Method for accurately regulating and controlling pores of MXene material by utilizing phosphonic acid ligand

Abstract

The invention provides a method for accurately regulating and controlling pores of an MXene material by utilizing a phosphonic acid ligand, which mainly comprises the following key steps of: directionally removing a main group element (A) layer of an MAX precursor by wet etching to obtain lamellar MXene, and then introducing a protonated quaternary amine compound intercalator to strip the MXene. And finally, carrying out functional modification and conversion by adopting a phosphonic acid ligand, and stably introducing phosphonic acid groups between layers and on the surface of MXene through solvothermal reaction to realize accurate regulation and control of interlayer spacing. The prepared material can realize efficient adsorption of uranyl in an acidic environment, shows high selectivity, high adsorption capacity and good acid stability and regeneration capacity to uranyl, provides a stable and efficient selective adsorption solution for treating high-acidity uranium-containing nuclear wastewater, and has a remarkable industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the field of material preparation technology, and in particular to a method for precisely controlling the pores of MXene-type materials using phosphonic acid ligands. Background Art

[0002] As a key zero-carbon baseload energy source for achieving the "dual carbon" goals, nuclear energy holds a strategic position in the global energy transition, with its core advantages of a continuous power supply capacity exceeding 8,000 h / a and a fuel energy density a million times greater than fossil fuels. However, with the development of the nuclear power industry, the acidic, radioactive uranium-containing waste generated by spent fuel reprocessing has become a major environmental safety hazard. The toxic half-life of uranium radioactivity is as long as 4.5 billion years. Current solidification treatment technologies suffer from a sharp drop in adsorption capacity and volume expansion of solid waste under high acidity and the coexistence of complex ions. There is an urgent need to develop new treatment materials that combine efficient selective adsorption with wastewater volume reduction.

[0003] Emerging two-dimensional layered transition metal carbide MXene (typically represented by Ti3C2T x ) is considered to be a promising uranium adsorbent due to its unique mechanical strength, designable surface chemistry (rich -O / -OH functional groups) and controllable interlayer channels. Its theoretical advantage shows that the ultra-high adsorption capacity is derived from the interaction between Ti active sites and UO2 2+ The strong coordination effect of MXene and the engineered interlayer confinement give it size selectivity. However, the current industrial application of MXene materials is still limited by their chemical stability. In strong acid environments, surface groups can fall off and cause the layers to dissolve. In addition, in real-world conditions, the actual uranium capture rate is significantly reduced due to competitive adsorption of coexisting cations, severely limiting their engineering potential.

[0004] However, existing MXene material modification technologies remain unable to overcome the triple-coupled dilemma of acidic alteration, irradiation degradation, and structural collapse. The root cause lies in the synergistic effect of chemical stability imbalance and dynamic loss of interlayer spacing: in a sustained strong acidic and irradiated environment, proton permeation alteration at the edges of the layers induces oxidative decomposition of surface functional groups, while organic intercalants easily migrate out of the dynamic aqueous phase due to weak van der Waals forces, leading to irreversible contraction of the interlayer channels. This disordered interlayer topology not only loses its spatial screening ability for hydrated uranyl ions, but also preferentially adsorbs competing ions at newly generated defect sites due to continuous structural degradation, causing a sharp drop in the actual capture efficiency of uranyl ions in complex wastewater systems. This becomes a core physicochemical barrier to efficient separation, making it difficult to construct an adsorption system that combines subnanometer screening accuracy with long-term stability.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] In order to solve the above technical problems, the first purpose of the present invention is to provide a method for precisely controlling the pores of MXene materials using phosphonic acid ligands. This method constructs a rigid pillared grid with sub-nanometer precision between MXene layers through organic phosphonic acid ligands, and provides a composite adsorption material that integrates the dual functions of directional control of interlayer spacing and surface coordination activation, breaking through the bottleneck of size screening failure and ligand dissolution caused by interlayer fluctuations in traditional materials.

[0007] The second object of the present invention is to provide a porous MXene material prepared by the above-mentioned method of precisely controlling the pores of MXene materials using phosphonic acid ligands. The material uses precisely controllable interlayer nanochannels to confine and screen hydrated uranyl ions of a specific size. At the same time, the phosphonic acid ligands between the layers and on the surface produce a strong and specific chelation effect on the uranyl ions, which can significantly improve the dynamic retention efficiency and structural stability of uranyl ions.

[0008] The third object of the present invention is to provide a method for precisely controlling the pores of MXene-type materials using phosphonic acid ligands and its application in preparing porous MXene materials.

[0009] The present invention provides a method for precisely controlling the pores of MXene materials using phosphonic acid ligands, comprising the following steps: The steps are as follows: S1. The MAX precursor is placed in an acidic wet etching solution containing HF environment, etched with constant temperature stirring, and then ultrasonically stripped and centrifuged under argon protection to obtain MXene colloid; S2. Adding the MXene colloid to a protonated quaternary ammonium compound intercalant to anchor the electronegative groups on the MXene surface through electrostatic interaction, centrifugally dispersing to obtain a two-dimensional MXene sheet material, and drying; S3. After ball milling, the dried two-dimensional sheet MXene material and the multidentate phosphonic acid ligand intercalation agent are mixed, and then dispersed into a DMF-water mixed solution for intercalation reaction, followed by centrifugal washing and drying to obtain.

[0010] In the present invention, the HF / LiF system selectively removes the Al layer in the MAX phase to generate a MXene colloid with a negatively charged surface; the protonated quaternary amine is inserted into the interlayer through electrostatic interaction, expanding the interlayer spacing and providing space for subsequent anchoring of the phosphonic acid ligand; the multidentate phosphonic acid forms a PO-Ti coordination bond (stronger than the van der Waals force) with the Ti on the MXene surface to construct a rigid pillared structure.

[0011] Furthermore, the protonated quaternary ammonium compound is in liquid form; Furthermore, the protonated quaternary ammonium compound is tetramethylammonium hydroxide; Furthermore, the multidentate phosphonic acid ligand is in solid state; Furthermore, the multidentate phosphonic acid ligand is 1,3,5,7-tetrakis(4-phosphonophenyl)methane and / or 1,3,5,7-tetrakis(4-phosphonophenyl)adamantane.

[0012] Furthermore, the stirring method in S1 is magnetic stirring, the etching temperature is 30°C-60°C, and the etching time is 12h-96h;. Furthermore, the etching temperature is 40° C., and the etching time is 48 h; The acidic wet etching solution is a mixed solution of HCl with a concentration of 5 mol / L-12 mol / L and LiF with a concentration of 1 mol / L-6 mol / L; Furthermore, the acidic wet etching solution is a mixed solution of 9 mol / L HCl and 4 mol / L LiF.

[0013] Furthermore, the ultrasonic stripping method in S1 is to ultrasonically strip for 0.5h-2h in an argon-protected atmosphere; Furthermore, the ultrasound time was 1 h; Furthermore, the centrifugal purification method is to centrifuge at 3000 rpm-12000 rpm for 5 min-30 min, and wash alternately with deionized water and anhydrous ethanol once until the pH is neutral; Furthermore, the centrifugal purification method is to centrifuge at 6000 rpm for 5 minutes.

[0014] By optimizing the etching conditions, the yield of high-purity MXene is guaranteed and structural defects are effectively avoided.

[0015] Furthermore, the MXene colloid in S2 is added with a protonated quaternary ammonium compound intercalant and then magnetically stirred at 20° C. to 30° C. for 12 h to 48 h; Furthermore, the MXene colloid in S2 was added with a protonated quaternary ammonium compound intercalant and then magnetically stirred at 25° C. for 24 h.

[0016] Furthermore, the centrifugal dispersion in S2 is carried out by centrifuging at 3000 rpm to 12000 rpm for 5 min to 30 min, and then washing with deionized water and anhydrous ethanol alternately until the pH value is neutral. Furthermore, the centrifugal dispersion in S2 is carried out by centrifugation at 6000 rpm for 5 minutes.

[0017] Furthermore, the drying temperature in S2 is 45°C-80°C, and the drying time is 12h-24h; Furthermore, the drying temperature in S2 is 60° C. and the drying time is 12 h.

[0018] Furthermore, the MXene in the two-dimensional sheet MXene material in S3 and the phosphorus element in the multidentate phosphonic acid ligand intercalant are mixed in a molar ratio of (0.5-1.5):0.4; Furthermore, the MXene in the two-dimensional sheet MXene material and the phosphorus element in the multidentate phosphonic acid ligand intercalant are mixed at a molar ratio of 1:0.4.

[0019] Furthermore, the MXene in the two-dimensional lamellae MXene material in S3 is ball-milled and mixed with the multidentate phosphonic acid ligand intercalant, and then sealed, and ball-milled at a rotation speed of 600 rpm to 1200 rpm for 12 h to 24 h; Furthermore, the sealing device is an agate jar; Furthermore, after sealing, the mixture was ball milled at a rotation speed of 600 rpm for 12 h.

[0020] Furthermore, DMF and water in S3 are mixed at a volume ratio of (0.5-1.5):2; Furthermore, DMF and water were mixed in a volume ratio of 1:2.

[0021] Furthermore, the ball-milled product is dispersed in a DMF-water mixed solution and reacted at 60° C.-120° C. for 12 h-48 h, wherein the reaction temperature is increased at a rate of 2° C. / min-5° C. / min; Furthermore, the ball-milled product was dispersed in a DMF-water mixed solution and reacted at 110° C. for 24 h, wherein the reaction heating rate was 3° C. / min.

[0022] Furthermore, the centrifugal washing method in S3 is to centrifuge at 3000 rpm-12000 rpm for 5 min-30 min, and then wash alternately with deionized water and anhydrous ethanol once after centrifugation until the pH value is neutral; The product after centrifugation is vacuum dried at 45°C-80°C for 12h-24h.

[0023] Furthermore, the centrifugal washing method in S3 is to centrifuge at 6000 rpm for 5 minutes, and then wash with deionized water and anhydrous ethanol alternately once after centrifugation; Furthermore, the product after centrifugation was vacuum dried at 60° C. for 12 h.

[0024] The present invention also provides a porous MXene material prepared by the above-mentioned method of precisely controlling the pores of MXene-type materials using phosphonic acid ligands.

[0025] The present invention also provides the use of the above-mentioned method of using phosphonic acid ligands to precisely control the pores of MXene-type materials in the preparation of porous MXene materials.

[0026] The embodiments of the present invention have the following technical effects: (1) Tetraphosphonic acid ligands enable precise control of the interlayer spacing of MXene. Organic phosphonic acid forms strong coordination bonds with Ti on the MXene surface through its oxygen end groups, precisely anchoring the interlayer spacing in the sub-nanometer windows of 1.36 nm and 1.48 nm.

[0027] (2) The dual synergistic effects of simultaneous activation in strong acid conditions were achieved to efficiently capture uranyl ions. The nano-confined channels formed by MXene and the chemical adsorption of phosphonic acid ligands to capture uranyl ions resulted in a saturated adsorption capacity of over 180 mg / g and a removal efficiency of 99% under acidic conditions.

[0028] (3) Compared with the existing technology, the present invention achieves a dual synergistic mechanism of nano-confined spatial screening and phosphonate uranyl coordination capture by precisely controlling the interlayer spacing of MXene with organic phosphonic acid ligands. This overcomes the bottlenecks of size screening failure and ligand dissolution caused by interlayer collapse in traditional adsorbents in acidic environments (pH = 1-5), significantly improving the dynamic retention efficiency and structural stability of uranyl ions. This technology provides a functional breakthrough for the highly selective removal of radioactive uranium from nuclear waste liquids, combining sub-nanometer precision control with chemical bonding enhancement, and has significant application prospects in the fields of nuclear environmental protection and resource recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a schematic diagram of the precise regulation of MXene materials by the phosphonic acid ligand of the present invention; Figure 2 1 is a comparison chart of XRD of Example 1, Example 2 and Comparative Example 1 of the present invention; Figure 3 are SEM and EDS images of Example 1 of the present invention; Figure 4 These are the SEM and EDS images of Example 2 of the present invention; Figure 5 These are the SEM and EDS images of Comparative Example 1 of the present invention; Figure 61 is an AFM comparison diagram of Example 1, Example 2 and Comparative Example 1 of the present invention; Figure 7 1 is an XPS comparison chart of Example 1, Example 2 and Comparative Example 1 of the present invention; Figure 8 FTIR comparison chart of Example 1, Example 2 and Comparative Example 1 of the present invention; Figure 9 1 is a comparison chart of uranyl kinetic adsorption of Example 1, Example 2 and Comparative Example 1 of the present invention; Figure 10 1 is a comparison chart of uranyl saturation adsorption of Example 1, Example 2 and Comparative Example 1 of the present invention; Figure 11 The uranyl removal rates of 5 ml of uranyl ion with a uranyl ion concentration of 10 ppm under different pH conditions are shown in Example 1, Example 2 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0032] In a first aspect, some embodiments of the present invention provide a method for precisely controlling the pores of MXene materials using phosphonic acid ligands, comprising the following steps: S1. The MAX precursor is placed in an acidic wet etching solution containing HF environment, etched with constant temperature stirring, and then ultrasonically stripped and centrifuged under argon protection to obtain MXene colloid; S2. Adding the MXene colloid to a protonated quaternary ammonium compound intercalant to anchor the electronegative groups on the MXene surface through electrostatic interaction, centrifugally dispersing to obtain a two-dimensional MXene sheet material, and drying; S3. After ball milling, the dried two-dimensional sheet MXene material and the multidentate phosphonic acid ligand intercalation agent are mixed, and then dispersed into a DMF-water mixed solution for intercalation reaction, followed by centrifugal washing and drying to obtain.

[0033] In some embodiments, the protonated quaternary ammonium compound intercalant is in liquid form; Furthermore, the protonated quaternary ammonium compound intercalant is tetramethylammonium hydroxide; Furthermore, the multidentate phosphonic acid ligand intercalant is in solid state; Furthermore, the multidentate phosphonic acid ligand intercalant is 1,3,5,7-tetrakis(4-phosphonophenyl)methane and / or 1,3,5,7-tetrakis(4-phosphonophenyl)adamantane.

[0034] In some embodiments, the stirring method in S1 is magnetic stirring, the etching temperature is 30° C.-60° C., and the etching time is 12 h-96 h; Furthermore, the etching temperature is 40° C., and the etching time is 48 h; The acidic wet etching solution is a mixed solution of HCl with a concentration of 5 mol / L-12 mol / L and LiF with a concentration of 1 mol / L-6 mol / L; Furthermore, the acidic wet etching solution is a mixed solution of 9 mol / L HCl and 4 mol / L LiF.

[0035] In some embodiments, the ultrasonic stripping in S1 is performed in an argon atmosphere for 0.5 h to 2 h. Furthermore, the ultrasound time was 1 h; In some embodiments, the centrifugal purification method is to centrifuge at 3000 rpm-12000 rpm for 5 min-30 min, and then wash alternately with deionized water and anhydrous ethanol once until the pH is neutral; Furthermore, the centrifugal purification method is to centrifuge at 6000 rpm for 5 minutes.

[0036] In some embodiments, the MXene colloid in S2 is added with a protonated quaternary ammonium compound intercalant and then magnetically stirred at 20° C. to 30° C. for 12 h to 48 h; Furthermore, the MXene colloid in S2 was added with a protonated quaternary ammonium compound intercalant and then magnetically stirred at 25° C. for 24 h.

[0037] In some embodiments, the centrifugal dispersion in S2 is performed by centrifuging at 3000 rpm to 12000 rpm for 5 min to 30 min, followed by washing with deionized water and anhydrous ethanol alternately until the mixture is neutral. Furthermore, the centrifugal dispersion in S2 is carried out by centrifugation at 6000 rpm for 5 minutes.

[0038] In some embodiments, the drying temperature in S2 is 45° C.-80° C., and the drying time is 12 h-24 h; Furthermore, the drying temperature in S2 is 60° C. and the drying time is 12 h.

[0039] In some embodiments, the MXene in the two-dimensional sheet MXene material and the phosphorus element in the multidentate phosphonic acid ligand intercalant are mixed in a molar ratio of (0.5-1.5):0.4; Furthermore, the MXene in the two-dimensional sheet MXene material and the phosphorus element in the multidentate phosphonic acid ligand intercalant are mixed at a molar ratio of 1:0.4.

[0040] In some embodiments, the MXene in the two-dimensional MXene material in S3 is ball-milled and mixed with the phosphonic acid ligand intercalant, and then sealed, and ball-milled at a rotation speed of 600 rpm to 1200 rpm for 12 hours to 24 hours; Furthermore, the sealing device is an agate jar; Furthermore, after sealing, the mixture was ball milled at a rotation speed of 600 rpm for 12 h.

[0041] In some embodiments, DMF and water in S3 are mixed at a volume ratio of (0.5-1.5):2; Furthermore, DMF and water were mixed in a volume ratio of 1:2.

[0042] In some embodiments, the ball-milled product is dispersed in a DMF-water mixed solution and reacted at 60° C.-120° C. for 12 h-48 h, wherein the reaction temperature is increased at a rate of 2° C. / min-5° C. / min. Furthermore, the ball-milled product was dispersed in a DMF-water mixed solution and reacted at 110° C. for 24 h, wherein the reaction heating rate was 3° C. / min.

[0043] In some embodiments, the centrifugal washing in S3 is performed at 3000 rpm to 12000 rpm for 5 min to 30 min, followed by alternating washing with deionized water and anhydrous ethanol until the pH is neutral. The centrifuged product is vacuum dried at 45°C-80°C for 12h-24h; Centrifuge at 6000 rpm for 5 min, then wash alternately with deionized water and anhydrous ethanol until the pH is neutral; Furthermore, the product after centrifugation was vacuum dried at 60° C. for 12 h.

[0044] In a second aspect, some embodiments of the present invention further provide a porous MXene material prepared by the above-mentioned method of precisely controlling the pores of MXene-type materials using phosphonic acid ligands.

[0045] In a third aspect, the present invention also provides the application of the above-mentioned method of using phosphonic acid ligands to precisely control the pores of MXene-type materials in the preparation of porous MXene materials.

[0046] The following is elaborated with reference to specific embodiments: Example 1

[0047] S1. Place the MAX precursor Ti3AlC2 in a mixed solution containing 9 mol / L HCl and 4 mol / L LiF (i.e., a green etching system) and stir in a hydrothermal reactor at 40°C for 48 hours to complete the etching. Ultrasonic exfoliation of MXene (Ti3C2) is performed under argon protection at a power of 300W for 1 hour. Then, centrifuge and purify the product by centrifugation at 6000 rpm for 5 minutes. Wash the product with deionized water and anhydrous ethanol repeatedly until neutral to obtain MXene colloid Ti3C2. S2: Add the MXene colloidal Ti3C2 from S1 to a 1 mol / L solution of a protonated quaternary ammonium compound intercalant in tetramethylammonium hydroxide (TMAOH). Magnetic stirring is performed at 25°C for 24 hours. This electrostatic interaction anchors the electronegative groups on the MXene surface, increasing the interlayer spacing. Centrifuge at 6000 rpm for 5 minutes and wash repeatedly with deionized water and anhydrous ethanol until neutral. The centrifuged MXene product is vacuum dried at 60°C for 12 hours to obtain an exfoliated two-dimensional MXene powder.

[0048] S3. The two-dimensional MXene powder in S2 is sealed in an agate jar with a molar mixing ratio of 1:0.4 with a multidentate phosphonic acid ligand intercalant, 1,3,5,7-tetrakis(4-phosphonophenyl)methane (TPM), and ball milled at 600 rpm for 12 hours. It is then dispersed into a DMF-water mixed solution with a volume ratio of DMF to water of 1:2. The functional modification of the phosphonic acid ligand and precise control of the interlayer spacing are achieved through solvent thermal reaction at a heating rate of 3°C / min and reaction at 110°C for 24 hours. Centrifuge at 6000 rpm for 5 minutes, wash 5 times in a cycle (washing medium: alternating deionized water and anhydrous ethanol), and dry the centrifuged product in a vacuum at 60°C for 12 hours, or the final product: MXene porous material Ti3C2-TPM with directionally regulated MXene by phosphonic acid ligands. The process of preparing Ti3C2-TPM to regulate MXene-type materials in this embodiment is as follows: Figure 1 shown.

[0049] Example 2

[0050] S1. Place the MAX precursor Ti3AlC2 in a mixed solution containing 9 mol / L HCl and 4 mol / L LiF (i.e., a green etching system) and stir in a hydrothermal reactor at 40°C for 48 hours to complete the etching. Ultrasonic exfoliation of MXene (Ti3C2) is performed under argon protection at a power of 300W for 1 hour. Then, centrifuge and purify the product by centrifugation at 6000 rpm for 5 minutes. Wash the product with deionized water and anhydrous ethanol repeatedly until neutral to obtain MXene colloid Ti3C2. S2: Add the MXene colloidal Ti3C2 from S1 to a 1 mol / L solution of a protonated quaternary ammonium compound intercalant in tetramethylammonium hydroxide (TMAOH). Magnetic stirring is performed at 25°C for 24 hours. This electrostatic interaction anchors the electronegative groups on the MXene surface, increasing the interlayer spacing. Centrifuge at 6000 rpm for 5 minutes and wash repeatedly with deionized water and anhydrous ethanol until neutral. The centrifuged MXene product is vacuum dried at 60°C for 12 hours to obtain an exfoliated two-dimensional MXene powder.

[0051] S3. The two-dimensional MXene powder in S2 is sealed in an agate jar with a molar mixing ratio of 1:0.4 with the phosphonic acid ligand intercalant, 1,3,5,7-tetrakis(4-phosphonophenyl)adamantane (TPA), and ball milled at 600 rpm for 12 hours. It is then dispersed into a DMF-water mixed solution with a volume ratio of DMF to water of 1:2. The functional modification of the phosphonic acid ligand and precise control of the interlayer spacing are achieved through solvent thermal reaction at a heating rate of 3°C / min and reaction at 110°C for 24 hours. Centrifuge at 6000 rpm for 5 minutes, wash 5 times in a cycle (washing medium: alternating deionized water and anhydrous ethanol), and dry the centrifuged product in a vacuum at 60°C for 12 hours, or the final product: Ti3C2-TPA, a MXene porous material directional controlled by phosphonic acid ligands. The process of preparing Ti3C2-TPA to regulate MXene materials in this embodiment is as follows: Figure 1 shown.

[0052] Comparative Example 1 The MAX precursor, Ti3AlC2, was placed in a mixed solution of 9 mol / L HCl and 4 mol / L LiF (i.e., a green etching system) and etched in a hydrothermal reactor at 40°C with constant stirring for 48 hours. Under argon protection, ultrasonic exfoliation of the MXene (Ti3C2) was performed at 300W for 1 hour. The product was then centrifuged and purified at 6000 rpm for 5 minutes. The product was then washed alternately with deionized water and anhydrous ethanol until neutral, yielding the MXene colloid Ti3C2.

[0053] Experimental Example 1: Characterization Comparison of Example and Comparative Example a. X-ray diffractometer (XRD) characterization Figure 2 is the XRD comparison diagram of Example 1, Example 2 and Comparative Example 1 in the present invention, as shown in Figure 2 As shown in the figure, it can be seen that the characteristic peak of the Al element disappears, confirming the successful etching of the precursor MAX phase Ti3AlC2. Compared with Comparative Example 1, the (002) crystal plane peak of Examples 1 and 2 of MXene modified with tetraphosphonic acid ligands shifts significantly to the left, and the interlayer spacing is significantly expanded from 1.18nm in Comparative Example 1 (Ti3C2) to 1.36nm in Example 1 (Ti3C2-TPM) and 1.48nm in Example 2 (Ti3C2-TPA). The peak shift phenomenon directly proves the successful embedding of the phosphonic acid ligand.

[0054] b. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) characterization Figure 3 Surface SEM image and corresponding EDS mapping image of phosphonic acid-modified MXene in Example 1 of the present invention. Figure 4 Surface SEM image and corresponding EDS mapping image of phosphonic acid-modified MXene in Example 2 of the present invention. Figure 5 The surface SEM image and corresponding EDS mapping image of phosphonic acid modified MXene in Comparative Example 1 of the present invention are shown. Figures 3 to 5 The nanosheets of the prepared phosphonic acid-modified high-entropy MXene are significantly larger. Elemental analysis reveals the main components of the MXene, Ti and C. The MXene modified with the phosphonic acid intercalant exhibits the element P. SEM analysis reveals no obvious agglomerates, and the phosphonic acid modification exhibits uniformity. This demonstrates the successful embedding of the phosphonic acid ligands in Examples 1 and 2.

[0055] c. Atomic force microscopy (AFM) characterization Figure 6 is an AFM comparison diagram of Example 1, Example 2 and Comparative Example 1 in the present invention, as shown in FIG. Figure 6 As shown, the MXene in Comparative Example 1 is only a single layer, while the MXene in Examples 1 and 2 are both multi-layer MXene materials, and the thickness of the nanosheets is also higher than that of the single-layer MXene in Comparative Example 1. This shows that the prepared MXene material is multi-layered, and the phosphonic acid is anchored between the layers of the MXene to form a stable pillared structure, preventing the MXene from self-stacking and resulting in reduced separation efficiency. This multi-layer structure also makes the prepared phosphonic acid intercalated MXene material thicker.

[0056] d. X-ray photoelectron spectroscopy (XPS) characterization Figure 7This is an XPS comparison chart of Example 1, Example 2 and Comparative Example 1 in the present invention, as shown in FIG. Figure 7 As shown, it can be seen that the MXene prepared in the whole spectrum has no prominent characteristic peak corresponding to the Al atom. The main Ti, C and terminal O peaks in Comparative Example 1 are obvious, while the MXene Examples 1 and 2 modified by phosphonic acid ligands both have obvious P characteristic peaks. It can be seen that the organic phosphonic acid forms a strong coordination bond with the Ti on the MXene surface through the oxygen end group, thereby achieving precise anchoring of the interlayer spacing.

[0057] e. Infrared spectroscopy and Fourier transform spectroscopy (FT-IR) characterization Figure 8 FT-IR comparison chart of Example 1, Example 2 and Comparative Example 1 of the present invention is shown in FIG. Figure 8 As shown in the figure, it can be seen that the MXene prepared in the whole spectrum has the characteristic peaks of -OH and Ti-C. Compared with the comparative example 1, the MXene examples 1 and 2 modified by the phosphonic acid ligands both have obvious P=O stretching vibration characteristic peaks (~1200-1250cm -1 ).

[0058] Experimental Example 2: Performance Test of Examples and Comparative Examples a. Kinetic adsorption experiment Figure 9 This is a comparison chart of the kinetic adsorption experiments of Example 1, Example 2 and Comparative Example 1 of the present invention, with an initial uranyl concentration of 10 ppm and a pH of 4.5; Figure 9 As shown, the removal rates of uranyl in Example 1, Example 2 and Comparative Example 1 all reached 100%. In the short time that the sample was in contact with the uranyl solution, the U(VI) removal rate increased significantly. As time went on, the U(VI) removal rate slowed down until adsorption equilibrium was reached. In the first 100 minutes of adsorption, Example 1 and Example 2 had similar adsorption kinetics and quickly reached adsorption equilibrium within 700 minutes, which was better than Comparative Example 1, which reached adsorption equilibrium at 2800 minutes, and increased the adsorption rate by 4 times. This was due to the dual adsorption effect of the stable nanoconfined channels and phosphonic acid ligand binding sites brought by the pillared structure, which achieved rapid adsorption of uranyl.

[0059] b. Saturated adsorption experiment Figure 10 The saturation adsorption test comparison chart of Example 1, Example 2 and Comparative Example 1 of the present invention is as follows: 5, 10, 25, 50, 100, 250, 500, 750 ppm of uranyl solution with pH = 4.5 were used for saturation adsorption test. The results are as follows: Figure 10 As shown in the figure, the adsorption amount of uranyl in Example 1, Example 2 and Comparative Example 1 increases with the increase of UO2 2+The adsorption capacity increased significantly with increasing initial concentration, but slowed down and ultimately reached saturation at an initial concentration of 250 ppm. It is clear that the saturated adsorption capacities of Examples 1 and 2 were far superior to those of Comparative Example 1 (111 mg / g). This is due to the increased interlayer spacing and the introduction of more uranyl adsorption sites, which increased the saturated adsorption capacities of uranyl in Example 1 (185 mg / g) and Example 2 (196 mg / g).

[0060] c. Uranyl removal experiment at different pH Figure 11 The uranyl removal rates of Example 1, Example 2 and Comparative Example 1 of the present invention under three different pH conditions (pH = 4.5, 1, 1M) with a uranyl ion concentration of 10 ppm in 5 mL. Figure 11 As shown, for Example 1, Example 2, and Comparative Example 1, it can be seen that the three materials have good uranyl removal efficiency under pH = 5. Due to their more stable interlayer structure and more adsorption sites, Examples 1 and 2 can achieve a removal rate of 100% under pH = 5. As the pH decreases, the acidity becomes stronger, and protons and uranyl undergo intense competitive adsorption. At pH = 1, the uranyl removal rate decreases significantly, while Examples 1 and 2 can still maintain a certain removal rate (> 30%), indicating that the materials have high application value in uranyl removal under acidic conditions.

[0061] Based on a systematic analysis of Examples 1 and 2, and Comparative Example 1, the targeted regulation of phosphonic acid ligands achieves precise subnanometer-scale expansion of the MXene interlayer spacing. The characteristic peak of the (002) crystal plane shifts significantly to the left. This expansion effect is verified by closed-loop multi-dimensional characterization. SEM / AFM reveals expanded layered structures, XPS detects characteristic peaks of P2p, and FT-IR reveals P=O coordination vibration peaks, confirming that the phosphonic acid ligands are anchored to the interlayers via coordination bonds. The resulting porous material exhibits excellent performance in uranyl purification: kinetic adsorption: adsorption equilibrium is reached within 700 minutes, a four-fold increase compared to the unmodified material; saturated adsorption capacity: saturated adsorption exceeds 180 mg / g under acidic conditions of pH = 4.5; and universality of acidic conditions: uranium capture rate remains excellent within the acidic range, completely overcoming the acid-sensitivity drawback of traditional adsorbents. The synergistic mechanism stems from the geometric screening of nano-confined channels activated by the functional sites of the phosphonic acid ligands and the chemical chelation of the phosphonic acid ligands, ultimately achieving deep purification of radioactive waste liquid and promoting the evolution of nuclear waste treatment towards intensive technologies.

[0062] Therefore, the core advantage of the present invention lies in achieving sub-nanometer-level precise control of the interlayer spacing of the two-dimensional material MXene through the phosphonic acid ligand intercalation strategy, and simultaneously breaking through the key performance bottleneck in the field of uranium adsorption: on the one hand, the phosphonic acid molecules form a strong coordination anchoring effect between the MXene layers, and the successful stable nano-confined channels confirmed by XRD, whose geometric dimensions precisely match the hydrated uranyl ions, this precise mapping relationship of "ligand structure-interlayer spacing-target size" enables the strategy to be extended to multiple types of ion screening scenarios; on the other hand, PO - / The P=O bidentate chelate site forms a high-binding energy coordination structure with uranyl, synergistically achieving ultrafast adsorption kinetics and ultra-high adsorption capacity through interlayer confinement. This design demonstrates revolutionary advantages in industrial-scale radioactive wastewater treatment—wide pH adaptability, deep purification capabilities, and exceptional cyclic stability. It offers a disruptive solution for nuclear waste management that combines atomic-level precision design with the efficiency of a 10,000-ton-scale project.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for precisely controlling the pores of MXene materials using phosphonic acid ligands, characterized in that: The steps include: S1. The MAX precursor is placed in an acidic wet etching solution containing HF environment, etched with constant temperature stirring, and then ultrasonically stripped and centrifuged under argon protection to obtain MXene colloid; S2. Adding the MXene colloid to a protonated quaternary ammonium compound intercalant to anchor the electronegative groups on the MXene surface through electrostatic interaction, centrifugally dispersing to obtain a two-dimensional MXene sheet material, and drying; S3. After ball milling, the dried two-dimensional sheet MXene material and the multidentate phosphonic acid ligand intercalation agent are mixed, and then dispersed into a DMF-water mixed solution for intercalation reaction, followed by centrifugal washing and drying to obtain.

2. The method for precisely controlling the pores of MXene materials using phosphonic acid ligands according to claim 1, characterized in that: The stirring method in S1 is magnetic stirring, the etching temperature is 30° C.-60° C., and the etching time is 12 h-96 h; The acidic wet etching solution is a mixed solution of HCl with a concentration of 5 mol / L-12 mol / L and LiF with a concentration of 1 mol / L-6 mol / L.

3. The method for precisely controlling the pores of MXene materials using phosphonic acid ligands according to claim 1, characterized in that: The ultrasonic stripping method in S1 is to ultrasonically strip for 0.5h-2h in an argon-protected atmosphere; The centrifugal purification method is to centrifuge at 3000rpm-12000rpm for 5min-30min, and wash alternately with deionized water and anhydrous ethanol once until the pH is neutral.

4. The method for precisely controlling the pores of MXene materials using phosphonic acid ligands according to claim 1, characterized in that: After the protonated quaternary ammonium compound intercalant is added to the MXene colloid in S2, the mixture is magnetically stirred at 20° C.-30° C. for 12 h-48 h.

5. The method for precisely controlling the pores of MXene materials using phosphonic acid ligands according to claim 1, characterized in that: The centrifugal dispersion method in S2 is to centrifuge at 3000 rpm-12000 rpm for 5 min-30 min, and then wash alternately with deionized water and anhydrous ethanol once after centrifugation until the pH value is neutral.

6. The method for precisely controlling the pores of MXene materials using phosphonic acid ligands according to claim 1, characterized in that: The MXene in the two-dimensional sheet MXene material in S3 and the phosphorus element in the multidentate phosphonic acid ligand intercalant are mixed in a molar ratio of (0.5-1.5):0.4; After mixing, seal the mixture in a grinding jar and ball mill at a rotation speed of 600 rpm to 1200 rpm for 12 hours to 24 hours.

7. The method for precisely controlling the pores of MXene materials using phosphonic acid ligands according to claim 1, characterized in that: In the S3, DMF and water are mixed in a volume ratio of (0.5-1.5):2; The ball-milled product is dispersed in a DMF-water mixed solution and reacted at 60° C.-120° C. for 12 h-48 h, wherein the reaction heating rate is 2° C. / min-5° C. / min.

8. The method for precisely controlling the pores of MXene materials using phosphonic acid ligands according to claim 1, characterized in that: The centrifugal washing method in S3 is to centrifuge at 3000 rpm-12000 rpm for 5 min-30 min, and then wash with deionized water and anhydrous ethanol alternately until the pH is neutral; The product after centrifugation is vacuum dried at 45°C-80°C for 12h-24h.

9. A porous MXene material prepared by the method of precisely controlling the pores of MXene-based materials using phosphonic acid ligands as described in any one of claims 1 to 8.

10. Use of the method of any one of claims 1 to 8 for precisely controlling the pores of MXene-based materials using phosphonic acid ligands in the preparation of porous MXene materials.

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