A method for preparing ZIF-based carbon sponge for efficient carbon dioxide reduction and oil-water separation

Abstract

This invention provides the preparation and application of ZIF-based carbon sponge for CO2 reduction and oil-water separation. The preparation method includes: immersing commercially available melamine sponge in anhydrous ethanol and deionized water for washing and drying; calcining the dried melamine sponge in a tube furnace to obtain a carbonized sponge; washing the carbonized sponge with deionized water and drying. Dispersing the prepared g-C3N4 in a solution of isopropanol:water at a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4; preparing Zn and Co-ZIF nanomaterials; mixing g-C3N4 with Zn and Co-ZIF powders in a 3:1 ratio, dispersing in n-hexane and PDMS, and drying to obtain a modified melamine carbonized sponge. The melamine carbonized sponge of this invention can be used for the separation and recovery of mixtures containing oil or organic solvents with water, as well as in the field of CO2 reduction.

Description

Technical Field

[0001] This invention belongs to the field of composite materials, specifically relating to the preparation and application of a reusable ZIF-based carbon sponge that can be used for CO2 reduction and oil-water separation. Background Technology

[0002] Industrial production processes and daily life generate large amounts of oily wastewater, which is one of the most common environmental problems. Furthermore, the large-scale combustion of fossil fuels produces significant amounts of greenhouse gases, such as CO2, leading to global warming, rising sea levels, and frequent extreme weather events, seriously threatening human production and safety. Therefore, developing materials that can effectively solve this problem is of great importance. To address oil pollution, scholars both domestically and internationally have conducted extensive research, employing methods such as gravity separation, centrifugal separation, flotation, electrocoagulation, sedimentation, condensation, and membrane separation for oil-water separation. Sponge materials, as materials with strong adsorption capacity, fast absorption speed, light weight, and low cost, have gradually attracted attention. A reusable functional sponge material meets the development requirements for sponges. In addition, this sponge can be used not only for oil-water separation but also for CO2 reduction.

[0003] Carbon sponges possess a micro- to nano-scale layered porous structure with numerous active sites on their skeletal surface. This unique multi-scale structure endows this three-dimensional structure with excellent oil absorption properties, including superior absorption selectivity due to hydrophobicity, high absorption capacity due to ultra-low density, exceptional recovery capability due to excellent resilience and compressibility, and high oil retention efficiency due to its robust skeleton. Furthermore, carbon sponges also possess other advantageous properties such as abundant Lewis alkalinity and excellent photothermal properties. These desirable characteristics endow carbon sponges with good CO2 adsorption capacity and provide opportunities for thermal and photothermal catalysis under mild conditions.

[0004] To date, existing research has explored various porous materials, including carbon-based porous materials, polymer sponges, aerogels, steel meshes, and fabrics, as substrates. These materials are used in a top-down approach, employing techniques such as photolithography, plasma etching, mechanical etching, template methods, and laser ablation, to increase the surface roughness of the substrate, transforming it from a hydrophilic-oleophilic state to a hydrophobic-oleophilic state, thus enabling the material to exhibit oil-water separation properties. However, this method requires sophisticated equipment and environmental conditions, involves complex fabrication processes, and suffers from low efficiency, making it unsuitable for large-area fabrication. On the other hand, some research has also explored using fluorinated substances such as polytetrafluoroethylene (PTFE), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and fluorinated polyols (FTOH) to lower the surface energy of materials, achieving a hydrophobic-oleophilic state. However, these fluorinated substances are extremely difficult to degrade, posing significant risks to the environment and human health. Therefore, developing a material that is environmentally friendly, simple, convenient, low-cost, and easily mass-producible has broad application prospects. Summary of the Invention

[0005] To address the problems and shortcomings of existing technologies, this invention provides a simple and low-cost method for preparing a superhydrophobic-superoleophilic sponge with high adsorption capacity, fast adsorption speed, easy separation and recovery, ultralight weight, high elasticity, and good photocatalysis.

[0006] To solve the above technical problems, the technical solution adopted by the present invention includes the following steps: Step 1, preparation of carbon sponge (CMS): Melamine sponge is placed in a first solvent for cleaning for 30-60 min, then ultrasonically cleaned in deionized water for 30-60 min, and dried to obtain dry melamine sponge; the cleaned MS material is placed in a tube furnace and calcined at 300-500℃ for 2-4 h in a flowing atmosphere, then ultrasonically cleaned in deionized water for 30-60 min, and dried to obtain carbon sponge.

[0007] Step 2: g-C3N4 / Zn, Co-ZIF loading. After mixing g-C3N4, Zn, and Co-ZIF in a certain proportion, the mixture is dispersed in a second solvent, sonicated for 2-3 hours, and dried to obtain g-C3N4 / Zn, Co-ZIF powder material. The mixed powder material is dispersed in a third solvent and drop-coated onto a carbon sponge. After drying, g-C3N4 / Zn, Co-ZIF carbon sponge material is obtained.

[0008] Step 3, PDMS loading: The sponge obtained in step 2 is immersed in PDMS solution, left to stand at room temperature for a period of time, and then removed and cured to obtain g-C3N4 / Zn, Co-ZIF / PDMS carbon sponge material.

[0009] In step 1, the drying temperature is 60–80 °C and the drying time is 4–8 h.

[0010] In step 1, the gas introduced into the flowing atmosphere includes at least one of helium, argon, and nitrogen.

[0011] In step 2, the mass ratio of g-C3N4 / Zn and Co-ZIF is 2:1, 1:1, 1:2, 1:3, or 1:4.

[0012] In step 2, the second solvent is one or more selected from anhydrous ethanol or methanol.

[0013] In step 2, the third solvent is selected from one or more of n-hexane or cyclohexane.

[0014] In step 2, the drying temperature is 70-85℃.

[0015] In step 3, the PDMS solution used is an alkane mixture of PDMS and curing agent. In the PDMS solution used, PDMS accounts for 1 to 8% of the solvent mass, and the curing agent accounts for 5 to 15% of the PDMS mass.

[0016] In step 3, the settling time is 60-120 min, the curing temperature is 100-120 ℃, and the curing time is 2-4 h.

[0017] The prepared carbon sponge is used to adsorb oil pollution in water, such as floating oil on the water surface and dichloromethane underwater; and it is applied in the field of photocatalytic CO2 reduction.

[0018] The beneficial effects of this invention are:

[0019] First, the introduction of nanosheets on the surface of the carbon sponge of this invention can effectively increase the surface roughness of the sponge. Furthermore, the PDMS coating can effectively reduce the surface energy of the sponge, thereby improving its hydrophobic effect. The modified carbon sponge of this invention possesses properties such as ultra-low density, high adsorption capacity, rapid adsorption, strong chemical stability, and high reusability, making it widely applicable and highly valuable for promotion in the separation of organic solvent and water mixtures.

[0020] Secondly, carbon sponges have a unique three-dimensional pore structure and a large specific surface area, which provides favorable conditions for CO2 adsorption. Metal-organic frameworks (MOFs) have been developed as a promising heterogeneous catalyst for CO2 conversion due to their significantly high surface area, controllable pore size, and tunable composition and structure. Importantly, their open metal ion sites and rationally designed functional linkers can serve as highly active catalytic sites to promote catalytic activity.

[0021] Third, we successfully integrated Zn, Co-ZIF, and g-C3N4 nanosheets onto a carbon sponge, achieving a synergistic composite structure. This not only generates highly efficient catalytic active sites but also enhances the adsorption of CO2 at the reaction sites, thereby activating CO2 molecules. Furthermore, the integration of Zn and Co-ZIF significantly promotes the directional energy migration of the g-C3N4 nanosheets, which greatly inhibits electron-hole recombination within the nanosheets and provides long-lived electrons for the reduction of adsorbed CO2, thus significantly improving the photocatalytic CO2 conversion efficiency. Attached Figure Description

[0022] Figure 1 This is a SEM image of the CMS sponge after calcination at 400℃.

[0023] Figure 2 Here is a SEM image of the ZIF catalyst.

[0024] Figure 3 This is a SEM image of the sample from Example 4.

[0025] Figure 4 The X-ray diffraction patterns of the sample from Example 4 with g-C3N4, ZCZIF, GZ4, and CMS are shown.

[0026] Figure 5 The DRS diagrams of the sample from Example 4 and g-C3N4, ZCZIF, and GZ4 are shown.

[0027] Figure 6 The BET plots are of the sample from Example 4 with g-C3N4, ZCZIF, and GZ4.

[0028] Figure 7 The CO2 adsorption diagrams for the sample in Example 4 with g-C3N4, ZCZIF, and GZ4 are shown.

[0029] Figure 8 The infrared absorption spectra of the sample in Example 4 and g-C3N4, ZCZIF, and GZ1-GZ5 are shown.

[0030] Figure 9 The water contact angle between the sample of Example 4 and the CMS at different temperatures is shown.

[0031] Figure 10 This is the effect of sample 4 on adsorbing water and floating oil.

[0032] Figure 11 Example 4 illustrates the effect of adsorbing heavy oil underwater.

[0033] Figure 12 This is the continuous oil-water separation effect of the sample in Example 4.

[0034] Figure 13 The effect of g-C3N4 on the samples of Examples 4 and 6 is shown.

[0035] Figure 14 The effect of carbonization temperature on the samples of Examples 4, 7, 8, and 9 is shown.

[0036] Figure 15 This is an example of CO2 reduction and its cycling performance for sample 4. Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0038] The present invention will now be described in detail with reference to embodiments.

[0039] Example 1

[0040] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 400°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0041] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0042] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0043] 4) Weigh 60 mg of CN and 120 mg of ZCZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 1:2. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0044] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, remove it and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded CN / ZC-ZIF carbon sponge (CMS / GZ1).

[0045] Example 2

[0046] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 400°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0047] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0048] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0049] 4) Weigh 60 mg of CN and 60 mg of ZC-ZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 1:1. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0050] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, take it out and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded CN / ZC-ZIF carbon sponge (CMS / GZ2).

[0051] Example 3

[0052] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 400°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0053] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0054] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0055] 4) Weigh 60 mg of CN and 30 mg of ZCZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 2:1. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0056] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, take it out and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded CN / ZC-ZIF carbon sponge (CMS / GZ3).

[0057] Example 4

[0058] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 400°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0059] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0060] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0061] 4) Weigh 60 mg of CN and 20 mg of ZCZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 3:1. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0062] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, take it out and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded CN / ZC-ZIF carbon sponge (CMS / GZ4).

[0063] Example 5

[0064] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 400°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0065] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0066] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0067] 4) Weigh 60 mg of CN and 15 mg of ZCZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 4:1. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0068] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, remove it and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded CN / ZC-ZIF carbon sponge (CMS / GZ5).

[0069] Example 6

[0070] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 400°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0071] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0072] 4) Weigh 20 mg of ZCZIF, disperse it in methanol solvent, sonicate for 2-3 hours, and dry it to obtain ZC-ZIF powder material. Disperse the mixed powder material in n-hexane and drop it onto carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0073] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, take it out and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded ZC-ZIF carbon sponge.

[0074] Example 7

[0075] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 200°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0076] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0077] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0078] 4) Weigh 60 mg of CN and 20 mg of ZCZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 3:1. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0079] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, take it out and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded ZC-ZIF carbon sponge.

[0080] Example 8

[0081] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 300°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0082] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0083] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0084] 4) Weigh 60 mg of CN and 20 mg of ZCZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 3:1. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0085] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, take it out and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded ZC-ZIF carbon sponge.

[0086] Example 9

[0087] 1) Place the sponge, which has been ultrasonically cleaned with anhydrous ethanol and deionized water, into a tube furnace and calcine it at 500°C for 2 hours under an argon atmosphere with an argon flow rate of 150 ml / min. Then clean it with deionized water to obtain carbonized melamine sponge (CMS).

[0088] 2) Add 10 mmol of 2-methylimidazole to 50 ml of deionized water, and label it solution A. Add 2.5 mmol of Zn(NO3)2·6H2O and 2.5 mmol of Co(NO3)2·6H2O to 50 ml of deionized water, and label it solution B. Stir each solution for 15 min. Then pour solution A into solution B and continue stirring for 30 min. After washing and drying, the prepared ZnCo-ZIF powder is obtained.

[0089] 3) g-C3N4 is synthesized through a typical thermal polymerization process. 20 g of urea is heated in a tube furnace at 10°C for [time missing]. -1 The heating rate was 550°C for 2 hours. After cooling to room temperature, the resulting light yellow solid was ground and dispersed in a solution of isopropanol:water in a ratio of 3:1 to obtain two-dimensional sheet-like g-C3N4 (labeled as CN).

[0090] 4) Weigh 60 mg of CN and 20 mg of ZCZIF, disperse them in methanol solvent, sonicate for 2-3 hours, and dry to obtain CN / ZC-ZIF powder material with a mass ratio of 3:1. Disperse the mixed powder material in n-hexane and drop it onto a carbon sponge. After drying, obtain CN / ZC-ZIF carbon sponge material.

[0091] 5) Add 5 mg of polydimethylsiloxane Sylgard 184 prepolymer A to 50 mL of dichloromethane, stir for 1 h, then add 0.5 mg of polydimethylsiloxane Sylgard 184 curing agent B to obtain solution C. Place the melamine sponge prepared in step (2) in solution C for 4 h, take it out and cure for 8 h, then wash it 3 times with anhydrous ethanol, and dry it at 60 ℃ for 6 h to obtain PDMS-loaded ZC-ZIF carbon sponge.

[0092] like Figure 1 The SEM image of the CMS sponge after calcination at 400℃ shows that the increase in temperature did not change the original three-dimensional network and high porosity structure of the sponge, and the pores were not blocked. Compared with the uncarbonized sponge, the CMS sponge has improvements in density, porosity, and nodal length.

[0093] like Figure 2 The SEM image of the ZIF catalyst shows that the ZIF catalyst retains its original dodecahedral crystal structure.

[0094] like Figure 3 The SEM image of the sample in Example 4 shows that ZIF crystals cover the surface of g-C3N4, and the two are tightly bonded to form a g-C3N4 / ZCZIF composite material grown on the surface of CMS framework. The surface roughness of the new sample is improved.

[0095] like Figure 4 X-ray diffraction patterns of the sample in Example 4 with g-C3N4, ZCZIF, GZ4, and CMS.

[0096] like Figure 5 The DRS diagrams of the sample in Example 4 and g-C3N4, ZCZIF, and GZ4 are shown. The UV-vis diagram shows that the light absorption characteristics of the integrated g-C3N4 and ZnCo-ZIF indicate that the composite material has better light absorption capacity, which also indicates that the composite material was successfully combined.

[0097] like Figure 6From the BET plots of the sample in Example 4 and g-C3N4, ZCZIF, and GZ4, it can be seen that the N2 adsorption-desorption isotherms are all identified as Type II, indicating the presence of both mesopores and macropores. Smaller pores are concentrated around 4 nm. It can be seen that the adsorption capacity of CO2 is improved after g-C3N4 is combined with ZnCo-ZIF. This improved CO2 adsorption capacity is one of the important reasons for the enhanced photocatalytic reduction ability of the sample.

[0098] like Figure 7 As shown in the CO2 adsorption diagrams of the sample in Example 4 with g-C3N4, ZCZIF, and GZ4, the CO2 adsorption capacity of the sample in Example 4 is significantly improved.

[0099] like Figure 8 The infrared absorption spectra of the sample in Example 4, along with those of g-C3N4, ZCZIF, and GZ1-GZ5, confirmed the presence of ZnCo-ZIF and g-C3N4 in the composite sample. The CMS spectrum showed prominent peaks at 812, 1142, 1631, and 3394 cm⁻¹, which were assigned to triazine ring bending, CO stretching, C=N stretching, and NH (secondary amine) stretching, demonstrating the successful synthesis of the composite material.

[0100] like Figure 9 As can be seen from the water contact angle diagrams of the sample in Example 4 and the CMS at different temperatures, the water contact angle of the sample in Example 4 is the highest, reaching 133° ± 3°.

[0101] like Figure 10 As shown in the image of Example 4, which illustrates the effect of adsorbing floating oil on water, this photograph depicts the process of placing the high-efficiency oil-water separation sponge prepared in Example 4 of this invention into a mixture of water and n-hexane (stained with Oil Red O) to adsorb n-hexane. When the sponge of this invention is placed in the mixture, due to its hydrophobic and oil-absorbing properties, n-hexane can be easily adsorbed by the melamine sponge, while the water is not adsorbed and remains in the original beaker containing the mixture, thus achieving selective adsorption of floating oil on water.

[0102] like Figure 11 As shown in Example 4, which illustrates the effect of adsorbing underwater heavy oil, a photograph depicts the process of placing the high-efficiency oil-water separation sponge prepared in Example 4 of this invention into a mixture of water and dichloromethane (stained with Oil Red O) to adsorb dichloromethane. When the sponge of this invention is placed in the mixture, due to the hydrophobic and oil-absorbing properties of the sponge, dichloromethane can be easily adsorbed by the melamine sponge, while the water is not adsorbed and remains in the original beaker containing the mixture, thereby achieving selective adsorption of underwater heavy oil.

[0103] like Figure 12As shown in Example 4, the continuous oil-water separation effect is illustrated by photographing the process of continuously adsorbing n-hexane by placing the sponge prepared in Example 4 of this invention in a mixture of water and n-hexane (stained with Oil Red). The beaker on the left contains the mixture, the beaker on the right is for receiving the mixture, and the middle is a peristaltic pump. The sponge is attached to the end of the tube on the left. When the sponge of this invention is placed in the mixture, due to the hydrophobic and oil-absorbing properties of the sponge, n-hexane is continuously adsorbed and drained away, while water is not adsorbed and remains in the original beaker containing the mixture. This achieves highly efficient continuous oil-water separation, meaning that the modified sponge of this invention has a very strong ability to separate oil and water (n-hexane / water).

[0104] like Figure 13 As shown in the effects of g-C3N4 on the samples in Examples 4 and 6, g-C3N4 has a significant effect on the CO2 reduction performance of the composite samples. g-C3N4 can not only promote CO2 reduction efficiency, but also improve the selectivity for CH4.

[0105] like Figure 14 As shown in Examples 4, 7, 8 and 9, the carbonization temperature significantly affects the CO2 reduction performance of the novel catalyst. 400 degrees Celsius is beneficial for improving the selectivity of CO, while 200 degrees Celsius is beneficial for improving the selectivity of CH4.

[0106] like Figure 15 As shown in the CO2 reduction and cycling performance of the sample in Example 4, the sample in Example 4 has a superior CO2 reduction capacity and a significant increase in CO production. This is mainly due to the unique three-dimensional pore structure of the carbon sponge, which provides a beneficial transfer path for electron-hole transfer.

[0107] It should be noted that the above-described technical content of this invention is merely an explanation and clarification to enable those skilled in the art to understand the technical essence of this invention, and therefore is not intended to limit the scope of protection of this invention. The scope of protection of this invention should be determined by the claims. Those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made based on the essential spirit of this invention should be within the scope of protection of this invention.

Claims

1. Use of a ZIF-based carbon sponge for photocatalytic reduction of CO2, characterized in that: The preparation method of the ZIF-based carbon sponge comprises the following steps: (1) The melamine sponge is cleaned in a first solvent for 30-60 min, and then ultrasonically cleaned in deionized water for 30-60 min, and dried to obtain a dried melamine sponge; (2) The cleaned melamine sponge material in step (1) is placed in a tube furnace, calcined at a temperature of 300-500°C under a flowing gas atmosphere for 2-4 h, ultrasonically cleaned in deionized water for 30-60 min, and dried to obtain a carbonized melamine sponge; (3) g-C3N4 and ZnCo-ZIF are dispersed in a second solvent, ultrasonically treated for 2-3 h, and dried to obtain a g-C3N4 / ZnCo-ZIF powder material; (4) The powder material obtained in step (3) is dispersed in a third solvent, and its surface is coated on the carbon sponge in step (2), washed, and dried to obtain a g-C3N4 / ZnCo-ZIF carbon sponge material; (5) PDMS loading, the sponge obtained in step (4) is immersed in a PDMS solution, and after standing at room temperature for a period of time, it is taken out and cured to obtain a g-C3N4 / ZnCo-ZIF / PDMS carbon sponge material.

2. Use according to claim 1, characterized in that, In step (1), the first solvent is selected from anhydrous ethanol, and the drying is performed at 60-80°C for 4-8 h.

3. Use according to claim 1, characterized in that, The gas flowing in the flowing gas atmosphere in step (2) includes at least one of helium, argon, and nitrogen.

4. Use according to claim 1, characterized in that, In step (3), the mass ratio of g-C3N4 to ZnCo-ZIF is 2:1, 1:1, 1:2, 1:3, or 1:4, and the second solvent is selected from one or more of anhydrous ethanol or methanol.

5. The use according to claim 1, characterized in that, In step (4), the third solvent is selected from one or more of n-hexane or cyclohexane.

6. Use according to claim 1, characterized in that, In step (5), the PDMS solution used is an alkane mixed solution of PDMS and a curing agent, and in the PDMS solution used, the mass of PDMS is 1-8% of the mass of the solvent, and the mass of the curing agent is 5-15% of the mass of the PDMS.

7. Use according to claim 1, characterized in that, In step (5), the standing time is 60-120 min, the curing temperature is 100-120°C, and the curing time is 2-4 h.

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