CN110862550A

CN110862550A - Cobalt-metal organic framework material and preparation method and application thereof

Info

Publication number: CN110862550A
Application number: CN201911226505.9A
Authority: CN
Inventors: 季长春; 韩素军; 杨光; 张东星; 尹丽
Original assignee: Anhui Normal University
Current assignee: Anhui Normal University
Priority date: 2019-12-04
Filing date: 2019-12-04
Publication date: 2020-03-06
Anticipated expiration: 2039-12-04
Also published as: CN110862550B

Abstract

The invention discloses a cobalt-metal organic framework material and a preparation method and application thereof, wherein the molecular formula of the cobalt-metal organic framework material is { [ Co (L) (H)₂O)₂]·CHO₂·1.5H₂O}_nWherein L is^‑Is deprotonated 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl]-4-carboxylic acid, n is a positive integer, CHO₂Represents deprotonated formic acid, 1.5H₂O is water which does not participate in coordination. The cobalt-goldThe cobalt-metal organic framework material has the characteristics of excellent photocatalytic performance and thermal stability, and meanwhile, the preparation method has the characteristics of simplicity and convenience in operation, good reproducibility and mild conditions, so that the cobalt-metal organic framework material can be widely applied to photocatalytic degradation of organic dyes.

Description

Cobalt-metal organic framework material and preparation method and application thereof

Technical Field

The invention relates to an organic framework material, in particular to a cobalt-metal organic framework material and a preparation method and application thereof.

Background

Metal-Organic Frameworks (MOFs) belong to coordination polymers, and are crystalline compounds with intramolecular gaps and periodic network structures formed by self-assembly of central Metal atoms/ions (clusters) and ligand molecules. The MOFs have rich structures, generally have structures such as zero-dimensional point, one-dimensional chain, two-dimensional layer and three-dimensional network, and the structural diversity is influenced by multiple factors such as temperature, organic ligands, central metal ions and counter ions. At present, MOFs materials are used as photocatalysts, and research on heterogeneous catalytic degradation of pollutants such as organic dyes is still in progress. Therefore, the preparation of the cobalt-metal organic framework material of the invention is necessary.

The degradation of the existing cobalt metal organic framework material to dye is generally photocatalytic degradation, for example, Shi Zhou et al synthesizes a copper-based metal organic framework and degrades 59 percent of methylene blue dye within 2 hours under an ultraviolet lamp, so that the cobalt metal organic framework material has better catalytic activity; the cobalt-based metal organic framework and the manganese-based metal organic framework which have the isomorphic structure are combined by the book of religious problems, and the methylene blue is degraded under an ultraviolet lamp, but the cobalt-based metal organic framework is unstable in water, while the manganese-based metal organic framework has better stability in water, and the degradation rate of the methylene blue after being photocatalyzed for ten hours is 52.5%.

Disclosure of Invention

The invention aims to provide a cobalt-metal organic framework material, a preparation method and application thereof, wherein the cobalt-metal organic framework material has excellent photocatalytic performance and thermal stability, and meanwhile, the preparation method has the characteristics of simplicity and convenience in operation, good reproducibility and mild conditions, so that the cobalt-metal organic framework material can be widely applied to photocatalytic degradation of dyes.

In order to achieve the above object, the present invention provides cobalt-goldBelongs to an organic framework material, the molecular formula of the cobalt-metal organic framework material is { [ Co (L) (H)₂O)₂]·CHO₂·1.5H₂O}_nWherein L is^-Is deprotonated 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl]-4-carboxylic acid, n is a positive integer, CHO₂Represents deprotonated formic acid (obtained by hydrolysis of DMF), 1.5H₂O is water which does not participate in coordination.

The invention also provides a preparation method of the cobalt-metal organic framework material, which is characterized by comprising the following steps: a cobalt source, 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl ] -4-carboxylic acid, is subjected to a solvothermal reaction in a solvent containing DMF.

The invention provides an application of the cobalt-metal organic framework material in photocatalytic degradation of organic dyes.

In the technical scheme, the invention uses 3 ', 5 ' -di (4-pyridyl) - [1,1 ' -biphenyl]4-carboxylic acid as ligand, and carrying out solvothermal reaction with cobalt source to obtain the cobalt-metal organic framework material { [ Co (L) (H)₂O)₂]·CHO₂·1.5H₂O}_n(ii) a The cobalt-metal organic framework material has excellent photocatalytic performance and is mainly prepared by O through photo-generated electrons in a reaction system₂The electron trapping agent is combined to form superoxide anion, the left hole directly oxidizes water or hydroxyl ion in the system to form hydroxyl radical, and the superoxide anion and the hydroxyl radical have strong oxidability and can oxidize most organic matters to a final product H₂O and CO₂Even some inorganic matters can be thoroughly decomposed, so that the cobalt-metal organic framework material can be used for degrading organic dye by photocatalysis; meanwhile, the cobalt-metal organic framework material has excellent thermal stability, so that the cobalt-metal organic framework material has wide application prospect.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is an ellipsoid plot of the complex of example 1 (ellipsoid probability 30%, hydrogen atoms and lattice molecules omitted for clarity; symmetrical operation: #1 ═ 2-x, y, 2.5-z; #2 ═ 0.5+ x, -0.5+ y,0.5+ z; #3 ═ 1.5-x, -0.5+ y, 2-z; #4 ═ 1-x, y, 1.5-z; # 5; -0.5+ x,0.5+ y, -0.5+ z; # 6; # 1.5-x,0.5+ y, 2-z; # 7; # 0.5+ x,0.5+ y,0.5+ z; # 8; # 2.5-x,0.5+ y, 3-z; # 1; (x, y + z); (1, 1+ z);

FIG. 2 is a schematic diagram of the complex in example 1 in the bc plane (H atom and lattice molecule are omitted for clarity);

FIG. 3 is a schematic diagram of the three-dimensional structure of the complex in example 1 (H atoms and molecules of the crystal lattice are omitted for clarity);

FIG. 4 is a thermogravimetric analysis of the complex of example 1;

FIG. 5a is a graph of the UV-VIS absorption spectrum of the complex of example 1;

FIG. 5b is a graph showing the kinetics of UV-visible absorption of the complex of example 1;

FIG. 5C shows UV-visible absorption of the complex of example 1 for ln (C)_t/C₀) Linear fitting relation graph is carried out on the curve about Kt;

FIG. 5d is a graph of the conversion of the complex to rhodamine B in example 1;

FIG. 6 is an X-ray powder diffraction pattern of crystals of the complex in example 1.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a cobalt-metal organic framework material, and the molecular formula of the cobalt-metal organic framework material is { [ Co (L) (H)₂O)₂]·CHO₂·1.5H₂O}_nWherein L is^-Is deprotonated 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl]-4-carboxylic acid, n is a positive integer, CHO₂Represents deprotonated formic acid, 1.5H, produced by hydrolysis of DMF₂O is water which does not participate in coordination.

In the present invention, the specific coordination mode and structure of cobalt ions in the cobalt-metal organic framework material can be selected in a wide range, but in order to make it have more excellent photocatalytic performance and thermal stability, it is preferable that cobalt ions of a coordination environment, labeled as Co1, exist in the cobalt-metal organic framework material; the Co1 is in a distorted octahedral configuration, with each Co1 coordinated with four oxygen atoms and two nitrogen atoms, where the two oxygen atoms are from the same L^-Carboxylate radical in ligand, and other two oxygen atoms from coordinated H₂In O, the two nitrogen atoms are each independently derived from two L^-The nitrogen atom of the pyridine ring of the ligand.

In the present invention, the crystal form of the cobalt-metal organic framework material can be selected in a wide range, but in order to make it have more excellent photocatalytic performance and thermal stability, preferably, the cobalt-metal organic framework material belongs to the monoclinic system, I2/c space group, and the unit cell parameters are respectively:

α＝90.00°，β＝96.09(5)°，γ＝90.00°。

In the above-mentioned production method, the specific conditions of the solvothermal reaction may be selected within a wide range, but in order to further improve the reaction rate and the yield of the cobalt-metal organic framework material, it is preferable that the solvothermal reaction satisfies the following conditions: the reaction temperature is 60-80 ℃, and the reaction time is 48-72 h.

In the above-mentioned production method, the amount of each material to be used may be selected within a wide range, but in order to further improve the reaction rate and the yield of the cobalt-metal organic framework material, it is preferable that the molar ratio of the cobalt source, 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl ] -4-carboxylic acid is 10: 0.5-3.

In the above preparation method, the specific composition and compounding ratio of the solvent may be selected within a wide range, but in order to further improve the reaction rate and yield of the cobalt-metal organic framework material, it is preferable that the solvent consists of DMF, water and acetonitrile in a volume ratio of 1-3: 2-4: 1.

in the above-mentioned production method, the amount of the solvent to be used may be selected within a wide range, but in order to further improve the reaction rate and the yield of the cobalt-metal organic framework material, it is preferable that the ratio of the amount of the cobalt source to the amount of the solvent to be used is 0.1 mmol: 4-8 mL.

In the present invention, the specific kind of the cobalt source may be selected within a wide range, but from the viewpoint of solubility and cost, it is preferable that the cobalt source is selected from Co (NO)₃)₂·6H₂O、Co(CH₃COO)₂·4H₂O、CoSO₄·7H₂O and CoCl₂·6H₂At least one of O.

In the present invention, in order to further allow sufficient contact between the raw materials and further improve the reaction rate and the yield of the cobalt-metal organic framework material, preferably, the preparation method further comprises, before the solvothermal reaction: subjecting the raw materials to ultrasonic oscillation for 3-5 min.

In the present invention, the post-treatment after the solvothermal reaction may be performed in multiple ways, such as direct filtration, centrifugation, or natural volatilization of the solvent, but in order to shorten the reaction flow and improve the purity of the product, it is preferable that the preparation method further comprises, after the solvothermal reaction: and (3) cooling the system, cooling to room temperature, carrying out solid-liquid separation, washing the solid with mother liquor, and naturally drying the solid to obtain the cobalt-metal organic framework material.

In the above application, the step of photocatalytically degrading the organic dye may be selected within a wide range, but in order to further improve the efficiency of photocatalytic degradation, it is preferable that the step of photocatalytically degrading the organic dye is: firstly, mixing the dye, the cobalt-metal organic framework material and the solvent for 0.5 to 1 hour under the dark condition, and then carrying out degradation reaction for 1 to 3 hours under ultraviolet light.

In the above application, the ratio of the raw materials in the photocatalytic degradation can be selected in a wide range, but in order to further improve the efficiency of the photocatalytic degradation, the ratio of the amount of the dye, the cobalt-metal organic framework material, and the solvent is preferably 0.3 mg: 5-15 mg: 30-50 mL.

In the above application, the kind of the dye may be selected in a wide range, but preferably, the dye is at least one of rhodamine B, methylene blue, and methyl orange in view of the efficiency of photocatalysis and the degree of prevalence of the dye.

The present invention will be described in detail below by way of examples.

Example 1

Mixing Co (NO)₃)₂·6H₂O (0.1mmol), 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl]The mixture of (0.017mmol) of (E) -4-carboxylic acid was charged into a 10mL reaction flask, followed by the addition of DMF/H₂Performing ultrasonic treatment at 25 deg.C for 4min with O/acetonitrile mixed solvent (volume ratio of 1.5: 2.5: 1, 5 mL); then the mixed solution in the reaction bottle is put into a stainless steel reaction kettle with a polytetrafluoroethylene lining, the temperature is slowly reduced after the solvent-thermal reaction is carried out for 72 hours at the temperature of 80 ℃, the solid-liquid separation is carried out at the temperature of 25 ℃, the supernatant fluid is taken by utilizing the mixed solution after the reaction, the solid complex is washed for many times, and then the complex is naturally dried at the temperature of 25 ℃ to obtain a small amount of red blocky crystalsYield 61.6%.

Example 2

The procedure is as in example 1, except that the solvothermal reaction is carried out at 70 ℃ for 72h, giving a yield of 47.3%.

Example 3

The procedure is as in example 1, except that the solvothermal reaction is carried out at 80 ℃ for 48h, 53.5% yield.

Example 4

The procedure is as in example 1, except that Co (NO)₃)₂·6H₂O is replaced by an equimolar amount of Co (CH)₃COO)₂·4H₂O, yield 58.83%.

Example 5

The procedure is as in example 1, except that the ligand HL is used in an amount of 0.009mmol, DMF/H₂The O/acetonitrile mixed solvent was 4mL, and the yield was 49.3%.

Example 6

The procedure is as in example 1, except that the ligand HL is used in an amount of 0.03mmol, DMF/H₂The O/acetonitrile mixed solvent was 8mL, and the yield was 64.57%.

Detection example 1

And (3) structure determination:

the complex obtained in example 1 was monochromated at room temperature using a graphite monochromator_αRadiation (λ. 0.071073nm), using

Scanning, collecting data on Bruker Smart Apex CCD single crystal diffractometer, and finding the results shown in FIGS. 1-3; the crystal structure is placed on a SHELXTL program by using a direct method to complete analysis, all non-hydrogen atom coordinates are obtained by Fourier synthesis, and anisotropic thermal parameter refinement is carried out. The coordinates of hydrogen atoms are obtained by theoretical calculation, and isotropic refinement is carried out; the specific results are shown in tables 1 and 2, and table 1 shows the crystal data of the complex; table 2 partial bond lengths of the complexes

And a key angle (°).

TABLE 1

TABLE 2

Symmetrical operation: (i)1-x, y, -z +3/2(ii) x-1/2, y +1/2, z-1/2; (iii) -x +3/2, y +1/2, -z +3/2.

As can be seen from FIGS. 1-3, in this complex, the smallest asymmetric unit contains a crystallographically independent Co ion, a deprotonated HL ligand, two coordinated H₂And O. As shown in FIG. 1, the Co atoms are in a distorted octahedral configuration, each Co ion being coordinated with four oxygen atoms and two nitrogen atoms, two of which (O2#5, O2#6) are from the same L^-The other two oxygen atoms (O1, O1#4) of the ligand come from coordinated water molecules. The bond length of the Co-O bond is in

To

In a variation, the two nitrogen atoms (N1, N1#4) are from deprotonated HL ligands, with a Co-N bond of length

Consistent with the reported bond length values in the Co-containing nitrogen-containing carboxylic acid complexes.

The left part in fig. 2 represents the 3D network framework structure and the right part represents the 2D layer structure on the bc plane; in fig. 3, the left part shows a schematic diagram of a three-dimensional structure in the bc direction, and the right part shows a schematic diagram of a three-dimensional structure in the ac direction.

In FIG. 2, L^-As a bridging ligand, cobalt ions are connected through oxygen atoms of carboxyl groups on the ligand and nitrogen atoms in pyridine to form a 2D layered structure in a bc plane, but holes appearing in the 2D plane are reduced due to dislocation superposition because of dislocation arrangement between two adjacent layers; FIG. 3 shows a 3D structure of the complex along different directions a and b.

Detection example 2

And (3) measuring the thermal stability:

to investigate the stability of the complex, a thermogravimetric analysis (TGA) was carried out on a sample of the crystals obtained in example 1, according to the invention, as follows: by using DSC/TG pan Al₂O₃Scanning the sample by a thermogravimetric analyzer, obtaining a TG curve at the temperature rise rate of 10 ℃/min and the temperature range of 30-800 ℃, and obtaining the specific result shown in figure 4.

Thermogravimetric analysis of the complex crystal shows that: in FIG. 4, the weight loss was first about 8.76% (theoretical 8.7%) at 86-135 ℃ corresponding to the loss of a deprotonated formic acid, and the second step was about 11.5% at 255-340 ℃ corresponding to the loss of 2 coordinated water molecules and 1.5 non-coordinated water molecules, which was about the same as the theoretical 12.2%. Then as the temperature is gradually increased, the ligand falls off after 340 ℃, and then the structure collapses.

Detection example 3

And (3) infrared spectrum property characterization:

the product of example 1 was mixed with KBr and ground into flakes and measured by an IR Prestige-21, Shimadzu model FT-IR infrared spectrometer having a wavelength range of 400-4000cm^-1(ii) a Characterization of the resulting Primary Infrared Spectrum data (KBr pellet, cm)^-1) Comprises the following steps: 2922(w),2426(w),1670(m),1614(s),1554(w),1510(m),1423(s),1383(s),1068(w),1026(w),867(w),828(m),786(m),711(m),671(w),630(m),616(w),530(w),513(w),490(w),470 (w). Thus illustrating that the product of example 1 has 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl]-infrared characteristic peak of 4-carboxylic acid.

Detection example 4

The performance of the photocatalytic degradation of RhB is characterized in that:

weighing 10mg of the product of example 1, degrading 30mL of rhodamine B solution (RhB,10mg/L), and stirring the rhodamine B solution in a dark place for 0.5h to ensure that the catalyst and the dye reach adsorption-resolution balance; then, the sample is illuminated by a 400W ultraviolet lamp, and is sampled by a rubber head dropper every 20min, and a centrifuge is used for centrifuging to obtain supernatant. The photocatalytic degradation performance of the complex is detected and analyzed by absorbance through an ultraviolet-visible spectrophotometer (model U-4100, Hitachi), specific results are shown in figures 5 a-5 d, and it can be seen from the figures that the color of the dye is obviously gradually lightened along with the increase of time under an ultraviolet lamp, which indicates that the complex has excellent catalytic activity on RhB under ultraviolet light.

Detection example 5

Characterization of X-ray powder diffraction spectrum:

the product of example 1 was examined on an X-ray powder diffractometer model D8-A25, Bruker-AXS, with an angle ranging from 5 to 50 degrees, and the results are shown in FIG. 6, from which it can be seen that the X-ray powder diffraction test pattern of the complex is consistent with the simulated pattern of single crystal diffraction, indicating that the purity of the tested sample is high.

The same tests were carried out on the products of examples 2 to 6 in the same manner as in test examples 1 to 5, and the results were substantially identical to those of example 1.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. The cobalt-metal organic framework material is characterized in that the molecular formula of the cobalt-metal organic framework material is { [ Co (L) (H)₂O)₂]·CHO₂·1.5H₂O}_nWherein L is^-Is deprotonated 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl]-4-carboxylic acid, n is a positive integer, CHO₂Represents deprotonated formic acid, 1.5H₂O is water which does not participate in coordination.

2. The cobalt-metal organic framework material of claim 1, wherein there is a coordination environment of cobalt ions present in the cobalt-metal organic framework material, labeled Co 1; the Co1 is in a distorted octahedral configuration, with each Co1 coordinated with four oxygen atoms and two nitrogen atoms, where the two oxygen atoms are from the same L^-Carboxylate radical in ligand, and other two oxygen atoms from coordinated H₂In O, the two nitrogen atoms belong to two L^-The nitrogen atom of the pyridine ring of the ligand.

3. The cobalt-metal organic framework material of claim 1, wherein the cobalt-metal organic framework material belongs to the monoclinic system, I2/c space group, and the unit cell parameters are respectively:

α＝90.00°,β＝96.09(5)°,γ＝90.00°。

4. a method of preparing a cobalt-metal organic framework material as claimed in any one of claims 1 to 3, comprising: a cobalt source, 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl ] -4-carboxylic acid, is subjected to a solvothermal reaction in a solvent containing DMF.

5. The production method according to claim 1, wherein the solvothermal reaction satisfies the following condition: the reaction temperature is 60-80 ℃, and the reaction time is 48-72 h.

6. The process according to claim 1, wherein the molar ratio of the cobalt source, 3 ', 5 ' -bis (4-pyridyl) - [1,1 ' -biphenyl ] -4-carboxylic acid is 10: 0.5-3.

7. The preparation method according to claim 1, wherein the solvent consists of DMF, water and acetonitrile in a volume ratio of 1-3: 2-4: 1

Preferably, the dosage ratio of the cobalt source to the solvent is 0.1 mmol: 4-8 mL.

8. The method of any one of claims 4-7, wherein the cobalt source is selected from Co (NO)₃)₂·6H₂O、Co(CH₃COO)₂·4H₂O、CoSO₄·7H₂O and CoCl₂·6H₂At least one of O;

preferably, before the solvothermal reaction, the preparation method further comprises: subjecting the raw materials to ultrasonic vibration for 3-5 min;

more preferably, after the solvothermal reaction, the preparation method further comprises: and (3) cooling the system to 15-25 ℃, carrying out solid-liquid separation, washing the solid, and naturally drying to obtain the cobalt-metal organic framework material.

9. Use of a cobalt-metal organic framework material according to any of claims 1 to 3 for photocatalytic degradation of organic dyes.

10. Use according to claim 9, wherein the step of photocatalytically degrading the organic dye is: firstly, mixing a dye, a cobalt-metal organic framework material and a solvent for 0.5-1h under a dark condition, and then performing degradation reaction for 1-3h under ultraviolet light;

preferably, the dosage ratio of the dye, the cobalt-metal organic framework material and the solvent is 0.3 mg: 5-15 mg: 30-50 mL;

more preferably, the dye is at least one of rhodamine B, methylene blue, and methyl orange.