Janus-MOF composite material as well as preparation method and application thereof

Abstract

The invention discloses a Janus-MOF composite material as well as a preparation method and application thereof. The material is formed by heterogeneously integrating an adsorption module and a signal module through a lattice orientation growth method, wherein the adsorption module adopts a zirconium-oxygen cluster and a tetrafluoroterephthalic acid ligand to construct a molecular imprinting pore channel to specifically capture PFAS; the signal module comprises a spiropyrane modified ligand and an electrochemically deposited gold nano needle tip array, and the SERS detection limit reaches 0.05 ppt through photoresponse aperture regulation and three-mode (electromagnetic-chemical-mechanical) synergistic enhancement; the shell layer is doped with titanium dioxide quantum dots, PFAS can be degraded under ultraviolet irradiation, and the substrate can be recycled for more than or equal to 5 times. The invention further provides a surface enhanced Raman spectroscopy (SERS) and electrochemical impedance spectroscopy (EIS) dual-mode coupling technology, the cross validation detection error is less than or equal to 15%, the problems that the traditional method is poor in selectivity, low in sensitivity and incapable of in-situ regeneration are solved, and the method is suitable for rapid detection of trace PFAS in complex matrixes such as food, surface (undersurface) water and industrial wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant detection, and more specifically, to a Janus-MOF composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Per- and polyfluoroalkyl substances (PFAS) are a class of widely existing persistent organic pollutants. Their strong carbon-fluorine bonds lead to environmental recalcitrance and pose risks such as carcinogenicity and immunosuppression to human health. The current PFAS detection technologies face the following challenges: Insufficient selectivity of adsorption materials: Traditional metal-organic frameworks (MOFs) such as UiO-66 and MIL-101 rely on electrostatic interactions to adsorb PFAS, but their efficiency significantly decreases in water bodies containing interfering substances such as Cl - , humic acid, etc. The modification of UiO-66 with amino groups for PFAS adsorption is disclosed in the prior art, but it does not involve specific recognition or detection functions, and the measured selectivity coefficient α = 1.2 - 2.5; Low detection sensitivity: Surface-enhanced Raman spectroscopy (SERS) substrates (such as Au / Ag nanoparticles) lack a pre-concentration function, and the detection limit for PFAS is usually higher than 1 ppt. In the prior art, Au NPs@ZIF-8 composite substrates are used to detect PFAS, and the SERS detection limit is 10 ppt, and they cannot be recycled; Non-renewable substrates: Molecularly imprinted MOFs (MIP-MOFs) are prone to template molecule elution or structural collapse in the aqueous phase, and the number of repeated uses ≤ 2 times. In the prior art, MIP-MOFs are proposed for PFAS adsorption, but they have poor water stability, and the adsorption capacity decreases by > 50% after template elution.

[0003] Therefore, how to provide a detection material and method to overcome the defects of the prior art is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the present invention provides a dynamic response type Janus-MOF composite material, a preparation method thereof, and an application in the dual-mode detection and regeneration of per- and polyfluoroalkyl substances (PFAS), solving the problems of poor selectivity, low sensitivity, and inability to regenerate in situ of traditional methods.

[0005] To achieve the above object, the present invention adopts the following technical solutions: First of all, the present invention provides a preparation method of a Janus-MOF composite material, including the following steps: Step 1: Preparation of the adsorption module ZrCl4, H2TFBDC and PFOS template molecules were dissolved in a DMF / acetic acid mixed solvent at a molar ratio of 4:4:0.5, and reacted at 120 ± 5 °C for 20 - 28 h. After centrifugation and washing, it was stirred with a methanol / acetic acid mixture at 60 ± 5 °C for 10 - 15 h to remove PFOS molecules, obtaining MI-MOF; Step 2: Interface modification MI-MOF was dispersed in an aqueous solution of polyethyleneimine with a mass percentage of 1 - 3 wt%, ultrasonicated for 20 - 40 min, and centrifuged to collect, obtaining surface aminated MOF; Step 3: Growth of signal module The surface aminated MOF was immersed in a DMF / methanol mixed solvent containing 0.2 - 0.5 mmol of spiropyran-modified ligand SP-H2BDC and 0.05 - 0.2 mmol of HAuCl4, and reacted at 75 - 85 °C for 10 - 14 h. A 0.05 - 0.2 M ascorbic acid solution was added dropwise, and reduced at 55 - 65 °C for 1 - 3 h to generate gold nanoparticles with a particle size of 10 - 20 nm. Then it was washed with NaOH solution to obtain Janus-MOF composite.

[0006] Preferably, in the DMF / acetic acid mixed solvent in Step 1, the volume ratio of DMF to acetic acid is 9:1; in the methanol / acetic acid mixture, the volume ratio of methanol to acetic acid is 9:1.

[0007] Preferably, in Step 3, the modification rate of the spiropyran-modified ligand SP-H2BDC is 20 - 40%, and its photoisomerization response time ≤ 30 s; in the DMF / methanol mixed solvent, the volume ratio of DMF to methanol is 6 - 8:2 - 4; the dropping rate of the ascorbic acid is 0.5 - 1 mL / min.

[0008] The present invention also provides a Janus-MOF composite prepared by the above technical solution.

[0009] In the Janus-MOF composite, the fluorine-containing ligand (H2TFBDC) of the adsorption module and the molecularly imprinted pore channels can target and capture PFAS, and the spiropyran-modified ligand (SP-H2BDC) of the signal module and the electrochemically deposited Au nanoneedle tip array can achieve light-responsive pore size regulation. Through PEI interface modification, the adsorption module and the signal module are synthesized in stages to form a Janus heterostructure.

[0010] The present invention also provides an application of the Janus-MOF composite prepared by the above technical solution or the Janus-MOF composite in the preparation of a renewable Janus-MOF-based dual-mode PFAS sensor.

[0011] The present invention also provides a method for preparing the renewable Janus-MOF-based dual-mode PFAS sensor, comprising the following steps: Preparing nano-tips by electrochemical deposition: Using the ITO electrode modified with Janus-MOF composite material as the working electrode, in an electrolyte containing 1-2 mM HAuCl4 and 0.1-0.5 M H2SO4, applying a constant potential of -0.1 to -0.3 V (vs. Ag / AgCl), depositing for 20-40 s to form a vertically oriented gold nano-tip array; Doping titanium dioxide: Immersing the material obtained in step (1) into a tetrabutyl titanate ethanol solution with a volume percentage of 0.5-2%, adding ammonia water until the pH = 8-10, and stirring at 50-70 °C for 1-3 h to generate a TiO2 quantum dot-doped Janus-MOF-based dual-mode PFAS sensor. Preferably, in step (1), the tip density of the gold nano-tip array is 50-200 tips / μm 2 , and the adjacent tip spacing is 10-30 nm.

[0012] The present invention also provides a renewable Janus-MOF-based dual-mode PFAS sensor prepared by the method as described in the above technical solution.

[0013] The present invention also provides an application of the renewable Janus-MOF-based dual-mode PFAS sensor prepared by the above method or the renewable Janus-MOF-based dual-mode PFAS sensor in the integrated adsorption-sensing detection of PFAS, comprising the following steps: S1. Contacting the water sample to be tested with the sensor, and the adsorption time is 20-60 min; S2. Irradiating with ultraviolet light with a wavelength of 365 ± 5 nm for 5-10 min to induce the MOF pore size to contract by 0.3-0.7 nm and lock the PFAS molecules; S3. SERS mode: Using a laser with a wavelength of 785 ± 5 nm, a power ≤ 10 mW, and an integration time ≤ 10 s to collect the CF2 characteristic peak in the range of 730-740 cm -1 of PFAS; S4. EIS mode: Testing the electrochemical impedance spectrum in the frequency range of 0.1-10 5 Hz and an amplitude of 5-15 mV, and obtaining the interfacial capacitance change rate through equivalent circuit fitting; S5. Regeneration: After detection, irradiating with ultraviolet light with a wavelength of 254 ± 5 nm for 20-40 min to degrade the adsorbed PFAS molecules.

[0014] Preferably, the laser wavelength for SERS detection is 785 nm, the power is 5 ± 0.5 mW, and the integration time is 5 ± 1 s; the equivalent circuit model for EIS detection is R(QR)(QR), where Q is a constant phase angle element.

[0015] As can be seen from the above technical solutions, compared with the prior art, the present invention discloses a Janus-MOF composite material, its preparation method and application, which have the following beneficial effects: The present invention constructs a Janus heterostructure MOF, integrating separation adsorption and signal conduction functions. Size screening is achieved through molecularly imprinted pores (1.2 ± 0.3 nm), and the selectivity is enhanced by fluorine-fluorine interactions (α > 5); the present invention introduces a spiropyran photo-responsive ligand, and ultraviolet light induces pore size contraction (Δ = 0.5 nm) to lock PFAS and reduce signal fluctuations; in the present invention, SERS-EIS dual-mode cross-validation improves reliability, and in-situ regeneration of the substrate is achieved by combining TiO2 photocatalytic degradation (degradation rate > 95%). The present invention is significantly superior to the existing solutions in terms of technical effects, with the detection limit reduced by 20 times and the number of cycles increased by 5 times, providing a new method for trace PFAS monitoring that is efficient and low-cost. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0017] Figure 1 It is a preparation flow chart. Detailed Embodiments

[0018] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0019] Example 1 Synthesis and Characterization of Janus-MOF: Step 1: Dissolve 0.4 mmol of zirconium chloride (ZrCl4), 0.4 mmol of tetrafluoroterephthalic acid (H2TFBDC), and 0.05 mmol of perfluorooctanesulfonic acid (PFOS) in N,N-dimethylformamide (DMF) / acetic acid (40 mL). Ultrasonically disperse for 15 min until completely dissolved. Transfer the mixed solution to a 100 mL polytetrafluoroethylene autoclave and react at 120 °C for 24 h. After natural cooling, centrifuge (8000 rpm, 10 min), wash three times with DMF and methanol successively, and dry in vacuum at 80 °C for 12 h. Immerse the MOF in a methanol / acetic acid mixed solution (volume ratio 9:1, 50 mL), stir at 60 °C for 12 h, centrifuge, wash, and dry to obtain molecularly imprinted MOF (MI-MOF); Step 2: Disperse MI-MOF in 10 mL of PEI solution, ultrasonicate for 30 min, and collect by centrifugation to obtain surface-aminated MOF; Step 3: Disperse the aminated MOF in a DMF / methanol solution containing 0.3 mmol of spiropyran-modified H2BDC (SP-H2BDC) and 0.1 mmol of chloroauric acid (HAuCl4), react at 80 °C for 12 h, dropwise add ascorbic acid solution (0.1 M, 2 mL), and reduce at 60 °C for 2 h to generate Au NPs (particle size 15 ± 3 nm). Treat with 0.1 M NaOH solution for 5 min to remove surface loose ligands, centrifuge, wash, and dry to obtain Janus-MOF material; Preparation of the sensor: Electrochemical deposition of gold nanopipette arrays: Immerse the Janus-MOF / ITO electrode (a working electrode prepared by immersing the ITO electrode in the Janus-MOF dispersion for 24 h) into the electrolyte, purge with nitrogen to remove oxygen for 10 min, apply a constant potential of -0.2 V, take it out after deposition for 30 s, rinse with ultrapure water, and dry with nitrogen. Scanning electron microscopy shows that the tip length is 50 ± 5 nm and the tip curvature radius is 3 ± 1 nm.

[0020] Example 2 Dual-mode detection performance test Prepare PFOS standard solutions (0.01 ppt, 0.1 ppt, 1 ppt, 10 ppt, 100 ppt, 1 ppb, 10 ppb, 100 ppb, 1 ppm). Take 1 mL of each concentration solution and add it to the Janus-MOF substrate (1 cm × 1 cm), let it stand for adsorption for 30 min, and irradiate with 365 nm ultraviolet light for 5 min to lock PFAS; SERS detection (laser wavelength 785 nm, power 5 mW, integration time 5 s, objective 50×), characteristic peak: 735 cm -1(CF2 stretching vibration), 1230 cm -1 (C-O-C skeletal vibration), LOD is 0.05 ppt; EIS quantitative detection verification: The substrate adsorbed with PFOS was used as the working electrode to test the EIS spectrum. The change rate of the detected EIS capacitance was linearly correlated with the concentration (1 ppt - 1 ppm, R 2 = 0.995).

[0021] Example 3 Cyclic regeneration performance test 1. Immerse the degraded substrate in 10 mL of methanol and ultrasonically wash for 30 min to elute the residual PFAS. Perform quantitative analysis by HPLC-MS. After detection, irradiate with ultraviolet light (254 nm) for 30 min. HPLC-MS shows that the degradation rate of PFOS > 95%.

[0022] 2. Repeat the "adsorption-detection-degradation" cycle 5 times for the same substrate. After each cycle, test the SERS signal intensity (735 cm -1 peak) and the change rate of the EIS capacitance. After the 5th cycle, the attenuation rate of the SERS signal is 92.5% of the initial value, and the EIS linearity R 2 > 0.99.

[0023] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same and similar parts among the embodiments, reference can be made to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple. For the relevant parts, reference can be made to the description in the method part.

[0024] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a Janus-MOF composite material, characterized in that, It includes the following steps: Step 1: Preparation of the adsorption module ZrCl4, H2TFBDC and PFOS template molecules are dissolved in a DMF / acetic acid mixed solvent at a molar ratio of 4:4:0.5, and reacted at 120 ± 5 °C for 20 - 28 h. After centrifugation and washing, it is stirred with a methanol / acetic acid mixed solution at 60 ± 5 °C for 10 - 15 h to remove PFOS molecules, obtaining MI-MOF. Step 2: Interface modification MI-MOF is dispersed in an aqueous solution of polyethyleneimine with a mass fraction of 1 - 3 wt%, ultrasonicated for 20 - 40 min, and collected by centrifugation to obtain surface-aminated MOF. Step 3: Growth of the signal module The surface-aminated MOF is immersed in a DMF / methanol mixed solvent containing 0.2 - 0.5 mmol of the spiropyran-modified ligand SP-H2BDC and 0.05 - 0.2 mmol of HAuCl4, and reacted at 75 - 85 °C for 10 - 14 h. A 0.05 - 0.2 M ascorbic acid solution is added dropwise and reduced at 55 - 65 °C for 1 - 3 h to generate gold nanoparticles with a particle size of 10 - 20 nm. Then it is washed with a NaOH solution to obtain the Janus-MOF composite material.

2. The preparation method of a Janus-MOF composite material according to claim 1, characterized in that, In the DMF / acetic acid mixed solvent in Step 1, the volume ratio of DMF to acetic acid is 9:1; in the methanol / acetic acid mixed solution, the volume ratio of methanol to acetic acid is 9:

1.

3. The preparation method of a Janus-MOF composite material according to claim 1, characterized in that, In Step 3, the modification rate of the spiropyran-modified ligand SP-H2BDC is 20 - 40%, and its photoisomerization response time ≤ 30 s; in the DMF / methanol mixed solvent, the volume ratio of DMF to methanol is 6 - 8:2 - 4; the dropping rate of the ascorbic acid is 0.5 - 1 mL / min.

4. A Janus-MOF composite material prepared by the method according to any one of claims 1 - 3.

5. Use of the Janus-MOF composite material prepared by the method according to any one of claims 1 - 3 or the Janus-MOF composite material according to claim 4 in the preparation of a renewable Janus-MOF-based dual-mode PFAS sensor.

6. A method for preparing the renewable Janus-MOF-based dual-mode PFAS sensor according to claim 5, characterized in that, It includes the following steps: Electrochemical deposition to prepare nano-tips: Using the ITO electrode modified with the Janus-MOF composite material as the working electrode, in an electrolyte containing 1 - 2 mM HAuCl4 and 0.1 - 0.5 M H2SO4, a constant potential of -0.1 to -0.3 V (vs. Ag / AgCl) is applied and deposited for 20 - 40 s to form a vertically oriented gold nano-tip array. Titanium dioxide doping: The material obtained in step (1) is immersed in a tetrabutyl titanate ethanol solution with a volume percentage of 0.5 - 2%, ammonia water is added dropwise until pH = 8 - 10, and stirred at 50 - 70 °C for 1 - 3 h to generate a TiO2 quantum dot-doped Janus-MOF-based dual-mode PFAS sensor.

7. The preparation method of the renewable Janus-MOF-based dual-mode PFAS sensor according to claim 6, wherein The tip density of the gold nano-tip array described in step (1) is 50 - 200 tips / μm 2 , and the adjacent tip spacing is 10 - 30 nm.

8. A renewable Janus-MOF-based dual-mode PFAS sensor prepared by the method according to any one of claims 6 - 7.

9. Use of a renewable Janus-MOF-based dual-mode PFAS sensor prepared by the method according to any one of claims 6-7 or the renewable Janus-MOF-based dual-mode PFAS sensor according to claim 8 in the integrated adsorption-sensing detection of PFAS, characterized in that, It includes the following steps: S1. Contact the water sample to be measured with the sensor, and the adsorption time is 20 - 60 min; S2. Irradiate with ultraviolet light with a wavelength of 365 ± 5 nm for 5 - 10 min to induce the pore size of the MOF to contract by 0.3 - 0.7 nm and lock PFAS molecules; S3. SERS mode: Use a 785 ± 5 nm laser with a power ≤ 10 mW and an integration time ≤ 10 s to collect the characteristic peak of CF2 in the range of 730 - 740 cm -1 of PFAS; S4. EIS mode: Electrochemical impedance spectroscopy was tested in the frequency range of 0.1 - 10 5 Hz and amplitude of 5 - 15 mV, and the change rate of interfacial capacitance was obtained by equivalent circuit fitting; S5. Regeneration: After detection, irradiate with ultraviolet light with a wavelength of 254 ± 5 nm for 20 - 40 min to degrade the adsorbed PFAS molecules.

10. The application according to claim 9, wherein The laser wavelength for the SERS detection is 785 nm, the power is 5 ± 0.5 mW, and the integration time is 5 ± 1 s; the equivalent circuit model for the EIS detection is R(QR)(QR), where Q is a constant phase angle element.

Images