in 16 ml of ethanol, and ultrasonicate until all the solids are dissolved. Vertically place the copper mesh fixed on the support into the ethanol solution containing copper nitrate trihydrate and trimesic acid, and place it in an oven for hydrothermal reaction at 80 °C for 12 h. After the reaction is completed, take out the hydrothermal reactor, let it stand on the experimental table and cool naturally to room temperature. Use clean tweezers to take out the copper mesh with Cu-BTC grown on it, wash it repeatedly in ethanol to remove the excess copper nitrate and trimesic acid on the surface, and place it in an oven for vacuum drying to obtain the Cu-BTC film.

[0029] Weigh 0.093 g (0.5 mmol) of ferrocene and place it in a 25 mL hydrothermal reactor. Fix the dried Cu-BTC film on the support and vertically place it into the reactor containing ferrocene, and place it in a gas phase for loading at 110 °C for 2 h. After the reaction is completed, cool it to room temperature and then take it out, and then calcine it at 180 °C for 2 h to obtain the FcCT@C-C film.

[0030] Example 2:

[0031] Preparation of FcCD@C-C film:

[0032] The difference from Example 1 lies in the preparation of the Cu-BDC film, where the solvent and ligand are replaced with N,N-dimethylformamide and terephthalic acid.

[0033] Example 3:

[0034] Preparation of FcNU@C-C film:

[0035] The difference from Example 1 is that the NH2-UiO-66 film is prepared by in-situ growth;

[0036] Example 4:

[0037] Preparation of FcCT@C-CF film:

[0038] The difference from Example 1 is that the copper mesh is replaced with copper foam.

[0039] Example 5:

[0040] Preparation of FcCT@C-N film:

[0041] The difference from Example 1 is that the copper mesh is replaced with a nickel mesh.

[0042] Example 6:

[0043] Preparation of FcCT@C-NF film:

[0044] The difference from Example 1 is that the copper mesh is replaced with nickel foam.

[0045] Example 7:

[0046] Preparation of 0.5FcCT@C-C membrane:

[0047] The difference from Example 1 is that 0.047 g (0.25 mmol) of ferrocene is used in the reaction.

[0048] Example 8:

[0049] Preparation of 2FcCT@C-C membrane:

[0050] The difference from Example 1 is that 0.1867 g (1 mmol) of ferrocene is used in the reaction.

[0051] Example 9:

[0052] Preparation of FcCT@C-C-150 membrane:

[0053] The difference from Example 1 is that the Fe / Cu-BTC membrane is calcined at 150 °C.

[0054] Example 10:

[0055] Preparation of FcCT@C-C-200 membrane:

[0056] The difference from Example 1 is that the Fe / Cu-BTC membrane is calcined at 200 °C.

[0057] Example 11:

[0058] Preparation of CoCT@C-C membrane:

[0059] The difference from Example 1 is that 0.093 g (0.5 mmol) of ferrocene is replaced with 0.095 g (0.5 mmol) of cobaltocene.

[0060] Example 12:

[0061] Preparation of NiCT@C-C membrane:

[0062] The difference from Example 1 is that 0.093 g (0.5 mmol) of ferrocene is replaced with 0.094 (0.5 mmol) of nickelocene.

[0063] Comparative Example 1:

[0064] Preparation of Cu-BTC membrane:

[0065] The difference from Example 1 is that the prepared Cu-BTC membrane is calcined at 180 °C for 2 h to obtain the Cu-BTC membrane.

[0066] Comparative Example 2:

[0067] Preparation of Fe / Cu-BTC membrane:

[0068] The difference from Example 1 is that the prepared Fe / Cu - BTC membrane is no longer heat - treated.

[0069] Separation and catalytic tests were carried out on the composite membranes prepared in Examples 1 - 12 and the composite membranes prepared in Comparative Examples 1 - 2. First, the membrane was horizontally fixed in a container, and a mixture of 300 mL of dye wastewater containing 50 mg / L X - 3B and 0.5 mL / L hydrogen peroxide and 300 mL of dichloromethane was poured on the upper layer of the membrane. The separation time was 30 min. Subsequently, the oil passed through the composite membrane layer by its own gravity, and the oil flux was recorded. Then, the ultraviolet lamp was turned on, and the absorbance was measured after 1 h of catalytic degradation.

[0070] The separation efficiency of the final membrane for oil - water was calculated by the following formula:

[0071] DE = D1 / D0 × 100% (1)

[0072] D0 is the theoretical amount under single - phase conditions, and D1 is the permeate flux through the membrane.

[0073] The catalytic degradation efficiency of the membrane was calculated by the following formula:

[0074] SE = (A0 - A1) / A0 × 100% (2)

[0075] A0 is the absorbance of the original solution, and A1 is the absorbance of the permeate at 535 nm.

[0076] The separation efficiency of oil - water and the photo - Fenton catalytic degradation efficiency were calculated, and the obtained results are shown in Table 1.

[0077] Table 1 Performance comparison of the prepared bifunctional metal - organic framework catalytic membranes

[0078]

Claims

1. A method for preparing a multilayer special infiltration MOF-derived composite membrane, characterized in that: The following steps are involved: (1) Using in situ growth method to grow dense and continuous MOF membrane on inorganic skeleton; The inorganic framework uses a metal mesh; MOF is Cu-BTC or NH2-UiO-66; (2) placing the inorganic skeleton with the MOF film grown thereon obtained in step (1) and the metal precursor into a reaction kettle, performing a vapor deposition reaction at 80 to 150° C. for 2 h, and then cooling to room temperature to obtain a nano-metal particle-MOF film; The metal precursor is selected from ferrocene, nickelocene or cobaltocene; (3) The nano-metal particle-MOF film obtained in step (2) is calcined at 180° C. for 2 hours to obtain the multi-layer special infiltration MOF-derived composite film.

2. The method for preparing a multilayer special infiltration MOF-derived composite membrane according to claim 1, characterized in that: In step (1), the inorganic framework is made of copper mesh, nickel mesh, foam copper or foam nickel, with a specification of 100 mesh to 400 mesh.

3. The method for preparing a multilayer special infiltration MOF-derived composite membrane according to claim 1, characterized in that: In step (1), the MOF is Cu-BTC; the in-situ growth method of the Cu-BTC film is as follows: a copper mesh is vertically placed in an ethanol solution containing copper nitrate trihydrate and trimesic acid, and subjected to a hydrothermal reaction at 80° C. for 12 hours to obtain a copper mesh with a Cu-BTC film grown thereon; wherein the molar ratio of copper nitrate trihydrate to trimesic acid is 1:

1.

4. The method for preparing a multilayer special infiltration MOF-derived composite membrane according to claim 1, characterized in that: In step (2), the metal precursor is ferrocene.

5. The method for preparing a multi-layer special infiltration MOF-derived composite membrane according to claim 1, characterized in that: In step (2), the loading amount of the metal precursor based on the contained metal is 1 to 20% of the mass of the MOF film.

6. A multilayer special infiltration MOF-derived composite membrane prepared by the preparation method according to any one of claims 1 to 5.

7. Application of the multilayer special infiltration MOF-derived composite membrane as claimed in claim 6 in oil-water separation and photo-Fenton degradation of water-soluble organic pollutants.

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