Dynamic response multicolor up-conversion luminescent material based on Ln-MOFs as well as preparation method and application of dynamic response multicolor up-conversion luminescent material

Abstract

The invention provides a dynamic response multicolor up-conversion luminescent material based on Ln-MOFs and a preparation method and application of the dynamic response multicolor up-conversion luminescent material. The method 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, and carrying out solvothermal reaction, separation, washing and drying to obtain the dynamic response multicolor up-conversion luminescent material based on the Ln-MOFs. The rare earth metal nitrate is one or a combination of two of Tb (NO3) 3 or Eu (NO3) 3. The method is simple and low in cost. The material provided by the invention has excellent up-conversion luminescence performance; the crystal lattice strain is dynamically regulated and controlled through a negative thermal expansion mechanism, and a plurality of lanthanide elements are doped, so that dynamic multicolor up-conversion emission can be realized, and a reliable method is provided for developing a response type up-conversion-MOF and an intelligent photonic device for advanced information security application.

Description

Technical Field

[0001] The invention relates to a dynamic response multicolor up-conversion luminescent material based on Ln-MOFs and a preparation method and application thereof, belonging to the technical field of optical anti-counterfeiting devices. Background Art

[0002] Upconversion luminescence is different from traditional photoluminescence. It is an anti-Stokes process that produces emission by absorbing multiple photons. Its application in the biological field and other fields has attracted widespread attention, such as imaging, multi-level anti-counterfeiting and information storage. Among the developed upconversion materials, lanthanide-doped micro / nanoparticles have attracted much attention due to their excellent photostability and narrow-band photoluminescence. At present, the developed upconversion particles are usually composed of a rigid skeleton of an inorganic host to stabilize the luminescence center. However, the rigid inorganic lattice environment leads to static upconversion luminescence and cannot be dynamically regulated, which seriously hinders its further development in information security. Therefore, there is an urgent need to develop new upconversion luminescent materials with responsiveness to expand the material library for multifunctional applications.

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

[0004] Therefore, rationally controlling the rigidity of MOF lattices is crucial for developing high-performance multicolor upconversion-MOFs with smart response characteristics. To this end, the present invention is proposed. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides a dynamic response multicolor upconversion luminescent material based on Ln-MOFs and a preparation method and application thereof. The method of the present invention is simple and low in cost; responsive Ln-MOFs are constructed by reasonably distorting the topological network; the fast crystal growth rate induces the high-energy molecular conformation of the ligand anchored in the MOF skeleton, thereby generating a tensile lattice strain, and the lattice strain caused by the distortion significantly promotes the energy transfer from the sensitizer to the emission center, and inhibits the non-radiative transition caused by the lattice vibration, thereby significantly enhancing the upconversion luminescence. The material of the present invention has excellent upconversion luminescence performance; the lattice strain is dynamically regulated by the negative thermal expansion mechanism, and the doping of a variety of lanthanide elements can achieve dynamic multicolor upconversion emission, which provides a reliable method for the development of responsive upconversion-MOF and intelligent photonic devices for advanced information security applications.

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

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

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

[0009] The method for preparing the above-mentioned Ln-MOFs-based dynamic response multicolor upconversion luminescent material comprises the following steps:

[0010] Rare earth metal nitrate, 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), and subjected to solvent thermal reaction, separation, washing, and drying to obtain a dynamic response multicolor upconversion luminescent material based on Ln-MOFs; the rare earth metal nitrate is one or a combination of Tb(NO3)3 or Eu(NO3)3.

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

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

[0013] Preferably according to 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] Preferably according to the present invention, the volume ratio of N,N-dimethylformamide (DMF) and deionized water (H2O) is 1-2:1; the volume ratio of the molar amount of 1,3,5-benzenetricarboxylic acid to the mixed solvent is 0.0006-0.15mmol / mL, preferably 0.03-0.15mmol / mL, and further preferably 0.15mmol / mL.

[0015] Preferably according to the present invention, the solvent thermal reaction temperature is 70-90° C. and the reaction time is 2-4 h.

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

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

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

[0019] 1. The present invention proposes a lattice strain engineering to construct a responsive upconversion-MOF through a simple, low-cost method and a purposefully rationally distorted topological network. The rapid crystal growth rate induces high-energy molecular conformations of ligands anchored in the MOF framework, thereby generating tensile lattice strain. The distortion-induced lattice strain significantly promotes the transfer of energy from the sensitizer to the emission center and suppresses the non-radiative transition caused by lattice vibration, thereby significantly enhancing the upconversion luminescence. More importantly, by thermally controlling the lattice strain and doping with a variety of lanthanide elements, multi-color dynamic response upconversion luminescence is effectively achieved, showing great potential in stimulus-responsive information encryption applications. These results provide a reliable method for the development of responsive UC MOFs and smart photonic devices for advanced information security applications.

[0020] 2. The present invention synthesizes Tb in the main Yb-MOF 3+ or / and Eu 3+ Doped Yb-MOFs, Yb 3+ ions act as sensitizers to absorb two incident photons and efficiently transfer energy to Tb 3+ or / and Eu 3+, a luminescent upconversion-MOF was synthesized.

[0021] 3. The present invention utilizes the flexible coordination polyhedron and open pore space of 1,3,5-benzenetricarboxylic acid (BTC) to enable upconversion-MOFs to adjust the spatial distribution of internal atoms without destroying the framework topology. Therefore, upconversion luminescence can be effectively modulated due to its sensitivity to the surrounding crystal environment. The present invention adjusts the crystallization rate by controlling the precursor concentration (BTC and metal salt), thereby controlling the molecular conformation. Higher concentrations can accelerate the crystal growth rate. Rapid crystallization rates lead to high-energy conformations anchored in the MOF framework because the linker does not have enough time to relax. This deformation further leads to significant lattice strain and suppresses non-radiative transitions caused by lattice vibrations, thereby initiating the response of transition upconversion luminescence.

[0022] 4. The present invention effectively activates upconversion luminescence through distortion-driven lattice strain, and combined with the different emission centers of Ln ions, it provides the possibility of constructing a wide range of upconversion luminescence. The present invention can achieve the regulation of upconversion luminescence color by regulating the doping type and ratio of Ln ions. Eu@Yb-MOF also exhibits distortion-induced lattice strain characteristics, in which high-strain MOF shows Eu 3+ The isostructural features of different emission centers help to extend the upconversion range by co-doping them in the MOF framework. Eu-doped Tb@Yb-MOFs exhibit different upconversion emission colors, which can be controllably tuned from green and intermediate yellow to red with increasing Eu doping ratio.

[0023] 5. The present invention dynamically modulates upconversion luminescence by adjusting crystal parameters in real time. Thermally induced local torsional vibration can overcome the potential barriers between different molecular conformations, thereby achieving dynamic regulation of upconversion emission. In addition, MOF exhibits excellent negative thermal expansion (NTE) characteristics, that is, the lattice shrinks as the temperature increases. Tb 3+ or Eu 3+ The upconversion emission intensity of the center increases dramatically with increasing temperature. In addition, the thermally driven upconversion response is fully reversible. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the energy dispersive X-ray spectroscopy (EDX) mapping spectrum of 10% Tb@Yb-BTC MOFs in Example 1; the scale size 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 spectrum plotted on a double logarithmic scale.

[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 spectra and fluorescence graphs of Tb@Yb-MOFs prepared with different precursor concentrations in Example 2.

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

[0029] Figure 6 Upconversion spectra and fluorescence graphs of Eu@Yb-MOFs prepared with different precursor concentrations in Example 3.

[0030] Figure 7 This is the energy dispersive X-ray spectroscopy (EDX) mapping spectrum of Eu-doped Tb@Yb-MOFs in Example 4; the scale size is 4 μm.

[0031] Figure 8 is Eu in Example 4 x Tb 0.1-x Yb 0.9 Up-conversion spectrum.

[0032] Fig. 9 is Eu in Example 4 x Tb 0.1-x Yb 0.9 Fluorescence image.

[0033] Fig.10 This is the temperature-dependent upconversion spectrum of Tb@Yb-MOF (0.002) in Experimental Example 1.

[0034] Fig.11 This is the temperature-dependent upconversion spectrum of Eu@Yb-MOF (0.002) in Experimental Example 2. DETAILED DESCRIPTION

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

[0036] Unless otherwise specified, the raw materials used in the examples are conventional raw materials and can be obtained commercially; the methods used in the examples are all prior arts unless otherwise specified.

[0037] Example 1

[0038] A method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs, comprising the steps of:

[0039] In the host Yb-MOFs, different doping ratios of Tb 3+ Preparation of Tb@Yb-MOFs. Tb@Yb-MOFs were synthesized by hydrothermal method. 3+ and Yb 3+ The total amount of ions is 0.1mmol. x Yb 100-x -BTC MOFs (x = 5, 10, 20, 30, 50 and 70) were synthesized as follows: 0.1mmol Tb(NO3)3·6H2O and Yb(NO3)3·5H2O (the molar amount of Tb(NO3)3·6H2O accounts for 5%, 10%, 20%, 30%, 50% or 70% of the total molar amount of Tb(NO3)3·6H2O and Yb(NO3)3·5H2O), 0.3mmol BTC was fully dispersed in a mixed solvent of 6mL DMF and 4mL deionized water, and sealed in a 20mL Teflon container. After heating at 80°C for 3 hours, it was centrifuged and washed 3 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 when the molar amount of Tb(NO3)3·6H2O accounts for 5%, 10%, 20%, 30%, 50% and 70% of the total molar amount of Tb(NO3)3·6H2O and Yb(NO3)3·5H2O are respectively recorded as x%Tb@Yb-BTC MOFs (x=5, 10, 20, 30, 50 and 70).

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

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

[0042] Figure 3 For different Tb 3+ The upconversion intensity of Tb@Yb-MOFs with different doping ratios is shown in Figure 2. The upconversion luminescence shows that the maximum emission occurs when the doping ratio is 9:1 (Yb3+ / Tb 3+ )hour.

[0043] Example 2

[0044] A method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs, comprising the steps of:

[0045] Tb 3+ and Yb 3+ The total molar weight of ions is 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+ 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 BTC molar ratio is 1:3). Tb@Yb-MOFs with different concentration gradients were synthesized as follows: x mmolTb(NO3)3·6H2O and Yb(NO3)3·5H2O, y mmol BTC were fully dispersed in a mixed solvent of 6mL DMF and 4mL deionized water and sealed in a 20mL Teflon container. After heating at 80°C for 3 hours, it was centrifuged and washed with DMF three times. The final product was dried in a vacuum oven at 80°C for 12 hours. Tb@Yb-MOFs prepared from x mmolTb(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 in Figure 1, the upconversion emission intensity increases dramatically with increasing precursor concentration. In samples prepared at low precursor concentrations (0.002), MOF exhibits almost unobservable upconversion emission. Bright upconversion emission is observed at high precursor concentrations (0.3), while the color changes from dark to bright green. And with increasing precursor concentrations, all diffraction peaks continuously move to higher angles, such as Figure 5 , indicating that Ln-MOF underwent continuous lattice contraction, but the crystal structure and phase of MOF itself did not change.

[0047] Example 3

[0048] A method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs, comprising the steps of:

[0049] Eu 3+ and Yb 3+ The total molar weight of ions is x mmol (x = 0.002, 0.02, 0.1, 0.3, 0.5), of which Eu 3 + The molar amount of Eu 3+ and Yb 3+ y mmol BTC (y = 0.006, 0.06, 0.3, 0.9, 1.5, Eu 3+ and Yb 3+ The total molar amount and BTC molar ratio is 1:3). Eu@Yb-MOFs with different concentration gradients were synthesized as follows: x mmol Eu(NO3)3·6H2O and Yb(NO3)3·5H2O, y mmol BTC were fully dispersed in a mixed solvent of 6mL DMF and 4mL deionized water and sealed in a 20mL Teflon container. After heating at 80°C for 3 hours, it was centrifuged and washed with DMF three times. The final product was dried in a vacuum oven at 80°C for 12 hours. Eu@Yb-MOFs prepared from x mmolEu(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-MOF also exhibits distortion-induced lattice strain properties, where the high-strain MOF shows Eu 3+ The upconversion is enhanced and the bright upconversion emission can be clearly observed with a color change from dark red to luminous red.

[0051] Example 4

[0052] A method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs, comprising the steps of:

[0053] The total amount of Eu(NO3)3·6H2O, Tb(NO3)3·6H2O and Yb(NO3)3·5H2O is 0.5mmol, and Yb(NO3)3·5H2O is fixed at 0.45mmol. The synthesis is as follows: Eu(NO3)3·6H2O, Tb(NO3)3·6H2O (the molar amount of Eu(NO3)3·6H2O accounts for 0.02, 0.15, 0.4, 0.5 and 0.9 of the total molar amount of Eu(NO3)3·6H2O and Tb(NO3)3·6H2O), Yb(NO3)3·5H2O and 1.5mmol BTC are fully dispersed in a mixed solvent of 6mL DMF and 4mL deionized water, and sealed in a 20mL Teflon container. After heating at 80℃ for 3 hours, it is centrifuged and washed with DMF 3 times. The final product is dried in a vacuum oven at 80℃ for 12 hours. Eu prepared from 0.5mmol 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 in the EDX spectrum of Yb-BTC particles doped with Tb and Eu, the distribution of Tb and Eu almost overlaps with the Yb spectrum, indicating that Tb 3+ and Eu 3+ The ions are well dispersed within the Yb-BTC particles. The isostructural features of different emission centers help to extend the upconversion range by co-doping them in 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 shown.

[0055] Test Example 1

[0056] In Example 2, Tb 3+ and Yb 3+ The Tb@Yb-MOFs prepared with a total molar amount of ions of 0.002 mmol showed excellent negative thermal expansion (NTE) characteristics, that is, the lattice contracted as the temperature increased (from 298 K to 433 K). Fig.10 As shown, Tb3 + The upconversion emission intensity of the center increases dramatically with increasing temperature.

[0057] Test Example 2

[0058] In Example 3, Eu3+ and Yb 3+ The Eu@Yb-MOFs prepared with a total molar amount of ions of 0.002 mmol showed excellent negative thermal expansion (NTE) characteristics, that is, the lattice contracted as the temperature increased (from 298 K to 433 K). Fig.11 As shown, Eu 3+ The upconversion emission intensity of the center increases dramatically with increasing temperature.

Claims

1. A dynamic response multicolor upconversion luminescent material based on Ln-MOFs, characterized in that: The up-conversion luminescent material is a Yb-MOFs material doped with a rare earth metal element, and the rare earth metal element is one or a combination of Tb or Eu.

2. According to claim 1, the Ln-MOFs-based dynamic response multicolor upconversion luminescent material is characterized in that: Yb-MOFs material is a metal organic framework material with Yb element as the coordination center and 1,3,5-benzenetricarboxylic acid as the ligand.

3. The method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs according to claim 1 or 2, comprising the steps of: Rare earth metal nitrate, 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), and subjected to solvent thermal reaction, separation, washing, and drying to obtain a dynamic response multicolor upconversion luminescent material based on Ln-MOFs; the rare earth metal nitrate is one or a combination of Tb(NO3)3 or Eu(NO3)3.

4. The method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs according to claim 3, characterized in that: The molar amount of the rare earth metal nitrate accounts for 5-70% of the total molar amount of the rare earth metal nitrate and Yb(NO3)3, preferably 5-50%, and more preferably 10%.

5. The method for preparing the dynamic response multicolor upconversion luminescent material based on Ln-MOFs according to claim 3, characterized in that: The molar ratio of the total molar amount of rare earth metal nitrate and Yb(NO3)3 to 1,3,5-benzenetricarboxylic acid is 1:

3.

6. The method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs according to claim 3, characterized in that: 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.

7. The method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs according to claim 3, characterized in that: The volume ratio of N,N-dimethylformamide (DMF) to deionized water (H2O) is 1-2:1; the volume ratio of the molar amount of 1,3,5-benzenetricarboxylic acid to the mixed solvent is 0.0006-0.15 mmol / mL, preferably 0.03-0.15 mmol / mL, and more preferably 0.15 mmol / mL.

8. The method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs according to claim 3, characterized in that: The solvent thermal reaction temperature is 70-90°C and the reaction time is 2-4h.

9. The method for preparing a dynamic response multicolor upconversion luminescent material based on Ln-MOFs according to claim 3, characterized in that: By regulating the concentrations of rare earth metal nitrate, Yb(NO3)3, and 1,3,5-benzenetricarboxylic acid in the reaction system, the upconversion emission of the material can be regulated; or / and, by regulating the amount of rare earth metal nitrate, the upconversion emission of the material can be regulated; or / and, when the rare earth metal nitrate is a combination of Tb(NO3)3 and Eu(NO3)3, by regulating the molar ratio of Tb(NO3)3 and Eu(NO3)3, the upconversion emission of the material can be regulated; or / and, by heating the material, the upconversion emission of the material can be regulated.

10. Application of the dynamic response multicolor upconversion luminescent material based on Ln-MOFs as claimed in claim 1 or 2 in information encryption.

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