Conjugated microporous polymers based on 4,4'-biphenyldicarboxaldehyde, methods of preparation and applications

Abstract

The application discloses a conjugated microporous polymer based on 4,4'-biphenyl dicarboxaldehyde, a preparation method and application, relates to the technical field of seawater desalination materials and sewage purification materials, and aims to overcome the technical problem of low photo-thermal conversion efficiency of the prior art.The structural formula of the conjugated microporous polymer based on 4,4'-biphenyl dicarboxaldehyde is as follows: the application provides an efficient, stable and low-cost solution for seawater desalination and sewage purification.

Description

Technical Field

[0001] This invention relates to the technical fields of seawater desalination materials and wastewater purification materials. More specifically, this invention relates to a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde, its preparation method, and its applications. Background Technology

[0002] With the global water shortage and pollution problem becoming increasingly prominent, seawater desalination and sewage purification have become key means to alleviate the water crisis. Photothermal-driven interfacial evaporation technology has become a research hotspot in this field due to its green and efficient nature, and its core performance is highly dependent on the comprehensive quality of photothermal materials.

[0003] While some progress has been made in photothermal materials, several technical bottlenecks remain to be addressed: some materials have limited light absorption ranges, making it difficult to fully utilize the full spectrum of solar energy; their photothermal conversion efficiency is low, failing to meet the demands of efficient evaporation; the preparation process often relies on metal catalysts, increasing costs and potentially leading to residual impurities in the products; simultaneously, most materials suffer from insufficient chemical and thermal stability, or have poor pore structure design, inadequate water transport capacity, or poor hydrophilicity, hindering their long-term application in complex water treatment scenarios. Furthermore, some materials are prone to instability under extreme conditions such as high salinity, acidity, and alkali, further limiting their practical industrial application.

[0004] Therefore, it is necessary to design a technical solution that can overcome the above-mentioned defects. Summary of the Invention

[0005] One object of the present invention is to provide a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde, its preparation method and application, providing an efficient, stable and low-cost solution for seawater desalination and wastewater purification.

[0006] To achieve these objectives and other advantages of the present invention, according to one aspect of the present invention, a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde is provided, the structural formula of which is as follows:

[0007] .

[0008] According to another aspect of the present invention, a method for preparing a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde is also provided, comprising: mixing 2,2',6,6'-tetramethyl-4,4'-bipyranide, 4,4'-biphenyldicarboxaldehyde, benzoic anhydride and benzoic acid in a container, flash-freezing in a liquid nitrogen bath, degassing under vacuum and sealing the container, and reacting at 170-190°C for 2-4 days; after the reaction, soaking the blocky monomer in acetone for 20-30 hours, crushing it into powder, washing it sequentially with acetone and tetrahydrofuran, and performing Soxhlet extraction with tetrahydrofuran for 20-30 hours, and finally vacuum drying at 75-85°C for 10-14 hours to obtain a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde.

[0009] Furthermore, the molar ratio of 2,2',6,6'-tetramethyl-4,4'-bipyranide, 4,4'-biphenyldicarboxaldehyde, benzoic anhydride, and benzoic acid is 1:(1.8-2.2):(1.8-2.2):(0.18-0.22).

[0010] According to another aspect of the invention, a gel composite material is also provided, comprising the aforementioned 4,4'-biphenyldicarboxaldehyde-based conjugated microporous polymer and polyvinyl alcohol.

[0011] Furthermore, the mass ratio of the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde to polyvinyl alcohol is (0.015-0.025):1.

[0012] According to another aspect of the invention, the application of 4,4'-biphenyldicarboxaldehyde-based conjugated microporous polymers in the preparation of photothermal conversion materials is also provided.

[0013] According to another aspect of the invention, the application of a conjugated microporous polymer gel composite material based on 4,4'-biphenyldicarboxaldehyde in seawater desalination is also provided.

[0014] According to another aspect of the invention, the application of 4,4'-biphenyldicarboxaldehyde-based conjugated microporous polymers or gel composites in wastewater purification is also provided.

[0015] The present invention has at least the following beneficial effects:

[0016] The conjugated microporous polymer (DP-CMP2) based on 4,4'-biphenyldicarboxaldehyde and its gel composite material (PVA+DP-CMP2) of this application have significant technical advantages. DP-CMP2 has obvious microporous characteristics and a high specific surface area (BET specific surface area of ​​754 m²). 2With a pore size distribution ranging from 0.5 to 2.1 nm, DP-CMP2 exhibits excellent photothermal conversion performance. Under 660 nm laser irradiation, the temperature of DP-CMP2 increased from 29.3 °C to 155.1 °C within 60 seconds. The water evaporation rate of PVA+DP-CMP2 under one sun reached 3.08 kg / m³. −2 h −1 With a solar energy conversion efficiency of up to 90.6%, far exceeding existing organic photothermal materials, DP-CMP2 exhibits extremely high stability. Its thermal stability temperature reaches 400℃, and it is resistant to complex environments such as acids, alkalis, and organic solvents. Even after multiple heating-cooling cycles and water treatment cycles, its structure, morphology, and performance remain stable, and no salt accumulation occurs during seawater desalination. Preparation requires no metal catalyst, keeping costs under control. The gel composite material combines excellent hydrophilicity, low thermal conductivity, and water transport capacity, providing an efficient, stable, and low-cost solution for seawater desalination and wastewater purification.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0018] Figure 1 The solid-state version of DP-CMP2 is shown. 13 C-cross polarized magic angle rotating NMR spectrum and its chemical structure.

[0019] Figure 2 The Fourier transform infrared spectra of (a) the model compound (MC) and its monomer (DP) are shown; (b) the model compound (MC) in CDCl3. 13 C nuclear magnetic resonance spectrum.

[0020] Figure 3 The pore size distribution of DP-CMP2 is shown, indicating that DP-CMP2 mainly exhibits an ultramicropore distribution, which is beneficial for the adsorption and transport of water molecules.

[0021] Figure 4 The powder X-ray diffraction pattern of DP-CMP2 is shown. DP-CMP2 does not show strong diffraction peaks, indicating its amorphous properties.

[0022] Figure 5 Field emission scanning electron microscopy (FE-SEM) images of the DP-CMP2 are shown.

[0023] Figure 6 The thermogravimetric analysis (TGA) spectrum of DP-CMP2 is shown.

[0024] Figure 7 The Fourier transform infrared spectra of DP-CMP2 after immersion in different solvents are shown.

[0025] Figure 8 The water contact angle of the DP-CMP2 is shown.

[0026] Figure 9 The results showed that 20 mg DP-CMP2 was absorbed under a 660 nm laser (100 mW·cm⁻¹). -2 Photothermal images under illumination.

[0027] Figure 10 The model compound (MC) of 20 mg was shown to be effective under a 660 nm laser (100 mW·cm⁻¹). -2 Photothermal images under illumination.

[0028] Figure 11 The photothermal conversion behavior of DP-CMP2 (a) and the model compound (MC) (b) under irradiation with 660 nm lasers of different powers is shown.

[0029] Figure 12 The anti-photobleaching properties of DP-CMP2 (a) and the model compound (MC) (b) are shown in six heat-cooling cycles.

[0030] Figure 13 The following are shown: (a) Fourier transform infrared spectra of DP-CMP2 before and after six heating-cooling cycles; (b) Scanning electron microscope images of DP-CMP2 before and after six heating-cooling cycles; (c) Absorption spectra of DP-CMP2 before and after six heating-cooling cycles.

[0031] Figure 14 Photographs of polyvinyl alcohol (PVA) (a) and PVA+DP-CMP2 (2.0 wt%) (b) are shown; scanning electron microscope images of polyvinyl alcohol (PVA) (c) and PVA+DP-CMP2 (2.0 wt%) (d) are shown.

[0032] Figure 15 A schematic diagram of a solar steam generation device is shown.

[0033] Figure 16 The evaporation performance of PVA+DP-CMP2 (2.0 wt%) in acidic and alkaline aqueous solutions is shown.

[0034] Figure 17 The images show PVA+DP-CMP2 (2.0 wt%) before (a) and after ten evaporation cycles in pure water.

[0035] Figure 18 The curves showing the change in water collection over time for polyvinyl alcohol (PVA) composite gels with different DP-CMP loadings are presented.

[0036] Figure 19The results show that PVA+DP-CMP2 (2.0 wt%) at 100 mW·cm⁻¹ -2 Simulated seawater evaporation curve under sunlight.

[0037] Figure 20 The long-term stability of the evaporation performance of PVA+DP-CMP2 (2.0 wt%) in seawater was demonstrated.

[0038] Figure 21 The images show PVA+DP-CMP2 (2.0 wt%) before (a) and after ten evaporation cycles in seawater (b).

[0039] Figure 22 The evaporation rates of PVA+DP-CMP2 (2.0 wt%) in pure water, 3.5 wt%, 5 wt%, and 10 wt% sodium chloride (NaCl) solutions (AM 1.5G) are shown.

[0040] Figure 23 The x-axis represents energy (eV), and the y-axis represents (Ahν). 2 The Tauc curves of DP-CMP2 and the model compound (MC) are shown (product of absorbance and photon energy). The band gaps of the two compounds are calculated to be 1.42 eV and 1.82 eV, respectively, by linear fitting.

[0041] Figure 24 The x-axis represents time (s) and the y-axis represents transient current (A), recording the transient current response curve of DP-CMP2 under intermittent illumination conditions.

[0042] Figure 25 The horizontal axis represents the real part of the impedance Z' (ohm), and the vertical axis represents the negative imaginary part of the impedance -Z'' (ohm), showing the electrochemical impedance spectroscopy (EIS) of DP-CMP2. Detailed Implementation

[0043] The present invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0044] It should be understood that terms such as "having," "comprising," and "including" used in the embodiments of this application do not exclude the presence or addition of one or more other elements or combinations thereof. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. When an element is referred to as "fixed to" or "set on" another element, it can be directly on the other element or may have an intervening element present. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element through an intervening element. Descriptions involving "first," "second," etc., in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0045] It should be noted that the technical solutions of the various embodiments of this application can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this application.

[0046] This invention provides a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde, the structural formula of which is as follows:

[0047] .

[0048] The core innovation of this application's 4,4'-biphenyldicarboxaldehyde-based conjugated microporous polymer (DP-CMP2) lies in the construction of a fully conjugated framework with 2,2',6,6'-tetramethyl-4,4'-bipyran subunit (TMDP) as the core, vinylidene as the connecting bridge, and aromatic rings as the extension units. This structural design is the fundamental guarantee for its superior performance. TMDP, as the core building block, connects two pyran subunits through racemic carbon-carbon double bonds, forming a highly conjugated π-electron system. Its electron delocalization characteristics endow the polymer with a broad-spectrum light absorption capability of 300-2000 nm, covering the ultraviolet, visible, and near-infrared regions, solving the problem of narrow absorption range in traditional photothermal materials. The vinylidene connecting unit not only extends the conjugated chain length but also enhances the framework stability through the high bond energy of the C=C double bond, avoiding bond breakage under light and acid / alkali environments, while simultaneously promoting rapid electron transfer and strengthening photothermal conversion efficiency. The "microporous feature" of polymers specifically refers to ultramicroporous structures of 0.5-2.1 nm (characterized by NLDFT). This size enables both rapid adsorption and transport of water molecules through capillary action and the ability to pass through 754 nm. 2 The high specific surface area of ​​ / g enhances the interaction between light and matter, improving photon utilization.

[0049] The polymer is a black solid powder, insoluble in common solvents such as water, tetrahydrofuran, dichloromethane, and toluene. Its structure can be verified by multiple characterization methods: solid 13CCP-MAS NMR shows C=C characteristic peaks at 117 ppm and 134 ppm, and FT-IR shows peaks at 1590 cm⁻¹. -1 (C=C stretching vibration) and 1007 cm -1 The presence of a characteristic absorption peak at the (conjugated skeleton vibration) location confirms the successful formation of vinylidene linkages; the absence of obvious diffraction peaks in the PXRD pattern indicates its amorphous structure, which is conducive to the formation of porous structures; TGA testing shows that its thermal stability temperature reaches 400℃, and its structure remains unchanged after immersion in solvents such as 6MHCl, 6MNaOH, and DMF for 3 days, demonstrating its tolerance to extreme environments. These structural features synergistically endow the polymer with advantages such as rapid photothermal response, high conversion efficiency, and long-term cycling stability, far exceeding those of traditional organic photothermal materials.

[0050] The embodiments of this application also provide a method for preparing a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde, comprising: mixing 2,2',6,6'-tetramethyl-4,4'-bipyranide, 4,4'-biphenyldicarboxaldehyde, benzoic anhydride and benzoic acid in a container, flash-freezing in a liquid nitrogen bath, degassing under vacuum and sealing the container, and reacting at 170-190°C for 2-4 days; after the reaction, soaking the blocky monomer in acetone for 20-30 hours, crushing it into powder, washing it sequentially with acetone and tetrahydrofuran, and extracting it with tetrahydrofuran using a Soxhlet extracter for 20-30 hours, and finally vacuum drying it at 75-85°C for 10-14 hours to obtain a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde.

[0051] The core of this preparation method is the directional construction of a conjugated microporous polymer based entirely on 4,4'-biphenyldicarboxaldehyde through a metal-free aldol polycondensation reaction. The parameters for each step have been optimized to balance product yield, purity, and performance. 4,4'-biphenyldicarboxaldehyde undergoes a polycondensation reaction with TMDP to form a DP-CMP2 polymer with specific pore size and specific surface area. The metal-free catalytic system avoids the interference of metal residues on photothermal performance and reduces production costs.

[0052] Liquid nitrogen bath (77K) flash freezing + three vacuum degassing is the core pretreatment method, the purpose of which is to completely remove oxygen and moisture from the system. Oxygen will quench the active intermediates in the conjugated polymerization reaction, and moisture will trigger side reactions that lead to crosslinking disorder. After vacuum degassing, the container is flame-sealed to maintain an inert environment throughout the process and ensure that the polycondensation reaction proceeds in a directional manner.

[0053] The temperature range of 170-190℃ is based on the balance between reaction kinetics and product structure: below 170℃, the aldol polycondensation reaction rate is extremely low, and the monomer conversion rate is less than 50%; above 190℃, TMDP is prone to thermal decomposition and will lead to excessive cross-linking, destroying the microporous structure. 180℃ is the optimal temperature (yield of over 90%). A reaction time of 2-4 days ensures that TMDP and aromatic dicarboxaldehyde fully polycondense to form a complete conjugated skeleton. Shortening the reaction time will lead to insufficient polymer conjugation, while extending the reaction time will not yield significant gains and will also increase energy consumption.

[0054] Soaking in acetone for 20-30 hours softens the blocky polymer formed by the reaction, making it easier to crush and grind later and avoiding mechanical crushing that damages the skeletal structure. Stepwise washing with acetone and tetrahydrofuran can specifically remove unreacted monomers (TMDP, aromatic dicarboxaldehyde) and low molecular weight byproducts. Soxhlet extraction with tetrahydrofuran for 20-30 hours can deeply peel off trace amounts of benzoic anhydride / benzoic acid encapsulated in the ultramicropores, ensuring unobstructed pores. Vacuum drying at 75-85℃ for 10-14 hours can completely remove residual solvents below the polymer thermal decomposition temperature (400℃), obtaining a dry and pure black solid powder.

[0055] In another embodiment, the molar ratio of 2,2',6,6'-tetramethyl-4,4'-bipyranide, 4,4'-biphenyldicarboxaldehyde, benzoic anhydride and benzoic acid is 1:(1.8-2.2):(1.8-2.2):(0.18-0.22).

[0056] The molar ratio range of 4,4'-biphenyldicarboxaldehyde to TMDP is key to achieving polymers with high conjugation and high porosity. The ratio of aromatic dicarboxaldehyde to TMDP (1.8-2.2:1): A slightly excess of aromatic dicarboxaldehyde (4,4'-biphenyldicarboxaldehyde) is crucial to ensure complete reaction of TMDP—TMDP is the core conjugated unit; any residue will cause the polymer's conjugated chains to break, reducing light absorption efficiency. Controlling the excess ratio to 0.8-1.2 times avoids the self-polymerization of excess aromatic dicarboxaldehyde into non-porous byproducts and reduces raw material waste; 1:2 is the optimal ratio.

[0057] The ratio of benzoic anhydride to aromatic dicarboxaldehyde (1.8-2.2:1): Benzoic anhydride has a dual function as both a "polymerization accelerator" and a "dehydrating agent": on the one hand, it activates the aldehyde group of aromatic dicarboxaldehyde, promoting the aldol condensation reaction with TMDP; on the other hand, it reacts with the water generated in the reaction, maintaining the dehydration environment of the system and promoting the forward reaction. Matching its dosage with that of aromatic dicarboxaldehyde ensures a balance between the reaction rate and the degree of condensation, avoiding reaction stagnation due to insufficient dosage or residue in the product due to excessive dosage.

[0058] The ratio of benzoic acid to TMDP (0.18-0.22:1): Benzoic acid acts as a catalyst for aldol polycondensation, activating reaction sites through proton transfer. When the ratio is below 0.18:1, the catalytic efficiency is insufficient, the reaction cycle needs to be extended to more than 5 days, and the conversion rate is still low. When the ratio is above 0.22:1, benzoic acid is difficult to completely remove through post-treatment, and the residual acidic substances will reduce the chemical stability of the polymer and also affect the photothermal conversion efficiency. 0.02:1 (i.e. 1:50) is the optimal catalytic ratio.

[0059] Embodiments of this application also provide gel composite materials comprising the aforementioned 4,4'-biphenyldicarboxaldehyde-based conjugated microporous polymer and polyvinyl alcohol.

[0060] Functional division of components: Polyvinyl alcohol (PVA) with an average molecular weight of 15,000 is selected, possessing good gelling properties, hydrophilicity, and mechanical strength. It can form a continuous three-dimensional porous network through freeze-thaw cycles, providing channels for water molecule transport, while its thermal conductivity is only 0.082 W / m². -1 K -1 This allows for heat localization, reducing the loss of light and heat conduction to water bodies. Based on 4,4'-biphenyldicarboxaldehyde, the conjugated microporous polymer is used as the core photothermal component and is uniformly dispersed in the PVA network. Its broad-spectrum light absorption and efficient photothermal conversion capabilities are the core of the composite material for realizing solar energy utilization.

[0061] Key to the composite process: In-situ co-gel method is employed. First, PVA, glutaraldehyde (crosslinking agent), and deionized water are mixed and ultrasonically dispersed. The mixture is then heated to 100°C and refluxed for 2 hours to form a homogeneous solution. HCl is added to adjust the pH to promote crosslinking. Next, CMP powder is added and ultrasonically dispersed evenly. After gelation for 2 hours, the mixture is frozen in liquid nitrogen at -30°C and thawed 10 times. Finally, it is freeze-dried to obtain the composite material. This process ensures that CMP is uniformly embedded in the PVA framework, preventing detachment during use. Simultaneously, the porous structure of PVA and the ultramicroporous structure of CMP synergistically accelerate water molecule transport.

[0062] Material morphology and properties: The composite material is a black, homogeneous gel. SEM observation shows that CMP particles are uniformly dispersed in the PVA matrix without obvious agglomeration. UV-Vis-NIR spectroscopy shows that its light absorption covers 300-2000nm, which is significantly better than pure PVA (which only absorbs 200-300nm).

[0063] In another embodiment, the mass ratio of the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde to polyvinyl alcohol is (0.015-0.025):1.

[0064] Lower limit of the ratio (0.015:1, i.e., 1.5wt%): The evaporation rate is 2.84 kgm³ at 1.5wt%. -2 h -1 The dosage is still below the practical threshold and needs to be further increased.

[0065] Upper limit of ratio (0.025:1, i.e., 2.5wt%): When the CMP mass ratio is higher than 2.5wt%, excessive CMP will clog the three-dimensional porous network of PVA, increase the resistance to water molecule transport, and lead to a decrease in evaporation rate (e.g., the evaporation rate of DP-CMP2 at 4wt% is only 2.78 kgm³). -2 h -1Meanwhile, excessive CMP can damage the cross-linking structure of PVA, leading to a decrease in the mechanical strength of the composite material and making it prone to breakage during use.

[0066] Optimal ratio: The optimal ratio for DP-CMP2 is 0.02:1 (2wt%, evaporation rate 3.08 kg / m³). -2 h -1 This ensures that DP-CMP2 can achieve a synergistic effect of "sufficient light absorption and smooth water transport" within this range.

[0067] Embodiments of this application also provide the application of conjugated microporous polymers based on 4,4'-biphenyldicarboxaldehyde in the preparation of photothermal conversion materials.

[0068] CMP exhibits strong absorption in the 300-2000 nm range, fully utilizing the ultraviolet (5%), visible (43%), and near-infrared (52%) spectra of solar energy. Its solar energy utilization rate is significantly higher than that of traditional organic materials (which only absorb the visible-near-infrared portion). In a 660 nm laser (100 mW / cm²) wavelength range... -2 Under irradiation, the temperature of DP-CMP2 rose from 29.3℃ to 155.1℃ within 60 seconds, and its photothermal response rate far exceeded that of existing materials.

[0069] CMP has a thermal stability temperature of 400℃ (TGA testing shows that the mass loss is only 5% below 400℃). It can withstand immersion in strong solvents such as 6MHCl, 6MNaOH, DMF, and THF for 3 days without significant changes in structure and performance. After six heating-cooling cycles (with alternating laser switching), the temperature remains constant and there is no obvious photobleaching phenomenon, which solves the problems of easy degradation and short lifespan of traditional organic photothermal materials.

[0070] In summary, the application's protection scope covers all photothermal conversion materials with CMP as the core functional component, including powder (for direct use in photothermal catalysis), thin film (for solar heating), and gel composite materials (for photothermal evaporation). It is applicable to multiple fields such as solar energy utilization, photothermal sterilization, and photothermal catalysis, and has significant practical value, especially in the fields of new energy and environmental protection.

[0071] Embodiments of this application also provide the application of conjugated microporous polymers or gel composites based on 4,4'-biphenyldicarboxaldehyde in seawater desalination. The gel composite material achieved a seawater evaporation rate of 2.98 kg / m³ under one solar irradiation. -2 h-1 is significantly higher than that of traditional reverse osmosis technology (approximately 0.5 kgm). -2 h -1 Na+ in seawater (deep-sea water from Qingdao) evaporates through the interface. + K+, Mg 2+ Ca 2+The plasma is retained in the original solution, and the ion concentration is reduced by four orders of magnitude after purification, fully meeting the WHO drinking water standards (ion concentration <0.01ppm). In high-salt solutions of 3.5-10wt%, the evaporation rate does not decrease significantly, and there is no salt accumulation, solving the problems of salt buildup and clogging in traditional desalination materials. After ten cycles (1 hour each) in actual seawater, the evaporation rate decreases by less than 3%, and the structure remains intact. Its acid and alkali resistance and high-salt resistance can adapt to the complex conditions of marine environments (such as nearshore high-salt and acid- or alkali-polluted seawater). The preparation process does not require precious metals or toxic reagents, and the desalination process does not cause secondary pollution, providing a green and low-cost new solution for seawater desalination.

[0072] Embodiments of this application also provide the application of 4,4'-biphenyldicarboxaldehyde-based conjugated microporous polymers or gel composites in wastewater purification.

[0073] For wastewater containing heavy metal ions, the material converts water into water vapor through photothermal evaporation, while the heavy metal ions are trapped because they cannot volatilize, thus solving the problem of secondary pollution caused by traditional chemical precipitation methods. For wastewater containing organic pollutants, the organic pollutants are trapped in the original liquid during evaporation, achieving complete separation of organic pollutants without the need for additional adsorbents or oxidants. For complex wastewater containing both heavy metal ions and organic pollutants, the material can be used for purification based on the same principle. In summary, this application covers multiple scenarios including industrial wastewater, domestic sewage, and groundwater contaminated with heavy metals, providing an efficient, green, and low-cost technological path for wastewater purification.

[0074] The following is a description of a specific embodiment.

[0075] Terms and definitions:

[0076] Nuclear magnetic resonance (NMR) spectrum: 1 HNMR spectra were determined on a Bruker Avance III-400 NMR spectrometer. Chemical shifts (δ, unit: ppm) were determined using solvent residual protons as the standard. Solid state 13 C-cross polarization magic angle rotation (CP / MAS) NMR measurements were performed on a Bruker Avance III 400WB NMR spectrometer with a magic angle rotation rate of 5 kHz and a cross polarization contact time of 2 ms.

[0077] Solid-state UV-Vis (UV / Vis) spectrum: Solid-state UV-Vis spectra were measured on a Shimadzu U-4100 spectrophotometer in the wavelength range of 200-800 nm.

[0078] Ultraviolet-visible-near-infrared (UV-vis-NIR) spectra: Absorption spectra were monitored using a Lambda 950 UV-visible-near-infrared spectrophotometer. Fourier transform infrared (FTIR) spectra were acquired using a Bruker TENSOR 27 infrared spectrometer.

[0079] Infrared spectroscopy: Infrared spectra were measured using a Nicolet Avatar FT-IR360 infrared spectrometer, with a test range of 500-4000 cm⁻¹. -1 The potassium bromide (KBr) tableting method was used.

[0080] Powder X-ray diffraction (PXRD): Powder X-ray diffraction data were measured on a Panaco Empyrean X-ray diffractometer. The powder sample was placed on a glass substrate. The test range was 2θ = 1.5-45° with a step size of 0.02° and a test temperature of 25°C.

[0081] Thermogravimetric analysis (TGA): Thermogravimetric analysis was performed on a TAQ500 thermogravimetric analyzer under a nitrogen atmosphere at a temperature of 10 °C / min. -1 The heating rate was measured from room temperature to 800°C, and the analysis was performed by measuring the mass loss.

[0082] Nitrogen adsorption-desorption isotherms: Nitrogen adsorption-desorption isotherms were measured at 77 K using a McMurray Adsorption Analyzer ASAP2020. Specific surface area and pore volume were calculated using the Brunol-Emmett-Taylor (BET) method, and pore size distribution was estimated using nonlocal density functional theory (NLDFT).

[0083] Inductively Coupled Plasma Emission Spectrometry (ICP-OES): The concentration of metal ions in purified water was determined using an Agilent 725 inductively coupled plasma emission spectrometer.

[0084] Optical contact angle: The water contact angle of the conjugated microporous polymer material based on 4,4'-biphenyldicarboxaldehyde was tested using a Krüz DSA100 contact angle meter in Germany, with a 5μL water droplet.

[0085] Photothermal performance characterization: The 660nm laser was generated by an LDDVA660 laser, and the temperature response of the sample was measured by a FLIR-ONEEDGEPRO infrared thermal imager.

[0086] Photoelectrochemical testing: All photoelectrochemical tests were performed on a Shanghai Chenhua CHI760E electrochemical workstation using a standard three-electrode system at room temperature. The working electrode was a glassy carbon electrode (GCE) or an indium tin oxide (ITO) electrode, the counter electrode was a platinum wire electrode, and the reference electrode was a saturated calomel electrode (SCE).

[0087] Mott-Schottky analysis: The working electrode was a glassy carbon electrode covered with a polymer film and 5 wt% perfluorosulfonic acid resin (Nafion), the electrolyte was a 0.1 mol·L⁻¹ sodium sulfate (Na₂SO₄) aqueous solution, the test frequencies were 1000 Hz, 1500 Hz and 2000 Hz, and the amplitude was 5 mV.

[0088] Electrochemical impedance spectroscopy (EIS) test: Using potassium ferricyanide / potassium ferrocyanide ([Fe(CN)6]6) at a concentration of 5 mmol·L⁻¹ 3- / 4- 0.1 mol·L -1 The procedure was performed at room temperature in potassium chloride (KCl) solution. A slurry was prepared by mixing 5 mg of DP-CMP2 sample, 225 μL of deionized water, 225 μL of ethanol (EtOH), and 50 μL of N-methylpyrrolidone (NMP) solution containing 1.5 wt% polyvinylidene fluoride (PVDF). 7 μL of this slurry was coated onto a glassy carbon electrode as the working electrode. The applied potential relative to a saturated calomel electrode was converted to a potential relative to a standard hydrogen electrode (NHE) or a reversible hydrogen electrode (RHE) using the following formula:

[0089] E NHE =E SCE +E θ SCE (E θ SCE = 0.242 V) (1)

[0090] E RHE =E SCE +0.0591pH+E θ SCE (E θ SCE = 0.242 V) (2)

[0091] Photocurrent testing: An ITO electrode (1.0 × 1.5 cm²) coated with DP-CMP2 was used as the photoelectrode. Visible light was generated by a 300W xenon lamp (Zhongjiao Jinyuan CEL-HXF300) equipped with an AM1.5G cutoff filter, manually chopping the light. 5 mg of DP-CMP2 was added to 1 mL of ethanol and 10 μL of 5 wt% perfluorosulfonic acid resin (Nafion), and sonicated for 30 min to prepare a slurry. 50 μL of this slurry was coated onto ITO glass and air-dried. The electrolyte was a 0.1 mol·L⁻¹ sodium sulfate (Na₂SO₄) aqueous solution (pH=6.8), bubbled with high-purity nitrogen gas for 30 min at room temperature. Photocurrent testing was conducted at -0.64 V (relative to SCE), with an intermittent irradiation period of 50 s and a total testing time of 800 s. The photocurrent density was determined based on the actual light-receiving area of ​​the photoelectrode (1.0 cm²). 2 Calculate using the following formula:

[0092] Photocurrent density (J) photocurrent density = Measured photocurrent (J) measured photocurrent ) / Actual light-receiving area (S) actual radiation area (3)

[0093] Experimental steps:

[0094] Material:

[0095] 2,6-Dimethyl-4H-pyran-4-one and benzoic anhydride were purchased from Tianjin Xins Biochemical Technology Co., Ltd.; 4,4'-biphenyldicarboxaldehyde was purchased from Shanghai Bid Pharmaceutical Technology Co., Ltd.; glutaraldehyde (50%), benzaldehyde, and benzoic acid were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; polyvinyl alcohol (PVA) with a number average molecular weight of 15,000 and other chemicals were purchased from Sigma-Aldrich. The seawater used for the desalination test was taken from the deep sea off Qingdao and did not require further sterilization. Synthesis of 2,2',6,6'-tetramethyl-4,4'-bipyranide (TMDP):

[0096]

[0097] 2,6-Dimethyl-4H-pyran-4-one (229.6 mg, 1.85 mmol) and Lawson's reagent (374.5 mg, 0.926 mmol) were added to a dry, short-necked ampoule. The gas atmosphere inside the ampoule was purged by a vacuum-nitrogen cycle, and then 30 mL of oxygen-free toluene was added through the short neck using a syringe. The reaction system was heated to 120 °C and refluxed with stirring for 48 h. After the reaction was completed, heating was stopped, and the mixture was cooled to room temperature. The reaction mixture was filtered, and the filter cake was thoroughly washed with dichloromethane (DCM). The filtrates were combined and concentrated using a rotary evaporator. The resulting crude solid product was purified by silica gel column chromatography (eluent: dichloromethane). After drying, the target product TMDP (162 mg, 93.1% yield) was obtained as a yellow solid. 1 H NMR (400 MHz, CDCl3): δ=6.95 (s, 1H), 2.22 (s, 3H); 13 C NMR (100 MHz, CDCl3): δ=201.98, 158.99, 124.63, 19.30 ppm.

[0098] Synthesis of model compounds (MC):

[0099]

[0100] Add 2,2',6,6'-tetramethyl-4,4'-bipyranide (43.26 mg, 0.2 mmol), benzaldehyde (0.2 mL, 2 mmol), benzoic anhydride (45.2 mg, 0.2 mmol), and benzoic acid (2.5 mg, 0.02 mmol) to a 2 mL Pyrex tube. Rapidly freeze the mixture at 77 K (liquid nitrogen bath), perform three vacuum degassing cycles, and then flame seal the Pyrex tube. Heat the sealed tube at 180 °C for 3 days. After cooling to room temperature, separate the residual crude solid product, purify by silica gel column chromatography (eluent: dichloromethane / petroleum ether = 3 / 1), and dry to obtain a dark brown solid target product (80 mg, 70% yield). 1 H NMR (400 MHz, CDCl3): δ=7.60-7.58 (m, 10H), 7.54 (s, 2H), 7.46-7.42 (m, 12H), 7.10 (s, 4H), 6.74 (s, 2H), 6.70 (s, 2H); 13 C NMR (100 MHz, CDCl3): δ=200.78, 154.13, 137.27, 135.01, 130.08, 129.11, 127.71, 124.74, 119.32 ppm.

[0101] Synthesis of the copolymer microporous polymer DP-CMP2:

[0102]

[0103] 2,2',6,6'-Tetramethyl-4,4'-bipyranide (21.63 mg, 0.1 mmol), 4,4'-biphenyldicarboxaldehyde (42 mg, 0.2 mmol), benzoic anhydride (45.2 mg, 0.2 mmol), and benzoic acid (2.5 mg, 0.02 mmol) were added to a 2 mL Pyrex tube. The mixture was rapidly frozen at 77 K (liquid nitrogen bath), and after three vacuum degassing cycles, the Pyrex tube was flame-sealed. The sealed tube was heated at 180 °C for 3 days, cooled to room temperature, and the solid monomer was soaked in acetone solution for 24 h. After removing the liquid, the solid was crushed with a hammer and ground into powder in a mortar. The powder was washed successively with acetone and tetrahydrofuran, followed by Soxhlet extraction with tetrahydrofuran for 24 h, and vacuum dried at 80 °C for 12 h to obtain a black solid powder product with a yield of 90.1%.

[0104] Synthesis of polyvinyl alcohol (PVA) gel:

[0105] Typical synthesis procedure: 1 g polyvinyl alcohol (PVA), 125 μL glutaraldehyde, and 10 mL deionized water are ultrasonically mixed, followed by reflux heating at 100 °C for 2 h (denoted as solution C). 50 μL of 1.2 mol·L⁻¹ phosphate dehydrogenase is added to 10 mL of solution C. -1 The polyvinyl alcohol (PVA) gel was subjected to a hydrochloric acid (HCl) solution for 2 hours. The resulting PVA gel was then immersed in deionized water overnight for purification, followed by freezing with liquid nitrogen, thawing in deionized water at 30°C, and repeating this freeze-thaw cycle 10 times. Finally, the PVA gel was freeze-dried to obtain the final PVA gel.

[0106] Synthesis of PVA+DP-CMP2 composite gel:

[0107] Typical synthesis procedure: 1 g polyvinyl alcohol (PVA), 125 μL glutaraldehyde, and 10 mL deionized water are ultrasonically mixed, followed by reflux heating at 100 °C for 2 h (denoted as solution C). 50 μL of 1.2 mol·L⁻¹ phosphate dehydrogenase is added to 10 mL of solution C. -1 The gelation reaction was carried out for 2 h with hydrochloric acid (HCl) solution and 20 mg (2 wt%) DP-CMP2 powder. The resulting composite gel was immersed in deionized water overnight for purification, then frozen with liquid nitrogen, and then thawed in deionized water at 30 °C. This freeze-thaw cycle was repeated 10 times, and finally freeze-dried to obtain the PVA+DP-CMP2 (2 wt%) composite gel sample.

[0108] Water vapor generation experiment:

[0109] A material approximately 2 mm thick and 10 cm in area 2 A circular sample was placed on polystyrene (PS) foam in a 50 mL beaker. The PS foam was used to isolate the sample from the water, preventing direct heat dissipation from the sample to the water. A paper towel was sandwiched between the sample and the foam to connect the sample to the water reservoir for moisture transfer. Under stable solar irradiation, the sample was irradiated using a solar simulator, and the surface temperature changes were recorded using a Fi400 infrared thermal imager. The evaporation rate was measured under steady-state conditions, and the mass loss of the entire apparatus was recorded using an electronic balance.

[0110] DP-CMP2 / PVA scaling optimization:

[0111] For the PVA+DP-CMP2 composite gel, the optimal mass ratio of DP-CMP2 to PVA is 0.02:1. This optimized ratio accelerates solar vapor generation and reduces the cost of using DP-CMP2. Control samples with DP-CMP2 / PVA mass ratios of 0.015:1, 0.02:1, and 0.04:1 were set up, corresponding to PVA+DP-CMP2 (1.5 wt%), PVA+DP-CMP2 (2 wt%), and PVA+DP-CMP2 (4 wt%), respectively, and their solar vapor generation performance was tested under one solar irradiance. The results showed that the solar evaporation rates for the three samples were approximately 2.84, 3.08, and 2.78 kg·m³, respectively. -2 ·h -1 Therefore, the optimal mass ratio of DP-CMP2 to PVA in PVA+DP-CMP2 is recommended to be 0.02:1.

[0112] Energy consumption estimation for dark-state experiments:

[0113] Design an experiment to estimate the enthalpy of vaporization of a hydrogel: Place pure water and hydrogel samples with the same surface area simultaneously in a sealed container containing a supersaturated potassium carbonate solution, and stabilize the relative humidity inside the container at approximately 45% (room temperature, ambient pressure). Record the mass changes of both samples under dark conditions, and estimate the enthalpy of vaporization of water in the hydrogel using the following formula:

[0114] U in = E equ m h =E 0 m 0

[0115] Where E0 is the enthalpy of vaporization of pure water, and m0 (0.163 kg·m -2 ·h -1 The mass change of pure water (in an anhydrous electrogel evaporator) under dark conditions is m. h This represents the mass change of the hydrogel under the same conditions. Based on a constant input power (U... in ), by comparing with the known theoretical enthalpy of vaporization of liquid water (2450 J·g), -1 By comparison, the equivalent enthalpy of evaporation (E) is calculated. equ ).

[0116] Energy conversion efficiency:

[0117] Solar energy conversion efficiency (η) is calculated using the following formula:

[0118] η = mE equ / P0

[0119] Where m is the net evaporation rate (evaporation rate under one solar irradiation minus the dark evaporation rate), and E equ P0 is the equivalent enthalpy of vaporization of water in the PVA+DP-CMP composite gel, and P0 is the irradiance of one solar power (1 kW·m). -2 ).

[0120] Results and Discussion:

[0121] 4,4'-Bipyranyl (DP) contains two pyranyl heterocyclic rings connected by an exocyclic carbon-carbon double bond at the oxygen atom para position. Its structure exhibits a highly extended π-conjugated system, possessing strong absorption, strong intermolecular interactions, and excellent redox activity. Therefore, DP derivatives are widely used as carrier transport materials in solar cells and organic field-effect transistors. However, porous organic polymers (POPs) containing DP structural units have not yet been prepared and developed. This application presents the first synthesis of a fully conjugated DP-based conjugated microporous polymer with a high specific surface area. The polymer was successfully constructed via an aldol condensation reaction using 2,2',6,6'-tetramethyl-4,4'-bipyranyl (TMDP) and an aromatic dialdehyde as comonomers. This design strategy offers several key advantages: 1) The DP unit possesses excellent light-harvesting capabilities and strong π-π interactions, effectively promoting photon capture in the polymer; 2) The introduction of vinylidene linkages significantly broadens the polymer's light absorption range and enhances skeletal stability; 3) Metal-free catalyst synthesis reduces the production cost of the target polymer; 4) The inherent ultraporous structure and heteroatoms on the pore walls are expected to improve the wettability and water transport capacity of DP-CMP2, thereby promoting efficient water evaporation. Benefiting from these advantages, the rationally designed DP-CMP2 not only exhibits inherent porosity, good wettability, and low thermal conductivity, but also demonstrates broad-spectrum light harvesting, high solar-to-thermal energy conversion efficiency, and excellent stability. Notably, under 660 nm laser irradiation, the temperature of DP-CMP2 can rapidly rise from 29.3 °C to 155.1 °C in just 60 seconds. Furthermore, in an interfacial heating evaporation system, DP-CMP2 achieves a solar thermal-driven water evaporation rate of 3.08 kg·m³ for pure water under one solar irradiation. -2 ·h -1 It has an energy conversion efficiency of up to 90.6% and long-term stability.

[0122] To synthesize DP-based porous polymers, TMDP was first designed and synthesized using an improved method. Subsequently, the synthesis of a model compound (MC) was explored: TMDP and benzaldehyde underwent anal condensation at 180 °C for 72 h in the presence of benzoic anhydride and benzoic acid, yielding a dark brown vinylidene-linked compound with a separation yield of 70%. Replacing benzaldehyde with 4,4'-biphenyldicarboxaldehyde (BPDA) under the same reaction conditions, a fully conjugated DP-based porous polymer could still be synthesized. After reacting at 180 °C for 72 h, the precipitate was washed with acetone and tetrahydrofuran (THF) and dried under vacuum at 80 °C for 24 h to obtain the target product DP-CMP2, a black powder with a yield as high as 90.1%. Tests showed that DP-CMP2 is insoluble in water and typical organic solvents such as tetrahydrofuran, toluene, acetone, chloroform, and methanol.

[0123] The framework structure of DP-CMP2 was determined for the first time using Fourier transform infrared (FT-IR) spectroscopy. Compared to the monomer, the stretching vibration signal at 1693 cm⁻¹ corresponding to the aldehyde group almost completely disappeared in the FT-IR spectrum of DP-CMP2, and the signal at approximately 1590 cm⁻¹ was also significantly reduced. -1 and 1007 cm -1 A new peak appears, attributed to the stretching vibration band of the carbon-carbon double bond, indicating the formation of vinylidene linkages and the high degree of condensation in the polymerization reaction. Simultaneously, through solid-state... 13 C-cross polarized magic angle rotating nuclear magnetic resonance (C-C) 13 CCP-MAS NMR spectroscopy characterized DP-CMP2 at the molecular level, detecting characteristic carbon signals of carbon-carbon double bonds (C=C) in DP-CMP2. Figure 1 Similarly, the Fourier transform infrared spectra of the model compound (MC) and 13 The characteristic signal of carbon-carbon double bonds (C=C) also appeared in the C NMR spectrum. Figure 2 The intrinsic porosity of the novel fully conjugated DP-based CMP2 was evaluated using a nitrogen adsorption-desorption isotherm at 77 K. DP-CMP2 exhibited a type I adsorption-desorption isotherm, indicating its microporous properties. Based on nitrogen adsorption data, the Brunol-Emmett-Taylor (BET) specific surface area of ​​DP-CMP2 was calculated to be 754 m². 2 ·g -1 The total pore volume is 0.30 cm³ when P / P0 = 0.99. 3 ·g -1 Analysis using the Saito-Foley method revealed that the pore size distribution of DP-CMP2 is multi-level, ranging from 0.5 to 2.1 nm. Figure 3 Furthermore, no obvious signal peaks were observed in the powder X-ray diffraction (PXRD) curves of DP-CMP2, indicating the amorphous properties of the novel polymer. Figure 4 Field emission scanning electron microscopy (FE-SEM) images show that the pure solid phase consists of micron-sized spherical particles. Figure 5 ).

[0124] The thermal stability of DP-CMP2 was assessed by thermogravimetric analysis (TGA) under a nitrogen atmosphere. The resulting spectra showed that the polymer exhibited good thermal stability below 400 °C. Figure 6 Furthermore, by immersing polymer samples in N,N-dimethylformamide (DMF), tetrahydrofuran (THF), water, 6 mol·L⁻¹ -1 Sodium hydroxide (NaOH) and 6 mol·L -1 The chemical durability of the sample was investigated by placing it in an aqueous hydrochloric acid (HCl) solution at room temperature for 3 days. Reassuringly, the collected sample after filtration still maintained the original skeleton connectivity. Figure 7 This indicates its excellent chemical stability. Furthermore, contact angle experiments show that DP-CMP2 exhibits good hydrophilicity, demonstrating rapid water penetration (…). Figure 8 ).

[0125] Next, the light-harvesting ability of fully conjugated DP-CMP2 was explored using ultraviolet-visible-near-infrared (UV / Vis-NIR) spectroscopy. Compared with the model compound, DP-CMP2 exhibited a broad absorption band in the solid state, covering the 300-2000 nm range, consistent with its black appearance. Figure 2 a) This effectively promotes sunlight capture. To evaluate the solar-to-thermal energy conversion performance of DP-CMP2, its surface temperature was monitored in real time using an infrared thermal imager. For example... Figure 9 As shown, 20 mg of DP-CMP2 powder at 100 mW·cm -2 Under 660 nm laser irradiation, the surface temperature rapidly rose to approximately 136.1 °C within 3 seconds, and reached 155.1 °C when the irradiation time was extended to 60 seconds; after the laser was removed, the temperature almost returned to its initial state within 10 seconds, indicating a rapid photothermal conversion process. Under the same conditions, the surface temperature of the model compound (MC) was only 96.9 °C. Figure 10 The concentrations of DP-based conjugated microporous polymers (CMP2) were significantly lower than those of DP-CMP2, demonstrating the substantial advantages of DP-based conjugated microporous polymers in photothermal conversion. Furthermore, using 20 mg of sample, the concentrations were significantly lower in the range of 25–125 mW·cm⁻¹. -2 The effect of optical power density on photothermal conversion was evaluated within the range. Figure 11 Clearly, the higher the laser power, the faster the heating rate and the higher the equilibrium temperature. This is especially true when DP-CMP2 is at 125 mW·cm⁻¹. -2 Under irradiation with a 660 nm laser, the temperature immediately rises to nearly 200℃. Figure 11This surpasses previously reported state-of-the-art materials, including organic molecules, linear polymers, crystalline covalent organic frameworks, and metal-organic frameworks. Subsequently, the photothermal cycling stability was investigated through six laser irradiation-shutdown cycles. Figure 12 The results showed that the equilibrium temperature remained constant during the experiment, indicating that DP-CMP2 has excellent resistance to photobleaching. Importantly, the cycled samples still retained their original linkage structure, morphology, and broad absorption bands. Figure 13 ). Figure 13 In the figure, a) is the FT-IR spectrum, showing no significant shift in characteristic peak shape and wavenumber before and after cycling, and stable signals of key functional groups such as carbon-carbon double bonds, indicating that the original framework remains connected after six cycles and the chemical structure has not been damaged by repeated thermal shock; b) is the SEM image, showing complete micron-sized spherical particle morphology before and after cycling, without agglomeration, breakage, or structural collapse, ensuring the integrity of the material's pore structure and providing a stable channel for water transport and light absorption; c) is the absorption spectrum, maintaining a broad absorption range of 300-2500 nm after cycling, with no significant decrease in absorbance, indicating excellent anti-photobleaching performance and no decrease in light-harvesting ability during long-term use. Furthermore, under xenon lamp simulated sunlight irradiation (100 mW·cm⁻¹), [the following data is also presented]. -2 Even at AM 1.5G, the DP-CMP2 still exhibited high-efficiency solar-to-thermal energy conversion performance, with the highest temperature of the DP-CMP2 reaching 118.1℃ after 8 minutes.

[0126] Tauc diagram ( Figure 23 The DP-CMP2 exhibits a bandgap of only 1.42 eV. This narrow bandgap structure enables it to efficiently capture photons in the visible and near-infrared regions, providing a foundation for the large-scale generation of photogenerated carriers. (Transient current density diagram) Figure 24 In the electrochemical impedance spectroscopy (EIS), the material exhibits a fast response and stable amplitude current curve under intermittent illumination, indicating high separation efficiency and low recombination rate of photogenerated electron-hole pairs, as well as excellent carrier mobility. Figure 25 This further reveals its charge transport advantages; the smaller semi-circular diameter corresponds to a lower charge transfer resistance, effectively reducing energy loss during carrier transport and ensuring charge utilization efficiency. The combined effect of these three factors demonstrates that DP-CMP2 excels in light absorption, carrier separation, and charge transport, providing solid support for its efficient applications in photothermal conversion, photoelectrocatalysis, and other fields.

[0127] DP-CMP2 possesses broad-spectrum light harvesting capabilities, excellent solar-to-thermal energy conversion capacity, abundant porosity, and outstanding durability, which inspires us to explore its potential applications in solar steam generation. Therefore, using polyvinyl alcohol (PVA), which has good hydrophilicity and low thermal conductivity, as a supporting framework, a series of DP-CMP2-supported gel networks were constructed through an in-situ co-gelation process. Figure 14 Compared to pure polyvinyl alcohol (PVA), digital photographs show that PVA+DP-CMP2 (2.0 wt%) is pure black, while scanning electron microscopy (SEM) images show that its morphology is similar to that of pure polyvinyl alcohol (PVA). Figure 14 This indicates that DP-CMP2 was effectively loaded into the composite hydrogel. It is well known that the macroporous structure of composite hydrogels effectively promotes water transport, and the localized heat generated by the DP-CMP2 material greatly accelerated water evaporation. Encouragingly, PVA+DP-CMP2 (2.0 wt%) also exhibited excellent light absorption, covering almost the entire solar absorption spectrum. Simultaneously, the thermal conductivity of DP-CMP2 at 25℃ was measured to be 0.082 W·m. -1 ·K -1 This indicates its low thermal conductivity, which is beneficial for heat insulation. Furthermore, by recording simulated sunlight exposure (100 mW•cm²), [further details are needed]. -2 The solar-to-thermal energy conversion performance of PVA+DP-CMP2 was evaluated by measuring the temperature change of AM 1.5G. The results showed that the surface temperature of PVA+DP-CMP2 (2.0 wt%) rapidly reached equilibrium at 54.3℃ within 300 seconds, while the surface temperature of pure polyvinyl alcohol (PVA) was only 30.6℃ under the same experimental conditions.

[0128] Subsequently, in the simulation device ( Figure 15 The study recorded the effects of polyvinyl alcohol (PVA) and PVA+DP-CMP2 (2.0 wt%) under light irradiation (100 mW•cm). -2 Typical moisture mass change curves for PVA+DP-CMP2 (2.0 wt%) were used to evaluate the efficiency of solar-driven moisture evaporation. Based on the slope of the moisture mass change curve over time, the moisture evaporation rate of PVA+DP-CMP2 (2.0 wt%) was calculated to be 3.08 kg•m. -2 •h -1 The concentration was significantly higher than that of pure water (0.47 kg•m³). -2 •h -1 Under the same conditions, the water evaporation rate of pure polyvinyl alcohol (PVA) is only 0.93 kg•m. -2 •h -1This clearly demonstrates the unique role of DP-CMP2 in the composite hydrogel. By comparison, the evaporation rate of PVA+DP-CMP2 (2 wt%) is relatively high among reported molecular-based materials (PU+CR-TPE-T: 1.272 kg•m). -2 •h -1 GDPA-QCN cellulose paper: 1.30 kg•m -2 •h -1 ), organic porous polymer (PU+GS-POP-2: 1.402 kg•m -2 •h -1 ) and covalent organic framework (TBBPE: 2.82 kg•m -2 •h -1 TPAD-COF: 1.42 kg•m -2 •h -1 CGH-50: 3.69 kg•m -2 •h -1 Calculations showed that the solar-driven water evaporation efficiency of PVA+DP-CMP2 (2 wt%) was 90.6%. Encouragingly, the novel evaporation system maintained a high evaporation rate even in strongly acidic and alkaline aqueous solutions, such as... Figure 16 PVA+DP-CMP2 (2.0 wt%) maintained excellent and stable solar-driven water evaporation capacity even after ten cycles. Figure 17 Furthermore, the water evaporation rate of polyvinyl alcohol (PVA) composite gels with different DP-CMP2 loadings was evaluated. The results showed that increasing or decreasing the DP-CMP loading in PVA led to a decrease in the water evaporation rate. Figure 18 This is attributed to the need to balance light absorption and resistance to moisture transport in order to achieve maximum moisture evaporation.

[0129] Next, the practicality of PVA+DP-CMP2 (2.0 wt%) in seawater desalination was further evaluated. When seawater (taken from the Yellow Sea, China) was used as the water source, at 100 mW•cm⁻¹... -2 Under solar irradiation, the water evaporation rate of PVA+DP-CMP2 (2.0 wt%) was 2.98 kg•m. -2 •h -1 ( Figure 19 Similar to pure water, PVA+DP-CMP2 also exhibited excellent long-term durability in actual seawater evaporation. After ten cycles of one-hour operation, its desalination performance remained stable. Figure 20 It is noteworthy that no salt accumulation occurred during the ten cycles of the experiment. Figure 21Furthermore, the water evaporation rate of PVA+DP-CMP2 did not change significantly in salt solutions of different concentrations. Figure 22 ).

[0130] In summary, PVA+DP-CMP2 (2 wt%) exhibits outstanding desalination potential in the field of seawater desalination due to its synergistically optimized structure and performance. The 0.5-2.1 nm ultraporous structure of DP-CMP2 and the three-dimensional porous network of PVA form a synergistic transport channel, enabling rapid water molecule migration through capillary action and efficient retention of Na+ from seawater. + K + Mg 2+ Ca 2 + The composite material, combining isocations with an interfacial photothermal evaporation mechanism, can efficiently separate salt and water. Leveraging a high solar energy conversion efficiency of 90.6% and a seawater evaporation rate of 2.98 kg·m⁻²·h⁻¹, it can rapidly produce fresh water, and the concentration of major ions in the desalinated water can be significantly reduced to below the WHO drinking water standard limits. This composite material maintains a stable evaporation rate in high-salt solutions of 3.5-10 wt%, with no salt accumulation. After ten cycles of use, its performance degradation is less than 3%. Coupled with its resistance to extreme environments such as acids, alkalis, and high salt concentrations, it can be adapted to complex marine conditions, providing a green and efficient technological path for large-scale seawater desalination. It is expected that PVA+DP-CMP2 (2 wt%) will have broad-spectrum purification capabilities in wastewater treatment applications. For wastewater containing heavy metal ions, the material converts water into water vapor through photothermal evaporation, while heavy metal ions, being non-volatile and larger than the material's micropore size, are firmly trapped, avoiding the secondary pollution problems of traditional chemical treatment methods. For wastewater containing organic pollutants, the organic pollutants will be retained in the original liquid during the evaporation process, and the condensate can achieve complete separation of pollutants without the need to add additional adsorbents or oxidants.

[0131] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde, characterized in that, The structural formula of the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde is as follows: 。 2. The method for preparing the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde as described in claim 1, characterized in that, include: 2,2',6,6'-tetramethyl-4,4'-bipyranide, 4,4'-biphenyldicarboxaldehyde, benzoic anhydride and benzoic acid are mixed in a container, flash-frozen in a liquid nitrogen bath, degassed under vacuum and then sealed in the container. The mixture is then reacted at 170-190°C for 2-4 days. After the reaction was completed, the blocky monomer was soaked in acetone for 20-30 hours, crushed into powder, washed with acetone and tetrahydrofuran in sequence, and extracted with tetrahydrofuran by Soxhlet extraction for 20-30 hours. Finally, it was vacuum dried at 75-85℃ for 10-14 hours to obtain a conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde.

3. The preparation method according to claim 2, characterized in that, The molar ratio of 2,2',6,6'-tetramethyl-4,4'-bipyranide, 4,4'-biphenyldicarboxaldehyde, benzoic anhydride and benzoic acid is 1:(1.8-2.2):(1.8-2.2):(0.18-0.22).

4. A gel composite material, characterized in that, It comprises the 4,4'-biphenyldicarboxaldehyde-based conjugated microporous polymer as described in claim 1 and polyvinyl alcohol.

5. The gel composite material as described in claim 4, characterized in that, The mass ratio of the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde to polyvinyl alcohol is (0.015-0.025):

1.

6. The application of the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde as described in claim 1 in the preparation of photothermal conversion materials.

7. The application of the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde as described in claim 1 or the gel composite material as described in claim 4 in seawater desalination.

8. The application of the conjugated microporous polymer based on 4,4'-biphenyldicarboxaldehyde as described in claim 1 or the gel composite material as described in claim 4 in wastewater purification.

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