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From China:Fujian Institute of Physical Structure has made progress in the research of pressure – responsive luminescent materials

Metal-organic frameworks (MOFs) are coordination polymers constructed by coordination bonds between metal central ions/metal clusters and organic ligands. As an inorganic-organic hybrid material, MOFs has the advantages of good crystallinity, adjustable pore size, clear structure and high functionalization. MOFs has abundant luminescence centers, and its luminescence mechanisms include metal ion luminescence, organic ligand luminescence and electron transfer luminescence. MOFs is a kind of excellent luminescence platform, among which, as a fluorescence sensing material is one of the most important applications. In recent years, MOFs based pressure stimulus response luminescent materials have attracted people’s attention, and their research field is mainly focused on high pressure response. Fluorescent stimulation-responsive materials at low pressure, especially at air pressure, require MOFs to have a higher sensitivity to pressure response, that is, changes in luminescent groups caused by subtle pressure changes, so it is difficult to achieve.

Aggregation-induced emission (AIE) refers to the phenomenon that organic luminescence groups show higher photoluminescence efficiency in the aggregated state than in solution. Restriction of Intramolecular motions RIM is the main cause of AIE. The control of intramolecular motion (including vibration and rotation) can directly affect fluorescence, thus becoming an important means of regulating luminescence and designing stimulus responsive fluorescence.

A new MOF: FJI-H31 based on lanthanide metal and AIE-type ligand was constructed by assembling semi-substituted AIE-type organic ligand and rare earth ions through rational ligand design. In FJI-H31, the phenyl rotation of AIEgen is between free rotation and completely restricted state, and the intramolecular movement of AIE group can be regulated by pressure reversible fine-tuning, so as to realize continuous changes in luminescence intensity, and finally realize pressure responsive photoluminescence MOF. Fji-h31 (Gd) was prepared by using H2TPDB and Gd3+, and the luminescence intensity of FJI-H31(Gd) increased gradually with the increase of atmospheric pressure in nitrogen atmosphere, showing a good linear relationship and excellent atmospheric pressure response performance. Further, different gases (nitrogen, carbon dioxide, argon and air) were gradually filled around fJI-H31 (Gd) in the closed chamber, and it could be seen that the fluorescence intensity gradually increased with the increase of air pressure, and had a good linear relationship. Fji-h31 (GDXEU1-X), a hybrid rare earth framework material prepared by partial incorporation of Eu3+ ions, shows the luminescence of the double emission center based on ligand and rare earth ions, and the fluorescence intensity of the double emission center gradually increases with the increase of air pressure. The dual emission luminescent MOF enriches the luminescent color and improves the accuracy of detection. Achieving gas pressure-dependent luminescence from an Aiegen-based metal-organic framework was recently published in Nature Communications.

The related research work has been supported by the National Key RESEARCH and Development Program, the Key Frontier Science Research Program of CAS, and the National Natural Science Foundation of China.

The paper links

Metal-organic framework materials with barofluorescence response were assembled by aggregation-induced luminescence ligands

Metal-organic frameworks (MOFs) are coordination polymers constructed by coordination bonds between metal central ions/metal clusters and organic ligands. As an inorganic-organic hybrid material, MOFs has the advantages of good crystallinity, adjustable pore size, clear structure and high functionalization. MOFs has abundant luminescence centers, and its luminescence mechanisms include metal ion luminescence, organic ligand luminescence and electron transfer luminescence. MOFs is a kind of excellent luminescence platform, among which, as a fluorescence sensing material is one of the most important applications. In recent years, MOFs based pressure stimulus response luminescent materials have attracted people’s attention, and their research field is mainly focused on high pressure response. Fluorescent stimulation-responsive materials at low pressure, especially at air pressure, require MOFs to have a higher sensitivity to pressure response, that is, changes in luminescent groups caused by subtle pressure changes, so it is difficult to achieve.

Aggregation-induced emission (AIE) refers to the phenomenon that organic luminescence groups show higher photoluminescence efficiency in the aggregated state than in solution. Restriction of Intramolecular motions RIM is the main cause of AIE. The control of intramolecular motion (including vibration and rotation) can directly affect fluorescence, thus becoming an important means of regulating luminescence and designing stimulus responsive fluorescence.

A new MOF: FJI-H31 based on lanthanide metal and AIE-type ligand was constructed by assembling semi-substituted AIE-type organic ligand and rare earth ions through rational ligand design. In FJI-H31, the phenyl rotation of AIEgen is between free rotation and completely restricted state, and the intramolecular movement of AIE group can be regulated by pressure reversible fine-tuning, so as to realize continuous changes in luminescence intensity, and finally realize pressure responsive photoluminescence MOF. Fji-h31 (Gd) was prepared by using H2TPDB and Gd3+, and the luminescence intensity of FJI-H31(Gd) increased gradually with the increase of atmospheric pressure in nitrogen atmosphere, showing a good linear relationship and excellent atmospheric pressure response performance. Further, different gases (nitrogen, carbon dioxide, argon and air) were gradually filled around fJI-H31 (Gd) in the closed chamber, and it could be seen that the fluorescence intensity gradually increased with the increase of air pressure, and had a good linear relationship. Fji-h31 (GDXEU1-X), a hybrid rare earth framework material prepared by partial incorporation of Eu3+ ions, shows the luminescence of the double emission center based on ligand and rare earth ions, and the fluorescence intensity of the double emission center gradually increases with the increase of air pressure. The dual emission luminescent MOF enriches the luminescent color and improves the accuracy of detection. Achieving gas pressure-dependent luminescence from an Aiegen-based metal-organic framework was recently published in Nature Communications.

The related research work has been supported by the National Key RESEARCH and Development Program, the Key Frontier Science Research Program of CAS, and the National Natural Science Foundation of China.

The paper links

Metal-organic framework materials with barofluorescence response were assembled by aggregation-induced luminescence ligands

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