CN109569521B - Rhodanine functionalized MOFs adsorbent and preparation method and application thereof - Google Patents

Rhodanine functionalized MOFs adsorbent and preparation method and application thereof Download PDF

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CN109569521B
CN109569521B CN201811500569.9A CN201811500569A CN109569521B CN 109569521 B CN109569521 B CN 109569521B CN 201811500569 A CN201811500569 A CN 201811500569A CN 109569521 B CN109569521 B CN 109569521B
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罗旭彪
丁琳
罗于
邵鹏辉
刘玲玲
殷晓翠
余海燕
张亚昆
余水平
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Nanchang Hangkong University
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J20/226—Coordination polymers, e.g. metal-organic frameworks [MOF], zeolitic imidazolate frameworks [ZIF]
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/285—Treatment of water, waste water, or sewage by sorption using synthetic organic sorbents
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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Abstract

The invention belongs to the technical field of adsorbents for heavy metal pollutants in water, and provides a rhodanine functionalized MOFs adsorbent and a preparation method and application thereof; the adsorbent comprises a UiO-66 MOFs matrix and modified rhodanine groups. The UO-66 MOFs matrix has the advantages of large specific surface area, high porosity, stable structure, easy surface modification and the like, and the rhodanine group and the UO-66 MOFs matrix can be coordinated and combined with Zr-O cluster of the UO-66 MOFs matrix through a compound containing the rhodanine group; or the rhodanine group is modified on the surface of Zr-MOFs by amidation combination of a rhodanine group-containing compound and an UO-66 MOFs matrix, so that high-selectivity adsorption of metallic silver in water is realized.

Description

Rhodanine functionalized MOFs adsorbent and preparation method and application thereof
Technical Field
The invention belongs to the technical field of adsorbents for heavy metal pollutants in water, and particularly relates to a rhodanine functionalized MOFs adsorbent and a preparation method and application thereof.
Background
The presence of a large amount of silver ions in industrial waste water can have serious effects on the ecological environment and human health if the silver ions are not treated. Moreover, silver is a precious metal with high market value, and certain economic benefits can be obtained by recovering silver ions in wastewater. The adsorption method is one of the most common methods for removing silver ions in water, and has the advantages of low cost, high efficiency, simple operation and the like. The traditional adsorbing materials, such as activated carbon, silicon dioxide, carbon nanotubes and the like, have the defects of low adsorption capacity, slow adsorption rate, poor selective adsorption capacity and the like in complex actual wastewater treatment. Therefore, it is very important to research and design a material capable of stably, efficiently and selectively adsorbing silver ions.
Metal-organic Framework Materials (MOFs) are a class of novel crystalline porous materials with a periodic infinite network structure formed by self-assembly of Metal ions or Metal clusters and organic ligands through coordination bonds. Although a large number of experimental studies show that MOFs have special selective adsorption and separation capacity for gas molecules, dyes, medicines and even isomers of organic matters, most MOFs have poor stability in aqueous solution, which greatly limits the application of MOFs in wastewater treatment; in addition, for the adsorption separation of metal ions, because the MOFs lacks redundant coordination sites, the adsorption effect of the MOFs on the external metal ions is very weak, the application of the MOFs as a metal adsorbent is greatly limited, and because the radiuses of most metal ions are very similar, the metal ions cannot be effectively adsorbed and separated through the pore size advantage. For example, in 2015, Cheng et Al [ Cheng X, Liu M, Zhang A F, et Al, Nanoscale,2015,7,9738-9745] successfully synthesized thiol-functionalized MIL-53(Al) by modifying MIL-53(Al) with thiol groups, but it has the disadvantages of low adsorption capacity, slow adsorption rate, poor selectivity, and poor water stability which limits its recycling capability.
Disclosure of Invention
In view of the above, the present invention aims to provide rhodanine functionalized MOFs adsorbent, and a preparation method and an application thereof, and the rhodanine functionalized MOFs adsorbent provided by the present invention has high adsorption capacity, high adsorption speed, and high selective adsorption on silver ions.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides a rhodanine functionalized MOFs adsorbent, which comprises a UiO-66 MOFs matrix and a modified rhodanine group.
Preferably, the UO-66 MOFs matrix comprises UO-66 or UO-66-NH2。
The invention provides a preparation method of the rhodanine functionalized MOFs adsorbent in the technical scheme, which comprises the following steps:
(1) reacting ZrCl4Mixing the organic solution with carboxylic acid organic ligand to obtain MOFs synthetic feed liquid;
(2) and (2) mixing the MOFs synthetic material liquid obtained in the step (1) with rhodaninic acid, and carrying out hydrothermal reaction to obtain the rhodanine functionalized MOFs adsorbent.
Preferably, the carboxylic organic ligand in the step (1) comprises terephthalic acid or 2-amino terephthalic acid;
the rhodanine acid in the step (2) comprises rhodanine-3-acetic acid or rhodanine-3-propionic acid;
ZrCl in the rhodanic acid and MOFs synthetic material liquid in the step (2)4The molar ratio of the carboxylic acid organic ligand is 0.1-10: 1: 1;
the temperature of the hydrothermal reaction in the step (2) is 110-150 ℃, and the time is 24-72 h.
The invention also provides a preparation method of the rhodanine functionalized MOFs adsorbent in the technical scheme, which comprises the following steps:
(1) reacting ZrCl4The organic solution is mixed with carboxylic acid organic ligand, and filtration is carried out after hydrothermal reaction to obtain UiO-66 MOFs;
(2) and (2) mixing the UiO-66 MOFs obtained in the step (1) with a rhodaninic acid organic solution, and carrying out modification synthesis reaction to obtain the rhodanine functionalized MOFs adsorbent.
Preferably, ZrCl is adopted in the step (1)4The molar ratio of the carboxylic acid organic ligand to the carboxylic acid organic ligand is 1:1, the carboxylic acid organic ligand comprises terephthalic acid or 2-amino terephthalic acid, the hydrothermal reaction temperature is 120 ℃, and the time is 48 hours;
the rhodanine acid in the step (2) comprises rhodanine-3-acetic acid or rhodanine-3-propionic acid;
when the carboxylic acid organic ligand is 2-amino terephthalic acid, mixing the organic solution of rhodanic acid with the 1-hydroxybenzotriazole alcoholic solution to obtain a functionalized feed liquid before mixing the UO-66 MOFs and the rhodanic acid organic solution in the step (2); mixing the functionalized feed liquid with UiO-66 MOFs, adding carbodiimide, and carrying out catalytic modification synthesis reaction;
the mass ratio of the UO-66 MOFs to the rhodaninic acid is 1: 0.2-5; the molar ratio of the 1-hydroxybenzotriazole to the rhodaninic acid in the 1-hydroxybenzotriazole alcoholic solution is 1-1.2: 1; the molar ratio of the carbodiimide to the rhodaninic acid is 1-1.5: 1.
The invention also provides a preparation method of the rhodanine functionalized MOFs adsorbent in the technical scheme, which comprises the following steps:
(1) reacting ZrCl4The organic solution is mixed with carboxylic acid organic ligand, and filtration is carried out after hydrothermal reaction to obtain UiO-66 MOFs;
(2) mixing the organic solution of rhodaninic acid with thionyl chloride to carry out acyl chlorination reaction to obtain rhodaninic acid chloride;
(3) and (3) mixing the organic solution of the rhodanine acyl chloride obtained in the step (2) with the UiO-66 MOFs obtained in the step (1), adding triethylamine, and reacting the acyl chloride with amine to obtain the rhodanine functionalized MOFs adsorbent.
Preferably, ZrCl is adopted in the step (1)4The molar ratio of the organic ligand of the carboxylic acid to the organic ligand of the carboxylic acid is 1: 1; the carboxylic acid organic ligand comprises terephthalic acid or 2-amino terephthalic acid;
the temperature of the hydrothermal reaction in the step (1) is 120 ℃, and the time is 48 hours;
the molar ratio of the rhodaninic acid to the thionyl chloride in the step (2) is 1: 1-2;
in the step (2), the temperature of the acyl chlorination reaction is 50-60 ℃, and the time is 6-12 h;
the dosage ratio of the rhodanine acyl chloride in the organic solution of the rhodanine acyl chloride in the step (3) to the added UiO-66 MOFs is 1-25 mmol:0.5 g;
the molar ratio of triethylamine to rhodanine acyl chloride in the step (3) is 1-1.5: 1;
in the step (3), the reaction temperature of acyl chloride and amine is 20-25 ℃, and the reaction time is 12-36 h.
The invention provides an application of the rhodanine functionalized MOFs adsorbent in the technical scheme or the rhodanine functionalized MOFs adsorbent prepared by the preparation method in the technical scheme in selective adsorption of silver ions in water.
Preferably, the application comprises: and (3) adding the rhodanine functionalized MOFs adsorbent into the water body to be adsorbed with the silver ions, and stirring and adsorbing.
The invention provides a rhodanine functionalized MOFs adsorbent, which comprises a UiO-66 MOFs matrix and a modified rhodanine group. The UiO-66 MOFs matrix has the advantages of large specific surface area, high porosity, stable structure, easy surface modification and the like, and the modified rhodanine group is coordinated and combined with the Zr-O cluster of the UiO-66 MOFs matrix; or modifying the rhodanine group to be amidated and combined with the amino group of the UiO-66 MOFs matrix, modifying the rhodanine group on the surface of the Zr-MOFs, and realizing the high-selectivity adsorption of metal silver ions in the water body; in the invention, the single bond S and the double bond S contained in the rhodanine group can be effectively coordinated with Ag. The example result shows that when the rhodanine functionalized MOFs adsorbent provided by the invention is used for selective adsorption in a mixed solution with the concentration of Ag (I), K (I), Li (I), Pb (II), Ni (II), Co (II) and Cu (II) of 10mmol/L, the rhodanine functionalized MOFs adsorbent has selective adsorption on Ag (I), the adsorption amount can reach 8.5mmol/g at most, and the adsorption amount of other metal ions is only 0.17mmol/g at most; the maximum adsorption capacity of the adsorbent provided by the invention can reach 923.9mg/g, which is about 44 times of the maximum adsorption capacity of the original UiO-66. In addition, the material has excellent adsorption rate, and the removal rate of silver ions with the initial concentration of 40mg/L can reach more than 99% within 2 min.
Drawings
FIG. 1 shows the rhodanine functionalized UiO-66 MOFs adsorbent and non-rhodanine functionalized UiO-66 and UiO-66-NH obtained in examples 1-122XRD pattern of (a);
FIG. 2 shows the Rodanine functionalized UiO-66 MOFs adsorbents and non-Rodanine functionalized UiO-66 and UiO-66-NH obtained in examples 13 and 142XRD pattern of (a);
FIG. 3 is an XRD pattern before and after adsorption of silver after 5 cycles of adsorption-desorption of the rhodanine functionalized UiO-66 MOFs adsorbents obtained in examples 13 and 14;
FIG. 4 shows the Rotannine-functionalized UiO-66 MOFs adsorbents and non-Rotannine-functionalized UiO-66 and UiO-66-NH obtained in examples 23 to 322XRD pattern of (a);
FIG. 5 is a graph showing the adsorption kinetics of the rhodanine functionalized UiO-66 MOFs adsorbent obtained in examples 23 and 24 on silver ions at an initial concentration of 40 mg/L.
Detailed Description
The invention provides a rhodanine functionalized MOFs adsorbent, which comprises a UiO-66 MOFs matrix and a modified rhodanine group.
In the invention, the modified rhodanine group is chemically bonded with a UiO-66 MOFs matrix in the form of: coordinated and combined with Zr-O cluster of UiO-66 MOFs matrix; combined with aminoamidation of the UiO-66 MOFs matrix.
The rhodanine functionalized MOFs adsorbent provided by the invention comprises a UiO-66 MOFs matrix and a modified rhodanine group. In the present invention, said UO-66 type MOFs matrix preferably comprises UO-66 and/or UO-66-NH2(ii) a When the MOFs matrix is UiO-66, the compound containing the rhodanine group can be coordinated and combined with the Zr-O cluster of the UiO-66, so that the modified rhodanine group is combined with the UiO-66; when the MOFs matrix is UiO-66-NH2When the compound containing the rhodanine group can react with UiO-66-NH2The Zr-O cluster is coordinated and combined with UiO-66-NH2The amino group of the amino group is amidated and combined to realize the modified rhodanine group and UiO-66-NH2And (4) combining. In the present invention, the compound having a rhodanine group may be rhodanine-3-acetic acid, rhodanine-3-propionic acid, or rhodanine acid chloride obtained by acid-chlorinating rhodanine-3-acetic acid and rhodanine-3-propionic acid, or the like.
In the rhodanine functionalized MOFs adsorbent, the UiO-66 MOFs matrix is composed of UiO-66 or UiO-66-NH2Providing; the UO-66 MOFs matrix has the advantages of large specific surface area, high porosity, stable structure, easy surface modification and the like, and the compound containing the rhodanine group is coordinated and combined with the Zr-O cluster of the UO-66 MOFs; or the rhodanine group is modified on the surface of the MOFs by the amidation combination of the rhodanine group-containing compound and UiO-66 MOFs, so that the high-selectivity adsorption of the metallic silver in the water body is realized.
In the present invention, the rhodanine group-containing compound is coordinately bound to the Zr-O cluster of UiO-66 in two ways: the carboxylic acid compound containing rhodanine can be coordinately combined with Zr in a Zr-O cluster under the auxiliary condition of a solvent; the carboxylic acid compound containing rhodanine can also be subjected to acyl chlorination reaction to obtain acyl chloride compound containing rhodanine, and then the acyl chloride compound can be reacted with Zr and mu in Zr-O cluster3-OH coordination bonding.
In the invention, the mass ratio of Zr to S element in the rhodanine functionalized MOFs adsorbent is preferably 1: 0.02-20, and more preferably 1: 1.0-18.
In the invention, the UO-66 MOFs has the advantages of large specific surface area, high porosity, stable structure, easy surface modification and the like, and is a potentially excellent water treatment adsorbent, and the rhodanine contains single bond C-S and double bond C ═ S and can be effectively coordinated with metal Ag ions, so that the rhodanine is modified on the surface of the UO-66 MOFs to realize high-selectivity adsorption of the Ag ions in the water body.
The invention provides a preparation method of the rhodanine functionalized MOFs adsorbent in the technical scheme, which comprises the following steps:
(1) reacting ZrCl4Mixing the organic solution with carboxylic acid organic ligand to obtain MOFs synthetic feed liquid;
(2) and (2) mixing the MOFs synthetic material liquid obtained in the step (1) with rhodaninic acid, and carrying out hydrothermal reaction to obtain the rhodanine functionalized MOFs adsorbent.
In the present invention, the starting materials used are commercially available products well known to those skilled in the art, unless otherwise specified.
ZrCl is added into the mixture4Is mixed with carboxylic acid organic ligands to obtain the MOFsAnd (4) synthesizing a feed liquid. In the present invention, the ZrCl4ZrCl in an organic solution4The dosage ratio of the organic solvent to the organic solvent is preferably 1mmol: 45-55 mL, and more preferably 1mmol: 45-50 mL; the organic solvent is preferably N, N-Dimethylformamide (DMF) and is used as a medium for subsequent reaction, so that metal ions and organic ligands are fully coordinated in the solvent to form crystal nuclei, and then the growth is continued under the solvent condition to obtain MOFs crystals. ZrCl is preferably used in the invention4Dissolving the ZrCl into N, N-Dimethylformamide (DMF), and carrying out ultrasonic stirring for 20-30 min to obtain clear ZrCl4An organic solution of (a).
In the present invention, the carboxylic acid-based organic ligand preferably comprises terephthalic acid or 2-aminoterephthalic acid; when the carboxylic acid organic ligand is terephthalic acid, the MOFs adsorbent of the rhodanine functionalized UiO-66 is finally obtained, and when the carboxylic acid organic ligand is 2-amino terephthalic acid, the rhodanine functionalized UiO-66-NH is finally obtained2The MOFs adsorbent of (1).
In the invention, the carboxylic acid organic ligand is preferably added into ZrCl4The organic solution is ultrasonically stirred for 30-40 min to realize ZrCl4Mixing the organic solution with carboxylic acid organic ligand. In the invention, ZrCl is contained in the MOFs synthetic material liquid4The molar ratio to the carboxylic organic ligand is preferably 1:1.
After the MOFs synthetic material liquid is obtained, the MOFs synthetic material liquid and the rhodaninic acid are mixed for hydrothermal reaction, and the rhodanine functionalized MOFs adsorbent is obtained. In the present invention, the rhodaninic acid preferably includes rhodanine-3-acetic acid or rhodanine-3-propionic acid; ZrCl in the rhodanic acid and MOFs synthetic material liquid4The molar ratio of the carboxylic acid organic ligand is preferably 0.1 to 10:1:1, and more preferably 3 to 8:1: 1. The rhodaninic acid is preferably added into the MOFs synthetic material liquid and then ultrasonically stirred for 20-30 min, so that the MOFs synthetic material liquid and the rhodaninic acid are mixed.
In the invention, the temperature of the hydrothermal reaction is preferably 110-150 ℃, and more preferably 120 ℃; the time of the hydrothermal reaction is preferably 24-72 hours, and more preferably 48 hours; the hydrothermal reaction is carried out in a reaction kettle.
The invention synthesizes the rhodanine functionalized MOFs adsorbent in one step in the hydrothermal reaction process, namely, the rhodanine is used for modifying a matrix while forming a UiO-66 MOFs matrix: octahedron and mu formed by 6 Zr atoms3-O and μ3-OH coordination to form the inorganic metal unit Zr6O4(OH)4After the metal cluster, coordinating with two carboxyl groups on the organic ligand terephthalic acid or amino terephthalic acid and one carboxyl group on rhodaninic acid; in addition, a small amount of the amino groups on the amino terephthalic acid will also bind to the carboxyl groups on the rhodaninic acid.
After the hydrothermal reaction, the hydrothermal reaction product is preferably subjected to filtration, solid material washing, drying and grinding in sequence to obtain the rhodanine functionalized MOFs adsorbent. The invention has no special requirements on the specific implementation mode of the filtration, and the solid-liquid separation can be realized. The invention preferably adopts the organic solvent to wash the solid material for a plurality of times to remove unreacted substances; the washing organic solvent preferably comprises DMF, methanol or dichloromethane. After washing, the solid washing material is preferably dried in vacuum for 10-12 hours at the temperature of 60-80 ℃ to remove residual solvent. The invention has no special requirements on the specific implementation mode of grinding, and the solid material grinding mode well known by the technical personnel in the field is adopted to obtain the powder with the particle size of 50-100 nm.
The invention also provides a preparation method of the rhodanine functionalized MOFs adsorbent in the technical scheme, which comprises the following steps:
(1) reacting ZrCl4The organic solution is mixed with carboxylic acid organic ligand, and filtration is carried out after hydrothermal reaction to obtain UiO-66 MOFs;
(2) and (2) mixing the UiO-66 MOFs obtained in the step (1) with a rhodaninic acid organic solution, and carrying out modification synthesis reaction to obtain the rhodanine functionalized MOFs adsorbent.
In the present invention, the carboxylic acid-based organic ligand preferably comprises terephthalic acid or 2-aminoterephthalic acid; when the carboxylic acid organic ligand is 2-amino terephthalic acid, the organic solution of the rhodanic acid is preferably mixed with the 1-hydroxybenzotriazole alcoholic solution before the UO-66 MOFs and the rhodanic acid organic solution are mixed to obtain the functionalized feed liquid; and mixing the functionalized feed liquid with UiO-66 MOFs, adding carbodiimide, and carrying out catalytic modification synthesis reaction.
Namely: reacting ZrCl4The organic solution is mixed with carboxylic acid organic ligand, and filtration is carried out after hydrothermal reaction to obtain UiO-66 MOFs; mixing the rhodaninic acid organic solution with the 1-hydroxybenzotriazole alcoholic solution to obtain a functionalized feed liquid;
and mixing the UiO-66 MOFs with the functional material liquid, adding carbodiimide, and performing modification synthesis reaction to obtain the rhodanine functionalized MOFs adsorbent.
In the present invention, the starting materials used are commercially available products well known to those skilled in the art, unless otherwise specified.
In the invention, the molar ratio of 1-hydroxybenzotriazole to rhodaninic acid in the 1-hydroxybenzotriazole alcoholic solution is preferably 1-1.2: 1; the molar ratio of the carbodiimide to the rhodaninic acid is preferably 1-1.5: 1.
ZrCl is added into the mixture4The organic solution is mixed with carboxylic acid organic ligand, and is filtered after hydrothermal reaction to obtain UiO-66 MOFs.
In the present invention, the ZrCl4ZrCl in an organic solution4The dosage ratio of the organic solvent to the organic solvent is preferably 1mmol: 45-55 mL, and more preferably 1mmol: 45-50 mL; the organic solvent is preferably N, N-Dimethylformamide (DMF), and also serves as a medium for subsequent reaction, so that metal ions and organic ligands are fully coordinated in the solvent to form crystal nuclei, and then the MOF crystals are continuously grown under the solvent condition. ZrCl is preferably used in the invention4Dissolving the ZrCl into N, N-Dimethylformamide (DMF), and carrying out ultrasonic stirring for 20-30 min to obtain clear ZrCl4An organic solution of (a).
In the invention, when the carboxylic acid organic ligand is terephthalic acid, the rhodanine functionalized MOFs adsorbent with the matrix of UiO-66 is finally obtained, and when the carboxylic acid organic ligand is 2-amino terephthalic acid, the rhodanine functionalized MOFs adsorbent with the matrix of UiO-66-NH is finally obtained2Rhodanine functionalized MOFs adsorptionAnd (3) preparing.
In the invention, the carboxylic acid organic ligand is preferably added into ZrCl4The organic solution is ultrasonically stirred for 30-40 min to realize ZrCl4Mixing the organic solution with carboxylic acid organic ligand. In the invention, ZrCl is contained in the MOFs synthetic material liquid4The molar ratio of the organic ligand of the carboxylic acid to the organic ligand of the carboxylic acid is 1:1.
Carrying out hydrothermal reaction on mixed feed liquid to generate UiO-66 MOFs; the temperature of the hydrothermal reaction is preferably 120 ℃; the time of the hydrothermal reaction is preferably 48 h.
In the hydrothermal reaction process, 6 Zr atoms form octahedron and mu3-O and μ3-OH coordination to form the inorganic metal unit Zr6O4(OH)4After the metal cluster is carried out, the metal cluster is coordinated with two carboxyl groups on an organic ligand terephthalic acid or an amino terephthalic acid to form UiO-66 MOFs with a three-dimensional network structure. When the carboxylic acid organic ligand is terephthalic acid, the generated UiO-66 MOFs is UiO-66; when the carboxylic acid organic ligand is amino terephthalic acid, the generated UiO-66 MOFs is UiO-66-NH2。
After the UiO-66 MOFs is obtained, the UiO-66 MOFs is mixed with a rhodaninic acid organic solution for modification synthesis reaction, and the rhodanine functionalized MOFs adsorbent is obtained.
In the invention, the dosage ratio of the rhodaninic acid to the organic solvent in the rhodaninic acid organic solution is preferably 1-10 mmol: 45-55 mL, more preferably 1-10 mmol:50mL, and even more preferably 2-5 mmol:50 mL; the organic solvent is preferably a mixed solvent comprising a first solvent and a second solvent, the first solvent preferably comprises one or more of dichloromethane, N-dimethylformamide, dimethyl sulfoxide and chloroform, and the second solvent preferably comprises one or more of ethyl acetate, methanol and ethanol; the volume ratio of the first solvent to the second solvent is preferably 1: 1-4, and more preferably 1: 2-3; the rhodaninic acid preferably comprises rhodanine-3-acetic acid or rhodanine-3-propionic acid.
In the invention, the mass ratio of the UO-66 MOFs to the rhodaninic acid is preferably 1: 0.2-4, more preferably 1: 0.5-3, and even more preferably 1: 2. In the invention, preferably, UiO-66 MOFs is added into organic solution of rhodaninic acid to carry out modification synthesis reaction.
In the invention, the temperature of the modification synthesis reaction is preferably 20-25 ℃; the time of the modification synthesis reaction is preferably 12-36 h, and more preferably 15-30 h. The modification synthesis reaction is preferably carried out under the condition of condensation reflux; in the modification synthesis reaction process, carboxyl of rhodaninic acid coordinates with Zr-O cluster of MOFs material or condenses with amino to generate amide, so as to form rhodanine functionalized MOFs adsorbent. Specifically, UiO-66 and UiO-66-NH2Under the auxiliary condition of solvent, a small amount
Deprotonated terephthalic acid (BDC)2-) The Zr-O metal cluster can be dissociated to have an empty orbit, and can coordinate with-COOH on rhodaninic acid (rhodanine-3-acetic acid or rhodanine-3-propionic acid) to modify rhodanine groups on the surface of the MOFs material.
When the carboxylic acid organic ligand is amino terephthalic acid, the invention preferably mixes the rhodaninic acid organic solution with the 1-hydroxybenzotriazole alcoholic solution to obtain the functionalized feed liquid. In the present invention, the dosage ratio of the rhodanic acid and the organic solvent in the rhodanic acid organic solution is consistent with the technical scheme, and is not described herein again.
In the invention, the volume ratio of 1-hydroxybenzotriazole to alcohol solvent in the 1-hydroxybenzotriazole alcohol solution is preferably 1mmol: 1.5-5 mL, and more preferably 1mmol: 2.0-4 mL; the alcohol solvent is preferably methanol and/or ethanol; according to the invention, 1-hydroxybenzotriazole is preferably added into an alcohol solvent, and ultrasonic stirring is carried out for 15-20 min to obtain a clear 1-hydroxybenzotriazole alcohol solution.
The method preferably comprises the steps of adding the 1-hydroxybenzotriazole alcohol solution into the rhodaninic acid organic solution, and carrying out ultrasonic stirring for 10-15 min to realize the mixing of the rhodaninic acid organic solution and the 1-hydroxybenzotriazole alcohol solution to obtain the functionalized feed liquid. In the present invention, the 1-hydroxybenzotriazole functions to promote the reaction of amino groups and carboxyl groups.
In the invention, the molar ratio of 1-hydroxybenzotriazole to rhodaninic acid in the 1-hydroxybenzotriazole alcoholic solution is preferably 1-1.2: 1.
After the UO-66 MOFs and the functional material liquid are obtained, the UO-66 MOFs and the functional material liquid are preferably mixed, and then carbodiimide is added for catalytic modification synthesis reaction, so as to obtain the rhodanine functionalized MOFs adsorbent.
In the invention, the mass ratio of the UO-66 MOFs to the rhodaninic acid in the functionalized feed liquid is preferably 1: 0.2-4, more preferably 1: 0.5-3, and even more preferably 1: 2. According to the invention, preferably, the UO-66 MOFs is added into the functionalized material liquid and then stirred for 10-15 min to obtain the mixed material liquid of the UO-66 MOFs and the functionalized material liquid.
The method mixes the mixed feed liquid with carbodiimide to carry out catalytic modification synthesis reaction, so as to obtain the rhodanine functionalized MOFs adsorbent. In the invention, the molar ratio of the carbodiimide to the rhodaninic acid is preferably 1-1.5: 1. In the present invention, the carbodiimide preferably includes dicyclohexylcarbodiimide or 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide acid salt.
In the invention, the catalytic modification synthesis reaction is a modification synthesis reaction under the action of a catalyst carbodiimide and 1-hydroxybenzotriazole. In the invention, the temperature of the catalytic modification synthesis reaction is preferably 20-25 ℃; the time of the modification synthesis reaction is preferably 12-36 h, and more preferably 15-30 h. The modification synthesis reaction is preferably carried out under the condition of condensation reflux; in the modification synthesis reaction process, carbodiimide activates carboxyl on rhodaninic acid, the generated intermediate product reacts with 1-hydroxybenzotriazole to obtain active ester, and the active ester reacts with amine to be converted into amide; carboxyl of the rhodaninic acid coordinates with Zr-O cluster of the MOFs material or condenses with amino to generate amide, so as to form the rhodanine functionalized MOFs adsorbent. Specifically, UiO-66 and UiO-66-NH2Under solvent assisted conditions, a small amount of BDC2-The Zr-O metal cluster can be dissociated to have an empty orbit and can coordinate with-COOH on rhodaninic acid (rhodanine-3-acetic acid or rhodanine-3-propionic acid) to modify rhodanine groups on the surface of the MOFs material; furthermore, UiO-66-NH2Surface free-NH2Can react with-COOH on rhodanine-3-acetic acid or rhodanine-3-propionic acid in the presence of an activating agent to obtain rhodanine modified UiO-66-NH2-Rd。
After the modification synthesis reaction or the catalytic modification synthesis reaction, the reaction product is preferably sequentially filtered, washed by solid materials, dried and ground to obtain the rhodanine functionalized MOFs adsorbent. The invention has no special requirements on the specific implementation mode of the filtration, and the solid-liquid separation can be realized. The invention preferably adopts the organic solvent to wash the solid material for a plurality of times to remove unreacted substances; the washing organic solvent preferably comprises DMF, methanol or dichloromethane. After washing, the solid washing material is preferably dried in vacuum for 10-12 hours at the temperature of 60-80 ℃ to remove residual solvent. The invention has no special requirements on the specific implementation mode of grinding, and the solid material grinding mode well known by the technical personnel in the field is adopted to obtain the powder with the particle size of 50-100 nm.
For convenience of illustration, the reaction mechanism of the one-step modification synthesis of the invention is shown as formula I:
Figure BDA0001898033780000111
in the formula I, (a) refers to that when the carboxylic acid organic ligand is terephthalic acid, UiO-66 is formed first, and then the rhodaninic acid is coordinated and combined with Zr-O cluster on the UiO-66 through carboxyl to realize one-step modification synthesis, so as to obtain the rhodanine functionalized MOFs.
In the formula I, (b) means that when the carboxylic acid organic ligand is amino-terephthalic acid, UiO-66-NH is formed firstly2Then, the rhodaninic acid passes through carboxyl and UiO-66-NH2The Zr-O cluster is coordinated and combined with UiO-66-NH2And the amino amidation is combined to realize one-step modification synthesis to obtain the rhodanine functionalized MOFs.
The invention also provides a preparation method of the rhodanine functionalized MOFs adsorbent in the technical scheme, which comprises the following steps:
(1) reacting ZrCl4And organic solution ofMixing carboxylic acid organic ligands, carrying out hydrothermal reaction and filtering to obtain UiO-66 MOFs;
(2) mixing the organic solution of rhodaninic acid with thionyl chloride to carry out acyl chlorination reaction to obtain rhodaninic acid chloride;
(3) mixing the organic solution of rhodanine acyl chloride obtained in the step (2) with the UiO-66 MOFs obtained in the step (1), adding triethylamine, and reacting acyl chloride with amine to obtain a rhodanine functionalized MOFs adsorbent;
in the present invention, the starting materials used are commercially available products well known to those skilled in the art, unless otherwise specified.
ZrCl is added into the mixture4The organic solution is mixed with carboxylic acid organic ligand, and is filtered after hydrothermal reaction to obtain UiO-66 MOFs. In the present invention, the preparation of the UO-66 MOFs is the same as the preparation of the UO-66 MOFs in the technical solution of the preparation method, and is not described herein again.
The invention mixes the rhodaninic acid organic solution with thionyl chloride to carry out acyl chlorination reaction to obtain rhodaninic acid chloride. In the invention, the dosage ratio of the rhodanic acid to the organic solvent in the rhodanic acid organic solution is 1-10 mmol:50 mL; the organic solvent is a mixed solvent and comprises a first solvent and a second solvent, wherein the first solvent comprises one or more of dichloromethane, N-dimethylformamide, dimethyl sulfoxide and chloroform, and the second solvent comprises one or more of ethyl acetate, methanol and ethanol; the mixed solvent is more preferably dichloromethane and ethyl acetate; the volume ratio of the first solvent to the second solvent is 1: 1-4; said rhodaninic acid comprises rhodanine-3-acetic acid or rhodanine-3-propionic acid. In the invention, the molar ratio of the rhodaninic acid to the thionyl chloride in the rhodaninic acid organic solution is preferably 1: 1-2.
The invention preferably adds the thionyl chloride into the organic solution of the rhodaninic acid dropwise, and performs condensation reflux under the atmosphere of nitrogen to perform acyl chlorination reaction to obtain the rhodaninic acid chloride. The invention improves the amide reaction efficiency after the carboxyl is subjected to acyl chlorination, and can greatly improve the amount of rhodanine loaded on the surface of UiO-66 MOFs.
After the UO-66 MOFs and the rhodanine acyl chloride are obtained, the organic solution of the rhodanine acyl chloride is mixed with the UO-66 MOFs, triethylamine is added, and the reaction of the acyl chloride and the amine is carried out, so that the rhodanine functionalized MOFs adsorbent is obtained.
In the present invention, the organic solvent in the organic solution of rhodanineacyl chloride is preferably dichloromethane or tetrahydrofuran; the dosage ratio of the rhodanine acyl chloride to the organic solvent in the organic solution of the rhodanine acyl chloride is preferably 1-25 mmol:60mL, and the rhodanine acyl chloride can be fully dissolved. According to the invention, preferably, the rhodanine acyl chloride is added into an organic solvent, and then the mixture is ultrasonically stirred for 15-20 min to obtain an organic solution of the rhodanine acyl chloride.
According to the invention, preferably, the UO-66 MOFs is added into the organic solution of the rhodanine acyl chloride, and then ultrasonic stirring is carried out for 15-20 min, so that the organic solution and the UO-66 MOFs are uniformly mixed, and the mixed material liquid is obtained.
According to the invention, triethylamine is added into the mixed feed liquid to react acyl chloride with amine, so as to obtain the rhodanine functionalized MOFs adsorbent. In the present invention, the molar ratio of the triethylamine to the rhodanineacyl chloride in the mixed solution is preferably 1 to 1.5:1, and more preferably 1 to 1.2: 1. In the invention, the triethylamine plays a role of an acid-binding agent and can react with HCl generated by the reaction of acyl chloride and amine, so that the target reaction is promoted to be carried out; according to the invention, the reaction of acyl chloride and amine occurs, and the rhodanine acyl chloride reacts with UiO-66 MOFs to realize coordination of the rhodanine-containing group and Zr-O cluster of the MOFs material or condensation with amino to generate amide, so that the rhodanine functionalized MOFs adsorbent is formed.
After the reaction of acyl chloride and amine, the reaction product is preferably sequentially filtered, solid material washed, dried and ground to obtain the rhodanine functionalized MOFs adsorbent. The invention has no special requirements on the specific implementation mode of the filtration, and the solid-liquid separation can be realized. The invention preferably adopts the organic solvent to wash the solid material for a plurality of times to remove unreacted substances; the washing organic solvent preferably includes DMF, methanol, tetrahydrofuran, or dichloromethane. After washing, the solid washing material is preferably dried in vacuum for 10-12 hours at the temperature of 60-80 ℃ to remove residual solvent. The invention has no special requirements on the specific implementation mode of grinding, and the solid material grinding mode well known by the technical personnel in the field is adopted to obtain the powder with the particle size of 50-100 nm.
For illustrative purposes, the reaction mechanism of the multi-step modification synthesis of the present invention is shown in formula II, formula III and formula IV:
Figure BDA0001898033780000131
Figure BDA0001898033780000141
the carboxylic acid organic ligand in the reaction is terephthalic acid and amino-terephthalic acid, and UiO-66 MOFs is formed by the carboxylic acid organic ligand and metal Zr firstly, and then subsequent modification synthesis is carried out. Rhodaninic acid first forms rhodaninic acid chloride (shown as formula II), and then the rhodaninic acid chloride and the Zr-O cluster on the MOFs substrate are mixed to form mu3-OH and Zr are coordinated to obtain the rhodanine functionalized MOFs (formula III); furthermore, rhodanine acid chloride can also react with UiO-66-NH2The amino group is subjected to amidation reaction, and the rhodanine group is modified on the surface of MOFs (formula IV).
The invention also provides the application of the rhodanine functionalized MOFs adsorbent in the technical scheme or the rhodanine functionalized MOFs adsorbent prepared by the preparation method in the technical scheme in selective adsorption of silver ions in water; the application preferably comprises: and (3) adding the rhodanine functionalized MOFs adsorbent into the water body to be adsorbed with the silver ions, and stirring and adsorbing. The invention has no special requirement on the source of the water body to be adsorbed with silver ions, and any water body needing selective adsorption of silver ions can be used; in the embodiment of the invention, the water body can contain ions corresponding to a plurality of metals, such as Cu, Co, Ni, Pb, Li, K and Ag; the concentration of each metal ion in the water body is preferably 0.1-10 mmol/L, and more preferably 1.0-8.0 mmol/L. In the invention, the dosage of the rhodanine functionalized MOFs adsorbent is preferably 1 g: 500-2500 mL, more preferably 1 g: 1500-2500 mL.
In the invention, the stirring and adsorbing time is preferably 5-8 h, more preferably 5.5-7.5 h, and more preferably 6-7 h; the stirring adsorption is preferably carried out at room temperature, no additional heating is needed, and the cost is low. After the stirring and adsorption, the invention preferably carries out filtration to realize the recovery of the adsorbent, thereby obtaining the water body after adsorption. The present invention does not require special embodiments of the filtration, and can be carried out in a manner known to those skilled in the art.
For further illustration of the present invention, the following detailed description of the rhodanine functionalized MOFs adsorbent provided by the present invention, its preparation method and application are described in conjunction with the accompanying drawings and examples, which should not be construed as limiting the scope of the present invention.
A. Directly synthesizing rhodanine functionalized UiO-66 MOFs adsorbent by a one-step hydrothermal method:
example 1
(1) 0.24g (ca. 1.03mmol) of ZrCl4Uniformly dissolving in 50mLN, N-Dimethylformamide (DMF), ultrasonically stirring for 20min to obtain a clear solution, adding 0.18g (about 1.08mmol) of organic ligand 2-amino terephthalic acid, and continuously ultrasonically stirring for 30min until the solid is completely dissolved to obtain a mixed solution;
(2) adding 0.96g (5mmol) of rhodanine-3-acetic acid into the mixed material liquid obtained in the step (1), continuing to perform ultrasonic stirring for 30min, transferring the mixture into a 100mL reaction kettle after the solid is completely dissolved to obtain a clear solution, and placing the mixture into a 120 ℃ oven for reaction for 48 h;
(3) cooling to room temperature, filtering, and repeatedly washing the obtained precipitate with a mixed organic solvent of DMF, methanol and dichloromethane for many times;
(4) drying the washed product in a vacuum drying oven at 80 ℃ for 12h, and grinding to obtain a light purple powder (marked as UiO-66-NH) which is a rhodanine functionalized UiO-66 MOFs adsorbent with the particle size of 50-100 nm2-5Rd-A)。
Example 2
Rhodanine functionalized MOFs adsorbents were prepared in the manner of example 1, except that in step (1), the organic ligand used was terephthalic acid in an amount of 0.16 g. Obtaining the rhodanine functionalized UiO-66 MOFs adsorbent (marked as UiO-66-5 Rd-A).
Examples 3 to 7
A rhodanine functionalized MOFs adsorbent was prepared as in example 1, except that in step (2), rhodanine-3-acetic acid was added in amounts of 0.096g, 0.192g, 0.576g, 1.536g and 1.92g, respectively, and the obtained rhodanine functionalized UiO-66 class MOFs adsorbent was designated as UiO-66-NH, respectively2-0.5Rd-A、UiO-66-NH2-1Rd-A、UiO-66-NH2-3Rd-A、UiO-66-NH2-8Rd-A、UiO-66-NH2-10Rd-A。
Examples 8 to 12
A rhodanine functionalized MOFs adsorbent was prepared as in example 2, except that rhodanine-3-acetic acid was added in amounts of 0.096g, 0.192g, 0.576g, 1.536g and 1.92g, respectively, and the obtained rhodanine functionalized UO-66 type MOFs adsorbent was designated as UO-66-0.5 Rd-A, UiO-66-1Rd-A, UiO-66-3Rd-A, UiO-66-8Rd-A, UiO-66-10Rd-A, respectively.
The adsorbents obtained in examples 1 to 12 and non-rhodanine functionalized UiO-66 and UiO-66-NH2Silver ion adsorption was performed separately.
The isothermal adsorption process comprises the following steps: adding 20mg of adsorbent and 20mL of Ag (I) solution with different concentrations (50-1000 mg/L) into a 100mL conical flask, oscillating for 6h in a constant-temperature oscillation box at 25 ℃, filtering after adsorption balance is achieved, and measuring the concentration of Ag (I) in the filtrate by using an atomic absorption spectrometer under certain conditions; the adsorption capacity of each adsorbent is shown in Table 1, taking as an example the adsorption of silver ions at initial concentrations of 50 and 500 mg/L.
TABLE 1 adsorbents obtained in examples 1 to 12 and non-rhodanine functionalized UiO-66 and UiO-66-NH2Adsorption conditions on silver ions with initial concentrations of 50 and 500mg/L
Figure BDA0001898033780000161
Figure BDA0001898033780000171
As can be seen from Table 1, with the increase of the added rhodanine amount, the adsorption capacity of the prepared adsorbent to silver is correspondingly increased and then slightly reduced, and the added rhodanine amount of 5mmol is the optimal adding proportion; under the condition that the adding amount of rhodanine is equal, the adsorption capacity of the adsorbent prepared from the amino-containing preparation is larger than that of the adsorbent prepared from the adsorbent without amino.
Dynamic adsorption experiment: adding 100mg of adsorbent and 100mL of 40mg/L Ag (I) solution into a 250mL beaker, magnetically stirring at room temperature, taking out a certain volume of solution at regular intervals, filtering, measuring the concentration of Ag (I) in the filtrate by using an atomic absorption spectrometer under certain conditions, and calculating the adsorption capacity.
Carrying out adsorption kinetics experiments on the adsorbents obtained in the embodiments 1-12 to obtain adsorption equilibrium time; and simultaneously carrying out isothermal adsorption experiments to obtain the maximum adsorption capacity. The experimental results show that: the adsorbent obtained in example 1 can reach adsorption equilibrium within 15min, and the maximum adsorption capacity can reach 100.25mg/g, which is about 5 times of the original UiO-66 adsorption capacity, UiO-66-NH22 times the adsorption capacity. When the adsorbent is in a mixed solution of Ag (I), K (I), Li (I), Pb (II), Ni (II), Co (II) and Cu (II) with the concentration of 1mmol/L, the adsorbent has selective adsorbability to Ag (I), the adsorbability is 0.58mmol/g, and the adsorbability of other metal ions is only 0.09mmol/g at most.
The adsorbents obtained in examples 1 to 12 and non-rhodanine functionalized UiO-66 and UiO-66-NH2XRD characterization and analysis are carried out on the material. FIG. 1 is an XRD pattern of UiO-66 for all adsorbent materials and simulated calculations. As can be seen from fig. 1: all prepared adsorbent materials are consistent with the characteristic peak of UiO-66 calculated by simulation, and the UiO-66 loaded with the rhodanine still keeps the original characteristic peak, which indicates that the topological structures of the adsorbent and the UiO-66 are the same.
B. Post-modification one-step modification synthesis of rhodanine functionalized UiO-66 MOFs adsorbent:
example 13
(1) 0.48g of ZrCl4Uniformly dissolving the precipitate in 100mL of DMF, performing ultrasonic stirring for 20min to obtain a clear solution, adding 0.36g of 2-aminoterephthalic acid, continuing ultrasonic stirring for 30min, putting the dissolved solid into a reaction kettle after the solid is completely dissolved, reacting for 48h in a 120 ℃ oven, cooling to room temperature, filtering, repeatedly washing the obtained precipitate with DMF for multiple times to remove unreacted substances, drying the filtered product in a 100 ℃ oven in vacuum, and grinding to obtain 50-100 nm light yellow powder UiO-66-NH2；
(2) 0.96g (5mmol) of rhodanine-3-acetic acid is dispersed in a mixed solvent of 25mL of dichloromethane and 25mL of ethyl acetate, and ultrasonic stirring is carried out for 10min until the rhodanine-3-acetic acid is completely dissolved;
(3) dissolving 0.75g of 1-hydroxybenzotriazole in 10mL of methanol solution, ultrasonically stirring for 15min, adding the solution into the step (2) after the solution is clarified, and ultrasonically stirring for 10min to uniformly mix the solution;
(4) taking 0.5g of the material UiO-66-NH synthesized in the step (1)2Uniformly dispersing the mixture in the mixed solution obtained in the step (3), stirring for 10min, slowly adding 1.15g of carbodiimide, and condensing and refluxing for 24h at room temperature;
(5) after the reaction is finished, repeatedly washing the product obtained by filtering with methanol for many times;
(6) drying the filtered product in a vacuum drying oven at 80 ℃ for 12h, and grinding to obtain a yellowish-brown powder with the particle size of 50-100 nm, which is a rhodanine functionalized UiO-66 MOFs adsorbent (marked as UiO-66-NH)2-5Rd-B)。
Example 14
Rhodanine functionalized MOFs adsorbents were prepared in the manner of example 13, except that: in the step (1), the used organic ligand is terephthalic acid, and the dosage is 0.32 g; step (3) does not need to be carried out; in the step (4), 0.5g of the material UiO-66 synthesized in the step (1) is directly taken without adding carbodiimide, uniformly dispersed in the mixed solution obtained in the step (2), and condensed and refluxed for 24 hours at room temperature. Obtaining the rhodanine functionalized UiO-66 MOFs adsorbent (marked as UiO-66-5 Rd-B).
Examples 15 to 18
Pressing to realRhodanine functionalized MOFs adsorbents were prepared in the manner of example 13, except that: in the step (2), the dosages of the added rhodanine-3-acetic acid are 0.192g, 0.576g, 1.536g and 1.92g respectively; in the step (3), the dosage of the added 1-hydroxybenzotriazole is 0.15g, 0.45g, 1.2g and 1.5g respectively; in the step (4), the amounts of carbodiimide added were 0.23g, 0.69g, 1.84g and 2.3g, respectively. The obtained rhodanine functionalized UiO-66 MOFs adsorbent is respectively marked as UiO-66-NH2-1Rd-B、UiO-66-NH2-3Rd-B、UiO-66-NH2-8Rd-B、UiO-66-NH2-10Rd-B。
Examples 19 to 22
Rhodanine-functionalized MOFs adsorbent was prepared as in example 14 except that in step (2), rhodanine-3-acetic acid was added in amounts of 0.192g, 0.576g, 1.536g and 1.92g, respectively. The obtained rhodanine functionalized UiO-66 MOFs adsorbent is respectively marked as UiO-66-1Rd-B, UiO-66-3Rd-B, UiO-66-8Rd-B, UiO-66-10 Rd-B.
The adsorbents obtained in examples 13 to 22 and non-rhodanine functionalized UiO-66 and UiO-66-NH2Silver ion adsorption experiments were performed separately. The isothermal adsorption and dynamic chemisorption experiments were the same as those in examples 1 to 12, and are not described herein again.
Taking the adsorption conditions of silver ions at initial concentrations of 50 and 500mg/L in the isothermal adsorption process as examples, the adsorption capacity of each adsorbent is shown in Table 2.
TABLE 2 adsorbents obtained in examples 13 to 22 and non-rhodanine functionalized UiO-66 and UiO-66-NH2Adsorption conditions on silver ions with initial concentrations of 50 and 500mg/L
Figure BDA0001898033780000191
As can be seen from Table 2, with the increase of the modified rhodanine amount, the adsorption capacity of the prepared adsorbent to silver is correspondingly increased and then slightly decreased, and the modified rhodanine amount of 5mmol is the optimal addition proportion; when the modified rhodanine is equivalent, the adsorption capacity of the adsorbent prepared from the amino group-containing preparation is larger than that of the adsorbent prepared without the amino group.
Carrying out adsorption kinetics experiments on the adsorbents obtained in the embodiments 13-22 to obtain adsorption equilibrium time; meanwhile, the maximum adsorption capacity is obtained through an isothermal adsorption experiment. The experimental results show that: the adsorbent can reach adsorption balance within 10min, and the maximum adsorption capacity can reach 149.6mg/g, which is about 7 times of the original UiO-66 adsorption capacity, UiO-66-NH23 times the adsorption capacity; when the adsorbent is in a mixed solution of Ag (I), K (I), Li (I), Pb (II), Ni (II), Co (II) and Cu (II) with the concentration of 1mmol/L, the adsorbent has selective adsorbability to Ag (I), the adsorbability is 0.78mmol/g, and the adsorbability of other metal ions is only 0.03mmol/g at most.
FIG. 2 shows the modified 5mmol of rhodanine amount of the UO-66 MOFs adsorbent, simulated UO-66, and non-rhodanine functionalized UO-66 and UO-66-NH obtained in examples 13 and 142XRD pattern of (a). As can be seen from FIG. 3, the characteristic peak of the material grafted with rhodanine is not changed, which indicates that the grafted adsorbent maintains the same pioneer structure of UiO-66.
FIG. 3 is XRD patterns before and after adsorption-desorption cycles using the 5 th silver adsorption of the rhodanine functionalized MOFs adsorbents obtained in examples 13 and 14 (UiO-66-NH in FIG. 3)2-5Rd-B and UiO-66-5Rd-B respectively represent XRD patterns before the 5 th cyclic adsorption, UiO-66-NH2-5Rd-B @ Ag (I) and UiO-66-5Rd-B @ Ag (I) respectively represent XRD patterns after the 5 th cyclic adsorption). As can be seen from fig. 3, the characteristic peaks all remain unchanged, indicating that the material has excellent water stability. In addition, the rhodanine functionalized MOFs adsorbent prepared in example 13 can still keep the adsorption capacity more than 85% of the original capacity when the adsorbent is recycled for the fourth time through adsorption-desorption, which indicates that the material has good regeneration performance.
C. Post-modification multi-step reaction modification synthesis of rhodanine functionalized UiO-66 MOFs adsorbent:
example 23
(1) 0.48g of ZrCl4Uniformly dissolving in 50ml DMF, ultrasonically stirring for 20min to obtain clear solution, adding 0.36g 2-amino terephthalic acid, continuously ultrasonically stirring for 30min, and reacting after the solid is completely dissolvedReacting in a kettle in an oven at 120 ℃ for 48 hours, cooling to room temperature, filtering, repeatedly washing the obtained precipitate with organic solvents such as dichloromethane and the like for many times to remove unreacted substances, drying the filtered product in the oven at 100 ℃ in vacuum, and grinding to obtain 50-100 nm yellowish powder of UiO-66-NH2；
(2) Dispersing 3.84g (20mmol) of rhodanine-3-acetic acid in a mixed solution of 30mL of chloroform and 30mL of ethyl acetate, and ultrasonically stirring for 20min until the solid is completely dissolved;
(3) slowly dripping 4mL of thionyl chloride into the mixed solution in the step (2), condensing and refluxing for 12h at 60 ℃ under the protection of nitrogen, cooling, performing rotary evaporation at 40 ℃, dissolving with toluene, and performing rotary evaporation at 60 ℃ to obtain rhodanine-3-acetyl chloride;
(4) dissolving the obtained rhodanine-3-acetyl chloride in 60mL of dichloromethane solvent, ultrasonically stirring for 20min, and adding 0.5g of UiO-66-NH prepared in the step (1) after the solution is uniform2Stirring the materials for 10min to uniformly disperse the materials;
(5) slowly dripping 4mL of triethylamine into the mixed solution in the step (4), and condensing and refluxing for 36h at 25 ℃ under the protection of nitrogen;
(6) after the reaction is finished, repeatedly washing the product obtained by filtering with tetrahydrofuran for many times;
(7) drying the filtered product in a vacuum drying oven at 80 ℃ for 12h, and grinding to obtain brown black powder which is a rhodanine functionalized UiO-66 MOFs adsorbent (marked as UiO-66-NH)2-20Rd-C)。
Example 24
Rhodanine functionalized MOFs adsorbents were prepared in the manner of example 23, except that: in the step (1), the used organic ligand is terephthalic acid, and the dosage is 0.32 g; in the step (4), 0.5g of the UiO-66 material prepared in the step (1) is added, and the mixture is stirred for 10min to uniformly disperse the material. Obtaining the rhodanine functionalized UiO-66 MOFs adsorbent (marked as UiO-66-20 Rd-C).
Examples 25 to 28
Rhodanine functionalized MOFs adsorbents were prepared in the manner of example 23, except that: in the step (2), the dosage of the added rhodanine-3-acetic acid0.96g, 1.92g, 2.88g and 4.8g respectively; in the step (3), the dosage of the added thionyl chloride is 1mL, 2mL, 3mL and 5mL respectively; in step (5), the amount of triethylamine added was 1mL, 2mL, 3mL, and 5mL, respectively. The obtained rhodanine functionalized UiO-66 MOFs adsorbent is respectively marked as UiO-66-NH2-5Rd-C、UiO-66-NH2-10Rd-C、UiO-66-NH2-15Rd-C、UiO-66-NH2-25Rd-C。
Examples 29 to 32
Rhodanine functionalized MOFs adsorbents were prepared in the manner of example 24, except that: in the step (2), the dosages of the added rhodanine-3-acetic acid are 0.96g, 1.92g, 2.88g and 4.8g respectively; in the step (3), the dosage of the added thionyl chloride is 1mL, 2mL, 3mL and 5mL respectively; in step (5), the amount of triethylamine added was 1mL, 2mL, 3mL, and 5mL, respectively. The obtained rhodanine functionalized UiO-66 MOFs adsorbent is respectively marked as UiO-66-5Rd-C, UiO-66-10Rd-C, UiO-66-15Rd-C, UiO-66-25 Rd-C.
The adsorbents obtained in examples 23 to 32 and non-rhodanine functionalized UiO-66 and UiO-66-NH2Silver ion adsorption experiments were performed separately. The isothermal adsorption and dynamic chemisorption experiments were the same as those in examples 1 to 12, and are not described herein again.
Taking the adsorption conditions of the initial concentration of 50 and 800mg/L silver ions in the isothermal adsorption process as examples, the adsorption capacity of each adsorbent is shown in Table 3.
TABLE 3 adsorbents obtained in examples 23 to 32 and non-rhodanine functionalized UiO-66 and UiO-66-NH2Adsorption conditions on silver ions with initial concentrations of 50 and 800mg/L
Figure BDA0001898033780000221
Figure BDA0001898033780000231
As can be seen from Table 3, the adsorption capacity of the modified material is significantly improved, and when the grafting amount is 20mmol of rhodanine, the adsorption capacity of the material is maximized, while when the rhodanine amount is continuously increased, the adsorption capacity of the material is significantly reduced. In addition, when the modified rhodanine is equivalent, the adsorption capacity of the adsorbent prepared from the amino group-containing preparation is larger than that of the adsorbent prepared without the amino group.
The adsorbents obtained in examples 23 to 32 and non-rhodanine functionalized UiO-66 and UiO-66-NH2XRD characterization analysis was performed, and the results are shown in FIG. 4. As can be seen from FIG. 4, the characteristic peak of the material remained consistent with that of the simulated UiO-66 when the amount of grafted rhodanine increased to 20mmol, while the XRD peak of the material obtained by continuously increasing the amount of rhodanine changed, indicating that the structure of the material collapsed after continuously increasing the amount.
The adsorbents obtained in examples 23 and 24 were combined with non-rhodanine functionalized UiO-66 and UiO-66-NH2Competitive adsorption experiments with mixed ions were performed. 50mg of an adsorbent and 50mL of a mixed solution containing Ag (I), K (I), Li (I), Pb (II), Ni (II), Co (II) and Cu (II) in a concentration of 10mmol/L were put into a 100mL Erlenmeyer flask, and the mixture was shaken in a 25 ℃ constant temperature shaking chamber for 6 hours to reach adsorption equilibrium, followed by filtration, and the concentration of metal ions in the filtrate was measured by an atomic absorption spectrometer under certain conditions, and the results of adsorption capacity are shown in Table 4. As can be seen from Table 4, the modified adsorbent prepared in example 23 has high selective adsorption for Ag (I), and has an adsorption capacity of 8.5mmol/g, while the adsorption capacity of other metal ions is only 0.17mmol/g at the maximum.
TABLE 4 LUO-functionalized UO-66 MOFs adsorbents obtained in examples 23 and 24 and non-LUO-66 and UO-66-NH which were not LUO-functionalized2Selective adsorption condition of mixed ions with initial concentrations of 10mmol/L
Figure BDA0001898033780000232
Figure BDA0001898033780000241
Adsorbents obtained from examples 23 and 24 and non-rhodanine functionalized UiO-66 and UiO-66-NH2The dynamic adsorption experiment is carried out to obtain a dynamic adsorption figure, the result is shown in figure 5, and as can be seen from figure 5, the adsorption rate of the material modified by the rhodanine is obviously improved, and the removal rate can reach more than 99% within 2 min.
Carrying out adsorption kinetics experiments on the adsorbents obtained in the embodiments 23-32 to obtain adsorption equilibrium time; meanwhile, the maximum adsorption capacity is obtained through an isothermal adsorption experiment. The experimental results show that: the maximum adsorption capacity of the adsorbent can reach 923.9mg/g, which is about 44 times of the original UiO-66 adsorption capacity, UiO-66-NH217 times the adsorption capacity. When the adsorbent is in a mixed solution with the concentration of Ag (I), K (I), Li (I), Pb (II), Ni (II), Co (II) and Cu (II) of 10mmol/L, the adsorbent has selective adsorbability to Ag (I), the adsorbability is 8.5mmol/g, and the adsorbability of other metal ions is only 0.17mmol/g at most; in addition, the material has excellent adsorption rate, and the removal rate of the silver ions with the initial concentration of 40mg/L can reach 99.2% within 2 min.
The rhodanine functionalized MOFs adsorbent obtained in the above embodiment is detected through XPS element analysis, and the mass ratio of Zr to S element in the obtained rhodanine functionalized MOFs adsorbent is proved to be 1: 0.02-20.
According to the embodiments, the rhodanine functionalized MOFs adsorbent provided by the invention takes stable Zr-MOFs as a substrate material, and rhodanine derivatives as functional groups with a targeted adsorption property on Ag, and rhodanine is introduced into a Zr-MOF structure to obtain the rhodanine functionalized MOFs adsorbent, so that the selective adsorption of Ag in a water body is realized.
The reaction raw materials used in the preparation process are rich in sources, low in price and low in production cost, and are easy to be applied to large-scale commercial application.
Although the present invention has been described in detail with reference to the above embodiments, it is only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and the embodiments are within the scope of the present invention.

Claims (10)

1. A rhodanine functionalized MOFs adsorbent for selectively adsorbing silver ions in a water body comprises a UiO-66 MOFs matrix and modified rhodanine groups.
2. The rhodanine functionalized MOFs adsorbent for selective adsorption of silver ions in water according to claim 1, wherein said UiO-66 type MOFs matrix comprises UiO-66 or UiO-66-NH2。
3. A method for preparing the rhodanine functionalized MOFs adsorbent for selective adsorption of silver ions in water body according to claim 1 or 2, comprising the following steps:
(1) reacting ZrCl4Mixing the organic solution with carboxylic acid organic ligand to obtain MOFs synthetic feed liquid;
(2) and (2) mixing the MOFs synthetic material liquid obtained in the step (1) with rhodaninic acid, and carrying out hydrothermal reaction to obtain the rhodanine functionalized MOFs adsorbent capable of selectively adsorbing silver ions in a water body.
4. The method according to claim 3, wherein the carboxylic acid-based organic ligand in the step (1) comprises terephthalic acid or 2-aminoterephthalic acid;
the rhodanine acid in the step (2) comprises rhodanine-3-acetic acid or rhodanine-3-propionic acid;
ZrCl in the rhodanic acid and MOFs synthetic material liquid in the step (2)4The molar ratio of the carboxylic acid organic ligand is 0.1-10: 1: 1;
the temperature of the hydrothermal reaction in the step (2) is 110-150 ℃, and the time is 24-72 h.
5. A method for preparing the rhodanine functionalized MOFs adsorbent for selective adsorption of silver ions in water body according to claim 1 or 2, comprising the following steps:
(1) reacting ZrCl4Mixing the organic solution with carboxylic acid organic ligand, carrying out hydrothermal reaction and filtering to obtain UiO-66 classes of MOFs;
(2) and (2) mixing the UiO-66 MOFs obtained in the step (1) with a rhodaninic acid organic solution, and carrying out modification synthesis reaction to obtain the rhodanine functionalized MOFs adsorbent capable of selectively adsorbing silver ions in a water body.
6. The method according to claim 5, wherein ZrCl is used in the step (1)4The molar ratio of the carboxylic acid organic ligand to the carboxylic acid organic ligand is 1:1, the carboxylic acid organic ligand comprises terephthalic acid or 2-amino terephthalic acid, the hydrothermal reaction temperature is 120 ℃, and the time is 48 hours;
the rhodanine acid in the step (2) comprises rhodanine-3-acetic acid or rhodanine-3-propionic acid;
when the carboxylic acid organic ligand is 2-amino terephthalic acid, mixing the organic solution of rhodanic acid with the 1-hydroxybenzotriazole alcoholic solution to obtain a functionalized feed liquid before mixing the UO-66 MOFs and the rhodanic acid organic solution in the step (2); mixing the functionalized feed liquid with UiO-66 MOFs, adding carbodiimide, and carrying out catalytic modification synthesis reaction;
the mass ratio of the UO-66 MOFs to the rhodaninic acid is 1: 0.2-5; the molar ratio of the 1-hydroxybenzotriazole to the rhodaninic acid in the 1-hydroxybenzotriazole alcoholic solution is 1-1.2: 1; the molar ratio of the carbodiimide to the rhodaninic acid is 1-1.5: 1.
7. A method for preparing the rhodanine functionalized MOFs adsorbent for selective adsorption of silver ions in water body according to claim 1 or 2, comprising the following steps:
(1) reacting ZrCl4The organic solution is mixed with carboxylic acid organic ligand, and filtration is carried out after hydrothermal reaction to obtain UiO-66 MOFs;
(2) mixing the organic solution of rhodaninic acid with thionyl chloride to carry out acyl chlorination reaction to obtain rhodaninic acid chloride;
(3) and (3) mixing the organic solution of the rhodanine acyl chloride obtained in the step (2) with the UiO-66 MOFs obtained in the step (1), adding triethylamine, and reacting acyl chloride with amine to obtain the rhodanine functionalized MOFs adsorbent capable of selectively adsorbing silver ions in a water body.
8. The method according to claim 7, wherein ZrCl is used in the step (1)4The molar ratio of the organic ligand of the carboxylic acid to the organic ligand of the carboxylic acid is 1: 1; the carboxylic acid organic ligand comprises 2-amino terephthalic acid;
the temperature of the hydrothermal reaction in the step (1) is 120 ℃, and the time is 48 hours;
the molar ratio of the rhodaninic acid to the thionyl chloride in the step (2) is 1: 1-2;
the rhodanine acid in the step (2) comprises rhodanine-3-acetic acid or rhodanine-3-propionic acid;
in the step (2), the temperature of the acyl chlorination reaction is 50-60 ℃, and the time is 6-12 h;
the dosage ratio of the rhodanine acyl chloride in the organic solution of the rhodanine acyl chloride in the step (3) to the added UiO-66 MOFs is 1-25 mmol:0.5 g;
the molar ratio of triethylamine to rhodanine acyl chloride in the step (3) is 1-1.5: 1;
in the step (3), the reaction temperature of acyl chloride and amine is 20-25 ℃, and the reaction time is 12-36 h.
9. The application of the rhodanine functionalized MOFs adsorbent for selectively adsorbing silver ions in water body, which is prepared according to any one of claims 1 to 2, or the rhodanine functionalized MOFs adsorbent for selectively adsorbing silver ions in water body, which is prepared according to any one of claims 3 to 8.
10. The application according to claim 9, wherein the application comprises: and (3) adding the rhodanine functionalized MOFs adsorbent for selectively adsorbing the silver ions in the water body into the water body to be adsorbed with the silver ions, and stirring and adsorbing.
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