Assembly And Sensing Properties Of Tetraphenylethene-Based Luminescent Metal-Organic Frameworks

Tetraphenylethene?TPE?is emerging as the most popular aggregation-induced emission?AIE?luminogen.TPE modified with the coordination groups of pyridine or carboxylic acid as ligands to construct TPE-based luminescent metal–organic frameworks?LMOFs?,which have shown great potential in the field of solid luminescent materials.In this paper,a variety of TPE-based LMOFs were designed and synthesized,and the luminescence property and sensing mechanism were studied.Mainly divided into the following three parts:1)With introducting of two pyridyl groups on TPE,the ligand of?E?-1,2-diphenyl-1,2-bis?4-?pyridin-4-yl?-phenyl?ethene?BPyTPE?is synthesized.And synthesis two novel pillared-layered entangled LMOFs[Zn₂?bpdc?₂?BPyTPE?]?1?and[Zn₂?bdc?₂?BPyTPE?]?2?by hydrothermal method.The crystal structure of complex 1 and 2 were determined by X-ray single crystal diffraction and the structural stability were characterized by powder X-ray diffraction pattern?PXRD?,thermogravimetric analysis?TGA?and IR spectra.Both complex 1 and complex 2have excellent absolute fluorescence quantum yields(?_fl)of 79%and 75%respectively.After removing of solvent molecules from the complex,the?_fll of activated 1 and activated 2 are 99%and 77%,respectively.The emission of activated1 can be quenched efficiently and selectively by 2,6-dichloro-4-nitroaniline?DCN?with the naked eye.Based on activated 1,we have established a reversible method to sensitively and quantitatively detect trace pesticide of DCN with a low detection limit of 0.13 ppm,which is lower than the maximum limit of pesticide residues in national standards.Therefore,activated 1 can be used as a luminescence sensor for pesticide testing.2)We have synthesized two pillared-layered LMOFs[Zn₂?TCPPE??bib?]?3?and[Zn₂?TCPPE??bpy?]?4?.The crystal structure of complex 3 and 4 were determined by X-ray single crystal diffraction and the structural stability was characterized by PXRD,TGA and IR spectra.The?_fll of complex 3,activitaed 3 and complex 4 are 46.3%,35.3%and 1.3%,respectively.We have designed a new process that activated 3coated on nonwoven fabric by the hot-pressing method.The flattened morphology of activitaed 3@nonwoven fabric was characterized by scanning electron microscope?SEM?and PXRD.Research indicates that activated 3@nonwoven fabric realized fast,selective and reversible sensing of nitrobenzene vapors with a maximum quenching efficiency of 90%.Interestingly,ammonia triggered an increase in luminescence intensity(?_fl=63.8%)with a red-shifted emission of activated 3@nonwoven fabric,which is obviously observed.3)A new TPE derivative ligand 4-[?3-carboxyphenyl?phenyl]ethene?H₄T³CPPE?was synthesized,and H₄T³CPPE with metal cation(e.g.Mg²⁺and Mn²⁺)were constructed into two isomorphous luminescent metal organic framework complexes[Mg₂?T³CPPE??DMF?₃]?5?and[Mn₂?T³CPPE??DMF?₃]?6?.The complexes were characterized by X-ray diffraction single crystal diffraction,IR and TGA.The fluorescence properties of the ligands and complexes were investigated.The ligand H₄T³CPPE with AIE effect exhibits the max emission wavelength of 508 nm.Compared with H₄T³CPPE,complexe 5 and complexe 6 show blue-shifted emission peaks at 443 and 445 nm,respectively.It was found that the complex 5 was gradually changed to white light?0.302,0.241?after soaking in methylene chloride solution of rhodamine 6G?20 mM?.