Covalent organic framework derived hollow spherical carbon superstructures, preparation and applications thereof

Abstract

The application belongs to the field of chromatographic stationary phase materials, and particularly relates to a hollow spherical carbon superstructure derived from a covalent organic framework and preparation and application thereof. The application provides a hollow spherical carbon superstructure derived from a covalent organic framework, which is obtained by taking PCP-CHO as a building unit and undergoing an aldehyde-amine condensation reaction with TAPD-NH2 to obtain spherical particles (COF-S) under solvothermal conditions, and then being self-assembled at an oil-water interface and being heat-treated. 177 Lu and the separation of lanthanide metal ions with similar physical and chemical properties provide a blueprint for further development of materials science, especially in chromatography and ion separation technology.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chromatographic stationary phase materials, and particularly relates to hollow spherical carbon superstructures derived from covalent organic frameworks and preparation and application thereof. BACKGROUND

[0002] Radiopharmaceuticals based on radionuclide labeling are important pillars of molecular imaging and precision medicine, providing innovative methods for tumor diagnosis and treatment, myocardial imaging, and neurodegenerative diseases. Notably, 177 Lu has attracted much attention due to its suitable gamma photon and beta particle emission and low radioactivity toxicity, becoming a key nuclide for clinical targeted radiotherapy and driving the demand for its large-scale production. However, due to the contraction effect of lanthanide elements, Yb 3+ and Lu 3+ have very similar physical and chemical properties, and their mass differs greatly (about 10 4 ~ 10 5 : 1) under actual industrial conditions, which poses a great challenge for effective separation. Although progress has been made in recent years in radiochemical separation methods such as ion exchange chromatography, solvent extraction, and electrochemical techniques, problems such as low separation efficiency, large amount of waste liquid, and low recovery rate still exist, hindering the acquisition of carrier-free 177 Lu(NCA 177 Lu). Extractive chromatography is a promising radiochemical separation technology with great potential due to its simple operation and excellent selectivity. Unfortunately, the current column separation process is limited by the efficacy of the separation material, which is not sufficient to adapt to the actual harsh environment. Therefore, the design and development of new functional column separation materials to improve the efficiency and selectivity of 177 Lu separation are crucial for large-scale production.

[0003] As ideal materials for chromatographic stationary phases, key factors include chemical stability, particle size and shape, and abundant pore structure. Porous carbon materials are known for their high specific surface area, excellent chemical stability, and adjustable surface properties, offering significant advantages over traditional packing materials such as silica gel, alumina, and proteins. Most importantly, coordinating and controlling the size and micro-morphology of the matrix particles is crucial for achieving high separation efficiency. From a morphological perspective, large and uniform spherical particles can enhance the uniformity and flowability of the chromatographic column, reduce the column pressure, and improve the separation efficiency and repeatability. Developing layered porous carbon superstructures with precisely designed characteristics by combining target precursor modules with pyrolytic carbonization is an ideal method for obtaining pure NCA 177 Lu.

[0004] Among various carbon materials, carbon superstructures formed by self-assembly or epitaxial growth of low-dimensional building blocks have attracted much attention due to their multi-scale hierarchical structures and ideal functional properties. One approach is to use superstructures of metal oxides or other low-dimensional materials as self-sacrificial templates. Carbon sources are first attached to the template interface to form a carbon layer, and then the carbon superstructure is prepared by etching off the template. Another more cost-effective strategy is to directly pyrolyze suitable precursors with pre-fabricated upper-layer structures, thereby achieving precise morphology control. For example, polytannic acid (PTA) rods or polyacrylonitrile nanosheets are assembled into one-dimensional ribbon-like or two-dimensional film-like upper-layer structures, which are then converted into carbon materials with similar structures. In addition, spherical structures are well recognized for their classic morphology and play an important role in various research fields, and breakthroughs have been made in the preparation of spherical carbon superstructures using various matrices. However, these reported materials often have limitations such as small size, metal contamination, and weak functional surface, which hinder their widespread application in column separation. Notably, large-sized spherical hollow superstructures with regular and enhanced surface morphology or micro / nano-structured surface have advantages such as close packing and high density of accessible active sites. As column-based materials, they can effectively enhance the interaction between the host and the guest, improve the efficiency of short-distance mass transfer, and show great potential. However, the synthesis of such hollow spherical carbon upper-layer structures with high carbon conversion rate and multi-functionality is still a major challenge, and new breakthroughs and synthesis concepts are urgently needed in this field.

[0005] Covalent organic frameworks (COFs) are a class of highly designable, morphology-controllable crystalline porous organic materials. Although they show strong advantages in many applications, most COFs perform poorly in harsh environments with high acidity or strong radiation. Interestingly, COFs composed of light elements such as C, H, O, and N are a potential high-quality carbon source. Carbon materials derived from COFs have high carbonization efficiency, excellent structural stability, hierarchical pore structure, and tunable functional morphology, which open up new ways for COFs to be used in various challenging environments. Unfortunately, there is currently no report on the synthesis of COF-derived carbon superstructures, especially large-sized hollow spherical structures with enhanced surface morphology. SUMMARY

[0006] To solve the problems of small size, metal contamination, and weak functional surface of existing materials, the present application provides a covalent organic framework-derived hollow spherical carbon superstructure.

[0007] The hollow spherical carbon superstructure derived from covalent organic frameworks is prepared by an aldehyde-amine condensation reaction of PCP-CHO (4,12-diformyl[2.2]paracyclophane) as a building unit and TAPD-NH2 (N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine) as a four-position linker under solvothermal conditions, self-assembly at an oil-water interface, and heat treatment.

[0008] The reaction formula of the aldehyde-amine condensation reaction to obtain the small spherical particles COF-S is as follows:

[0009]

[0010] The preparation method of the hollow spherical carbon superstructure derived from covalent organic frameworks is schematically shown in the following figure: Figure 1 .

[0011] The preparation method of the hollow spherical carbon superstructure derived from covalent organic frameworks comprises the following steps:

[0012] a. Ultrasonic dispersion of PCP-CHO and TAPD-NH2 in a mixed solvent, then addition of acetic acid, heating reaction until the mixture gradually turns into a transparent dissolved black-red solution, then precipitation at 50℃ for 1 hour to obtain COF-S particles;

[0013] b. After the reaction solution is prepared into a large amount of water-in-oil emulsion droplets, it is left overnight; the solid is collected by filtration, washed with DMF and methanol respectively, and vacuum dried overnight to obtain the hollow spherical superstructure COF-HSS;

[0014] c. The COF-HSS is then pyrolyzed in an argon stream at 700-900℃ for 2 hours, cooled to room temperature, treated with a 0.1M HNO3 solution at 70℃ for 12h, then washed with deionized water and methanol for 2-5 times, and vacuum dried overnight to obtain the hollow spherical carbon superstructure derived from covalent organic frameworks COF-CHSS.

[0015] In the preparation method of the hollow spherical carbon superstructure derived from covalent organic frameworks, the mixed solvent in step a is o-dichlorobenzene and n-butanol. The volume ratio of the o-dichlorobenzene, n-butanol and acetic acid is 5:5:2. The concentration of the acetic acid is 4-7M.

[0016] In the preparation method of the hollow spherical carbon superstructure derived from covalent organic frameworks, the heating temperature in step a is 100℃-130℃.

[0017] In the preparation method of the hollow spherical carbon superstructure derived from covalent organic frameworks, the molar ratio of PCP-CHO to TAPD-NH2 in step a is 1:1-1.2:1.

[0018] In the above-mentioned method for preparing hollow spherical carbon superstructures derived from covalent organic frameworks, the vacuum drying temperature in steps b and c is 60–90 °C.

[0019] In the above-mentioned method for preparing hollow spherical carbon superstructures derived from covalent organic frameworks, the pyrolysis described in step c is performed by heating at a rate of 5°C / min starting from 30°C.

[0020] This invention also provides the use of the aforementioned covalent organic framework-derived hollow spherical carbon superstructure in the preparation of chromatographic stationary phase materials. Preferably, the chromatographic stationary phase material is used for Yb 3+ / Lu 3+ Separated active composite materials.

[0021] This invention provides a novel hollow spherical carbonaceous upper structure prepared from COFs. By establishing dynamic interface boundaries within the matrix composite material constrained by the upper structure, Yb is achieved. 3+ / Lu 3+ Highly efficient separation was achieved. Furthermore, the unique mass transfer effect of this superstructure and single-stage primitive particles on target ions during column separation was effectively studied. This included synthesizing hollow spherical ultrafine particles COF-HSS by in-situ assembly of uniform small spherical particles COF-S, followed by direct high-temperature pyrolysis to generate porous carbonaceous spherical superstructures COF-CHSS with unchanged morphology. COF-CHSS possesses a complete upper structure and enhanced surface morphology, as well as unusual micro / nano surface structures, making it an excellent carrier for immobilizing the active molecule "2-ethylhexylphosphonic acid mono-2-ethylhexyl ester" (P507). The above-mentioned method provided by this invention has prepared a series of separation... 177 Lu-potential active composite materials for Yb during column separation 3+ / Lu 3+ It exhibits significant selective retention capability, even at a mass ratio of 10. 5 Highly efficient separation can be achieved even under harsh conditions of 1:1. Compared to small-sized and monolayered pristine spherical particles, larger, more spatially complex superstructured particles exhibit lower column pressure, higher separation efficiency (optimal separation factor up to 106.1), and excellent cycling stability. This performance surpasses that of traditional commercial chromatographic column materials. This invention not only introduces a novel method for constructing carbon superstructures with controllable morphology but also provides a means to obtain NCA... 177 Lu and the separation of lanthanide metal ions with similar physical and chemical properties provide a blueprint, highlighting the potential for further development in materials science, particularly in chromatography and ion separation techniques. Attached Figure Description

[0022] Figure 1(a) Schematic diagram of the synthesis mechanism of COF-HSS and COF-CHSS. (b) SEM images of COF-S, (c) COF-HSS and (d) COF-CHSS. (e) TEM image of COF-CHSS. (f) ADF-STEM and elemental spectrum images of COF-CHSS. (g) EDS spectrum and elemental composition analysis of COF-CHSS.

[0023] Figure 2 Characterization of COF-HSS and COF-CHSS: (a) PXRD pattern; (b) Fourier transform infrared spectrum; (c) Raman spectrum; (d) N2 adsorption-desorption isotherm at 77 K.

[0024] Figure 3 (a) Schematic diagram of the synthesis of COF-CHSS@P507. Characterization of COF-CHSS@P507-25%: (b) EDS spectrum; (c) FT-IR spectrum; (d) TGA curve.

[0025] Figure 4 COF-CHSS@P507-25% respectively for Yb 3+ Or Lu 3+ Adsorption behavior and mechanism: (a) Adsorption kinetics (C0(Yb)=C0(Lu)=20.0mg L) -1 (a) Adsorption isotherm (V = 9.0 mL, m = 4.5 mg, pH = 5); (b) Adsorption isotherm (V = 9.0 mL, m = 4.5 mg, pH = 5, t = 24 h); (c) Effect of HNO3 concentration (C0(Yb) = C0(Lu) = 20.0 mg L). -1 (d) Dynamic column breakthrough (C0(Yb) = C0(Lu) = 100.0 mg L) -1 (e) XPS full spectrum before and after adsorption; (f) XPS high-resolution spectrum of O1s before and after adsorption; (g) P507 and Yb 3+ Or Lu 3+ DFT calculation of the binding energy.

[0026] Figure 5 Separate Yb 3+ / Lu 3+Dynamic elution curves of different materials (inner diameter = 0.3 cm, height = 7.5 cm, mYb = mLulO.0 pg, the gray and white areas represent the eluent as 0.1 M HNO3and 1.5 M HNO3solution, respectively): (a) the effect of different mass of P507 on column separation (h = 7.5 cm); (b) the effect of COF-CHSS@P507-25% packing column eluted with 1.0, 1.5 and 2.0 M HNO3, respectively (h = 7.5 cm); (c) the height of COF-CHSS@P507-25% packing column is 5.0, 7.5 and 10.0 cm, respectively; (d) the effect of carbonization temperature of packing column material (h = 7.5 cm, P507 = 25%); (e) the reuse-recovery cycle of COF-CHSS@P507-25% packing column (h = 7.5 cm); (f) the effect of simulated target solution (Yb 3+ / 177 Lu 3+ = 105 / 1) concentration on COF-CHSS@P507-25% packing column (h = 7.5 cm).

[0027] Figure 6 (a-b) are scanning electron microscope images of COF-CHSS@P507 and CCSM-SiO2, respectively; (c) the particle size and flow rate diagram of different column materials; (d) the effect of different material packing column on the separation of Yb 3+ / Lu 3+ Dynamic elution curves of different materials (inner diameter = 0.3 cm, height = 7.5 cm, mYb = mLulO.0 pg, the gray and white areas represent the eluent as 0.1 M HNO3and 1.5 M HNO3solution, respectively); (e) the effect of different material packing column on the separation of Yb 3+ / Lu 3+ . DETAILED DESCRIPTION

[0028] Example 1 Preparation and characterization of covalent organic framework derived hollow spherical carbon superstructure COF-CHSS

[0029] PCP-CHO (9.9 mg, 0.0375 mmol) and TAPD (8.85 mg, 0.0187 mmol) were placed in a 15 mL pressure tube, followed by the addition of 1,2-dichlorobenzene / n-butanol (1:1 v / v, 2 mL) and sonicated for 10 min to homogeneously disperse. Subsequently, 0.4 mL of 6 M acetic acid was added, and the tube was sealed under a nitrogen purge. The vessel was heated to 120 °C until the mixture gradually turned into a transparent, dissolved black-red solution, and then precipitated at 50 °C for 1 h to obtain COF-S. Then 200 uL of the solution was pipetted and extruded to generate a large amount of water-in-oil emulsion droplets. Next, the product was allowed to stand at room temperature overnight to assemble into spherical supraparticles. The resulting solid was collected by filtration and washed with DMF and methanol, respectively. Finally, it was dried at 80 °C under vacuum overnight to obtain COF-HSS powder. 0.5 g of prepared COF-HSS was pyrolyzed at 900 °C for 2 h with a heating rate of 5 °C / min starting from 30 °C. After cooling to room temperature, it was treated with 0.1 M HNO3 solution at 70 °C for 12 h to remove impurities. Then, it was washed with deionized water and methanol several times and dried at 80 °C under vacuum overnight to obtain 0.256 g of final product COF-CHSS (yield: 51.3%). The preparation process is shown in Figure 1 a.

[0030] Figure 1 b, Scanning electron microscope (SEM) images in 1c reveal the unique features of the single-layered raw material COF-S and the upper-layered self-assembled suprastructure product COF-HSS. The monodispersed COF-S particles are uniformly distributed between 500-600 nm, while the upper-layered structure product COF-HSS presents a hollow spherical morphology with a size mainly distributed around 7-10 pm. Impressively, during the conversion of COF-HSS to COF-CHSS, Figure 1 d, not only the macro-scale spherical structure of COF-HSS is well preserved, but also the surface groove morphology formed by the mutual stacking of COF-HSS spheres is clearly visible. In addition, the increase in carbon defects and micropore numbers caused by the N pyrolysis process further enhances the micro-nano structural features of the surface, exposing more active sites that can interact with guest molecules. As shown in Figure 1 e, we used transmission electron microscopy (TEM) to study the details of the hollow structure of COF-CHSS. Its shell is composed of single-layered COF-CS with a total diameter of about 7.8 pm and an inner cavity diameter of about 6.9 pm. Annular dark-field scanning TEM (ADF-STEM) and corresponding energy dispersive spectroscopy (EDS) analysis further confirmed the structure and element distribution of COF-CHSS Figure 1 f and 1g). The carbon content is as high as 96.9%, indicating that COF-HSS has a very high carbon conversion advantage as a carbon source.

[0031] Powder X-ray diffraction (PXRD) patterns confirmed the crystalline nature of COF-HSS Figure 2 a). To reveal its intrinsic microstructure more clearly, the COF-HSS obtained under solvent heating condition B (m-xylene / dioxane) has higher crystallinity compared to condition A (o-dichlorobenzene / n-butanol), which is consistent with the simulated XRD of the two-dimensional AA stacking product. However, under pyrolysis condition, the structure of COF-CHSS was partially destroyed, leading to an increase in amorphous degree. Fourier transform infrared spectroscopy (FT-IR) was used to determine the chemical composition of the imine linkers in COF-HSS and the carbon structure of COF-CHSS Figure 2 b). In addition, Raman spectroscopy also confirmed the successful conversion of carbon materials. As shown in Figure 2 c, two peaks at 1360 and 1605 cm - 1 correspond to the D band and G band, respectively. The D band is derived from the stretching vibration of C-C bonds, corresponding to structural defects in carbon materials; while the G band is derived from the stretching vibration of sp 2 hybrid carbon atoms and π electrons in the material, reflecting the integrity of the material lattice. The ID / IG value of COF-CHSS is about 0.94, indicating that the carbon material has a short-range ordered graphite structure. The BET specific surface area and porosity of COF-HSS are 56 m 2 / g and 0.14 cm 3 / g, respectively. Through thermal carbon conversion Figure 2 d), the stability and specific surface area of the material were significantly improved (up to 729.5 m 2 / g and 0.34 cm 3 / g), while retaining its main morphological characteristics, which positively improved the performance of the material in harsh environments. Compared with the pore size of 2.3 nm in COF-HSS, a large number of additional micropores (0.8-1.5 nm) were observed in the pore size distribution curve of COF-CHSS. This can be attributed to structural defects caused by the pyrolysis of unreacted groups and nitrogen sites, as well as the inherent slit pores of carbon materials. Various characterization methods confirmed that COF-HSS was successfully converted to COF-CHSS while retaining its inherent morphology, and the resulting structural defects and micropores significantly enhanced its internal pore and surface micro-nano structure characteristics. These features are expected to provide a wide range of active sites for functional components.

[0032] Example 2 Preparation and characterization of COF-CHSS@P507 composite materials

[0033] The fine screening and controllable transport of target ions / molecules can be achieved by preparing and reconstituting solid-liquid composites through the introduction of functional liquid into porous matrix. 2-Ethylhexyl phosphonic acid mono 2-ethylhexyl ester (P507) is an active functional molecule with different affinities for lanthanides. COF-CHSS has strong surface structure advantages and adsorption capacity, which can produce closer interaction and adhesion with P507, thereby deriving solid-liquid composites with stronger mechanical integrity and ideal dynamic interfacial behavior.

[0034] In Figure 3 a, a series of COF-CHSS@P507 composites with different P507 contents were prepared by uniformly confining P507 on COF-CHSS in dichloromethane. Specifically, the prepared COF-CHSS was placed in a 50 mL round-bottom flask, and a dichloromethane solution containing different amounts of P507 was added. After ultrasonic treatment for 30 min and stirring at room temperature for 3 h, the obtained powder was dried at 80°C overnight after removing dichloromethane to obtain COF-CHSS@P507-n with different P507 mass fractions (n = 15%, 25%, and 35%).

[0035] The grooves and micropore features on the surface of COF-CHSS microspheres can serve as firm anchors to accommodate P507, preventing liquid from falling off. Taking COF-CHSS@P507-25% with 25wt% P507 content as an example, various characterization results show that P507 can be well loaded on COF-CHSS.

[0036] SEM and mapping images Figure 3 b) show that P507 is uniformly distributed on the surface and surface pores of the microspheres. In addition, the large particle size and uniform self-supporting morphology of COF-CHSS not only avoid high column pressure in the dynamic separation process, but also provide clear internal space for guest molecules to move, improving their theoretical plate number. Fourier transform infrared spectroscopy of COF-CHSS@P507-25% shows several characteristic peaks: C-H stretching vibration at 2860-2960 cm -1 , P=O stretching vibration at 1195 cm -1 , P-OH bending vibration at 1035 cm -1 , P-O-C stretching vibration at 973 cm -1 ( Figure 3 c). From the thermogravimetric analysis (TGA) curve Figure 3 ​d) It can be seen that COF-CHSS exhibits no mass loss at temperatures up to 900℃, indicating its excellent thermal stability. In contrast, COF-CHSS@P507-25% shows a significant weight loss before 500℃, which is attributed to the thermal degradation of the small molecule P507. The actual mass loss is approximately 27%, consistent with the theoretical value (25%).

[0037] Example 3: Separation of Yb from COF-CHSS@P507 composite material 3+ / Lu 3+ Conditional screening experiment

[0038] 1) Static separation experiment

[0039] Static adsorption experiment procedure: Mix 4.5 mg of adsorbent (COF-CHSS@P507-25% composite material) with 9.0 mL of Yb 3+ Or Lu 3+ Aqueous solutions of different initial ion or acid concentrations were mixed and then shaken at 150 rpm for a specific time. All samples were then filtered through a 0.22 μm nylon membrane filter. Finally, the Yb content in the filtrate was determined by ICP-OES. 3+ Or Lu 3+ The concentration.

[0040] Static batch adsorption experiments on individual Yb or Lu showed that the COF-CHSS@P507 composite material has the ability to separate Yb. 3+ / Lu 3 + The potential. For example... Figure 4 As shown in Figure a, under the conditions of initial concentration C0 = 20 ppm and pH = 5, COF-CHSS@P507-25% rapidly captured Yb within the first 2 hours. 3+ Or Lu 3+ It reaches adsorption equilibrium within 10 hours. Figure 4 The adsorption thermodynamics experiments of b also clearly demonstrate the adsorption selectivity of this material; COF-CHSS@P507-25% obviously has a stronger binding affinity for Lu. For example... Figure 4 As shown in c, the adsorption capacity of COF-CHSS@P507-25% for the two lanthanides decreases with increasing solution acidity, indicating that highly acidic solutions can be used as potential eluents. Using Yb 3+ / Lu 3+ Column breakthrough experiments using mixed feed solutions provided more practical insights into ion competition and interactions, demonstrating the competitive adsorption behavior of COF-CHSS@P507-25% for Yb and Lu under real-world conditions. Figure 4 As shown in d, when using Yb with C0 = 100 ppm and pH = 5...3+ / Lu 3+ In column breakthrough experiments using the mixed feed solution, excellent purification was observed in the first 40 mL of feed. However, in subsequent breakthroughs, Lu... 3+ With Yb 3+ The separation difference is small, Lu 3+ Only in Yb 3+ Then it flows out slightly until adsorption equilibrium is reached.

[0041] Further exploration of COF-CHSS@P507 separation of Yb 3+ / Lu 3+ To investigate the mechanism, researchers performed X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analyses. Compared to the full XPS spectrum of COF-CHSS@P507-25%, the materials after adsorption of Yb or Lu exhibited corresponding characteristic peaks. Figure 4 e). High-resolution spectra of O 1s and P 2p also showed significant differences ( Figure 4 f). Due to the inherent carbon matrix, all XPS spectra were peak-corrected using unsaturated carbon (284.1 eV). The high-resolution O1s XPS spectra of COF-CHSS@P507 show two distinct characteristic peaks at 532.34 eV and 530.72 eV, corresponding to PO / CO and P=O / C=O, respectively. Adsorption of Yb 3+ Or Lu 3+ Subsequently, the characteristic peaks of O 1s and P 2p both shifted to lower binding energies, indicating that the phosphoroyl group is the main factor in the adsorption of metal ions. Furthermore, to reveal the intrinsic driving force behind the adsorption capacity, DFT calculations were performed on the adsorption of P507 and Yb. 3+ / Lu 3+ The adsorption binding energy. For example... Figure 4 As shown in g, the molecular distance between P507 and Lu(NO3)3 is compared to that of Yb(NO3)3. The closer the binding point, the higher the binding energy, approximately 7.7 kcal / mol, indicating that P507 has a preferential affinity for Lu. Both experimental and theoretical calculations confirm that the prepared COF-CHSS@P507 exhibits a strong affinity for Yb. 3+ / Lu 3+ They exhibit significantly different affinities.

[0042] Although in the static adsorption experiment, COF-CHSS@P507 showed good adsorption performance for Yb 3+ / Lu 3+The selectivity is weak, but the continuous mass transfer process of the dynamic interface can accelerate the interaction between ions and adsorbents, and improve the separation efficiency through repeated adsorption and desorption processes in the chromatographic column separation process. Therefore, we loaded the COF-CHSS@P507 with ideal structure into the chromatographic column to further study the dynamic separation of Yb 3+ / Lu 3+ (1:1 mass ratio).

[0043] 2) Dynamic separation experiment

[0044] Dynamic separation experiment steps: Yb 3+ / Lu 3 + The upper and lower ends of the adsorbent (COF-CHSS@P507 composite material) are filled with glass fibers to prevent glass fiber leakage. The dry adsorbent placed in the column must be gradually filled and continuously tamped. The upper end of the column is connected to the solution reservoir through a silica gel tube, and the lower end is connected to the pump-driven collection device. In order to obtain the best performance of the chromatographic column, the chromatographic column needs to be immersed in dilute nitric acid before the subsequent experiment. The simulated target solution (PH = 5, HNO3) is a mixture of Yb 3+ / Lu 3+ with a mass ratio of 1:1, and the total mass of metal cations is 20.0 μg. The simulated target solution is added to the column through the reservoir, first washed with 5.0 mL of 0.1M HNO3 to ensure that Yb 3+ and Lu 3+ flow into the column. Then elute Yb 3+ and Lu 3+ with 1.0-2.0M HNO3. Collect 1.0 mL of eluent each time, and determine the concentration of Yb 3+ and Lu 3+ by ICP-OES method. The recovery rate (R) and decontamination factor (D.F.) of Lu 3+ are calculated according to the following formula:

[0045]

[0046] where and Q i are the contents of metal ion i in the initial sample and the sample after separation, respectively.

[0047] As shown in Figure 5 a, we first studied the effect of different P507 loadings of COF-CHSS@P507 on the dynamic separation of Yb 3+ / Lu 3+Impact on separation performance. Surprisingly, COF-CHSS@P507 achieved impressively high separation efficiency during column separation. When the loading of P507 was low, Yb... 3+ / Lu 3+ The elution curves showed a small overlap, indicating that P507 enhances the adsorption capacity for metal ions. However, overloading P507 significantly reduced its mass transfer rate, resulting in a broader elution peak and lower separation efficiency. In fact, the tailing effect also led to a decrease in recovery rate (RLu) and detergency factor (DF). Therefore, this study set the P507 loading at 25% to achieve optimal separation efficiency. Figure 5 The separation curve in b shows that the acidity of the eluent has a significant impact on the separation performance. Using 1.0M HNO3 can improve the separation performance of Yb. 3+ and Lu 3+ The detergency factor (DF) reached 169.1, but at the cost of a wider elution peak. 3+ The leaching volume reached 23 mL, and the overall separation efficiency was unsatisfactory. The results showed that 1.5 M HNO3 could significantly reduce the leaching volume to 5 mL while maintaining a high detergency factor (DF) of 106.1. However, under 2.0 M HNO3 conditions, the elution curves severely overlapped, making effective separation impossible.

[0048] 3) The effect of column length on separation efficiency

[0049] Longer columns can provide a higher theoretical plate number and total equilibrium adsorption capacity, thereby improving separation efficiency. Therefore, we selected several column height gradients (5.0 cm, 7.5 cm, and 10.0 cm) to investigate the effect of column length on separation performance.

[0050] like Figure 5 As shown in Figure c, a consistent separation pattern was observed under different column lengths and elution acidities. With increasing column height, Yb... 3+ and Lu 3+ The overlap area of ​​the elution curves gradually decreased, and the detergency factor (DF) increased. However, this also led to a decrease in flow rate and an increase in elution volume. In conclusion, the optimal column height was determined to be 7.5 cm.

[0051] 4) Effect of COF-CHSS prepared at different pyrolysis temperatures on separation performance

[0052] Different carbonization temperatures have a significant impact on separation performance, such as Figure 5 As shown in Figure d, the COF-CHSS elution peak is broader when pyrolyzed at 700℃, increasing the elution volume and separation time cost. However, the COF-CHSS elution at 900℃ achieves better separation results.

[0053] Taking into account the above factors, the optimal separation conditions determined by this invention are as follows: carbonization temperature 900℃, P507 loading 25% (COF-CHSS@P507-25%), column height 7.5cm, and elution with 1.5M HNO3.

[0054] Example 4: Stability of COF-CHSS@P507

[0055] Separation conditions: carbonization temperature 900℃, P507 loading 25% (COF-CHSS@P507-25%), column height 7.5 cm, elution with 1.5 M HNO3. The column exhibited excellent cyclic stability, with the detergency factor (DF) remaining above 80 after three cycles. Figure 5 e and Table 1).

[0056] Table 1 COF-CHSS@P507-25% Packed Column Separation of Yb 3+ / Lu 3+ Reusability test results

[0057] Cycle Volume Lu (mL) Recovery Lu (%)]] Decontamination factor 1 15～20 97.1 106.1 2 16～22 95.5 82.4 3 16～22 94.8 89.4

[0058] In Table 1: mYb = mLu = 10 μg, column height h = 7.5 cm, eluent C HNO3 =1.5M, column diameter =3mm, P507 load capacity =25wt%.

[0059] Example 5: Separation Experiment with Different Amounts

[0060] This invention simulates the composition of an actual target solution and performs tracer experiments related to the actual radioactive nucleus 177Lu. Separation conditions: carbonization temperature 900℃, P507 loading 25% (COF-CHSS@P507-25%), column height 7.5cm, elution with 1.5M HNO3.

[0061] In Yb / 177 Separation experiments were conducted under harsh conditions with a Lu mass ratio of 105:1, involving different total amounts. For example... Figure 5 As shown in f, although the masses differ greatly, Yb 3+ / Lu 3+The elution curves maintained similar retention volumes and peak positions. Even when the Yb content in the simulated target solution was increased from 10 μg to 50 μg, the detergency factor (DF) remained above 20 (Table 2). However, when the Yb content increased to 100 μg, the column capacity decreased significantly, leading to a broadening of the elution curve and ultimately a decrease in resolution. The main reason for the decreased separation efficiency was mass overload, which occurs when the sample concentration is too high relative to the column's ability to retain analytes. Consequently, the stationary phase near the peak bands becomes saturated, resulting in peak tails and reduced column efficiency. Using a larger capacity column can alleviate this problem.

[0062] Table 2. Yb of COF-CHSS@P507-25% packed column for simulated target solution concentration 3+ / 177 Lu 3+ Separation effect

[0063] Yb 3+ Injection amount (pg) Volume Lu (mL) Recovery Lu (%)]] Decontamination factor 10.0 16～25 96.31 35.2 50.0 17～27 93.1 20.8 100.0 13～30 89.2 1.8

[0064] Example 6: Influence of the microstructure and physical properties of carbon superstructures on Yb / Lu separation performance

[0065] This invention selected COF-CS, COF-CHSS, and CCSM-SiO2, which have significant differences in morphology and structure, for comparative research. COF-CS is prepared from original spherical particles (COF-S) through high-temperature pyrolysis, with a smooth surface and a size distribution in the submicron range of 500–600 nm. In contrast, the upper-layer assembled product, COF-CHSS, is a large-sized (7–10 μm) hollow spherical superstructure with a prominent surface morphology, exhibiting obvious grooves and micro / nano structures. Furthermore, CCSM-SiO2 is a commercially available column separation material composed of relatively large (50–80 μm) inorganic spherical silica particles with a smooth surface. Figure 6 (a, 6b). In fact, the host's microstructure (including morphology, size, and surface topology) and flow rate are crucial to chromatographic separation performance because these factors significantly affect the dynamic interactions and partitioning behavior between host and guest molecules.

[0066] Under the same experimental conditions, a series of Yb chromatography experiments were performed using a column of the same height. 3+ / Lu 3+ Separation experiments. For example... Figure 6 As shown in c, the elution flow rates for COF-CS, COF-CHSS, and CCSM-SiO2 were approximately 28 min / mL, 12.5 min / mL, and 1.5 min / mL, respectively. This is in line with expectations, as increasing the size of spherical particles can significantly reduce column pressure, thereby effectively reducing time costs. However, the separation performance of different materials exhibits a diverse trend. Figure 6The data shows that COF-CS and COF-CHSS materials exhibit excellent separation performance, while CCSM-SiO2, with the largest particle size and fastest flow rate, shows superior separation performance for Yb. 3+ / Lu 3+ The separation effect was poor. These experimental results indicate that the microstructure of the material and the flow rate play a crucial role in chromatographic separation. Figure 6 As shown in Figure e, COF-S, due to its small particle size, high mass transfer resistance, smooth surface, and relatively few adsorption sites, results in a large elution volume and relatively poor separation efficiency. On the other hand, CCSM-SiO2, commonly used in industry, cannot achieve complete separation due to its excessively large particles and smooth surface. Furthermore, this reduces the number of effective active sites, and excessively high flow rates lead to insufficient contact time between the solute and the adsorbent. Notably, within a suitable flow rate range, COF-CHSS, with its complex upper structure, exhibits the best separation performance. Its complex micro / nano structure on the surface and its hollow internal structure increase its potential theoretical plate number and provide more active sites. At moderate flow rates, the balance between the host and mobile phases at the dynamic interface is improved, promoting surface turbulence, thereby enhancing mass transfer efficiency and facilitating effective separation. Another key factor contributing to the superior separation performance of COF-CHSS is its hollow internal structure. Compared to a solid structure, it has lower density and higher porosity, thus reducing material and time costs. Furthermore, the hollow pores can absorb or load more functional molecules, allowing the material's interior to participate in the separation process, significantly improving separation efficiency.

[0067] This invention provides a surface-morphology-enhanced hollow spherical carbon superstructure, formed by the self-assembly of basic spherical COF particles at the oil-water interface followed by heat treatment. During pyrolysis, it not only maintains its inherent morphology but also exhibits significantly improved stability and pore structure. The enhanced surface structure allows it to effectively carry the functional molecule P507, and a series of COF-CHSS@P507 composite materials were constructed to obtain NCA 177Lu. The application of COF-CHSS@P507 to Yb... 3+ / Lu 3+ The static adsorption capacity and mechanism of Yb were investigated in depth. Importantly, based on numerous simulated separation experiments and radioactive tracing methods, a dynamic interfacial boundary separation process for the COF-CHSS@P507 column was established. Under a mass ratio of 105:1, a high separation performance with a detergency factor (DF) greater than 20 was achieved, far exceeding that of traditional commercial materials. Furthermore, this invention effectively investigated the separation effect of superstructures and pristine particles on the chromatographic column; the microstructure of the material and the flow rate play a crucial role in dynamic separation. This invention not only emphasizes the Yb 3+ / Lu 3+The efficient separation of other lanthanides and actinides, and the extension of the study of morphology-controllable carbon superstructures provide a powerful framework for understanding the structure-property relationship and pave the way for the development of advanced separation materials.

Claims

1. The application of covalent organic framework-derived hollow spherical carbon superstructures in the preparation of chromatographic stationary phase materials, characterized in that: The chromatographic stationary phase material is used for Yb 3+ / Lu 3+ The isolated active composite material; the hollow spherical carbon superstructure derived from the covalent organic framework is prepared by the following steps: a. 4,12-dicarboxy[2.2]-cycloarane and N,N,N',N'-tetra(4-aminophenyl)-1,4-phenylenediamine were ultrasonically dispersed in a mixed solvent, acetic acid was added, and the mixture was heated until it gradually turned into a transparent, dissolved blackish-red solution. Then, it was precipitated at 50°C for 1 hour to obtain a reaction solution containing COF-S particles. b. After preparing a large number of water-in-oil emulsion droplets from the above reaction solution, let it stand overnight; filter and collect the solid, wash it with DMF and methanol respectively, and then vacuum dry it overnight to obtain hollow spherical superstructure COF-HSS; c. The COF-HSS was then pyrolyzed in an argon gas flow at 700-900℃ for 2 hours, cooled to room temperature, treated with 0.1M HNO3 solution at 70℃ for 12 hours, washed 2-5 times with deionized water and methanol, and vacuum dried overnight to obtain the covalent organic framework-derived hollow spherical carbon superstructure COF-CHSS.

2. The use according to claim 1, characterized in that: The mixed solvent in step a is o-dichlorobenzene and n-butanol; the volume ratio of o-dichlorobenzene, n-butanol and acetic acid is 5:5:2; and the concentration of acetic acid is 4~7M.

3. The use according to claim 1, characterized in that: The heating temperature in step a is 100℃~130℃.

4. The use according to claim 1, characterized in that: The molar ratio of 4,12-dicarboxy[2.2]-cycloarane to N,N,N',N'-tetra(4-aminophenyl)-1,4-phenylenediamine in step a is 1:1 to 1.2:

1.

5. The use according to claim 1, characterized in that: The vacuum drying temperature described in steps b and c is 60~90℃.

6. The use according to claim 1, characterized in that: The pyrolysis described in step c involves heating from 30°C at a heating rate of 5°C / min.

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