Ln-mofs-based dynamic response multicolor upconversion luminescent material, and preparation method and application thereof

Abstract

The application provides a kind of dynamic response multicolor upconversion luminescent material based on Ln-MOF and its preparation method and application.The method of the application comprises the following steps: fully dispersing rare earth metal nitrate, Yb (NO3) 3 and 1, 3, 5-benzene tricarboxylic acid in a mixed solvent of N, N-dimethylformamide and deionized water, carrying out a solvothermal reaction, and then separating, washing and drying to obtain a dynamic response multicolor upconversion luminescent material based on Ln-MOF; the rare earth metal nitrate is one of Tb (NO3) 3 or Eu (NO3) 3 or a combination of the two. The method of the application is simple and low in cost. The material of the application has excellent upconversion luminescence performance; through a negative thermal expansion mechanism to dynamically control lattice strain, and the doping of multiple lanthanide elements, dynamic multicolor upconversion emission can be achieved, which provides a reliable method for developing responsive upconversion-MOF and intelligent photonic devices for advanced information security applications.

Description

Technical Field

[0001] This invention relates to a dynamic response multicolor upconversion luminescent material based on Ln-MOFs, its preparation method and application, belonging to the field of optical anti-counterfeiting device technology. Background Technology

[0002] Upconversion luminescence, unlike traditional photoluminescence, is an anti-Stokes process that generates emission by absorbing multiple photons. Its applications in fields such as biology have attracted widespread attention, including imaging, multi-level anti-counterfeiting, and information storage. Among developed upconversion materials, lanthanide-doped micro / nanoparticles have garnered significant attention due to their excellent photostability and narrowband photoluminescence. Currently, developed upconversion particles typically consist of a rigid inorganic framework to stabilize the luminescent center. However, the rigid inorganic lattice environment leads to static upconversion luminescence, hindering dynamic control and severely impeding its further development in information security. Therefore, there is an urgent need to develop novel upconversion luminescent materials with responsive capabilities to expand the material library for multifunctional applications.

[0003] Rare-earth metal-organic frameworks (Ln-MOFs), structurally composed of trivalent rare-earth element nodes and flexible organic ligands, have attracted widespread interest in the upconversion field due to their excellent luminescence properties and unique framework structure. The soft lattice within the MOF framework provides them with great flexibility in developing responsive upconversion materials. However, achieving efficient upconversion luminescence and dynamic tuning is a trade-off due to the deactivation of excited states in the soft lattice caused by intramolecular vibrations. Although recent studies have successfully synthesized multicolor luminescent upconversion-MOFs, the construction of dynamically responsive multicolor upconversion-MOFs remains to be explored.

[0004] Therefore, properly controlling the rigidity of the MOF lattice is crucial for developing high-performance multicolor upconversion MOFs with intelligent response characteristics. To this end, this invention is proposed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a dynamically responsive multicolor upconversion luminescent material based on Ln-MOFs, its preparation method, and its applications. The method of this invention is simple and low-cost; it constructs responsive Ln-MOFs by rationally twisting the topological network; the rapid crystal growth rate induces high-energy molecular conformations of ligands anchored within the MOF framework, thereby generating tensile lattice strain. The lattice strain caused by distortion significantly promotes energy transfer from the sensitizer to the emission center and suppresses non-radiative transitions caused by lattice vibrations, thus significantly enhancing upconversion luminescence. The material of this invention exhibits excellent upconversion luminescence performance; by dynamically controlling the lattice strain through a negative thermal expansion mechanism and by doping with various lanthanide elements, dynamic multicolor upconversion emission can be achieved, providing a reliable method for developing responsive upconversion-MOFs and smart photonic devices for advanced information security applications.

[0006] The technical solution of the present invention is as follows:

[0007] A dynamic response multicolor upconversion luminescent material based on Ln-MOFs, wherein the upconversion luminescent material is a Yb-MOFs material doped with rare earth metal elements, and the rare earth metal elements are one or a combination of two of Tb or Eu.

[0008] According to a preferred embodiment of the present invention, the Yb-MOFs material is a metal-organic framework material with Yb as the coordination center and 1,3,5-benzenetricarboxylic acid as the ligand.

[0009] The above-mentioned method for preparing dynamically responsive multicolor upconversion luminescent materials based on Ln-MOFs includes the following steps:

[0010] Rare earth metal nitrates, Yb(NO3)3, and 1,3,5-benzenetricarboxylic acid are fully dispersed in a mixed solvent of N,N-dimethylformamide (DMF) and deionized water (H2O). After solvothermal reaction, the materials are separated, washed, and dried to obtain a dynamic response multicolor upconversion luminescent material based on Ln-MOFs. The rare earth metal nitrates are one or a combination of two of Tb(NO3)3 or Eu(NO3)3.

[0011] According to the present invention, the molar amount of rare earth metal nitrate accounts for 5-70% of the total molar amount of rare earth metal nitrate and Yb(NO3)3, preferably 5-50%, and more preferably 10%.

[0012] According to a preferred embodiment of the present invention, the total molar amount of rare earth metal nitrate and Yb(NO3)3 to 1,3,5-benzenetricarboxylic acid is 1:3.

[0013] According to a preferred embodiment of the present invention, when the rare earth metal nitrate is a combination of Tb(NO3)3 and Eu(NO3)3, the molar amount of Eu(NO3)3 accounts for 2-90% of the molar amount of the rare earth metal nitrate.

[0014] According to the present invention, the volume ratio of N,N-dimethylformamide (DMF) to deionized water (H2O) is preferably 1-2:1; the molar amount of 1,3,5-benzenetricarboxylic acid and the volume ratio of the mixed solvent are 0.0006-0.15 mmol / mL, preferably 0.03-0.15 mmol / mL, and more preferably 0.15 mmol / mL.

[0015] According to a preferred embodiment of the present invention, the solvothermal reaction temperature is 70-90°C and the reaction time is 2-4 hours.

[0016] According to a preferred embodiment of the present invention, the upconversion emission of the material can be regulated by adjusting the concentrations of rare earth metal nitrates, Yb(NO3)3, and 1,3,5-benzenetricarboxylic acid in the reaction system; or / and, the upconversion emission of the material can be regulated by adjusting the amount of rare earth metal nitrates; or / and, when the rare earth metal nitrates are a combination of Tb(NO3)3 and Eu(NO3)3, the upconversion emission of the material can be regulated by adjusting the molar ratio of Tb(NO3)3 and Eu(NO3)3; or / and, the upconversion emission of the material can be regulated by heating the material.

[0017] The above-mentioned application of dynamic response multicolor upconversion luminescent materials based on Ln-MOFs in information encryption.

[0018] The technical features and beneficial effects of this invention are as follows:

[0019] 1. This invention proposes a lattice strain engineering method to construct responsive upconversion MOFs through a simple, low-cost approach and purposefully twisted topological networks. Rapid crystal growth induces high-energy molecular conformations of ligands anchored within the MOF framework, resulting in tensile lattice strain. The distortion-induced lattice strain significantly promotes energy transfer from the sensitizer to the emission center and suppresses nonradiative transitions caused by lattice vibrations, thereby significantly enhancing upconversion luminescence. More importantly, by thermally controlling the lattice strain and doping with various lanthanides, multicolor dynamic responsive upconversion luminescence is effectively achieved, demonstrating great potential in stimulus-responsive information encryption applications. These results provide a reliable method for developing responsive UC MOFs and smart photonic devices for advanced information security applications.

[0020] 2. This invention synthesizes Tb in the main Yb-MOF. 3+ or / and Eu 3+ Doped Yb-MOFs, Yb 3+ Ions act as sensitizers, absorbing two incident photons and effectively transferring energy to Tb. 3+ or / and Eu 3+A light-emitting upconversion-MOF was synthesized.

[0021] 3. This invention utilizes the flexible coordination polyhedra and open pore space of 1,3,5-benzenetricarboxylic acid (BTC) to enable upconversion MOFs to modulate the spatial distribution of internal atoms without disrupting the framework topology. Therefore, upconversion luminescence can be effectively modulated due to its sensitivity to the surrounding crystal environment. This invention controls the molecular conformation by adjusting the crystallization rate through controlling the precursor concentrations (BTC and metal salts). Higher concentrations accelerate the crystal growth rate. A rapid crystallization rate leads to high-energy conformations anchored within the MOF framework because the linkers do not have sufficient time to relax. This deformation further results in significant lattice strain and suppresses nonradiative transitions caused by lattice vibrations, thereby initiating the upconversion luminescence response.

[0022] 4. This invention effectively activates upconversion luminescence through distortion-driven lattice strain. Combined with the different emission centers of Ln ions, this provides the possibility of constructing a wide range of upconversion luminescence. The color of the upconversion luminescence can be controlled by adjusting the doping type and ratio of Ln ions. Eu@Yb-MOF also exhibits distortion-induced lattice strain characteristics, with high-strain MOFs showing Eu... 3+ Significant upconversion enhancement. The isomorphic characteristics of different emission centers facilitate the expansion of the upconversion range by co-doping them in the MOF framework. Eu-doped Tb@Yb-MOFs exhibit different upconversion emission colors, which can be controlled and tuned from green and intermediate yellow to red with increasing Eu doping ratio.

[0023] 5. This invention dynamically modulates upconversion luminescence by adjusting crystal parameters in real time. Thermally induced local torsional vibrations can overcome the potential barriers between different molecular conformations, thereby achieving dynamic control of upconversion emission. Furthermore, MOFs exhibit excellent negative thermal expansion (NTE) characteristics, meaning their lattice contracts with increasing temperature. Tb 3+ Or Eu 3+ The upconversion emission intensity at the center increases sharply with increasing temperature. Furthermore, the thermally driven upconversion response is completely reversible. Attached Figure Description

[0024] Figure 1 The energy-dispersive X-ray (EDX) mapping of 10% Tb@Yb-BTC MOFs in Example 1 is shown; the scale bar is 5 μm.

[0025] Figure 2 The upconversion emission spectra of 10% Tb@Yb-BTC MOFs in Example 1 under 980nm laser irradiation at different power densities and the power density-dependent upconversion spectra plotted on a double logarithmic scale are shown.

[0026] Figure 3 For different Tb in Example 1 3+ Comparison of upconversion intensities of Tb@Yb-MOFs with different doping ratios.

[0027] Figure 4 The upconversion and fluorescence spectra of Tb@Yb-MOFs prepared with different precursor concentrations in Example 2 are shown.

[0028] Figure 5 The image shows the PXRD patterns of Tb@Yb-MOFs prepared with different precursor concentrations in Example 2.

[0029] Figure 6 The upconversion and fluorescence spectra of Eu@Yb-MOFs prepared with different precursor concentrations in Example 3 are shown.

[0030] Figure 7 The image shows the energy dispersive X-ray (EDX) mapping of Eu-doped Tb@Yb-MOFs in Example 4; the scale bar is 4 μm.

[0031] Figure 8 Eu in Example 4 x Tb 0.1-x Yb 0.9 The upconversion spectrum.

[0032] Figure 9 Eu in Example 4 x Tb 0.1-x Yb 0.9 The fluorescence image.

[0033] Figure 10 The temperature-dependent upconversion spectrum of Tb@Yb-MOF(0.002) in Experimental Example 1 is shown.

[0034] Figure 11 The temperature-dependent upconversion spectrum of Eu@Yb-MOF(0.002) in Experimental Example 2 is shown. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but is not limited thereto.

[0036] Unless otherwise specified, all raw materials used in the embodiments are conventional raw materials that can be purchased commercially; unless otherwise specified, all methods used in the embodiments are existing technologies.

[0037] Example 1

[0038] A method for preparing dynamically responsive multicolor upconversion luminescent materials based on Ln-MOFs includes the following steps:

[0039] In host Yb-MOFs, Tb with different doping ratios 3+ Preparation of Tb@Yb-MOFs. Tb@Yb-MOFs were synthesized using a hydrothermal method. 3+ and Yb 3+ The total ion concentration was 0.1 mmol. (Tb) x Yb 100-x -BTC MOFs (x = 5, 10, 20, 30, 50, and 70) were synthesized as follows: 0.1 mmol Tb(NO3)3·6H2O and Yb(NO3)3·5H2O (the molar amount of Tb(NO3)3·6H2O accounted for 5%, 10%, 20%, 30%, 50%, or 70% of the total molar amount of Tb(NO3)3·6H2O and Yb(NO3)3·5H2O), and 0.3 mmol BTC were thoroughly dispersed in a mixed solvent of 6 mL DMF and 4 mL deionized water, and sealed in a 20 mL Teflon container. After heating at 80 °C for 3 hours, the mixture was centrifuged and washed three times with DMF. The final product was dried in a vacuum oven at 80 °C for 12 hours to obtain colorless microrod crystals. The samples obtained by assigning 5%, 10%, 20%, 30%, 50%, and 70% of the total molar amount of Tb(NO3)3·6H2O to Tb(NO3)3·6H2O and Yb(NO3)3·5H2O are respectively denoted as x%Tb@Yb-BTC MOFs (x=5, 10, 20, 30, 50, and 70).

[0040] Figure 1 Energy-dispersive X-ray spectroscopy (EDX) mapping of 10% Tb@Yb-BTC MOFs. The EDX maps of Tb-doped Yb-BTC particles show that the Tb distribution almost overlaps with the Yb spectrum, indicating that Tb... 3+ The ions are well dispersed within the Yb-BTC particles.

[0041] Figure 2 The upconversion emission spectra of 10% Tb@Yb-BTC MOFs under 980 nm laser irradiation at different power densities and the power density-dependent upconversion spectra plotted on a double logarithmic scale are shown. Figure 2 As shown, the slope of the upconversion emission spectrum related to power density, plotted on a double logarithmic scale, is 2.4, confirming the existence of the two-photon emission process. The results indicate that Yb 3+ Ions act as sensitizers, absorbing two incident photons and effectively transferring energy to Tb. 3+ .

[0042] Figure 3 For different Tb 3+ The upconversion intensity of Tb@Yb-MOFs with different doping ratios shows that the maximum emission occurs at a doping ratio of 9:1 (Yb:1).3+ / Tb 3+ )hour.

[0043] Example 2

[0044] A method for preparing dynamically responsive multicolor upconversion luminescent materials based on Ln-MOFs includes the following steps:

[0045] Tb 3+ and Yb 3+ The total molar amounts of ions were x mmol (x = 0.002, 0.02, 0.1, 0.3, 0.5), of which Tb 3 + The molar amount of Tb 3+ and Yb 3+ 10% of the total molar amount. y mmol BTC (y = 0.006, 0.06, 0.15, 0.3, 0.9, 1.5, Tb 3+ and Yb 3+ The total molar amount and the molar ratio of BTC were 1:3. The synthesis of Tb@Yb-MOFs with different concentration gradients was as follows: x mmol Tb(NO3)3·6H2O and Yb(NO3)3·5H2O, and y mmol BTC were thoroughly dispersed in a mixed solvent of 6 mL DMF and 4 mL deionized water, and sealed in a 20 mL Teflon container. After heating at 80 °C for 3 hours, the mixture was centrifuged and washed three times with DMF. The final product was dried in a vacuum oven at 80 °C for 12 hours. The Tb@Yb-MOFs prepared from x mmol Tb(NO3)3·6H2O and Yb(NO3)3·5H2O were denoted as S. T0.002 S T0.02 S T0.1 S T0.3 S T0.5 .

[0046] like Figure 4 As shown, the upconversion emission intensity increases sharply with increasing precursor concentration. In samples prepared at low precursor concentrations (0.002), the MOF exhibits almost unobservable upconversion emission. At high precursor concentrations (0.3), bright upconversion emission is observed, with the color changing from dark to bright green. Furthermore, with increasing precursor concentration, all diffraction peaks continuously shift to higher angles, such as... Figure 5 This indicates that Ln-MOF underwent continuous lattice contraction, but the crystal structure and phase of the MOF itself remained unchanged.

[0047] Example 3

[0048] A method for preparing dynamically responsive multicolor upconversion luminescent materials based on Ln-MOFs includes the following steps:

[0049] Eu 3+ and Yb 3+ The total molar amounts of ions were x mmol (x = 0.002, 0.02, 0.1, 0.3, 0.5), where Eu 3 + The molar amount of Eu 3+ and Yb 3+ 10% of the total molar amount. y mmol BTC (y = 0.006, 0.06, 0.3, 0.9, 1.5, Eu 3+ and Yb 3+ The total molar amount and the molar ratio of BTC were 1:3. Eu@Yb-MOFs with different concentration gradients were synthesized as follows: x mmol Eu(NO3)3·6H2O and Yb(NO3)3·5H2O, and y mmol BTC were thoroughly dispersed in a mixed solvent of 6 mL DMF and 4 mL deionized water, and sealed in a 20 mL Teflon container. After heating at 80 °C for 3 hours, the mixture was centrifuged and washed three times with DMF. The final product was dried in a vacuum oven at 80 °C for 12 hours. Eu@Yb-MOFs prepared from x mmol Eu(NO3)3·6H2O and Yb(NO3)3·5H2O were denoted as S. E0.002 S E0.02 S E0.1 S E0.3 S E0.5 .

[0050] like Figure 6 As shown, Eu@Yb-MOFs also exhibit distortion-induced lattice strain characteristics, with high-strain MOFs displaying Eu... 3+ The upconversion enhancement allows for a clear observation of bright upconversion emission, while the color changes from dark red to luminous red.

[0051] Example 4

[0052] A method for preparing dynamically responsive multicolor upconversion luminescent materials based on Ln-MOFs includes the following steps:

[0053] The total amount of Eu(NO3)3·6H2O, Tb(NO3)3·6H2O, and Yb(NO3)3·5H2O was 0.5 mmol, with Yb(NO3)3·5H2O fixed at 0.45 mmol. The synthesis was as follows: Eu(NO3)3·6H2O, Tb(NO3)3·6H2O (with molar amounts of Eu(NO3)3·6H2O accounting for 0.02, 0.15, 0.4, 0.5, and 0.9% of the total molar amounts of Eu(NO3)3·6H2O and Tb(NO3)3·6H2O, respectively), Yb(NO3)3·5H2O, and 1.5 mmol BTC were thoroughly dispersed in a mixed solvent of 6 mL DMF and 4 mL deionized water, and sealed in a 20 mL Teflon container. After heating at 80 °C for 3 hours, the mixture was centrifuged and washed three times with DMF. The final product was dried in a vacuum oven at 80 °C for 12 hours. Eu prepared from 0.5 mmol of metal ions x Tb 0.1-x Yb 0.9 -BTC MOFs are denoted as Eu x Tb 0.1-x Yb 0.9 (x = 0.002, 0.015, 0.04, 0.05 and 0.09).

[0054] like Figure 7 As shown, the EDX spectra of Yb-BTC particles doped with Tb and Eu indicate that the distributions of Tb and Eu almost overlap with the Yb spectrum, suggesting that Tb... 3+ and Eu 3+ Ions are well dispersed within Yb-BTC microparticles. The isomorphic characteristics of different emission centers facilitate the expansion of the upconversion range by co-doping them into the MOF framework. Eu-doped Tb@Yb-MOFs exhibit different upconversion emission colors, ranging from green and intermediate yellow-green, yellow, orange to red emission colors with increasing Eu doping ratio, such as... Figure 8 , 9 As shown.

[0055] Experimental Example 1

[0056] In Example 2, Tb 3+ and Yb 3+ Tb@Yb-MOFs prepared with a total ion molar amount of 0.002 mmol exhibited excellent negative thermal expansion (NTE) characteristics, i.e., lattice contraction with increasing temperature (from 298 K to 433 K). Figure 10 As shown, Tb3 + The upconversion emission intensity at the center increases sharply with increasing temperature.

[0057] Experimental Example 2

[0058] Eu in Example 33+ and Yb 3+ Eu@Yb-MOFs prepared with a total ion molar amount of 0.002 mmol exhibited excellent negative thermal expansion (NTE) characteristics, i.e., lattice contraction with increasing temperature (from 298 K to 433 K). Figure 11 As shown, Eu 3+ The upconversion emission intensity at the center increases sharply with increasing temperature.

Claims

1.A method for preparing a Ln-MOFs-based dynamic response multicolor upconversion luminescent material, the upconversion luminescent material being a rare earth metal element-doped Yb-MOFs material, the rare earth metal element being one or a combination of Tb or Eu; the Yb-MOFs material being a metal organic framework material in which Yb element is a coordination center and 1, 3, 5-benzenetricarboxylic acid is a ligand; the method comprising the steps of: dispersing a rare earth metal nitrate, Yb (NO3) 3 and 1, 3, 5-benzenetricarboxylic acid in a mixed solvent of N, N-dimethylformamide (DMF) and deionized water (H2O) to obtain the Ln-MOFs-based dynamic response multicolor upconversion luminescent material through a solvothermal reaction, separation, washing and drying; the rare earth metal nitrate being one or a combination of Tb (NO3) 3 or Eu (NO3) 3; the molar amount of the rare earth metal nitrate accounting for 10% of the total molar amount of the rare earth metal nitrate and Yb (NO3) 3; when the rare earth metal nitrate is a combination of Tb (NO3) 3 and Eu (NO3) 3, the molar amount of Eu (NO3) 3 accounting for 2-90% of the molar amount of the rare earth metal nitrate; the molar ratio of the total molar amount of the rare earth metal nitrate and Yb (NO3) 3 to the molar amount of 1, 3, 5-benzenetricarboxylic acid being 1:3; the solvothermal reaction temperature being 80℃ and the reaction time being 3h; the molar amount of 1, 3, 5-benzenetricarboxylic acid and the volume ratio of the mixed solvent being 0.03-0.15mmol / mL; the volume ratio of N, N-dimethylformamide (DMF) and deionized water (H2O) being 1.5:1; the upconversion emission of the material being controlled by adjusting the concentrations of the rare earth metal nitrate, Yb (NO3) 3 and 1, 3, 5-benzenetricarboxylic acid in the reaction system; or / and, the upconversion emission of the material being controlled by adjusting the amount of the rare earth metal nitrate; or / and, when the rare earth metal nitrate is a combination of Tb (NO3) 3 and Eu (NO3) 3, the upconversion emission of the material being controlled by adjusting the molar ratio of Tb (NO3) 3 to Eu (NO3) 3; and the upconversion emission of the material being controlled by heating the material. 2.The application of the Ln-MOFs-based dynamic response multicolor upconversion luminescent material prepared by the method of claim 1 in information encryption. ​ ​ ​ ​

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