Synthesis of single-valence metal organic framework and research on single-crystal two-photon fluorescence performance
By constructing two-photon fluorescent metal-organic framework materials using alkaline earth metals and bis(triarylamine) derivatives, the problems of high cost and difficulty in performance control of existing materials have been solved, enabling high-performance and low-cost materials to be applied in multiple fields.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF SCI & TECH
- Filing Date
- 2026-03-13
- Publication Date
- 2026-05-26
AI Technical Summary
Existing two-photon fluorescent materials are expensive and difficult to tune. Most existing materials use transition metals and carboxylic acid ligands, which makes it difficult to achieve targeted optimization of performance.
Using alkaline earth metal ions (Mg²⁺, Ca²⁺, Sr²⁺) as nodes and bis(triarylamine) derivatives as ligands, three two-photon fluorescent metal-organic framework materials were formed by self-assembly via a solvothermal method. The reaction conditions were controlled to achieve the controlled synthesis of the materials.
We have developed high-performance, low-cost two-photon fluorescent materials suitable for applications such as two-photon excited fluorescence imaging, information storage and anti-counterfeiting, and nonlinear optical devices.
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Figure CN122080432A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional materials technology, specifically involving three types of two-photon fluorescent metal-organic framework materials, their preparation methods and applications, and particularly two-photon fluorescent metal-organic framework materials based on alkaline earth metals and bis(triarylamine) derivative ligands. Background Technology
[0002] Two-photon fluorescence technology, with its deeper tissue penetration, less optical damage, and higher signal-to-noise ratio, has broad application prospects in fields such as information storage and nonlinear optical devices. The core performance of two-photon fluorescent materials depends on the two-photon absorption cross-section and fluorescence quantum yield. How to achieve precise control of material properties while reducing costs is currently a research hotspot and challenge in this field.
[0003] Metal-organic frameworks (MOFs), as crystalline porous materials formed by the self-assembly of metal nodes and organic ligands, combine the stability of inorganic materials with the structural tunability of organic materials, providing a novel platform for the design of two-photon fluorescent materials. Existing two-photon fluorescent MOF materials mostly use transition metals (such as Cd²⁺ and Zn²⁺) or lanthanides as inorganic nodes, resulting in high costs. Furthermore, ligand selection is largely concentrated on carboxylic acid ligands, limiting structural modulation methods and hindering targeted optimization of two-photon performance.
[0004] Alkaline earth metals (Mg²⁺, Ca²⁺, Sr²⁺) are abundant, environmentally friendly, and biocompatible, and their ionic radii differ, allowing for the diversification of framework structures through the regulation of coordination modes. Bistriarylamine derivatives possess large conjugated systems and excellent electron transport capabilities, and as ligands, they can endow metal-organic frameworks with good optical properties. Currently, there are no reports on the construction of high-performance two-photon fluorescent metal-organic frameworks by combining alkaline earth metals with bistriarylamine derivative ligands; therefore, the development of such materials has significant theoretical and practical application value. Summary of the Invention
[0005] To address the technical challenges of high cost and difficulty in performance control of existing two-photon fluorescent materials, this invention provides three types of two-photon fluorescent metal-organic framework materials, their preparation methods, and applications. These materials use alkaline earth metals as nodes and bis(triarylamine) derivatives as ligands, and have advantages such as excellent performance, low cost, and simple synthesis, making them widely applicable in multiple fields.
[0006] Technical solution:
[0007] To achieve the above objectives, the present invention provides the following technical solution:
[0008] Three two-photon fluorescent metal-organic frameworks (MOFs) were developed, using the bis(triarylamine) derivative ligand H4TPBD as the organic linker and alkaline earth metal ions (Mg²⁺, Ca²⁺, and Sr²⁺) as inorganic nodes, to form crystalline porous structures through coordination bonds. These materials exhibit well-defined crystal parameters, and the materials constructed with different metal ions possess different topologies and optical properties. Among them, Ca-TPBD, due to its moderate π···π packing distance, demonstrates the best two-photon fluorescence performance.
[0009] The above-mentioned method for preparing two-photon fluorescent metal-organic framework materials adopts a solvothermal method. By adjusting the ratio of reactants, solvent system and reaction conditions, the materials can be synthesized in a controlled manner. The steps are simple, convenient and reproducible, and suitable for large-scale preparation.
[0010] The aforementioned two-photon fluorescent metal-organic framework materials can be used in fields such as two-photon excited fluorescence imaging, information storage and anti-counterfeiting, and nonlinear optical devices. Attached Figure Description
[0011] Figure 1 Powder diffraction patterns of Mg-TPBD (a), Ca-TPBD (b), and Sr-TPBD (c) materials prepared in Examples 1-3 of this invention;
[0012] Figure 2 Schematic diagrams of the crystal structures of Mg-TPBD (a), Ca-TPBD (b), and Sr-TPBD (c) materials prepared in Examples 1-3 of this invention;
[0013] Figure 3 Two-photon fluorescence spectra of Mg-TPBD (a), Ca-TPBD (b), and Sr-TPBD (c) materials prepared in Examples 1-3 of this invention under excitation at 690-820 nm.
[0014] Figure 4 Thermogravimetric curves of Mg-TPBD (a), Ca-TPBD (b), and Sr-TPBD (c) materials prepared in Examples 1-3 of this invention;
[0015] Figure 5 Schematic diagram of the weak interaction (π···π stacking) between benzene rings in the Mg-TPBD (a), Ca-TPBD (b), and Sr-TPBD (c) materials prepared in Examples 1-3 of this invention. Detailed Implementation
[0016] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
[0017] Example 1
[0018] Preparation of Mg-TPBD two-photon fluorescent metal-organic framework materials
[0019] (1) Weigh 5.0 mg of H4TPBD ligand with a purity ≥ 98% and 10.0 mg of Mg(NO3)2·6H2O with a purity ≥ 99% and add them to a 10 mL glass reaction flask;
[0020] (2) Add 2 mL of N,N-dimethylformamide, 30 μL of hydrochloric acid and 0.5 mL of water to the reaction flask, and sonicate for 20 min to fully dissolve the reactants and form a homogeneous mixed solution;
[0021] (3) Seal the reaction flask and place it in an oven at 80°C for 48 hours.
[0022] (4) After the reaction is complete, the mixture is allowed to cool naturally to room temperature and then centrifuged to obtain a pale yellow crystalline product;
[0023] (5) The crystal product was washed three times each with N,N-dimethylformamide and ethanol, and then dried at room temperature to obtain Mg-TPBD two-photon fluorescent metal-organic framework material.
[0024] Characterization revealed that the material exhibits a fluorescence quantum yield of 19%, a π···π interplanar spacing of 4.61 Å between adjacent benzene rings, and a stable two-photon fluorescence response at the optimal excitation wavelength of 740 nm.
[0025] Example 2
[0026] Preparation of Ca-TPBD two-photon fluorescent metal-organic framework materials
[0027] (1) Weigh 5.0 mg of H4TPBD ligand with a purity ≥98% and 10.0 mg of Ca(NO3)2·4H2O with a purity ≥99% and add them to a 10 mL glass reaction flask;
[0028] (2) Add 2 mL of N,N-dimethylformamide, 20 μL of hydrochloric acid and 0.5 mL of water to the reaction flask, and sonicate for 25 min to fully dissolve the reactants and form a homogeneous mixed solution;
[0029] (3) Seal the reaction flask and place it in an oven at 100°C for 48 hours.
[0030] (4) After the reaction is complete, the mixture is allowed to cool naturally to room temperature and then centrifuged to obtain a pale yellow crystalline product;
[0031] (5) The crystal product was washed three times each with N,N-dimethylformamide and ethanol, and then dried at room temperature to obtain Ca-TPBD two-photon fluorescent metal-organic framework material.
[0032] Characterization revealed that the material exhibits a fluorescence quantum yield of 35%, a π···π interplanar spacing of 5.28 Å between adjacent benzene rings, and a two-photon absorption cross-section enhancement factor of 34.91 relative to Mg-TPBD. It also demonstrates excellent two-photon fluorescence performance at the optimal excitation wavelength of 760 nm.
[0033] Example 3
[0034] Preparation of Sr-TPBD two-photon fluorescent metal-organic framework materials
[0035] (1) Weigh 5.0 mg of H4TPBD ligand with a purity ≥98% and 10.0 mg of Sr(NO3)2 with a purity ≥99% and add them to a 10 mL glass reaction flask;
[0036] (2) Add 2 mL of N,N-dimethylformamide, 20 μL of hydrochloric acid and 0.5 mL of water to the reaction flask, and sonicate for 25 min to fully dissolve the reactants and form a homogeneous mixed solution;
[0037] (3) Seal the reaction flask and place it in an oven at 80°C for 72 hours.
[0038] (4) After the reaction is complete, the mixture is allowed to cool naturally to room temperature and then centrifuged to obtain a pale yellow crystalline product;
[0039] (5) The crystal product was washed three times each with N,N-dimethylformamide and ethanol, and then dried at room temperature to obtain Sr-TPBD two-photon fluorescent metal-organic framework material.
[0040] Characterization revealed that the material exhibited a fluorescence quantum yield of 25%, a π···π interplanar spacing of 4.80 Å between adjacent benzene rings, and a two-photon absorption cross-section enhancement factor of 12.46 relative to Mg-TPBD. It also demonstrated a stable two-photon fluorescence response at the optimal excitation wavelength of 740 nm.
[0041] Example 4
[0042] Material property testing
[0043] The performance of the Mg-TPBD, Ca-TPBD, and Sr-TPBD materials prepared in Examples 1-3 was tested, and the test results are as follows:
[0044] 1. Crystal structure test: X-ray single crystal diffractometer (SC-XRD) was used to confirm that all three materials have a clear crystal structure and high crystallinity, and the unit cell parameters are consistent with those described in claim 1.
[0045] 2. Fluorescence quantum yield test: The fluorescence quantum yields of Mg-TPBD, Ca-TPBD and Sr-TPBD were 19%, 35% and 25% respectively, measured by a fluorescence spectrophotometer.
[0046] 3. Two-photon fluorescence performance testing: Solid-state two-photon excitation fluorescence (TPEF) technology was used for testing. The optimal two-photon excitation wavelength for Mg-TPBD and Sr-TPBD was 740 nm, and the optimal two-photon excitation wavelength for Ca-TPBD was 760 nm. Ca-TPBD had the best two-photon absorption performance, with an enhancement factor of 34.91 relative to Mg-TPBD, while Sr-TPBD had an enhancement factor of 12.46 relative to Mg-TPBD.
[0047] 4. Thermal stability test: Thermogravimetric analysis (TGA) was used to test the three materials. All three materials showed good thermal stability below 200℃, with a weight loss rate of less than 5%.
Claims
1. A metal-organic framework material based on the bis(triarylamine) derivative tetra(1,1'-biphenyl-4-carboxylic acid)-1,4-phenylenediamine (H4TPBD) as the organic ligand. The structural formula of the tetra(1,1'-biphenyl-4-carboxylic acid)-1,4-phenylenediamine ligand is as follows:
2. Three types of two-photon fluorescent metal-organic framework materials, characterized in that, The material uses the bis(triarylamine) derivative tetra(1,1'-biphenyl-4-carboxylic acid)-1,4-phenylenediamine ligand H4TPBD as an organic linker and alkaline earth metal ions as inorganic nodes, forming a crystalline porous structure through coordination bonds; the alkaline earth metal ions are one or more of Mg²⁺, Ca²⁺, and Sr²⁺; the chemical formulas of the material are Mg-TPBD, Ca-TPBD, and Sr-TPBD, respectively, wherein: Mg-TPBD is a triclinic crystal system with space group P-1 and cell parameters a=10.383(13)Å, b=11.707(13)Å, c=22.21(3)Å, α=102.49(2)°, β=97.72(3)°, γ=96.25(2)°. The Ca-TPBD is a monoclinic crystal system with space group C2 and cell parameters a=44.330(12)Å, b=10.537(3)Å, c=23.039(6)Å, α=90°, β=101.288(14)°, γ=90°; Sr-TPBD is a monoclinic crystal system with space group P21 / c and cell parameters a=22.5705(16)Å, b=16.4568(12)Å, c=7.2606(5)Å, α=90°, β=93.988(2)°, γ=90°.
3. A method for preparing a two-photon fluorescent metal-organic framework material according to any one of claims 1 to 3, characterized in that, The preparation method is a solvothermal method, and the specific steps are as follows: (1) Add the organic ligand H4TPBD and the alkaline earth metal salt to the reaction vessel in a molar ratio of 1:1 to 1:3; the alkaline earth metal salt is one of magnesium nitrate, calcium nitrate, and strontium nitrate. (2) Add the corresponding metal nitrate (Mg(NO3)2·6H2O, Ca(NO3)2·4H2O or Sr(NO3)2) and ligand H4TPBD to the reaction vessel, then add solvent, and sonicate until the solution is clear to fully dissolve the reactants and form a homogeneous mixed solution; the solvent is a mixed solvent of N,N-dimethylformamide, hydrochloric acid and water, wherein, based on 1 volume part of water, the volume of N,N-dimethylformamide is 4 parts, and the volume of hydrochloric acid is 0.04 parts or 0.06 parts; (3) After sealing the mixed solution, place it in an oven and react at a constant temperature of 80~100℃ for 24~72h; (4) After the reaction is complete, the mixture is allowed to cool naturally to room temperature and then filtered to obtain the crystalline product. (5) The crystal product was washed three times with N,N-dimethylformamide and ethanol, and then vacuum dried at room temperature for 6-12 hours to obtain a two-photon fluorescent metal-organic framework material.
4. The preparation method according to claim 3, characterized in that, The purity of the organic ligand H4TPBD mentioned in step (1) is ≥98%, and the purity of the alkaline earth metal salt is ≥99%.
5. An application of the two-photon fluorescent metal-organic framework material according to any one of claims 1 to 3, characterized in that, The material is used in the fabrication of two-photon excited fluorescence imaging, information storage and anti-counterfeiting or nonlinear optical devices.