CN111621027B

CN111621027B - Preparation method and application of cationic porous material

Info

Publication number: CN111621027B
Application number: CN202010354583.3A
Authority: CN
Inventors: 郑盛润
Original assignee: South China Normal University
Current assignee: South China Normal University
Priority date: 2020-04-29
Filing date: 2020-04-29
Publication date: 2022-04-19
Anticipated expiration: 2040-04-29
Also published as: CN111621027A

Abstract

The invention belongs to the field of metal-organic frameworks, and particularly relates to a preparation method of a cationic porous material, which comprises the following steps: s1, preparing aMOC-1; s2, preparing CL-aMOC-1: s21, mixing aMOC-1 and BAPB obtained in the step S1 according to the mass ratio of (2-3) to 1, and then grinding for 25-40 min; and S22, washing the mixture ground in the step S21 by using an organic solvent, and drying to obtain the catalyst. Pd-based catalyst constructed by solid-phase reaction₁₂L₂₄The cation framework CL-aMOC-1 has simple and easy operation and high yield. The CL-aMOC-1 obtained by the invention can rapidly adsorb oxygen-containing anions (CrO) through an anion exchange process₄ ^2‑，Cr₂O₇ ²) And has the advantages of high adsorption capacity, good selectivity, recyclability and the like.

Description

Preparation method and application of cationic porous material

Technical Field

The invention belongs to the field of metal-organic frameworks, and particularly relates to a preparation method and application of a cationic porous material.

Technical Field

Cr (VI) oxyanions (including CrO) which are generally generated during industrial production (metal plating industry, leather manufacturing and industry, and cement manufacturing industry)₄ ^2-，Cr₂O₇ ^2-And HCrO^4-) Has been classified as a class a human carcinogen by the united states environmental protection agency. Therefore, the removal of Cr (VI) oxyanions from wastewater is of great importance. At present, methods for removing Cr (VI) oxyanions include a redox method, a precipitation method, biological treatment, membrane filtration and the like, wherein an adsorption method is simple and convenient to operate, few in byproducts, high in feasibility and high in efficiency, and is one of the best choices for removing the oxyanions in water.

Cationic porous materials having cationic nanocavities and exchangeable anions in their structure are of interest because such materials can be used as anion adsorbents for the removal of anionic contaminants by anion exchange adsorption. However, the amount of cationic porous material is smaller compared to neutral and anionic porous materials. Currently, the main cationic porous materials are anion exchange resins, layered hydroxides (LDHs), cationic metal-organic frameworks (MOFs), Cationic Polymer Networks (CPNs), and the like. These cationic materials also have disadvantages such as low adsorption capacity, slow adsorption rate, low reuse rate, poor stability in water, etc. in the adsorption of oxoanions, and therefore, it is very necessary to develop a novel cationic porous material.

The coordination cage is a discrete coordination molecule with a special geometric shape and an inner cavity, and has potential application in the research fields of drug delivery, molecular recognition, homogeneous catalysis and the like at present. Some coordination cages have large cavities and high positive charges and can adsorb and contain anions, but are often used for molecular recognition, catalysis and the like in a solution due to the solubility of the coordination cages, and are rarely used as solid adsorbents in liquid phase adsorption. And at present, no cationic porous material based on coordination cage with efficient adsorption effect for heavy metal chromium exists.

Disclosure of Invention

The invention aims to solve the problems that the solubility of a coordination cage in the prior art is difficult to apply as a solid adsorbent to liquid phase adsorption, and a cation type porous material based on the coordination cage and having high-efficiency adsorption action for heavy metal chromium does not exist, and provides a preparation method and application of the cation type porous material.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a cationic porous material comprises the following steps:

s1, preparing aMOC-1

S11, dissolving 3, 5-bis (4-pyridyl) -benzaldehyde and palladium nitrate in a solvent according to a molar ratio of 2 (1-3), and reacting the solution at 60-80 ℃ for 5-10 hours after gas in the solution is removed;

s12, after the reaction in the step S11 is finished, adding dioxane with the volume 3-5 times of that of the solution into the solution, filtering and washing after complete precipitation, and keeping the precipitate;

s2, preparing CL-aMOC-1

S21, mixing aMOC-1 and BAPB obtained in the step S1 according to the mass ratio of (2-3) to 1, and then grinding for 25-40 min;

and S22, washing the mixture ground in the step S21 by using an organic solvent, and drying to obtain the catalyst.

The method of the invention forms an expanded coordination cage-based framework material by linking coordination cages together further through covalent bonds, which can reduce the solubility of the material in water and improve the stability, making it suitable for liquid phase adsorption applications. As shown in figure 1, the method for constructing the cationic porous material comprises the steps of firstly selecting an organic ligand which simultaneously comprises coordination sites and covalent reaction sites and Pd (II) ions to assemble a coordination cage with the covalent reaction sites, namely forming a molecular cage Pd through the reaction of 3, 5-di (4-pyridyl) -benzaldehyde and palladium nitrate₁₂L₂₄(L is 3, 5-di (4-pyridyl) -benzaldehyde), and then reacting 1, 4-di (4-aminophenyl) benzene (BAPB) with aldehyde groups on the molecular cages to form covalent bonds, so that a plurality of molecular cages are connected to form the porous material with a three-dimensional framework.

Preferably, in the step S11, the molar ratio of the 3, 5-bis (4-pyridyl) -benzaldehyde to the palladium nitrate is 2: 1.

Preferably, in the step S11, the reaction time is 8 h.

Preferably, in the step S12, the precipitate is washed with acetone and then dried at 60-80 ℃ for 5-7 h.

Preferably, in step S21, the mass ratio of aMOC-1 to BAPB is 2.5: 1.

preferably, in step S22, the washing specifically includes: washing the mixture for 3-6 times by using dimethyl sulfoxide at the temperature of 60-75 ℃, and then washing the mixture for 2-5 times by using acetone.

The cationic porous material prepared by the preparation method of the cationic porous material.

The cationic porous material is used for adsorbing CrO₄ ^2-And Cr₂O₇ ^2-The application of (1).

Preferably, CrO is treated in an environment with pH of 2-8₄ ^2-And Cr₂O₇ ^2-Adsorption of (3).

Compared with the prior art, the invention has the following technical effects:

the preparation method of the cationic porous material provided by the invention has mild reaction conditions, and under the reaction condition of normal-temperature grinding, the aldehyde group-containing cationic coordination cage (aMOC-1) and 1, 4-bis (4-aminophenyl) benzene (BAPB) are connected into the amorphous cationic porous framework material CL-aMOC-1 through an aldehyde-amine condensation reaction. CL-aMOC-1 can quickly and efficiently adsorb CrO in water₄ ^2-And Cr₂O₇ ^2-The saturated adsorption capacities were 245.1mg/g and 311.5mg/g, respectively. The adsorbed Cr (VI) oxyanion can be quickly eluted, and the recycling performance of the material is good. In addition, the CL-aMOC-1 can be used for removing Cr (VI) in the electroplating waste liquid.

Drawings

FIG. 1 is a schematic flow diagram of the synthetic principle of the present invention;

FIG. 2 PXRD pattern of CL-aMOC-1 obtained in the example (a), IR spectra of aMOC-1, CL-aMOC-1 and BAPB (b), and Raman spectra of aMOC-1 and CL-aMOC-1 (c);

FIG. 3 thermogravimetric curve (a) of CL-aMOC-1 obtained in example, CL-aMOC-1N at 77K₂Adsorption isotherms (inset corresponding pore size distribution) (b);

FIG. 4 is a scanning electron micrograph of CL-aMOC-1 obtained in the example;

FIG. 5 CL-aMOC-1 and Cr₂O₇ ^2-(a) And CrO₄ ^2-(b) Time-varying ultraviolet spectra of ionic interactions;

FIG. 6 CL-aMOC-1 adsorption data for three oxoanions were fitted to a pseudo-first order kinetic model (a) and a pseudo-second order kinetic model (b);

fig. 7 CL-aMOC-1 adsorption isotherms for two oxoanions (T48 h, T30 ℃) (a); fitting oxoanion adsorption data to Langmuir (b), Freundlich (c), and Temkin (d) adsorption equations, respectively;

FIG. 8 Cr₂O₇@ CL-aMOC-1 in NaNO₃Ultraviolet spectrum (a) desorbed in solution for 20 min; CL-aMOC-1 to Cr₂O₇ ^2-The cyclable adsorption performance of (b);

FIG. 9 influence of pH on the adsorption of Cr (VI) by CL-aMOC-1 (a); the influence of competing anions on the removal rate of the adsorbed oxoanions of CL-aMOC-1 (b);

FIG. 10 shows the UV spectrum (a) of the CL-aMOC-1 adsorption of Cr (VI) -containing electroplating wastewater at different times; a change (b) in the concentration of Cr in the electroplating wastewater when the CL-aMOC-1 adsorbs Cr (VI) at different time points; and (c) desorption experiments (the color change of the corresponding solution or solid is shown in an inset) after the electroplating waste liquid Cr (VI) is adsorbed.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below with reference to specific examples and comparative examples. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

Unless otherwise specified, the devices used in the present examples, comparative examples and experimental examples were all conventional experimental devices, the materials and reagents used were commercially available without specific reference, and the experimental methods without specific reference were also conventional experimental methods.

Examples

S1, preparing aMOC-1

To a 15mL reaction flask were added 3, 5-bis (4-pyridyl) -benzaldehyde (52mg, 0.20mmol), palladium nitrate dihydrate (26.6mg, 0.10mmol), and 6mL dimethyl sulfoxide. Argon gas was blown into the reaction flask for 30 seconds to sufficiently replace the gas. Putting the mixture into a constant-temperature oven at 70 ℃ and heating the mixture for 8 hours to obtain a clear orange solution. Slowly adding 24mL of dioxane into the solution to obtain white floccule, performing centrifugal separation, collecting white solid, washing with acetone for three times, soaking for 3 days, and vacuum drying at 70 ℃ for 6 hours to obtain a product;

s2, preparing CL-aMOC-1

75mg of aMOC-1 and 27mg of BAPB were put in a mortar, mixed well with a small spatula, and then ground for 30 minutes. The color of the mixture changed from light gray to yellow as observed by the naked eye. The resulting solid was washed 4 times with 70 ℃ dimethyl sulfoxide (15 mL each) followed by 3 times with acetone (15 mL each) in order to wash away unreacted aMOC-1 and BAPB. Finally, the yellow solid was dried under vacuum at 100 ℃ for 12h to give CL-aMOC-1 with a yield of 86%.

Examples of the experiments

(1) An experimental instrument:

nippon Rigaku X-ray powder diffractometer (room temperature, 40kV, 40mA), Germany platinum Elmer Spectrum Two Fourier transform infrared spectrometer (data collection range is 4000 to 400cm-1), Renishaw inVia confocal micro-Raman spectrometer (data collection range is 2000 to 200 cm)^-1Laser wavelength 785nm), Germany relaxation-resistant TG209F3 thermogravimetric analyzer (nitrogen atmosphere, heating rate 10 ℃ for min^-130-800 ℃), U.S. mike ASAP 2460 gas adsorber (77K, pore structure evaluated by adsorption-desorption of nitrogen), british marwen Zetasizer Nano ZS90 nanosized potential analyzer (25 ℃, suspension sample concentration 0.5mg/mL), U.S. Phenom Pro X desktop scanning electron microscope-energy spectrometer, U.S. seemer feishel K-Alpha⁺An X-ray photoelectron spectrometer, an ultraviolet-visible spectrophotometer (with an integrating sphere) of Shimadzu Japan UV-2700, and an inductively coupled plasma emission spectrometer of Saimer Feishale ICAP-7400 USA.

(2) Experimental reagent:

ligand 3, 5-bis-4-pyridinebenzaldehyde was purchased from Guangzhou research Biotechnology development, Inc.; pd (NO)₃)₂·2H₂O was purchased from chemical ltd, warburg, beijing; k₂CrO₄、K₂Cr₂O₇And 1, 4-bis (4-aminophenyl) benzene (BAPB) from Shanghai Allantin Biotech Co., Ltd; solvent reagents were purchased from Tianjin Daloco chemical reagent works.

(3) The cationic porous material (CL-aMOC-1) obtained in the example was characterized by PXRD, infrared spectrum and Raman spectrum, and the characterization results are shown in FIG. 2.

The PXRD pattern of the synthesized CL-aMOC-1 has only one broad peak, which shows that the CL-aMOC-1 is amorphous powder (figure 2 a). From the IR spectrum analysis, it can be seen that CL-aMOC-1 is largeThe majority of the peaks were similar to those of aMOC-1, meaning that the cage structure was retained in CL-aMOC-1. Comparison of the IR spectra of the reaction raw materials BAPB and aMOC-1, the amino group of CL-aMOC-1 (3200-3600 cm)^-1) And aldehyde group (1699 cm)^-1) The peak intensity of (b) is significantly reduced (fig. 2b), indicating that the amino and aldehyde groups have reacted. In addition, at 1491cm^-1A new peak appears, which may be attributed to the stretching vibration of the phenyl group in BAPB. In Raman spectroscopy (FIG. 2c), 1705cm^-1The peak at aldehyde disappeared in CL-aMOC-1, further confirming that C ═ O reacted; at the same time, 1608cm^-1The peak at (a) is enhanced and broadened, which may be caused by the enhancement of stretching vibration of C ═ C bond after biphenyl is bonded to CL-aMOC-1; at 1174 and 1199cm^-1Some new peaks were observed, which may be caused by C-N bond vibrations of BAPB.

(4) Thermogravimetric analysis of the cationic porous material (CL-aMOC-1) obtained in the example, on N₂Adsorption-desorption and SEM characterization of (a) and the results are shown in fig. 3.

As shown in FIG. 3a, CL-aMOC-1 had only a slight weight loss before 120 ℃; a weight loss of about 9.5% was observed at 160 ℃, which may be the loss on release of some BAPB molecules that reacted only one amino group. The frame has a plateau at about 270 c, before the frame temperature, above which the entire frame begins to decompose at temperatures above 270 c. CL-aMOC-1 to N₂Belonging to the type IV isotherm with a hysteresis loop of H3, indicating the presence of a mesoporous structure (fig. 3 b). The specific surface area of CL-aMOC-1 was 11.13m²(ii) in terms of/g. The fact that the specific surface area is so small may be due to the cavity being filled with a large amount of NO₃ ^-Anion occupancy, which is a common phenomenon in cationic backbones. In addition, the BJH pore size distribution indicates the presence of two types of pores in CL-aMOC-1 (FIG. 3b inset): one of about 2nm, probably due to the pore cavity of MOC; the other is about 10nm, probably caused by the connection between MOCs via BAPB. As can be seen from the SEM image, CL-aMOC-1 exhibits irregular particle sizes ranging from about 500 to 2000nm (FIG. 4).

(5) Adsorption kinetics experiment: add 10mg of CL-aMOC-1 solid to 30mL of 10^-4M is a group containingThe suspension was stirred continuously in the aqueous oxyanion solution, and about 2.5mL of supernatant was taken at the given time points to determine the concentration of the oxyanion. The concentration of Cr (VI) oxoanions is determined by UV-Vis.

Selection of two oxoanions CrO₄ ^2-And Cr₂O₇ ^2-The adsorption performance of CL-aMOC-1 was investigated. As shown in FIG. 5, after addition of CL-aMOC-1, CrO₄ ^2-、Cr₂O₇ ^2-The concentration of (c) rapidly decreases. After only 3min, CrO₄ ^2-And Cr₂O₇ ^2-The removal rates of (A) were about 99.7% and 88.0%, respectively, which reached adsorption equilibrium almost within 5min, corresponding to removal rates of 99.7% and 97.85%, respectively.

The adsorption capacity data changing along with time is analyzed by using a first-order dynamics simulation equation and a second-order dynamics simulation equation, and the result shows that the fitting effect of the second-order dynamics simulation is obviously better than that of the first-order dynamics simulation. As shown in fig. 6 and table 1, CrO₄ ^2-、Cr₂O₇ ^2-Fitting of quasi-second order kinetic equation of²Values are 0.9996, 0.9949 (FIG. 6b), respectively, and R fitted to a first order kinetic equation²The values are only 0.5269-0.7303 (FIG. 6 a). The results indicate that the CL-aMOC-1 adsorption rate determining step for oxoanions may be a chemical process.

TABLE 1 equilibrium capacity, Rate constant and related coefficient R for adsorption of oxoanions by CL-aMOC-1²

(6) 5mg of CL-aMOC-1 is added into a series of oxyanion aqueous solution (25mL) with the concentration range of 10-400 ppm, the mixture is kept stand for 24 hours, and then the equilibrium concentration of each oxyanion is measured. The experiments were performed in parallel 3 times, and the average value was used for the calculation of the adsorption capacity and the fitting of the relevant data.

The adsorption isotherm of the oxoanion was determined and the adsorption capacity of CL-aMOC-1 was further investigated. As shown in FIG. 7a, the maximum adsorption capacity of CL-aMOC-1 to CrO 42-and Cr2O72-The amounts were 224mg/g and 323mg/g, respectively. Adsorption isotherm data for different oxoanions were fitted using three different adsorption isotherm equations, a Langmuir model, a Freundlich model, and a Temkin model. The results of the fit are shown in FIGS. 7b-7d and Table 2. The data relating to Cr2O 72-most closely fit the Langmuir model, R²0.9633, indicating that CL-aMOC-1 is for Cr₂O₇ ^2-May be typical monolayer adsorption. And CrO₄ ^2-In addition to the better fit of the Langmuir equation, the better fit of the Freundlich equation indicates that the adsorption of the two anions is not only monolayer adsorption, but also adsorption may be affected by the uneven distribution of the CL-aMOC-1 surface active sites.

TABLE 2 adsorption parameters of CL-aMOC-1 for different oxoanions

(7) To test the recycle properties of CL-aMOC-1, the adsorbent subjected to the adsorption experiment was recovered by centrifugation and then added to a volume of 1M NaNO₃The solution is eluted, and desorption balance can be achieved after 1 h. The concentration of the oxoanion was determined by UV-Vis spectroscopy.

The recovery of the adsorbent plays a crucial role in practical industrial applications. Therefore, 50ppm of Cr is selected₂O₇ ^2-Saturated adsorbed Cr in solution₂O₇@ CL-aMOC-1. When mixing Cr₂O₇@ CL-aMOC-1 immersion in 1M NaNO₃In aqueous solution, approximately 70% of the adsorbed ions were desorbed after only 1min and the desorption equilibrium was reached within 20min (fig. 8 a). The desorbed sample is washed, dried and activated and then is used for Cr again₂O₇ ^2-The result of the adsorption of (2) is shown in FIG. 8 b. After 5 cycles, the relative adsorption capacity remained 85% of the original, indicating that CL-aMOC-1 has good recyclability.

(8) Selective adsorption experiments: 5mg of CL-aMOC-1 was added to 25mL of an oxoanion and an interfering ion (Cl)^-，NO^3-，ClO^4-，SO₄ ^2-) The equilibrium concentration of the analyte was measured after allowing the mixed solution to stand at an equimolar ratio (1:1, 1mM) for 24 hours.

The pH of actual industrial wastewater is usually acid or alkali biased, so it is necessary to explore the effect of pH on the adsorption of Cr (VI) by CL-aMOC-1. As can be seen from FIG. 9a, the removal rate of Cr (VI) by the adsorbent is over 80% in the pH range of 2-8. When the pH is greater than 9, the removal rate begins to decrease. The CL-aMOC-1 shows better adsorption in weak base, neutral and acid environments.

By adding the same molar equivalent of competing ion (Cl)^-，NO^3-，ClO^4-，SO₄ ^2-) The effect of competing ions on oxoanion removal was explored. As shown in fig. 9b, the relative removal of the target oxoanion still exceeded 85% in most cases.

(9) Adsorption test of Cr (VI) in electroplating waste liquid

The electroplating wastewater containing Cr (VI) is a common pollution source in the electroplating industry, and can be discharged into natural water bodies only by decontamination treatment. The electroplating wastewater containing Cr (VI) is generally acidic and contains sulfate ions, and from the results of the adsorption studies, CL-aMOC-1 can be suitable for removing Cr (VI) oxyanions from the electroplating wastewater. To confirm this, 20mg of CL-aMOC-1 was added to 30mL of the plating wastewater (diluted appropriately so that it can be used for instrument detection), and the change in the concentration of Cr (VI) with time was detected by UV-Vis and ICP. From the results of the uv absorption spectrum, it can be seen that the concentration of cr (vi) is greatly reduced within only 1min, and substantially reaches the adsorption equilibrium within 3min (fig. 10 a). The ICP test showed that the concentration of cr (vi) had decreased from 22.4ppm before adsorption to 0.47ppm after adsorption (fig. 10b), which had reached the pollutant emission standard. In addition, the color of the solution changed from pale yellow to colorless, and the color of the powder became darker, which confirmed the adsorption of the cr (vi) oxyanion. Cr (VI) Desorption experiments found that the oxoanion adsorbed on CL-aMOC-1 could be desorbed (the solution changed from colorless to pale yellow), indicating that the material could be reused (FIG. 10 c).

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a cationic porous material is characterized by comprising the following steps:

s1, preparing aMOC-1

s2, preparing CL-aMOC-1

S21, mixing aMOC-1 obtained in the step S1 and 1, 4-bis (4-aminophenyl) benzene according to the mass ratio of (2-3) to 1, and then grinding for 25-40 min;

2. The method of claim 1, wherein in step S11, the molar ratio of 3, 5-bis (4-pyridyl) -benzaldehyde to palladium nitrate is 2: 1.

3. The method for preparing a cationic porous material according to claim 1, wherein the reaction time in step S11 is 8 h.

4. The method for preparing a cationic porous material according to claim 1, wherein in step S12, the precipitate is washed with acetone and then dried at 60-80 ℃ for 5-7 h.

5. The method for preparing the cationic porous material according to claim 1, wherein in step S21, the mass ratio of the aMOC-1 to the 1, 4-bis (4-aminophenyl) benzene is 2.5: 1.

6. the method for preparing a cationic porous material according to claim 1, wherein the grinding is performed at normal temperature in step S21.

7. The method for preparing the cationic porous material according to claim 1, wherein in step S22, the washing steps are: washing the mixture for 3-6 times by using dimethyl sulfoxide at the temperature of 60-75 ℃, and then washing the mixture for 2-5 times by using acetone.

8. A cationic porous material prepared by the method of any one of claims 1 to 7.

9. The method of claim 8 wherein the cationic porous material adsorbs CrO₄ ^2-And Cr₂O₇ ^2-The application of (1).

10. The method for adsorbing CrO by using the cationic porous material according to claim 9₄ ^2-And Cr₂O₇ ^2-The application is characterized in that the pH value of the solution is 2-8 for CrO₄ ^2-And Cr₂O₇ ^2-Adsorption of (3).