Co-MOF (at) Ag composite material and preparation method and application thereof

Abstract

The invention discloses a Co-MOF (at) Ag composite material and a preparation method and application thereof. The composite material is composed of Co-MOF and silver nanoparticles loaded on the surface of the Co-MOF, the chemical formula of the Co-MOF is Co (btyp) (ppda), btyp represents 3, 5-bis (triazole) pyridine, and ppda represents phenylenediacetic acid. The composite material has a large specific surface area, can be used for removing dyes in water, has an adsorption capacity of 47.28-55mg / g on Congo red, and can be reused.

Description

Technical Field

[0001] This invention relates to a metal complex, and more specifically, to a Co-MOF@Ag composite material, its preparation method, and its uses. Background Technology

[0002] Dyes, commonly used raw materials in the food, pharmaceutical, and printing and dyeing industries, are a major contributor to water pollution. These dyes generally exhibit poor stability, difficulty in biodegradation, high organic content, complex composition, and intense color, making dye pollution a global environmental problem. Currently, various technologies for removing dyes from wastewater have been developed both domestically and internationally, including physical adsorption, biological methods, chemical oxidation, coagulation, and membrane separation. Among these, adsorption remains the most commonly used method in practical applications due to its advantages such as ease of operation, reusability, wide applicability, and the ability to selectively concentrate certain compounds in an environmentally friendly and efficient manner.

[0003] Porous materials with abundant specific surface areas, such as activated carbon, metal-organic frameworks (MOFs), zeolites, porous organic polymers (POPs), and covalent organic frameworks (COFs), are often used as adsorbents. Activated carbon adsorption is a traditional method for removing dyes from aqueous solutions, but these materials suffer from high cost, limited adsorption capacity, difficult regeneration, insufficient selectivity, and may even cause secondary pollution. MOFs have attracted much attention in the field of dye removal due to their excellent adsorption performance; however, their practical application is significantly limited by their low adsorption performance. Studies have shown that doping MOFs with metal-organic frameworks can adjust the pore size, specific surface area, and micropore volume, thereby significantly improving the adsorption performance of MOFs. For example, YJ Zhang et al. used Al... 3+ Fe 3+ and Cu 2+ The CO2 adsorption performance of doped MOFs such as UiO-66 and UiO-66-NH2 at different temperatures was evaluated, and it was found that Fel 3+The doped sample exhibited the best performance, with adsorption capacities of 2.22 and 3.5 mmol / g for UiO-66 (Zr1Fe1) and UiO-66-NH2 (Zr5Fe1), respectively. JR Li et al. (JR Li, H. Wang, XF Wang, JM Ye, XDWang, BC Xue, Nickel-doped Zn-MOF for efficient adsorption of norfloxacin antibiotic: Adsorption behaviors and mechanisms, Mater. Chem. Phys. 343(2025) 131005) prepared Ni@Zn-MOF using a hydrothermal method, which effectively removed norfloxacin from pharmaceutical wastewater over a wide pH range, achieving a removal rate of approximately 94% under optimal conditions. S. Soni et al. (S. Soni, PK Bajpai, J. Mittal, C. Arora, Utilisation of cobalt doped Iron based MOF for enhanced removal and recovery of methylene blue dye from waste water, J. Mol. Liq. 314) (2020)113642.) By improving the adsorption performance of iron-benzenedicarboxylic acid MOF through cobalt doping, the removal efficiency of methylene blue in wastewater was increased from 8.56 to 23.92 mg / g.

[0004] Congo red (CR) dye, a typical anionic azo dye, has been widely used in the textile industry and other fields. Residual Congo red in industrial wastewater can have various adverse effects on the environment, ecosystems, and human health. Furthermore, due to its stable chemical properties, difficulty in natural degradation, and toxicity, improper treatment of Congo red dye can directly poison aquatic organisms, pollute soil, inhibit soil microbial activity, and its harmful effects can be amplified through the food chain, posing a multifaceted and serious threat to human health. Therefore, in various practical applications, removing CR from industrial wastewater is of great significance for protecting aquatic ecosystems and human health. Summary of the Invention

[0005] In one aspect, the present invention provides a Co-MOF@Ag composite material, which is composed of Co-MOF and silver nanoparticles loaded on its surface. The chemical formula of Co-MOF is Co(btyp)(ppda), where btyp represents 3,5-bis(triazolyl)pyridine and ppda represents terephthalic acid.

[0006] In another preferred embodiment, the Co-MOF belongs to the monoclinic crystal system, with space group P21 / n, a=4.8051(18) Å, b=21.350(8) Å, c=17.664(7) Å, α=γ=90°, β=91.299(6) °, the unit cell volume of the Co-MOF is V=1811.7(11)Å3, and the number of molecules in the unit cell of the Co-MOF is 4.

[0007] This invention also provides a method for preparing the above-mentioned Co-MOF@Ag composite material, which includes the following steps:

[0008] (1) Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid and NaOH and / or KOH are subjected to hydrothermal treatment in water, and then naturally cooled to 0~30℃. The reaction solution is filtered to obtain Co-MOF.

[0009] (2) After mixing Co-MOF, AgNO3 and water evenly, react them under light with a wavelength of 300~500nm for 1~6 hours, filter the reaction solution, and obtain Co-MOF@Ag composite material.

[0010] In another preferred embodiment, in step (1), the molar ratio of Co(Ac)2, 3,5-bis(triazole)pyridine, and terephthalic acid is 1:0.8~1.2:0.8~1.2. In another more preferred embodiment, the molar ratio of Co(Ac)2, 3,5-bis(triazole)pyridine, and terephthalic acid is 1:1:1.

[0011] In another preferred embodiment, in step (1), the molar ratio of Co(Ac)2 to NaOH and / or KOH is 1:2 to 10. In another more preferred embodiment, in step (1), the molar ratio of Co(Ac)2 to NaOH and / or KOH is 1:2 to 5.

[0012] In another preferred embodiment, in step (1), the weight-to-volume ratio of Co(Ac)2 to water is 0.1~15 mg / mL. In another more preferred embodiment, in step (1), the weight-to-volume ratio of Co(Ac)2 to water is 0.3~8 mg / mL.

[0013] In another preferred embodiment, in step (1), the hydrothermal treatment is performed by heating a mixture of Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid, NaOH and / or KOH and water in a sealed container at 80-120°C for 50-90 hours. In another more preferred embodiment, the hydrothermal treatment is performed by heating a mixture of Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid, NaOH and / or KOH and water in a sealed container at 90-100°C for 65-76 hours.

[0014] In another preferred embodiment, the sealed container is a reaction vessel.

[0015] In another preferred embodiment, step (1) further includes vacuum drying of the Co-MOF obtained by filtering the reaction solution. In another preferred embodiment, the vacuum drying temperature is 50~80°C and the time is 3~10 hours. In another more preferred embodiment, the vacuum drying temperature is 50~70°C and the time is 4~8 hours.

[0016] In another preferred embodiment, step (1) further includes sonicating an aqueous solution of NaOH and / or KOH containing Co(Ac)2, 3,5-bis(triazolyl)pyridine and terephthalic acid prior to hydrothermal treatment.

[0017] In another preferred embodiment, in step (2), the weight ratio of the Co-MOF composite material to AgNO3 is 1:1 to 2. In another more preferred embodiment, the weight ratio of the Co-MOF composite material to AgNO3 is 1:1.0 to 1.5.

[0018] In another preferred embodiment, in step (2), the weight-to-volume ratio of Co-MOF to water is 0.1 mg / mL to 15 mg / mL. In another more preferred embodiment, the weight-to-volume ratio of Co-MOF to water is 0.3 mg / mL to 8 mg / mL.

[0019] In another preferred embodiment, the temperature of the reaction in step (2) is 0~40°C. In another more preferred embodiment, the temperature of the reaction in step (2) is 20~30°C.

[0020] In another preferred embodiment, the wavelength of the light used in step (2) is 320~400nm. In another preferred embodiment, the wavelength of the light used in step (2) is 365nm.

[0021] In another preferred embodiment, step (2) further includes vacuum drying the Co-MOF@Ag composite material obtained by filtering the reaction solution. In another preferred embodiment, the vacuum drying temperature is 50~80°C and the time is 3~10 hours. In another more preferred embodiment, the vacuum drying temperature is 50~70°C and the time is 4~8 hours.

[0022] This invention also provides the use of Co-MOF@Ag composite materials in the removal of dyes from water.

[0023] In another preferred embodiment, the dye is selected from anionic dyes.

[0024] In another preferred embodiment, the anionic dye is selected from one or more of Congo red, methyl orange, methylene blue, and indigo.

[0025] In another preferred embodiment, the anionic dye is selected from Congo red.

[0026] The present invention also provides a method for removing dye from water, the method comprising adding the above-mentioned Co-MOF@Ag composite material to water containing dye and stirring for 20 to 72 hours, so that the dye in the water is adsorbed by the Co-MOF@Ag composite material.

[0027] In another preferred embodiment, the dye is selected from anionic dyes.

[0028] In another preferred embodiment, the anionic dye is selected from one or more of Congo red, methyl orange, methylene blue, and indigo.

[0029] In another preferred embodiment, the anionic dye is selected from Congo red.

[0030] In another preferred embodiment, the stirring time is 24 to 48 hours.

[0031] In another preferred embodiment, the method for removing dye from water further includes filtering the Co-MOF@Ag composite material adsorbed with dye, and washing the Co-MOF@Ag composite material adsorbed with dye in sequence with methanol and / or ethanol and water, so that the adsorbed dye is washed off the Co-MOF@Ag composite material, so that the Co-MOF@Ag composite material can be reused to adsorb dye.

[0032] In another preferred embodiment, the Co-MOF@Ag composite material has an adsorption capacity of 47.28~55 mg / g for Congo red. Attached Figure Description

[0033] Figure 1 The crystal structure of the Co-MOF obtained by the present invention is shown in Figure (a), where Co(II) ions are 6-coordinated twisted octahedra, four carboxyl oxygens form the equatorial plane, and N atoms on two btyp atoms form the axis; (b) shows the btyp connected with Co(II) ions to form a one-dimensional wireless chain; (c) shows the two-dimensional structure of Co-MOF; and (d) shows the three-dimensional structure of Co-MOF.

[0034] Figure 2 In the figure, (a) shows the simulated and experimental PXRD patterns of Co-MOF, and the experimental PXRD pattern of Co-MOF@Ag; (b) shows the FT-IR plots of Co-MOF and Co-MOF@Ag; (c) shows the TGA curves of Co-MOF and Co-MOF@Ag; and (d) shows the N2 adsorption-desorption isotherms of Co-MOF and Co-MOF@Ag at 77 K (inset: pore size distribution).

[0035] Figure 3In the figure, (a) shows the total XPS spectrum of Co-MOF and Co-MOF@Ag; (b) shows the C 1s spectrum of Co-MOF and Co-MOF@Ag XPS; (c) shows the N 1s spectrum of Co-MOF and Co-MOF@Ag XPS; (d) shows the O 1s spectrum of Co-MOF and Co-MOF@Ag XPS; (e) shows the Co 2p spectrum of Co-MOF and Co-MOF@Ag XPS; and (f) shows the Ag 3d spectrum of Co-MOF and Co-MOF@Ag XPS.

[0036] Figure 4 In the figure, (a) shows the SEM-EDX mapping image of Co-MOF; (b), (c), (d) and (e) show the mapping images of C, N, O and Co elements of Co-MOF, respectively.

[0037] Figure 5 In the figure, (a) shows the SEM-EDX mapping image of Co-MOF@Ag; (b), (c), (d), (e) and (f) show the mapping images of C, N, O, Co and Ag elements of Co-MOF, respectively.

[0038] Figure 6 The concentration-absorption standard curve of the CR solution is shown.

[0039] Figure 7 The graphs showing the adsorption capacity of Co-MOF, Co-MOF@Ag, and AgNO3 for CR as a function of time (T = 298 K, C) are displayed. CR = 200 mg / L).

[0040] Figure 8 In the figures, (a) shows a pseudo-first-order kinetic model of CR adsorption; (b) shows a pseudo-second-order kinetic model of CR adsorption; and (c) shows an intraparticle diffusion model. In these models, T = 298 K, C... CR = 200 mg / L.

[0041] Figure 9 Figures (a), (b), (c), (d), and (e) show the relationship between the adsorption capacity of CR by 5 mg, 15 mg, 25 mg, 35 mg, and 45 mg of Co-MOF and Co-MOF@Ag and time (T = 298 K, C). CR = 200 mg / L); (f) Figure shows the adsorption capacity of Co-MOF and Co-MOF@Ag at different doses.

[0042] Figure 10The graph shows the relationship between the initial CR concentration and the adsorption amounts of Co-MOF, Co-MOF@Ag, and AgNO3 (T = 298 K, C). CR = 200 mg / L).

[0043] Figure 11 In the figures, (a) shows the Langmuir model, (b) shows the Freundlich model, and (c) shows the Temkin model. In these models, T = 298K, C CR = 50-450 mg / L.

[0044] Figure 12 In the figure, (a), (b), and (c) show the kinetic adsorption processes of Co-MOF, AgNO3, and Co-MOF@Ag at different temperatures, respectively. CR =20 mg / L).

[0045] Figure 13 In the figure, (a) shows the relationship between the adsorption amount of Co-MOF@Ag and pH value, and (b) shows the relationship between the zeta potential of Co-MOF@Ag and pH value.

[0046] Figure 14 The number of times Co-MOF@Ag was reused to adsorb Congo red from the solution and its adsorption capacity were shown (T = 298 K, pH = 7, dose = 5 mg, C0 = 200 mg / L, V = 20 mL).

[0047] Figure 15 The adsorption kinetics of Co-MOF@Ag on Congo red in Yanhe River water are shown, with T = 298 K, pH = 7, dose = 5 mg, CO = 200 mg / L, and V = 20 mL. Detailed Implementation

[0048] In the process of researching Co-MOF materials, the inventors of this application discovered that Co-MOFs prepared by hydrothermal synthesis under alkaline conditions using Co(Ac)2, 3,5-bis(triazole)pyridine and terephthalic acid, followed by photoreduction to load silver nanoparticles onto their surface, yield a Co-MOF@Ag composite material with a large surface area and high adsorption capacity for anionic dyes in water, such as Congo red. This composite material can be reused multiple times, providing a feasible method for removing Congo red dye from water in industrial production. This method is not only low-cost but also environmentally friendly. Based on this, the present invention was completed.

[0049] The Co-MOF@Ag composite material of the present invention consists of Co-MOF and silver nanoparticles loaded on its surface. The chemical formula of Co-MOF is Co(btyp)(ppda), where btyp represents 3,5-bis(triazole)pyridine and ppda represents terephthalic acid. Co-MOF belongs to the monoclinic crystal system, space group P21 / n, a=4.8051(18) Å, b=21.350(8) Å, c=17.664(7) Å, α=γ=90°, β=91.299(6) °, the unit cell volume of Co-MOF is V=1811.7(11) Å3, and the number of molecules in the unit cell of Co-MOF is 4. Co-MOF is a novel material.

[0050] In this invention, the preparation method of Co-MOF@Ag composite material includes two steps: (1) Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid and NaOH and / or KOH are subjected to hydrothermal treatment in water, and then naturally cooled to 0~30℃. The reaction solution is filtered to obtain Co-MOF. (2) Co-MOF, AgNO3 and water are mixed evenly and reacted under light irradiation with a wavelength of 300~500nm for 1~6 hours. The reaction solution is filtered to obtain Co-MOF@Ag composite material.

[0051] In step (1), the optimal molar ratio of Co(Ac)2, 3,5-bis(triazole)pyridine and terephthalic acid is 1:1:1. The role of NaOH and / or KOH is to neutralize the protonated hydrogens of terephthalic acid. Water provides the reaction medium, and the final product Co-MOF precipitates from the water.

[0052] Hydrothermal treatment involves heating a mixture of Co(Ac)₂, 3,5-bis(triazole)pyridine, terephthalic acid, NaOH and / or KOH, and water in a closed container, preferably at 80–120°C, for example, 80°C, 85°C, 90°C, 95°C, 100°C, 120°C, etc. The hydrothermal treatment time is preferably 50–90 hours, for example, 60 hours, 70 hours, 80 hours, 90 hours, etc.

[0053] In some specific embodiments of the present invention, the mixture of Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid, and NaOH and / or KOH is subjected to ultrasonic treatment before hydrothermal treatment in water, so as to make the raw materials in the reaction solution more uniformly mixed. In some specific embodiments of the present invention, the temperature of the mixture during ultrasonic treatment is room temperature, and the time is 30 minutes. In some specific embodiments of the present invention, the power of the ultrasonic device used during ultrasonic treatment is 240W.

[0054] In some specific embodiments of the present invention, the hydrothermally treated reaction solution is naturally cooled to 0~30°C, more preferably 10~25°C, such as 15°C, 20°C, 25°C, etc., so that Co-MOF precipitates from the reaction solution.

[0055] In some specific embodiments of the present invention, step (1) further includes vacuum drying of the Co-MOF obtained by filtering the reaction solution. The purpose of vacuum drying is to remove water from the surface of the solid. In one specific embodiment of the present invention, the vacuum drying temperature is 50~80℃, for example, 55℃, 60℃, 64℃, 68℃, 70℃, etc. The vacuum drying time is 3~10 hours.

[0056] In step (2), after mixing Co-MOF, AgNO3, and water, Ag atoms are loaded onto the cobalt-based metal-organic framework through photoreduction. The wavelength of the light used is preferably 320-400 nm. In some specific embodiments of the present invention, a 300 W mercury lamp is used to provide light of the aforementioned wavelength.

[0057] In step (2), AgNO3 dissolves in water to form Ag + After being reduced, it forms Ag nanoparticles.

[0058] In some specific embodiments of the present invention, step (2) further includes vacuum drying of the Co-MOF@Ag composite material obtained by filtering the reaction solution. The purpose of vacuum drying is to remove water from the surface of the solid. In one specific embodiment of the present invention, the vacuum drying temperature is 50~80℃, for example, 55℃, 60℃, 64℃, 68℃, 70℃, etc. The vacuum drying time is 3~10 hours.

[0059] The Co-MOF@Ag composite material of the present invention can adsorb dyes, especially anionic dyes, including but not limited to Congo red, methyl orange, methylene blue, and indigo.

[0060] The beneficial effects of the Co-MOF@Ag composite material of this invention are as follows:

[0061] (1) The preparation method of this composite material is simple, requires no special instruments, and the raw materials are readily available.

[0062] (2) It has a good adsorption effect on dyes in water, especially anionic dyes, such as Congo red, with an adsorption capacity of 47.28~55 mg / g. It can be reused many times, providing a feasible method for removing dyes from water in industrial production.

[0063] The present invention will be further illustrated below with reference to specific embodiments. These specific embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and operating procedures are provided. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally carried out under conventional conditions. Unless otherwise stated, proportions and percentages are by weight, and "concentration" refers to mass concentration unless otherwise specified.

[0064] Experimental reagents and instruments

[0065] All chemical reagents and solvents used in this invention were purchased from the commercial market. C, H, and N were determined and analyzed using a Flash 2000 organic elemental analyzer. Powder X-ray diffraction (PXRD) scanning was performed using a Bruker D2 phase-interval X-ray diffractometer (Cu-Kα, λ = 0.15406 nm) at a scan rate of 10 °C min⁻¹. Single-crystal X-ray diffraction (XRD) data for Zn-MOF were acquired using a Brooke SMART APEX CCD diffractometer (Mo Kα, λ = 0.071073 nm). Thermogravimetric analysis (TGA) was performed using a Rigaku TG-DTA8122 at a heating rate of 10 °C / min, covering a temperature range of 30–800 °C. Fourier transform infrared spectroscopy (FT-IR) scanning was performed using a Fourier transform infrared spectrometer. UV-Vis absorption and diffuse reflectance spectra were measured using UV-2600 and UV-2700 spectrophotometers. Surface area data for BET were obtained using a Micromeritics ASAP 2460 instrument. Scanning electron microscopy (SEM) images were captured on a Zeiss Sigma 300 SEM. Morphological and energy spectrum lenticular images were captured in SE2 secondary electron detectors at accelerating voltages of 3 kV and 15 kV, respectively. X-ray photoelectron spectroscopy (XPS) was acquired on a Thermo Scientific ESCALAB 250Xi (Al Kα, hν = 1486.6 eV).

[0066] Example 1:

[0067] 1.1 Synthesis of Co-MOF

[0068] Co(Ac)2 (24.9 mg, 0.1 mmol), 3,5-bis(triazole)pyridine (21.3 mg, 0.1 mmol), terephthalic acid (19.4 mg, 0.1 mmol), NaOH (8.0 mg, 0.2 mmol) and 50 mL were mixed and sonicated at room temperature for 30 min in a 240 W sonicator. The mixture was then placed in a reaction vessel, sealed, and heated in a 95 °C oven for 72 h. After that, the mixture was removed, allowed to cool naturally to room temperature (25 °C), and the reaction solution was filtered to obtain dark purple spiky crystals. The crystals were washed with water and then dried under vacuum at 60 °C for 3 h to obtain 35 mg of Co-MOF.

[0069] The chemical formula of Co-MOF is Co(btyp)(ppda)]. C 19 H 15 Calculated elemental values ​​(%) of CoN7O4: C 49.11, H 3.23, N 21.11; Experimental values ​​(%): C 49.03, H 3.45, N 21.54.

[0070] 1.2 Synthesis of Co-MOF@Ag

[0071] 20 mg Co-MOF and 20 mg AgNO3 were mixed with water (30 ml) and stirred at room temperature for 1 hour. The mixture was then placed in a quartz tube and irradiated at room temperature with a 300 W mercury lamp (wavelength 365 nm) for 2 hours. The reaction solution was filtered to obtain a dark purple powder. This powder was washed successively with a small amount of water and ethanol to remove residual NO3. - The mixture was then vacuum dried at 60°C for 6 hours to obtain 24 mg of solid, which is the Co-MOF@Ag composite material.

[0072] 1.3 Single Crystal Diffraction Data

[0073] Using a Bruker Smart 1000 CCD single-crystal diffractometer (Mo-K) α X-ray single-crystal diffraction data were collected (λ=0.071073 nm). The crystal structure of Co-MOF was resolved using SHELXT and optimized using SHELXL. The crystallographic parameters of Co-MOF are shown in Table 1, some bond angles and bond lengths are shown in Table 2, and the crystal structure is shown in [Table 1]. Figure 1 The crystal data is stored at the Cambridge Crystal Data Centre in the UK, and the Co-MOF's CCDC number is 2393497.

[0074] Table 1 Crystal structure data of Co-MOF

[0075]

[0076] a R1=Σ||F o |–|F c || / Σ|F o |, wR2=[Σw(F o 2 –F c 2 ) 2 / Σw(F o 2 ) 2 ] 1 / 2

[0077] Table 2. Main bond lengths and bond angles in Co-MOF

[0078]

[0079] Symmetry codes for 1 :1+X, +Y, +Z; 2 : -3 / 2+X, 1 / 2-Y, 1 / 2+Z; 3 : -1 / 2-X, -1 / 2+Y, 3 / 2-Z.

[0080] From Table 1, Table 2 and Figure 1 It can be seen that the Co-MOF obtained in this invention belongs to the monoclinic crystal system and space group P21 / n. The asymmetric unit of the crystal consists of one Co(II), one ppda, and one btyp. The Co(II) ion is a 6-coordinate twisted octahedron, with four carboxyl oxygen atoms forming the equatorial plane, and the N atoms on the two btyp atoms forming the axis (see...). Figure 1 (Figure (a)). btyp connects with Co(II) ions to form a one-dimensional wireless chain (see Figure (a)). Figure 1 (Figure (b)). The two carboxyl groups of the trans-ppda ligand coordinate with the Co(II) ion via bidentate chelation and bidentate bridging, forming a two-dimensional wavy surface (see Figure (b)). Figure 1 (Figure (c)). One-dimensional chains support links to form a three-dimensional network structure (see Figure (c)). Figure 1 (d) diagram).

[0081] 1.4 Characterization of Co-MOF and Co-MOF@Ag

[0082] 1.4.1 Powder X-ray Diffraction (PXRD)

[0083] The above Co-MOF and Co-MOF@Ag composite materials were tested by PXRD, and the results are shown in the figure. Figure 2Figure (a) shows the simulated PXRD spectrum of Co-MOF. The figure shows that the diffraction peaks of the experimental PXRD spectrum of Co-MOF match well with its simulated PXRD spectrum, indicating both successful synthesis of Co-MOF and that it is a single-phase pure product. Minor differences between the two may be due to different crystal and powder orientations. The figure also shows that the PXRD diffraction peaks of Co-MOF@Ag and Co-MOF are basically consistent, indicating that the formation of the composite material did not destroy the crystal structure of Co-MOF.

[0084] 1.4.2 Fourier Transform Infrared Spectroscopy (FT-IR)

[0085] Co-MOF and Co-MOF@Ag materials were characterized by FT-IR, and the results are shown in the figure. Figure 2 Figure (b) shows the infrared spectrum of Co-MOF, from 1700 to 1500 cm⁻¹. -1 Belongs to -COO - Symmetric and asymmetric stretching vibration peaks of functional groups, 1600–1400 cm⁻¹ -1 The stretching vibration peaks attributed to ν(CN) are 540 and 438 cm⁻¹. -1 The weak peaks at 3600–3200 cm⁻¹ are attributed to the stretching vibrations of Co-O and Co-N. In the infrared spectrum of Co-MOF@Ag, the peaks at 3600–3200 cm⁻¹ are due to residual water from the sample washing process. -1 The broad peak at [location missing] is attributed to the stretching vibration of water molecule v(OH); the positions of the remaining characteristic absorption peaks are consistent with those of Co-MOF. This indicates that Co-MOF and Co-MOF@Ag were synthesized using 3,5-bis(triazolyl)pyridine and terephthalic acid ligands, consistent with the crystal structure analysis results.

[0086] 1.4.3 Thermogravimetric Analysis (TGA)

[0087] The Co-MOF and Co-MOF@Ag composites were characterized by TGA, and the results are shown below. Figure 2 Figure (c) shows that Co-MOFs exhibit almost no weight loss from room temperature to 350°C, but significant weight loss occurs from 350°C to 450°C. This is attributed to the ligands btyp and ppda. 2- The ligands gradually decompose, leading to the collapse of the skeletal framework and ultimately forming CoO. Co-MOF@Ag experiences slight weight loss from room temperature to 300°C, due to residual water from sample washing. Significant weight loss occurs upon further heating to 400°C, due to the ligands btyp and ppda. 2-The ligands gradually decompose, leading to the collapse of the framework and the eventual formation of CoO and AgO. In summary, the temperature-induced weight loss phenomena of Co-MOF and Co-MOF@Ag are basically similar, and the basic material framework remains stable up to 300°C, indicating that both materials have excellent thermal stability at room temperature.

[0088] 1.4.4 Pore size distribution, N 2 Adsorption-desorption isotherms and specific surface area analysis

[0089] The Co-MOF and Co-MOF@Ag composites were characterized and tested using N2 adsorption-desorption isotherms. The results are shown below. Figure 2 Figure (d) shows that Co-MOF and Co-MOF@Ag exhibit a type Ш isotherm at 77 K, with specific surface areas (BET method) of 0.8 and 2.8 m², respectively. 2 The average pore size (BJH method) was 38.6 nm / g and 31.6 nm, respectively, indicating that the materials have mesoporous characteristics. Compared with the former, Co-MOF@Ag has a larger specific surface area, thus providing more active sites.

[0090] 1.4.5 X-ray photoelectron spectroscopy (XPS) analysis

[0091] The Co-MOF and Co-MOF@Ag composites were characterized by XPS, and the results are as follows: Figure 3 As shown. XPS analysis of Co-MOF revealed four distinct peaks in the 0-1200 eV range: C 1s, N 1s, O 1s, and Co 2p (see [reference]). Figure 3 (Figure a); XPS analysis of the Co-MOF@Ag composite material showed five distinct peaks in the 0-1200 eV range: C 1s, N 1s, O 1s, Co 2p, and Ag 3d (see Figure a). Figure 3 (See Figure a). To calibrate the high-resolution spectra, the major peak positions of C 1s in Co-MOF and Co-MOF@Ag were obtained by using the C 1s binding energy peak of 284.80 eV as the calibration reference: CC / C=C (284.80 eV), CN (286.93 eV), CO (288.52 eV), and π-π* (293.91 eV) (see Figure a). Figure 3 (See Figure b). The XPS spectrum of N 1s shows that the binding energy at 400.15 eV belongs to the N-Co bond, the binding energy at 402.38 eV belongs to the NC bond, and the binding energy at 408.02 eV is the π excitation of the N element (see Figure b). Figure 3(See Figure c). The O 1s spectrum shows a prominent peak at 532.82 eV, belonging to the CO bond, and another peak at 531.55 eV, related to the C=O bond (see Figure c). Figure 3 (See d plot). The main peak positions of Co 2p in Co-MOF are: 781.92, 786.53, 797.47 and 801.86 eV (see d plot). Figure 3 (See the e-plot). Two distinct peaks are observed at 781.92 and 797.47 eV, representing Co 2p3 / 2 and Co 2p1 / 2 respectively, indicating that Co... 2+ The presence of [a specific component / factor] is also evident. Furthermore, the peak positions of C 1s, N 1s, O 1s, and Co 2p in Co-MOF@Ag are essentially similar to those in Co-MOF. Figure 3 In the f-plot, the two peaks observed at 368.48 and 374.49 eV belong to Ag 3d3 / 2 and 3d5 / 2, respectively. The presence of these peaks indicates that Ag exists in monomeric form. Based on the above analysis, it can be found that the peak position of Co element in Co-MOF@Ag shifts to a lower direction compared to the Co-MOF binding energy, indicating that the electron cloud density of Co-MOF decreases after Ag combines with Co-MOF. It can be inferred that when Ag comes into contact with Co-MOF, electrons from Co-MOF flow towards Ag.

[0092] 1.4.6 Scanning Electron Microscopy (SEM)

[0093] The Co-MOF and Co-MOF@Ag composites were characterized by SEM, and the results are as follows: Figure 4 and 5 As shown. SEM revealed that the surface of Co-MOF was smooth and free of particle agglomeration (see...). Figure 4 (See Figure a). After photoreduction-induced Ag nanoparticles are deposited on the surface of Co-MOF, the surface becomes rougher (see Figure a). Figure 5 (Figure a). The elemental composition of Co-MOF and Co-MOF@Ag was characterized in detail using energy-dispersive X-ray (EDX) spectroscopy, and the results are shown in Figure a. Figure 4 be and Figure 5 As shown in the figures, these figures demonstrate that C, O, N, Co, and Ag elements are uniformly distributed in Co-MOF and its further prepared form, Co-MOF@Ag, further confirming the successful preparation of Co-MOF@Ag.

[0094] Example 2

[0095] 2.1 Kinetics of adsorption of Congo Red (CR) dyes by Co-MOF and Co-MOF@Ag composite materials

[0096] CR solutions of different concentrations (50-450 mg / L) were prepared, and the absorption peak at 497 nm was measured using a UV-Vis spectrophotometer. A concentration-absorption standard curve for the CR solutions was obtained (see...). Figure 6 ).

[0097] 5 mg of Co-MOF and 5 mg of Co-MOF@Ag composite material were added to 20 mL of Congo red solution with pH=7 and an initial concentration of 200 mg / L, and stirred. The absorbance of the solution was measured at different time points: 5 min, 10 min, 20 min, 30 min, 60 min, 120 min, 180 min, 300 min, 1260 min, and 1440 min. The change of CR concentration in the solution over time was obtained according to the above concentration-absorbance standard curve.

[0098] The equilibrium adsorption capacity q of the dye for Co-MOF and Co-MOF@Ag was calculated using Equation 1. e (mg / g); The adsorption capacity q of the dye by Co-MOF and Co-MOF@Ag at t min was calculated using Equation 2. t (mg / g); The dye removal rate R of Co-MOF and Co-MOF@Ag was calculated by Equation 3.

[0099] Equation 1

[0100] Equation 2

[0101] Equation 3

[0102] Where C0 (mg / L) and Ce (mg / L) are the initial concentration and equilibrium concentration of the dye solution (i.e., the concentration when adsorption reaches equilibrium), respectively, V (L) is the total volume of the dye solution, and m (g) is the amount of adsorbent used.

[0103] The adsorption of Congo red in water by 5 mg Co-MOF and 5 mg Co-MOF@Ag composite materials is shown in the figure. Figure 7 .from Figure 7 It can be seen that the adsorption capacity of Co-MOF and Co-MOF@Ag for CR gradually increases with time. When the time reaches 1440 min, the adsorption capacity gradually tends to equilibrium, indicating that the adsorption capacity has reached saturation at this point. tThe concentrations of Congo red were 38.44 mg / g and 55 mg / g, respectively, and the removal rates (R) of Congo red were 66.92% and 95.75%, respectively. The adsorption capacity and removal rate of Co-MOF@Ag were improved after doping, which is due to the increase in the specific surface area and the increase in active sites of Co-MOF@Ag.

[0104] To investigate its adsorption mechanism and rate-controlling steps, the kinetic data were fitted using a pseudo-first-order kinetic model, a pseudo-second-order kinetic model, and an intraparticle diffusion model. Wherein, q e (mg / g) and q t (mg / g) represents the adsorption capacity of Co-MOF@Ag for CR at adsorption equilibrium and at time t, respectively, k1 (min) −1 k2 (g / mg / min) is the adsorption rate constant, k dit (mg / g / min 1 / 2 ) is the diffusion rate constant, C i (mg / g) is the intercept. The three equations are shown below:

[0105] Pseudo-first-order dynamic model: Equation 4

[0106] Pseudo-second-order dynamic model: Equation 5

[0107] Intraparticle diffusion model: Equation 6

[0108] The parameters of the three dynamic models are shown in Table 3, and the R values ​​for equations 4 and 5 are also shown in Table 3. 2 The values ​​are 0.89 and 0.99 respectively. The calculated values ​​of the equilibrium adsorption amount in Equation 4 are closer to the experimental values ​​(see [references]). Figure 8 Figures (a), (b), and (c) demonstrate that the pseudo-second-order kinetic model can better describe the adsorption process, indicating that the adsorption process is chemisorption. The intraparticle diffusion model shows that k2 > k1 > k3. This is because the concentration difference between the CR dye solution and the Co-MOF@Ag is large. In the first step, CR gradually enters the pores from the outer surface of Co-MOF@Ag. Due to the steric hindrance within the pores, the rate k1 < k2. In the second step, the adsorption rate of Co-MOF@Ag is relatively fast. In the third step, CR gradually fills the pores of Co-MOF@Ag, reducing the number of active sites and slowing down intraparticle diffusion, reaching adsorption equilibrium. Furthermore, none of these three steps pass through the origin, indicating that intraparticle diffusion participates in the adsorption process, but it is not the only rate-controlling step; rather, external and internal diffusion occur simultaneously.

[0109] Table 3. Kinetic model parameters for Co-MOF@Ag adsorption CR

[0110]

[0111] 2.2 Screening of Adsorption Capacity

[0112] The properties and quality of the adsorbent significantly affect its dye adsorption capacity. Therefore, this paper investigates the effect of Co-MOF and Co-MOF@Ag dosages on CR removal through adsorption experiments. The specific experimental procedure is as follows:

[0113] At 298 K, 5 mg, 15 mg, 25 mg, 35 mg, and 45 mg of Co-MOF and 5 mg, 15 mg, 25 mg, 35 mg, and 45 mg of Co-MOF@Ag composite material were added to 20 mL of Congo red solution with pH=7 and an initial concentration of 200 mg / L, and stirred. The absorbance of the solution was measured at different time points: 5 min, 10 min, 20 min, 30 min, 60 min, 120 min, 180 min, 300 min, 1260 min, and 1440 min. Based on the concentration-absorbance standard curve, the change in CR concentration in the solution over time was obtained.

[0114] The changes in CR concentration in the solution are shown in the figure. Figure 9 Figures (a) to (e) show that the final removal rate (R) of CR remained above 80% as the dose of Co-MOF and Co-MOF@Ag increased from 5 mg to 45 mg. Figure 9 As shown in the f-plot, with increasing adsorption time, due to the increased number of adsorption sites occupied by CR, the CR adsorption capacity decreased sharply from 55 mg / g to 47.28 mg / g as the dosage of Co-MOF and Co-MOF@Ag increased from 5 mg to 45 mg. Therefore, 5 mg of Co-MOF@Ag was selected for research on adsorption behavior, adsorption mechanism, practical application, and reusability.

[0115] 2.3 Adsorption Isotherm

[0116] At 298 K, 5 mg Co-MOF, 5 mg Co-MOF@Ag, and 5 mg AgNO3 were added to 20 mL of Congo red solution with pH=7 and an initial concentration of 200 mg / L, and stirred. The absorbance of the solution was measured, and the concentration of CR in the solution after 24 h of adsorption was obtained according to the concentration-absorbance standard curve.

[0117] Equations 7, 8, and 9 were used to explore the adsorption isotherms of CR by Co-MOF@Ag.

[0118] Langmuir: Equation 7

[0119] Freundlich: Equation 8

[0120] Temkin: Equation 9

[0121] Where, q m With q e (mg / g) represent the maximum and equilibrium adsorption capacities of Co-MOF@Ag, respectively, C e (mg / L) represents the concentration of CR at equilibrium, K L (L / mg), K F [(L / mg)1 / n ·mg / g]、K T (L / mg) are Langmuir, Freundlich and Temkin constants, respectively, n is the Freundlich parameter, b (J / mol·g / mg) is the adsorption heat constant, R (8.314 J / mol / K) is the gas constant, and T (K) is the adsorption temperature.

[0122] By fitting the isotherm data using equations 7, 8, and 9, we obtain... Figure 10 And Table 4. From Figure 10 It is evident that the adsorption capacity of Co-MOF@Ag increases with increasing initial concentration of the CR solution. This is because a higher initial concentration of the CR solution results in a stronger concentration gradient driving force, leading to more effective collisions between CR molecules and Co-MOF@Ag.

[0123] Figure 11 Figures (a), (b), and (c) show the R-squared values ​​of the Langmuir, Freundlich, and Temkin models, respectively. 2 The values ​​were 0.99 (closer to 1), 0.96, and 0.91, respectively, and the maximum adsorption capacity calculated from the Langmuir fitting curve was close to the experimental value. Therefore, the Langmuir model fits the adsorption isotherm well, and the adsorption process is mainly monolayer adsorption.

[0124] Through the dimensionless constant separation factor (R) L Further determination of the affinity between CR and Co-MOF@Ag. Dimensionless constant segregation factor (R0) L Equation 10 is as follows:

[0125] Equation 10

[0126] When 0 <R L A value less than 1 indicates that the adsorption process is favorable, when R...L >1 indicates that the adsorption process is unfavorable. This study found that for Co-MOF@Ag composites, 0 <R L The value is <1, therefore the adsorption process of CR by Co-MOF@Ag is good.

[0127] Table 4. Parameters of the Co-MOF@Ag adsorption CR isotherm model

[0128]

[0129] 2.4 Adsorption Thermodynamics

[0130] Adsorption thermodynamics is of great significance for studying the adsorption mechanism of CR by Co-MOF@Ag. This paper designs experiments to test the adsorption of CR by Co-MOF@Ag and Co-MOF at 25℃, 35℃, and 45℃. The specific experimental procedures are as follows:

[0131] At 25℃, 35℃, and 45℃, 5 mg of Co-MOF, 5 mg of Co-MOF@Ag composite material, and 5 mg of AgNO3 were added to 20 mL of Congo red solution with pH=7 and an initial concentration of 200 mg / L, respectively, and stirred. The absorbance of the solution was measured at different time points: 5 min, 10 min, 20 min, 30 min, 60 min, 120 min, 180 min, 300 min, 1260 min, and 1440 min. Based on the concentration-absorbance standard curve, the change in CR concentration in the solution over time was obtained.

[0132] The adsorption of CR by the Co-MOF@Ag composite material at 25℃, 35℃ and 45℃ are shown in the figure. Figure 12 Figure (a) shows the adsorption of AgNO3 on CR at 25℃, 35℃, and 45℃. Figure 12 Figure (b) shows the adsorption of CR by Co-MOF at 25℃, 35℃, and 45℃. Figure 12 Figure (c) shows that the maximum adsorption capacity of Co-MOF@Ag, Co-MOF, and AgNO3 for CR gradually decreases with increasing temperature. At all temperatures, Co-MOF@Ag exhibits the highest adsorption capacity for CR.

[0133] Meanwhile, the Gibbs free energy (ΔG), enthalpy change (ΔH), and entropy change (ΔS) are calculated using equations 11, 12, and 13 (Table 5).

[0134] Equation 11

[0135] Equation 12

[0136] Equation 13

[0137] K d R is the thermodynamic equilibrium constant, R (8.314 J / mol / K) is the gas constant, and T (K) is the adsorption temperature.

[0138] As can be seen from Table 5, ΔH, ΔG, and ΔS are all negative at the three temperatures, indicating that the adsorption process below 45℃ is an exothermic, entropy-reducing spontaneous reaction, which meets the adsorption removal requirements at room temperature.

[0139] Table 5 Thermodynamic parameters of Co-MOF@Ag adsorption CR

[0140]

[0141] 2.5 Adsorption Mechanism

[0142] Studying the adsorption mechanism of dyes by adsorbents can provide a clearer understanding of their interaction, which is of great significance for their application in actual production. Since pH value has a significant impact on the adsorption process, the adsorption performance of Co-MOF@Ag for CR was investigated at different pH values. The following experiments were designed in this paper:

[0143] 5 g of Co-MOF@Ag was added to 20 mL of CR solutions with a concentration of 200 mg / L at pH values ​​of 3, 4, 5, 6, 7, 8, 9, 10, and 11. The solutions were stirred and incubated at 25 °C for 24 h to allow the adsorption of CR by Co-MOF@Ag to reach equilibrium. The absorbance of the solution at adsorption equilibrium was measured, and the concentration of CR in the solution at this point was obtained according to the concentration-absorbance standard curve described above. The amount of CR adsorbed by Co-MOF@Ag at equilibrium was then calculated. The results are shown below. Figure 13 Figure (a) shows that Co-MOF@Ag has the highest adsorption capacity for CR when pH=7.

[0144] Testing the zeta potential of the Co-MOF@Ag surface revealed that the Co-MOF@Ag surface was positively charged at pH values ​​from 5 to 9 (see...). Figure 13 (Figure (b)). CR is an anionic dye, and its molecule contains a sulfurous acid group (SO3). -This indicates that there is an electrostatic attraction between the CR solution and Co-MOF@Ag. According to the literature (J. Chen, JB Ouyang, WQ Chen, ZP Zheng, Z. Yang, ZR Liu, LM Zhou, Fabrication and adsorption mechanism of chitosan / Zr-MOF (UiO-66) composite foams for efficient removal of ketoprofen from aqueous solution, Chem. Eng. J. 431 (2022) 134045), this process can be explained by electrostatic interactions.

[0145] 2.6 Recyclability of the Adsorbent

[0146] In actual production, a good adsorbent should have excellent reusability, which is crucial for environmental protection and resource conservation. To investigate the recovery performance of Co-MOF@Ag, the following experiments were designed:

[0147] 5 mg of Co-MOF@Ag was added to 20 mL of a 200 mg / L CR solution at pH 7. The solution was stirred and adsorbed at 25 °C for 24 h to allow the adsorption of CR by Co-MOF@Ag to reach equilibrium. The mixture was then filtered, and the CR-adsorbed Co-MOF@Ag was soaked in 5 mL of ethanol for 2 h. After filtration, the solid was washed successively with 2 mL of ethanol and 4 mL of water, and then vacuum dried at 60 °C for 3 h. The CR-free Co-MOF@Ag was then added to 20 mL of a 200 mg / L CR solution at pH 7, and the solution was stirred and adsorbed at 25 °C for 24 h to allow the adsorption of CR by Co-MOF@Ag to reach equilibrium. This process of adsorbing CR by Co-MOF@Ag was repeated 5 times. After each adsorption equilibrium was reached, the absorbance of the solution was measured. Based on the concentration-absorbance standard curve, the concentration of CR in the solution was obtained, and the amount of CR adsorbed by Co-MOF@Ag at equilibrium was calculated.

[0148] The experimental results are shown in Figure 14 ,from Figure 14 The results show that after five repeated experiments, the adsorption capacity of this Co-MOF@Ag for CR still reached over 50 mg / g, proving that the Co-MOF@Ag adsorbent has good reusability and promising application prospects. Figure 14It can also be seen that the slight decrease in the adsorption performance of Co-MOF@Ag for CR after repeated use may be due to the non-recyclable adsorption caused by chemical adsorption and the destruction of some adsorption sites caused by the decrease in the crystallinity of the adsorbent material after repeated washing.

[0149] 2.7 Practical Application

[0150] To explore the potential of Co-MOF@Ag in practical applications, the following experiments were designed:

[0151] To simulate the scenario of pollution in the Yan'an River, a 200 mg / L CR solution was prepared using Yan'an River water. 5 mg of Co-MOF@Ag was added to 20 mL of this solution, and the mixture was stirred at 25°C. The absorbance of the solution was measured at different time points: 5 min, 10 min, 20 min, 30 min, 60 min, 120 min, 180 min, 300 min, 1260 min, and 1440 min. Based on the above concentration-absorbance standard curve, the change in CR concentration in the solution over time was obtained.

[0152] See results Figure 15 .from Figure 15 It can be seen that the adsorption capacity of Co-MOF@Ag for CR gradually increases with time. When the time reaches 1440 min, the adsorption capacity gradually tends to equilibrium, indicating that the adsorption capacity has reached saturation at this point. e The concentration of the active ingredient was 31 mg / g, and the removal rate (R) was 76.43%. This indicates that Co-MOF@Ag has potential practical adsorption performance applications.

[0153] In summary, the Co-MOF@Ag composite material of this invention possesses high porosity and high specific surface area. Both Co-MOF and Co-MOF@Ag exhibit adsorption performance for Congo Red (CR) dye, with maximum adsorption capacities (qm) of 38.44 mg / g and 55 mg / g, respectively. The adsorption capacity of Co-MOF@Ag is 1.43 times higher than that of Co-MOF. This enhanced performance stems from the larger specific surface area and more abundant adsorption active sites of the Co-MOF@Ag composite material compared to Co-MOF. Mechanism analysis shows that the adsorption of CR by Co-MOF@Ag is mainly achieved through electrostatic interactions. Practical application verification demonstrates that Co-MOF@Ag can serve as a novel and highly efficient adsorbent, effectively removing CR dye pollutants from the Yanhe River.

[0154] Example 3 Preparation of Co-MOF@Ag composite material

[0155] (1) Co(Ac)2 (24.9 mg, 0.1 mmol), 3,5-bis(triazole)pyridine (21.3 mg, 0.1 mmol), terephthalic acid (19.4 mg, 0.1 mmol), KOH (15.1 mg, 0.27 mmol) and 45 mL of water were mixed and sonicated at room temperature for 30 min in a 240 W sonicator. The mixture was then placed in a reaction vessel, sealed, and heated in a 95 °C oven for 72 hours. After cooling naturally to room temperature (25 °C), the reaction solution was filtered to obtain dark purple spiky crystals. The filtered crystals were rinsed with a small amount of water and dried at 55 °C for 6 hours to obtain 32 mg of solid, i.e., Co-MOF.

[0156] (2) Take 20 mg of Co-MOF obtained in step (1), 20 mg of AgNO3 and 30 mL of water, stir at room temperature for 1 hour, place in a quartz tube, irradiate with a 300 W mercury lamp (wavelength 365 nm) for 2 hours, filter the reaction solution, wash the obtained solid with ethanol and water in sequence, and dry in vacuum at 60 °C for 6 hours to obtain 23 mg of Co-MOF@Ag composite material.

[0157] Powder X-ray diffraction was performed on the dark purple spiky crystal obtained in step (1). Based on the obtained PXRD, the crystal was basically consistent with the Co-MOF obtained in Example 1.

[0158] Powder X-ray diffraction was performed on the Co-MOF@Ag crystal form obtained in step (2). Based on the obtained PXRD, the composite material was basically consistent with the Co-MOF@Ag obtained in Example 1.

[0159] Example 4: Preparation of Co-MOF@Ag composite material

[0160] (1) Co(Ac)2 (24.9 mg, 0.1 mmol), 3,5-bis(triazole)pyridine (25.6 mg, 0.12 mmol), terephthalic acid (23.3 mg, 0.12 mmol), NaOH (14.0 mg, 0.35 mmol) and 60 mL of water were sonicated in a 240 W ultrasonic instrument at room temperature for 30 min. The mixture was then placed in a reaction vessel, sealed, and heated in a 100 °C oven for 68 hours. After being removed and allowed to cool naturally to room temperature (20 °C), the reaction solution was filtered to obtain dark purple spiky crystals. The obtained crystals were rinsed with a small amount of water and dried at 65 °C for 2.5 hours to obtain 34 mg of solid, which is Co-MOF.

[0161] (2) Take 20 mg of Co-MOF obtained in step (1), 25 mg of AgNO3 and 30 mL of water, stir at room temperature for 1 hour, place in a quartz tube, irradiate with a 300 W mercury lamp (wavelength 400 nm) for 2.5 hours, filter the reaction solution, wash the obtained solid with ethanol and water in sequence, and dry in vacuum at 80 °C for 3 hours to obtain 24 mg of Co-MOF@Ag composite material.

[0162] Powder X-ray diffraction was performed on the dark purple spiky crystal obtained in step (1). Based on the obtained PXRD, the crystal was basically consistent with the Co-MOF obtained in Example 1.

[0163] Powder X-ray diffraction was performed on the Co-MOF@Ag crystal form obtained in step (2). Based on the obtained PXRD, the composite material was basically consistent with the Co-MOF@Ag obtained in Example 1.

[0164] The above embodiments can be scaled up for production. Multiple experiments can also be conducted in parallel in a laboratory environment to obtain sufficient Co-MOF@Ag composite materials.

[0165] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A Co-MOF@Ag composite material, characterized in that, The composite material consists of Co-MOF and silver nanoparticles loaded on its surface. The chemical formula of Co-MOF is Co(btyp)(ppda), where btyp represents 3,5-bis(triazolyl)pyridine and ppda represents terephthalic acid.

2. The Co-MOF@Ag composite material according to claim 1, characterized in that, Co-MOF belongs to the monoclinic crystal system, space group P21 / n, a=4.8051(18) Å, b=21.350(8) Å, c=17.664(7) Å, α=γ=90°, β=91.299(6) °. The unit cell volume of Co-MOF is V = 1811.7(11) Å. 3 , The number of molecules in the unit cell of Co-MOF is 4.

3. The method for preparing the Co-MOF@Ag composite material according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid and NaOH and / or KOH are subjected to hydrothermal treatment in water, and then naturally cooled to 0~30℃. The reaction solution is filtered to obtain Co-MOF. (2) After mixing Co-MOF, AgNO3 and water evenly, react them under light with a wavelength of 300~500nm for 1~6 hours, filter the reaction solution, and obtain Co-MOF@Ag composite material.

4. The preparation method according to claim 3, characterized in that, Step (1) satisfies one or more of the following characteristics: (i) The molar ratio of Co(Ac)2, 3,5-bis(triazol)pyridine, and terephthalic acid is 1:0.8~1.2:0.8~1.2, more preferably, 1:1:

1. (ii) The molar ratio of Co(Ac)2 to NaOH and / or KOH is 1:2 to 10, more preferably 1:2 to 5. (iii) The weight-to-volume ratio of Co(Ac)2 to water is 0.1~15 mg / mL, more preferably 0.3~8 mg / mL. (iv) The hydrothermal treatment involves heating a mixture of Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid, NaOH and / or KOH and water in a sealed container at 80-120°C for 50-90 hours, more preferably at 90-100°C for 65-76 hours. (v) Step (1) also includes vacuum drying and filtering the reaction solution to obtain Co-MOF. (vi) Step (1) further includes sonicating a mixture of Co(Ac)2, 3,5-bis(triazole)pyridine, terephthalic acid, NaOH and / or KOH and water prior to hydrothermal treatment.

5. The preparation method according to claim 3 or 4, characterized in that, Step (2) meets one or more of the following characteristics: (i) The weight ratio of Co-MOF to AgNO3 is 1:1 to 2, more preferably 1:1.0 to 1.

5. (ii) The weight-to-volume ratio of Co-MOF to water is 0.1~15 mg / mL, more preferably 0.3 mg / mL~8 mg / mL. (iii) The reaction temperature is 0~40℃. (iv) The wavelength of the light used is 320~400nm. (iv) Step (2) also includes vacuum drying and filtering the reaction solution to obtain the Co-MOF@Ag composite material.

6. Use of the Co-MOF@Ag composite material according to claim 1 in the removal of dyes from water.

7. The use according to claim 6, characterized in that, The dye is selected from anionic dyes, preferably selected from one or more of Congo red, methyl orange, methylene blue, and indigo, and more preferably Congo red.

8. A method for removing dye from water, characterized in that, The method includes adding the Co-MOF@Ag composite material according to claim 1 or 2 to water containing dye, and stirring for 20 to 48 hours, so that the dye in the water is adsorbed by the Co-MOF@Ag composite material. Preferably, the dye is selected from anionic dyes. Preferably, the anionic dye is selected from one or more of Congo red, methyl orange, methylene blue, and indigo, and more preferably, Congo red.

9. The method for removing dye from water according to claim 8, characterized in that, The method further includes filtering the Co-MOF@Ag composite material adsorbed with dye, and washing the Co-MOF@Ag composite material adsorbed with dye sequentially with methanol and / or ethanol and water, so that the adsorbed dye is washed off the Co-MOF@Ag composite material, so that the Co-MOF@Ag composite material can be reused to adsorb dye.

10. The method for removing dye from water according to claim 8 or 9, characterized in that, At 25℃, the adsorption capacity of the Co-MOF@Ag composite material for Congo red is 47.28~55 mg / g.

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