Conjugated microporous polymer porous composite hydrogel material based on interface evaporation coupling adsorption and preparation and application thereof

Abstract

The invention provides a conjugated microporous polymer porous composite hydrogel material based on interface evaporation coupling adsorption as well as a preparation method and application thereof. According to the material, hollow CMPs microspheres are synthesized through a Sonogashira-Hagihara reaction, the hollow CMPs microspheres are embedded into a hydrogel matrix after carbonization and hydrophilic modification, a composite structure with graded pore channels is formed, the composite structure has high iodide ion adsorption capacity and efficient interface evaporation performance, and pollutant adsorption and purified water recovery of iodine-containing wastewater can be synchronously achieved. Adsorption and photo-thermal evaporation technologies are coupled, pollutant capture and solar-driven water purification are synchronously completed through a pi conjugated structure of CMPs, and the problems that purified water cannot be produced through a traditional adsorption method and volatile pollutants cannot be treated through an evaporation technology are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of porous adsorption materials and photothermal materials, and specifically relates to a conjugated microporous polymer (CMPs) porous composite hydrogel with high adsorption capacity and photothermal evaporation performance based on interfacial evaporation coupling adsorption, and a preparation method thereof, and its application in the treatment of iodine-containing wastewater, realizing the synchronous adsorption of iodide ions and solar-driven interfacial evaporation. Background Art

[0002] Radioactive iodide ions, as a pollutant harmful to the human body and the environment, are an important topic in the treatment of nuclear industry waste liquid and environmental protection. There are various methods for treating radioactive iodide ions, including adsorption, ion exchange, membrane separation, and chemical precipitation methods. Among them, the adsorption method is one of the most promising methods for treating iodine-containing wastewater due to its high efficiency, simple operation, and excellent removal performance. However, a key problem with the adsorption method is that it cannot produce a completely clean aqueous solution, while the interfacial evaporation technology can produce pure water. Therefore, combining the adsorption and interfacial evaporation technologies can prevent iodide ions from overflowing with steam while producing pure water. The solar-driven adsorption-coupled interfacial evaporation technology is a clean, effective, and promising technology that can effectively treat various wastewater and also solve the problem that wastewater containing volatile components cannot be purified by evaporation technology.

[0003] So far, reported adsorption materials, such as porous materials, silver-based materials, and bismuth-based materials, have been widely used as adsorption materials for iodide ion treatment. Among them, porous materials have been studied and reported as good absorbent materials for iodide ions due to their high specific surface area and stability, mainly including porous carbon materials, zeolites, MOFs, and COFs. Porous carbon materials, such as activated carbon and zeolites, show relatively low efficiency in capturing radioactive iodide ions, and due to the complex and irregular pore structure of the materials, the pores are often blocked during the adsorption process, resulting in limited adsorption capacity and unable to achieve the expected adsorption effect. MOFs and COFs have also made great progress in iodine removal through specific adsorption of metal sites, but they also have some defects, such as harsh reaction conditions, inherent metal toxicity, and complex regeneration procedures. Iodide ions are easily detached in silver-based adsorption materials, and the detached silver ions are extremely harmful to the ecological environment. As for bismuth-based materials, although some successful cases of iodide ion adsorption have been reported, the adsorption performance of iodide ions still needs to be further explored. Compared with the above-mentioned porous organic materials, conjugated microporous polymers (CMPs) with regular π-conjugated structures can promote in-layer charge transfer and separation of pollutants, and can also control the pore size distribution and specific surface area of the materials by changing the building units, providing regular and smooth pore diameters and more iodide ion adsorption sites, thereby further enhancing the adsorption effect.

[0004] In addition to exploring excellent adsorption materials, materials with excellent interfacial evaporation performance are also very important for treating wastewater by evaporation. Organic polymer photothermal conversion materials require polymer molecules to have a large π-conjugated system, and one of the characteristics of conjugated microporous polymers is that they have a large π-conjugated system. The mechanical stability of CMPs as photothermal conversion materials is one of the key issues to be considered, and combining them with functional substrates is the way to solve the problem. An ideal solar-driven interfacial evaporation generator should have high photothermal conversion ability, excellent thermal management ability, and excellent water / vapor transport channels. Hydrogel is an excellent solar-driven interfacial evaporation functional substrate, with low thermal conductivity, salt tolerance, and its structure can quickly immerse in water and retain a large amount of water, which helps the transport and evaporation of water molecules. By fabricating a solar-driven adsorption-coupled interfacial evaporator with hydrogel and CMPs, adsorption and interfacial evaporation can be carried out simultaneously to obtain clean water, leaving most of the pollutants in the residual liquid, and a small part of the volatile pollutants will be blocked in the evaporator, and then the concentrate can be solidified and separated. Pollutants can be driven by solar energy into the interfacial evaporator and captured by the CMPs capturer in the interfacial evaporator. Therefore, the solar-driven adsorption-coupled interfacial evaporation process that can efficiently treat wastewater has received extensive attention from many teams and has become a very promising topic.

[0005] In this invention, hollow microsphere-shaped CMPs with high porosity, matched pore size, and extensive π-conjugated structure are synthesized through Sonagashira-Hagihara cross-linking condensation reaction, which have good π-π interaction, mechanical stability, and adsorption ability. At the same time, the hydrogel has excellent pore structure, high water absorption ability, and low thermal conductivity, which makes the CMPs-based porous composite hydrogel an excellent material for solar-driven adsorption-coupled interfacial evaporation technology. In this invention, by compounding CMPs with hydrogel, adsorption-evaporation synergistic purification is innovatively realized. Summary of the Invention

[0006] Aiming at the technical bottleneck that existing adsorption materials are difficult to reduce the pollutant ion concentration to the recoverable standard when treating wastewater, this invention innovatively combines the efficient adsorption method with the interfacial evaporation technology, and successfully develops a conjugated microporous polymer (CMPs) porous composite hydrogel material based on interfacial evaporation coupling adsorption. This material not only has excellent pollutant adsorption performance, but also can simultaneously achieve efficient water purification. Its unique hierarchical pore structure and functionalized surface can effectively capture ions and organic pollutants in wastewater, and at the same time produce high-purity recoverable water through the interfacial evaporation effect, providing a new technical solution for solving the deep treatment and resource utilization of industrial wastewater.

[0007] Based on the solar-driven adsorption-coupled interfacial evaporation technology proposed in this invention, a CMPs-based porous composite hydrogel is prepared, and its preparation process is as follows: (1) Using 1,3,5-triethynylbenzene and a halogenated nitrogen-containing compound as monomers, CuI and Pd(0) as catalysts, and silica spheres as templates, add them to a mixed solution of triethylamine and toluene. Under a nitrogen atmosphere, stir and react at 60-90 °C in the dark for 40-70 h. After the reaction, let it cool naturally, wash, perform Soxhlet extraction with a methanol solution and then dry. Acid-etch the obtained dry powder, wash until neutral to obtain hollow CMPs microspheres; the halogenated nitrogen-containing compound is 1,3-dichloroisoquinoline or N,N-bis(tetrabromobenzyl)amine. The synthesis route of the hollow CMPs microspheres is as Figure 1 (a), obtaining hollow CMPs microspheres with high adsorption, sensitive recognition, strong affinity and good stability.

[0008] Among them, the molar ratio of the alkynyl group in 1,3,5-triethynylbenzene to the halogenated group in the halogenated nitrogen-containing compound is 1:0.5 - 1:2, preferably 1:1. The mass ratio of 1,3,5-triethynylbenzene to Pd(0) is 1:2 - 1:10. The mass ratio of CuI to Pd(0) is 1:1 - 1:3. The particle size of the silica spheres is 280 - 320 nm (preferably 300 nm), and the mass ratio of the silica spheres to 1,3,5-triethynylbenzene is 1:4 - 1:8. In the mixed solution of triethylamine and toluene, the volume ratio of triethylamine to toluene is 1:0.5 - 1:2. The drying temperature is 55 - 65 °C, and the drying time is 10 - 15 h. Acid-etching is carried out in a solution of hydrofluoric acid: water: methanol = 1:2:3 (volume ratio) for 4 - 6 hours.

[0009] (2) Heat the CMPs microspheres in a tubular furnace to 700 - 900 °C and keep them at this temperature for 1 - 3 hours. Then add them to a sulfuric acid solution saturated with ammonium persulfate and stir for 20 - 25 h to hydrophilically modify the carbonized conjugated microporous polymer to obtain hydrophilic carbonized CMPs microspheres. Among them, the heating rate is 3 - 8 °C min -1 ; in the sulfuric acid solution saturated with ammonium persulfate, the mass fraction of sulfuric acid is 1%.

[0010] (3) In the presence of α-ketoglutaric acid, use 365 nm, 8 mW cm −2The sodium 4-vinylbenzenesulfonate solution and the [3-(methacryloylamino)propyl]trimethylammonium chloride solution were irradiated with ultraviolet light for 6-10 h, and then ethanol was added to the two solutions to precipitate them. The precipitates were sodium 4-vinylbenzenesulfonate polymer and [3-(methacryloylamino)propyl]trimethylammonium chloride polymer, respectively. The two polymers were dissolved in water to obtain the corresponding polymer solutions. The hydrophilic carbonized CMPs microspheres were added as a photothermal conversion material to the two polymer solutions and stirred well to obtain a uniform and viscous mixed solution. The two mixed solutions were added to deionized water for mixing to produce a precipitate. After standing, it was layered, and the precipitate in the lower layer was the CMPs-based porous composite hydrogel (PCH-CMP). The synthesis route is as Figure 1 shown in (b), and the prepared CMPs-based porous composite hydrogel with low thermal conductivity, good photothermal conversion ability and hierarchical porous structure was obtained.

[0011] Among them, the mass ratio of the hydrophilic carbonized CMPs microspheres to the sodium 4-vinylbenzenesulfonate polymer is 1:3 to 1:5; the mass ratio of the hydrophilic carbonized CMPs microspheres to the [3-(methacryloylamino)propyl]trimethylammonium chloride polymer is 1:3 to 1:5.

[0012] The hollow CMPs microspheres of the present invention provide a high specific surface area (≥600 m² / g) and adsorption sites; the micro-nano hierarchical pore channels of the hydrogel enable rapid water transportation (capillary action) and steam escape. The π-conjugated structure of CMPs simultaneously captures iodide ions (through charge transfer) and absorbs solar energy (photothermal conversion efficiency ≥93%); the low thermal conductivity (≤0.02 W / m·K) of the hydrogel limits heat loss and improves the evaporation efficiency. Adsorption performance: the maximum adsorption capacity for iodide ions reaches 15.96 mg / g, which is better than that of commercial activated carbon (3.2 mg / g); evaporation rate: the evaporation rate is 1.50-2.42 kg / m²·h under 1 sun intensity, and the attenuation rate is <5% for 10 consecutive days.

[0013] The mechanism of the CMPs-based porous composite hydrogel of the present invention in the solar interfacial evaporation treatment of iodine-containing wastewater is as follows: CMPs generated by Sonogashhara-Hagihara cross-coupling condensation reaction have a strong attraction to iodide ions. Conjugated microporous polymers can adjust the monomer structure, making the molecular surface charge more positive and having a stronger attraction to iodide ions. The hollow-shaped CMPs have a larger specific surface area, providing more active sites for iodide ion adsorption. The high interfacial evaporation rate of CMP-based porous composite hydrogels is based on the multi-level pore structure provided by the hydrogel. Nanopores help to rapidly absorb water through capillary action, and micropores help the generated water vapor to overflow smoothly. The most important thing is that the π-conjugated structure of the conjugated microporous polymer doped in the hydrogel attracts water molecules, promotes the entry of water molecules into the interfacial evaporation material, and then is evaporated.

[0014] In summary, the present invention ingeniously designs and constructs the molecular chain length, type, and unit ratio of monomers, and regulates the pore size of the CMPs adsorbent according to the size of the target iodide ion, so that 1,3,5-triethynylbenzene and 1,3-dichloroisoquinoline or N,N-bis(tetrabromobenzyl)amine undergo Sonogashhara-Hagihara cross-reaction to construct CMPs adsorbent materials with different pore size structures and spatial structures. The CMPs adsorbent material is doped into the hydrogel to prepare a CMP-based porous composite hydrogel for solar-driven interfacial evaporation treatment of wastewater. The present invention combines solar-driven interfacial evaporation technology with adsorption technology for the first time and has achieved excellent results in treating various types of wastewater. The adsorption capacity of the conjugated microporous polymer adsorbent prepared by the present invention for iodide ions reaches 15.96 mg g -1 , and the evaporation rate of the iodine-containing wastewater of the CMP-based hydrogel can reach 1.50 kg m -2 h -1 . In the solar-driven adsorption-coupled interfacial evaporation technology, due to the excellent hierarchical pore structure and low thermal conductivity of the CMP-based porous composite hydrogel, it is divided into an evaporation layer (upper) and a water supply layer (lower). The extensive π-conjugated structure provided by CMPs plays a crucial role. The π-conjugated structure attracts water molecules into the water supply layer and adsorbs iodide ions in the water. In the evaporation layer, CMPs act as light-absorbing substances to provide energy for interfacial evaporation.

[0015] Through the composite design of conjugated microporous polymers (CMPs) and hydrogels, the present invention realizes the synergistic purification of adsorption-evaporation, and has the following significant advantages compared with the prior art: 1. High-efficiency adsorption and evaporation synergy: Couple the efficient adsorption of CMPs with the interfacial evaporation of hydrogels to break through the limitations of traditional technologies that can only perform single adsorption or evaporation; Adsorption end: The π-conjugated structure captures iodide ions through charge transfer; Evaporation end: The hierarchical pores (nano-capillaries + micro-cavities) enable rapid water transportation and steam escape, with a photothermal conversion efficiency ≥ 93%. The iodine adsorption capacity of the material reaches 15.96 mg g⁻¹, and the evaporation rate reaches 1.50 - 2.42 kg m⁻² h⁻¹ (under 1 sun intensity); The adsorption layer fixes iodide ions, and the evaporation layer produces pure water, avoiding the escape of pollutants with steam (the iodine concentration in the condensed water is detected as 0), solving the industry problem of the escape of volatile iodine during the evaporation process.

[0016] 2. Molecular design and structure regulation: The hollow structure synthesized by the template method provides a larger specific surface area and regular pore sizes. By regulating the ratio of 1,3,5-triethynylbenzene to nitrogen-containing monomers through the Sonogashira-Hagihara cross-coupling reaction, a pore structure matching the size of iodide ions is constructed, solving the problem of low utilization rate of adsorption sites in traditional porous materials.

[0017] 3. Advantages of material stability and environmental adaptability: CMPs materials with excellent stability (under pH 2 - 12, 10% NaCl, the evaporation performance attenuation < 5%) and great rigid strength not only have high adsorption capacity and evaporation rate, but also enable the materials to adapt to various different environments and can effectively treat various wastewaters. Thanks to the inclusiveness brought by the rigid structure and π-conjugated system of CMPs, these materials can maintain stable adsorption performance under harsh conditions such as acidity and high temperature, and can treat complex systems such as nuclear wastewater (iodine adsorption), seawater (desalination rate > 99%), and dye wastewater (interception rate 95%), with a wider application range than traditional materials (such as bismuth-based materials which are only applicable to specific iodine forms).

[0018] 4. Potential for industrial application and sustainability: The evaporation rate under sunlight intensity is 2.42 kg m⁻² h⁻¹, and no external energy input is required. The performance attenuation is < 5% after continuous 10-day testing, with a long life cycle. Description of the drawings

[0019] Figure 1 (a) Synthesis process and molecular structure model of CMPs; (b) Schematic diagram of the preparation of PCH-CMP.

[0020] Figure 2 (a) SEM images of CMPs-1 and (b) CMPs-2; (c) TEM images of CMPs-1 and (d) CMPs-2; (e) SEM images of PCH-CMP-1 and (f) PCH-CMP-2.

[0021] Figure 3 (a)XRD curves and (b) FT-IR curves of CMPs-1, CMPs-2, PCH-CMP-1 and PCH-CMP-2; (c) N2 adsorption / desorption curves and BJH pore size distribution curves of CMPs-1 and (d) CMPs-2; (e) mercury intrusion / extrusion curves of PCH-CMP-1 and (f) PCH-CMP-2.

[0022] Figure 4 (a)XPS measurement spectra and (b) C1s spectra of CMPs-1, CMPs-2, PCH-CMP-1 and PCH-CMP-2; (c) Cl2p spectra of CMPs-1 and PCH-CMP-1, Br3d spectra of CMPs-2 and PCH-CMP-2.

[0023] Figure 5 (a)Droplet jumping photos on CMPs-1, (B) CMPs-2, (c) PCH-CMP-1 and (d) PCH-CMP-2; (e) water contact angle photos of CMPs-1, (f) CMPs-2, (g) PCH-CMP-1 and (h) PCH-CMP-2.

[0024] Figure 6 (a)UV-visible spectra of CMPs for 30 min, and standard curve of iodide ion concentration and absorbance; (b) absorption curves of CMPs-1 and (c) CMPs-2 at different initial concentrations.

[0025] Figure 7 (a)Pseudo-first-order kinetic fitting curves and pseudo-second-order kinetic fitting curves of CMPs-1 and (b) CMPs-2; (c) intraparticle diffusion fitting curves of CMPs-1 and (d) CMPs-2; (e) Langmuir isothermal adsorption curves and Freundlich isothermal adsorption curves of CMP-1 and (f) CMP-2.

[0026] Figure 8(a)Solar interfacial evaporation experimental device; (b) UV-vis-NIR curves of PCH-CMP-1 and PCH-CMP-2; (c) Temperature rise curves under wet conditions of pure water, PCH-CMP-1 and PCH-CMP-2; (d) Infrared images of pure water, PCH-CMP-1 and PCH-CMP-2 under wet conditions; (e) Temperature change of PCH-CMP-1 and PCH-CMP-2 over time under dry conditions; under natural conditions and at different light intensities, (f) Water mass change of PCH-CMP-1 and (g) PCH-CMP-2 per unit time; (h) Evaporation rate of PCH-CMP-1 and (i) PCH-CMP-2 in water for 10 consecutive days.

[0027] Figure 9 (a)Water mass change of PCH-CMP-1 and (b) PCH-CMP-2 at different salt concentrations; (c) Ion concentration content in simulated seawater before and after evaporation; (d) Water mass change of PCH-CMP-1 and PCH-CMP-2 in iodide solution under 1 sun; (e) UV-visible absorption spectra of PCH-CMP-1 and PCH-CMP-2 distilling iodide solution under 1 sun; (f) UV-visible absorption spectra of the impregnation solution of PCH-CMP-1 and PCH-CMP-2 after interfacial evaporation.

[0028] Figure 10 (a)FT-IR of adsorbed and unadsorbed CMPs-1 and CMPs-2; (b) ESP distribution of CMPs-1 and CMPs-2; (c) Schematic diagram of the mechanism of PCH-CMP. Detailed implementation mode

[0029] The present invention will be further described in detail below in conjunction with the embodiments and the drawings, but the implementation manners of the present invention are not limited thereto.

[0030] In the embodiments of the present invention, those not specified in specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents, etc. not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0031] In the embodiments of the present invention, a set monomer is selected as an example, and a preparation method of a conjugated microporous polymer-based porous hydrogel based on solar-driven adsorption-coupled interfacial evaporation technology is given. The specific steps are as follows: Example 1 Preparation of CMPs-based porous composite hydrogel PCH-CMP-1 (1) Using the compounds of 1,3,5-triethynylbenzene (1 mmol) and 1,3-dichloroisoquinoline (1 mmol) as monomers, CuI (20 mg) and Pd(0) (30 mg) as catalysts, 300 nm silica spheres (300 mg) as templating agents, add them to a mixed solution of triethylamine (30 mL) and toluene (30 mL). Under a nitrogen atmosphere, react at 80 °C in the dark for 48 h. After the reaction, let it cool naturally, wash it several times with methanol, acetone, chloroform, and water respectively, and then perform Soxhlet extraction with a methanol solution for 24 h. Then, dry the product at 60 °C. Etch the obtained dry powder in a solution of hydrofluoric acid:water:methanol = 1:2:3 for 5 h. After etching, rinse it with water until neutral to obtain the final product, hollow CMPs microspheres (CMPs-1).

[0032] (2) Heat the CMPs-1 powder in a tube furnace to 800 °C and hold for 2 h, with a heating rate of 5 °C min -1 , to obtain carbonized CMPs-1. Add it to a 1% sulfuric acid solution saturated with ammonium persulfate and stir for 24 h to modify the obtained carbonized conjugated microporous polymer, and obtain hydrophilic carbonized CMPs-1.

[0033] (3) In the presence of 0.1 mol% α-ketoglutaric acid, irradiate a 1 mol L −2 sodium 4-vinylbenzenesulfonate solution and a 1 mol L -1 [3-(methacrylamido)propyl]trimethylammonium chloride solution with ultraviolet light of 365 nm and 8 mW cm -1 for 8 h. Add ethanol to the two solutions to precipitate them. The precipitate is a polymer of sodium 4-vinylbenzenesulfonate and [3-(methacrylamido)propyl]trimethylammonium chloride, which is a white solid to the naked eye. Then, dissolve the sodium 4-vinylbenzenesulfonate polymer in water to obtain a 100 mL 0.11 mol L -1 solution with repeated sodium salt units, and dissolve the [3-(methacrylamido)propyl]trimethylammonium chloride polymer in water to obtain a 100 mL 0.1 mol L -1 solution with repeated chloride salt units. Add the hydrophilic carbonized CMPs-1 (1 g) as a photothermal conversion material to the two solutions (150 mL) and stir well for 10 h to obtain a uniform and viscous mixed solution. Subsequently, add the two mixed solutions evenly and slowly to deionized water and mix them. Precipitation is observed. After standing for 24 h, a layering phenomenon is observed. Take out the lower-layer precipitate, which is the CMPs-based porous composite hydrogel (PCH-CMP-1).

[0034] Example 2 Preparation of CMPs-based porous composite hydrogel PCH-CMP-2 (1) Using 1,3,5-triethynylbenzene (1 mmol) and N,N-bis(tetrabromobenzyl)amine (1.5 mmol) as monomers, CuI (20 mg) and Pd(0) (30 mg) as catalysts, and 300 nm silica spheres (300 mg) as templating agents, add them to a mixed solution of triethylamine (30 mL) and toluene (30 mL). Under a nitrogen atmosphere, react at 80 °C in the dark for 48 h. After the reaction, let it cool naturally, wash it several times with methanol, acetone, chloroform, and water respectively, and then perform Soxhlet extraction with methanol solution for 24 h. Then, dry the product at 60 °C. Etch the obtained dry powder in a solution of hydrofluoric acid:water:methanol = 1:2:3 for 5 h. After etching, rinse it with water until neutral to obtain the final product, hollow CMPs microspheres (CMPs-2).

[0035] (2) Heat the CMPs-2 powder in a tube furnace to 800 °C and hold for 2 h, with a heating rate of 5 °C min -1 , to obtain carbonized CMPs-2. Add it to a 1% sulfuric acid solution saturated with ammonium persulfate and stir for 24 h to modify the obtained carbonized conjugated microporous polymer, obtaining hydrophilic carbonized CMPs-2.

[0036] (3) In the presence of 0.1 mol% α-ketoglutaric acid, irradiate 1 molL −2 sodium 4-vinylbenzenesulfonate solution and 1 mol L -1 [3-(methacrylamido)propyl]trimethylammonium chloride solution with ultraviolet light of 365 nm and 8 mW cm -1 for 8 h. Add ethanol to the two solutions to precipitate them. The precipitate is a polymer of sodium 4-vinylbenzenesulfonate and [3-(methacrylamido)propyl]trimethylammonium chloride, which is a white solid to the naked eye. Then, dissolve the sodium 4-vinylbenzenesulfonate polymer in water to obtain a 100 mL 0.11 mol L -1 solution with repeated sodium salt units, and dissolve the [3-(methacrylamido)propyl]trimethylammonium chloride polymer in water to obtain a 100 mL 0.1 mol L -1 solution with repeated chloride salt units. Add the hydrophilic carbonized CMPs-2 (1 g) as a photothermal conversion material to the two solutions (150 mL) and stir well for 10 h to obtain a homogeneous and viscous mixed solution. Subsequently, add the two mixed solutions evenly and slowly to deionized water and mix. Precipitation is observed. After standing for 24 h, a layering phenomenon is observed. Take out the lower-layer precipitate, which is the CMPs-based porous composite hydrogel (PCH-CMP-2).

[0037] Example 3 Structural Characterization of CMPs-based Porous Composite Hydrogel From Figure 2 Figure 2 It can also be clearly seen from above that the CMPs-1 (Example 1) and CMPs-2 (Example 2) prepared by the present invention. CMPs-1 (Example 1) presents as microspheres with a diameter of about 300 nm, and CMPs-2 (Example 2) presents as a ball-and-stick model. Both are hollow shapes. The hollow shape provides more adsorption sites for iodine ion adsorption, increasing the adsorption capacity; the macroporous structure in the hydrogel provides a smooth path for interfacial evaporation, improving the interfacial evaporation rate.

[0038] As Figure 3 shown in a. The peaks of CMPs-1 and PCH-CMP-1 (Example 1), CMPs-2 and PCH-CMP-2 (Example 2) all appear at 22°, which is a very broad peak, indicating that they are amorphous materials. In addition, through Fourier transform infrared spectrometer ( Figure 3 b), it is found that the characteristic peaks of the π-conjugated system on the benzene ring appear at 1350 cm −1 and 1609 cm −1 . The characteristic absorption peak near the wavenumber of 2345 cm -1 is the C-C stretching vibration of the conjugated microporous polymer. From the above graphical analysis, it is concluded that we have successfully synthesized the conjugated microporous polymers CMPs-1, CMPs-2, and the porous composite hydrogels PCH-CMP-1, PCH-CMP-2.

[0039] Subsequently, in order to study the pore size and pore structure, which is very meaningful in terms of adsorption. N2 adsorption and desorption curves were used to determine the pore size, pore volume and specific surface area of CMP-1 (Example 1) and CMP-2 (Example 2) ( Figure 3 c-d and Table 1). According to the IUPAC classification, CMPs-1 is a typical type curve (the adsorption and desorption curves do not overlap, there is a hysteresis loop) in response to the micropore filling phenomenon on the conjugated microporous polymer adsorbent, while CMPs-2 is a type IV curve with an H3 hysteresis loop, indicating that CMP-2 is a mesoporous structure. CMPs-1 has a large specific surface area. A large specific surface area can expose a large ion adsorption area, while a small pore size can prevent the detachment after ion adsorption. The suitable pore structure and large specific surface area of CMPs-1 provide the basis for its excellent adsorption performance. The TEM photo also shows the hollow structure of CMPs-1, providing more active sites for adsorption. For the hydrogels PCH-CMP-1 (Example 1) and PCH-CMP-2 (Example 2) with large pore sizes, the mercury intrusion method was used to measure their pore structure ( Figure 3(e - f). The pore size distribution diagram shows that PCH-CMP-1 has a multi-layer pore structure, including macropores with diameters in the hundreds of nm and cavities with diameters less than 50 μm, which is the reason for the relatively small average pore size of PCH-CMP-1. In addition, the nanoporous structure improves the water supply efficiency through capillary action and contributes to the adsorption and dissociation of water. Such cavity structures can provide deeper solar entry channels and smoother water transport channels, better balancing the relationship between solar evaporation and water supply, and also facilitating the smooth over-flow of the generated steam. Such a multi-layer pore distribution is one of the important reasons for the high interfacial evaporation rate of PCH-CMP-1.

[0040] Using X-ray photoelectron spectroscopy (XPS) analysis, it was found that CMPs-1 and PCH-CMP-1 (Example 1), CMPs-2, and PCH-CMP-2 (Example 2) contain abundant C, O, and N ( Figure 4 a). As Figure 4 shown in Figure 4 b, CMPs-1 shows two peaks at 284.8 eV and 285.8 eV in the carbon binding energy region. The first peak is C-C, and the second peak is C-N. Similarly, the two peaks in the carbon binding energy region of CMPs-2 are C-C at 284.8 eV and -C6H5 at 284.4 eV. The two peaks in the C1s spectrum of PCH-CMP-1 are C-C at 284.8 eV and -C6H5 at 286.4 eV. In the C1s spectrum of PCH-CMP-2, there is a C-C peak at 284.8 eV and a C-N peak at 286.3 eV. As

[0041] shown in Figure 5 c, the surface of PCH-CMP-1 contains C-Cl bonds, while no bromine-containing functional groups are detected in the fine spectrum of PCH-CMP-2, and even no spin-orbit splitting is detected, indicating that the surface of PCH-CMP-1 contains more obvious CMP-1 substances. Figure 5 As Figure 5 shown in

[0042] Example 4 Study on the treatment of radioactive iodine ions Adsorption conditions of hollow CMPs microspheres for radioactive iodine ions: The hollow CMPs microspheres were first soaked in methanol and then placed in 30 mL of potassium iodide solutions with different concentrations (0.02 mmol L -1 , 0.04 mmol L -1 , 0.06 mmol L -1 , 0.08 mmol L -1 and 0.10 mmol L -1 ), shake and mix to obtain a mixed solution of CMPs microspheres and potassium iodide, adsorb at 10-50°C for 2-12 hours, and use an ultraviolet-visible spectrophotometer (UV-VIS) to monitor the absorbance change of the potassium iodide solution containing the adsorbent material under static conditions. Test 3 mL of the clear solution regularly until the absorbance remains constant and is in equilibrium. The change in absorbance can directly reflect the change in iodine ion concentration.

[0043] Conditions for treating wastewater using interfacial evaporation using CMPs-based porous composite hydrogels: The experiment was conducted indoors in the summer in northwest China, with an average laboratory temperature of 25°C and an average humidity of 51%. The solar interface evaporation device consists of a xenon lamp, an analytical balance, and data processing software, which truly records the evaporation of pure water under sunlight. First, turn on the xenon lamp for 20 minutes to preheat the light source to make the light intensity more stable. Then adjust the light intensity and the distance between the light source and the material so that the light intensity in contact with the material surface is 1 kW m −2 or 2 kW m −2 Then, the CMPs-based porous composite hydrogel was placed in a container containing wastewater and irradiated under different solar light intensities, and the mass loss was recorded by an analytical balance. At the same time, the temperature change on the surface of the material was recorded using an infrared thermal imager.

[0044] The ability of the two materials to adsorb iodine ions was verified under static conditions. -1 After being stored in the iodide ion solution for 30 min, the absorbance of the solution decreased significantly, indicating that the CMPs material has the ability to adsorb iodide ions. Subsequently, according to the Lambert-Beer law, 0.02 mmol L -1 , 0.04 mmol L -1 , 0.06 mmolL -1 , 0.08 mmol L -1 and 0.10 mmol L -1Iodide ion solutions were prepared and their absorbances were measured. Standard curves of absorbance versus iodide ion concentration were plotted. Then, the adsorption capacities of CMPs-1 (Example 1) and CMPs-2 (Example 2) at different initial concentrations were tested to explore the relationship between the initial concentration of iodide ion solutions and the adsorption performance. The results are as follows Figure 6 , when the initial concentration was 0.10 mmol L -1 , the adsorption amounts of CMPs-1 and CMPs-2 were the largest. Comparing the adsorption effect diagrams of the two materials, the adsorption effect of CMPs-1 was better, reaching 15.96 mg g -1 , while that of CMPs-2 was only 11.40 mg g -1 . However, CMPs-2 reached the adsorption equilibrium faster and had already started to reach equilibrium at 2 h, while CMPs-1 showed an equilibrium trend at 7 h, indicating that CMPs-2 had a faster adsorption rate. Analyzing from the perspective of the material structure, CMPs-2 had larger and smoother pore sizes, resulting in faster and more efficient iodide ion adsorption. Correspondingly, CMPs-2 had a smaller specific surface area, which could not provide more defect sites, leading to lower adsorption performance. In contrast, the special hollow spherical structure of CMPs-1 provided more defect sites. Moreover, the smaller pore size was not conducive to the entry of iodide ions, resulting in a slower adsorption rate of CMPs-1.

[0045] To further study the adsorption mechanism of iodide ions by CMPs materials, pseudo-first-order kinetic equation, pseudo-second-order kinetic equation, intraparticle diffusion equation, Langmuir isotherm equation, and Freundlich isotherm equation were used to explore the adsorption process. The results are as follows Figure 7 , and it was found that the pseudo-second-order kinetic curves (R2 2 = 0.9877, 0.9840) of CMPs-1 (Example 1) and CMPs-2 (Example 2) were closer to 1 than the determination coefficients of the pseudo-first-order kinetic curves (R1 2 = 0.9785, 0.9744), and the chi-square values (χ 2 = 0.1324, 0.0327) of the pseudo-second-order kinetic curves were smaller than those of the pseudo-first-order kinetic equations (χ 2 = 0.2305, 0.0523), indicating a smaller deviation between the actual observed values and the theoretical values. From the perspective of model fitting and statistics, the adsorption processes of CMPs-1 and CMPs-2 were more in line with the pseudo-second-order kinetic model, and the adsorption process was chemisorption. Secondly, the intraparticle diffusion equation was used to analyze the iodide ions in the adsorption process of CMPs materials. The intraparticle diffusion fitting curves of both adsorption materials showed the characteristic of C≠0, indicating that intraparticle diffusion was not the only rate-limiting step. In addition, the diffusion parameter showed k P1 > kP2 >k P3 The trend indicates that the adsorption sites on the adsorbent are occupied by the adsorbed iodide ions during the adsorption process, resulting in a gradual decrease in the adsorption rate of the material and finally reaching adsorption saturation. Finally, the Langmuir isotherm model and the Freundlich isotherm model were used to explore the kinetic behavior of iodide ion adsorption in water. From the curves fitted by the two isotherm models, it can be seen that CMPs-1 is more in line with the Freundlich isotherm model, and its absolute coefficient (0.9901) is greater than the R 2 (0.9017) of the Langmuir isotherm model, and the χ 2 value (0.9433) of the Freundlich isotherm model is much smaller than that of the Langmuir isotherm model (12.2284), indicating that CMPs-1 is monolayer adsorption. CMPs-2 is more in line with the Langmuir isotherm model (R L 2 = 0.9998 > R F 2 = 0.9992), and its χ 2 value is also smaller (0.0077 < 0.0272), indicating that CMPs-2 is multilayer adsorption.

[0046] The test system for solar-driven interfacial evaporation is shown in Figure 8 Figure a. As is well known, excellent water transport ability is the key to a solar interfacial steam generator, and the pore size and distribution have an important impact on the overall water transport ability. Through pore size distribution observation, PCH-CMP-1 (Example 1) has a multi-layer pore structure, including nanopores with diameters in the hundreds of nanometers and cavities with diameters less than 50 μm. The nanopores help to rapidly absorb water by capillary action, while the cavities help the generated steam to overflow smoothly. In contrast, PCH-CMP-2 (Example 2) has a more uniform pore size, which is basically micron-sized cavities. In addition, during the interfacial evaporation process, not only is the water transport ability crucial, but also the thermal conductivity and light absorption ability are key. The thermal conductivity of PCH-CMPs-1 is 0.0175 W m -1 K -1 , and the thermal conductivity of PCH-CMPs-2 is 0.0120 W m -1 K -1, both are relatively low, indicating that the material can be automatically divided into two parts without interfacial evaporation. The bottom is responsible for water transportation, and the upper part is responsible for heat preservation. This zoning treatment concentrates all the heat above the evaporation, and the water vaporizes and easily volatilizes into the air after evaporation, improving the evaporation rate. It is worth noting that PCH-CMP has excellent light absorption in the entire solar spectrum, with an absorption rate of more than 94% in the entire solar spectrum and an absorption rate of more than 93% for PCH-CMP-2 ( Figure 8 b), and the most important reason for the high absorption rate is that the CMP material contains a large range of π-conjugated structures. The hydrogel with a porous structure allows water to form water molecular clusters inside it, and hydrogen bonds are formed between the hydrophilic groups in the hydrogel polymerization network and water molecules. Under light illumination, the temperature rises rapidly and reaches 65.5 °C within 10 minutes ( Figure 8 c). This temperature is higher than that of PCHCMP-2 (47 °C). In addition, after the temperature drops rapidly, it reaches room temperature within 10 minutes, indicating that PCH-CMP has excellent photothermal conversion performance. A xenon lamp is used to simulate solar radiation, and the light power density is measured as 0 sun, 1 sun, and 2 sun by a light power density meter, and the weight of the interfacial evaporation device changes with time under solar radiation. Under 1 sun illumination, the natural evaporation rate of water is 0.59 kg m -2 h -1 ( Figure 8 f). The interfacial evaporation rate of PCH-CMP-1 is 0.22 kg m -2 h -1 . Under 1 sun, the interfacial evaporation rate of PCH-CMP-1 is 2.42 kgm -2 h -1 ,. Under 2 suns, the interfacial evaporation rate of PCH-CMP-1 is 3.55 kg m -2 h -1 , which is 1.47 times higher than the evaporation rate under 1 sun and 6.0 times higher than the evaporation rate under natural conditions. The interfacial desorption rate of PCH-CMP-2 is 0.20 kg m -2 h -1 in the dark, 1.89 kg m -2 h -1 under 1 sun, and 2.77 kg m -2 h -1 ( Figure 8 g). The interfacial evaporation rates of PCH-CMP-1 and PCH-CMP-2 also increase with the increase in sunlight intensity. It is worth noting that PCH-CMP-1 can achieve an average value of 2.42 kg m -2 h -1With an effective evaporation of variance 0.0248, PCH-CMP-2 can achieve an average of 1.83 kg m for 10 consecutive days -2 h -1 With an effective evaporation of variance 0.0352, it indicates that PCHCMP has excellent durability ( Figure 8 h-i). The evaporation rate of PCH-CMP-1 in pure water under 1 sun is 2.4 kg m -2 h -1 , and then we measured its interfacial evaporation rates in seawater, 5% NaCl, and 10% NaCl under 1 sun to be 2.28 kg m -2 h -1 , 2.24 kg m -2 h -1 and 2.10 kg m -2 h -1 ( Figure 9 a). The evaporation rate of PCH-CMP-2 for pure water is 1.89 kg m -2 h -1 , and for seawater, 5% NaCl, and 10% NaCl are 1.83 kg m -2 h -1 , 1.78 kg m -2 h -1 and 1.69 kgm -2 h -1 , ( Figure 9 b). To further verify the effect of seawater desalination, inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the residual ion concentration of the desalinated clear water sample. It was found that the concentrations of the four main ions in seawater (Na + , Ca 2+ , Mg 2+ and K + ) had been significantly reduced by about three to five orders of magnitude ( Figure 9 c), which meets the drinking water standards of the World Health Organization (WHO). One of the most important reasons is that the perfect π-conjugated structure of CMPs-1 captures water molecules and affects the interfacial evaporation performance. And the high evaporation ability of efficient PCH-CMP-1 is the product of the synergistic effect of its unique special pore structure, which consists of a combination of nanoscale capillary pores and microscale cavities, and its low thermal conductivity and high light absorption ability. To verify that the treatment of iodine-containing wastewater by PCH-CMP is a process combining adsorption and interfacial evaporation. The iodide ion solution was placed in a solar-driven interfacial evaporation device, and under 1 sun irradiation, the interfacial evaporation rate of PCH-CMP-1 and the content of iodide ions in the condensate were measured. The interfacial evaporation rate was 1.50 kg m -2 h-1 ( Figure 9 d). In addition, when using this device to collect distilled water, it was detected that the distilled water contained no iodide ions and iodine ( Figure 9 e). Then, the PCH-CMP material was immersed in an aqueous solution for 3 hours, and it was detected that it contained a large amount of iodide ions, which verified the adsorption effect of PCH-CMP on iodide ions ( Figure 9 f). The solar-driven adsorption-coupled interfacial evaporation technology has the dual functions of adsorbing and removing iodide ions and solar interfacial evaporation to enrich iodide ions, and has broad application prospects.

[0047] To explore the adsorption mechanism of this material and verify the fitting results of the above equation, we measured the changes in FT-IR and Zeta potential of the material before and after adsorption, and searched for the electrostatic potential map (ESP) of the CMPs material. From the FT-IR comparison chart ( Figure 10 a), it can be seen that the peaks decreased after adsorption, especially at 1350 cm −1 and 1609 cm −1 . This can be considered the result of chemical adsorption, which verifies again that the CMPS adsorption process conforms to the pseudo-second-order kinetic model. More importantly, for CMPs-1 (Example 1), the characteristic peaks of π-conjugation (1629 cm −1 and 1596 cm −1 ) showed a red shift after adsorbing iodide ions (1634 cm −1 and 1598 cm −1 ). This is because the charge transfer caused by the adsorption of strong electron acceptors (iodide ions) reduces the electron cloud density, so the absorption peak shows a red shift. Similarly, CMPs-2 (Example 2) also showed a red shift after adsorption, from 1631 cm −1 and 1596 cm −1 red-shifted to 1635 cm −1 and 1598 cm −1 . This deeply proves the role of π-conjugation in the iodide ion adsorption process. In particular, the changes in Zeta potential before and after material adsorption were used to verify again the fitting results of CMPs materials in the isotherm model. See Table 2 for details. After CMPs-1 adsorbed iodide ions, the absolute value of the Zeta potential decreased, indicating that iodide ions tended to exist in an aggregated form, which was consistent with the multi-molecular layer adsorption described by the Freundlich isotherm model. Although the absolute value of the zeta potential increased after iodide ion adsorption by CMP-2, the molecular adsorption tended to be in a dispersed form, exactly as shown in the Langmuir isotherm model. In addition, according to the charge distribution in the ESP of CMP-1 and CMP-2, it can be seen that CMPs-1 obviously has stronger positive charges than CMPs-2, which is beneficial to the adsorption of iodide ions ( Figure 10b). The excellent iodine adsorption performance of CMPs is due to their excellent pore structure, special hollow structure, large specific surface area, and perfect π-conjugated system. The high interfacial evaporation rate of CMP is the result of the combined effect of straight water transport channels and π-conjugation ( Figure 10 c).

[0048] .

Claims

1. A preparation method of a conjugated microporous polymer porous composite hydrogel material based on interfacial evaporation coupling adsorption, comprising the following steps: (1) Using 1,3,5-triethynylbenzene and a halogenated nitrogen-containing compound as monomers, CuI and Pd(0) as catalysts, and silica as a template, adding them into a triethylamine / toluene mixed solvent, reacting at 60-90 °C in the dark under a nitrogen atmosphere for 40-70 h, washing, drying, and then acid etching to obtain hollow CMPs microspheres; the halogenated nitrogen-containing compound is 1,3-dichloroisoquinoline or N,N-bis(tetrabromobenzyl)amine; (2) Carbonizing the CMPs microspheres at 700-900 °C for 1-3 h, and then hydrophilically modifying them in a sulfuric acid solution saturated with ammonium persulfate for 20-25 h; (3) Adding the hydrophilically carbonized CMPs microspheres into a sodium 4-vinylbenzenesulfonate polymer solution and a [3-(methacrylamido)propyl]trimethylammonium chloride polymer solution, mixing, and then precipitating and separating layers to obtain a porous composite hydrogel.

2. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of the alkynyl group in 1,3,5-triethynylbenzene to the halogenated group in the halogenated nitrogen-containing compound is 1:0.5-1:2; the mass ratio of 1,3,5-triethynylbenzene to Pd(0) is 1:2-1:10; the mass ratio of CuI to Pd(0) is 1:1-1:

3.

3. The preparation method according to claim 1, characterized in that: In step (1), the particle size of the silica is 280-320 nm, the mass ratio of the silica to 1,3,5-triethynylbenzene is 1:4-1:8; in the triethylamine / toluene mixed solvent, the volume ratio of triethylamine to toluene is 1:0.5-1:2; the drying temperature is 55-65 °C, and the drying time is 10-15 h.

4. The preparation method according to claim 1, wherein: In step (1), the acid etching uses a solution of hydrofluoric acid:water:methanol = 1:2:3 (volume ratio), and the etching time is 4-6 h.

5. The preparation method according to claim 1, characterized in that: In step (3), the sodium 4-vinylbenzenesulfonate polymer and the [3-(methacrylamido)propyl]trimethylammonium chloride polymer are prepared by ultraviolet light-initiated polymerization. The wavelength of the ultraviolet light is 365 nm and the intensity is 8 mW cm -2 , and the irradiation time is 6 to 10 h.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of the hydrophilically carbonized CMPs microspheres to the sodium 4-vinylbenzenesulfonate polymer is 1:3-1:5; the mass ratio of the hydrophilically carbonized CMPs microspheres to the [3-(methacrylamido)propyl]trimethylammonium chloride polymer is 1:3-1:

5.

7. A porous composite hydrogel material prepared by the method according to claim 1, characterized in that: The material is formed by embedding carbonized and hydrophilically modified hollow CMPs microspheres into a hydrogel matrix, has a hierarchical porous structure and a π-conjugated system, the hierarchical porous structure includes nanoscale capillary pores and micron-scale cavities, and the π-conjugated structure can simultaneously capture iodide ions and absorb solar energy; the water contact angle of the material is ≤60°, and the solar light absorption rate is ≥93%.

8. Use of the porous composite hydrogel material according to claim 1 or 7 in the treatment of iodine-containing wastewater, characterized in that: Synchronously achieve iodide ion adsorption and solar-driven interfacial evaporation.

9. The application according to claim 8, characterized in that: Under 1 sun intensity, the iodine adsorption capacity reaches ≥ 15.96 mg g -1 , and the solar-driven interfacial evaporation rate is ≥ 1.50 kg m -2 h -1 .

10. The application according to claim 8, characterized in that: The iodine-containing wastewater includes nuclear industry wastewater, seawater, dye wastewater or oily wastewater.

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