Synthesis,Structures And Luminescence Properties Of Dye-encapsulated Metal-organic Frameworks

Encapsulation of guest molecules is taking more interest after the synthesis of functional porous metal-organic frameworks(MOFs).Recently,fluorescent dyes are used to incorporate into the channels of MOFs for restraining aggregation-induced quenching(ACQ)effect that greatly hampers their practical use.MOFs contain periodically repeated channel structures and controllable pore sizes that are facilitating the confinement effect of encapsulated dye molecules.As a result,encapsulated dyes exhibit enhanced emission quantum yield and fascinating photochemical stability.However,due to the crystal structure of most MOFs is inevitably distorted or destroyed with the incorporation,the experimental determination of the distribution and intermolecular interaction of encapsulated dye molecules in confined space of MOFs is still in infancy and has formidable challenges.Besides,the multi-step process is time-consuming and problematic.Therefore,investigation on dye@MOF composites is desired.The main points and topics in this dissertation are summarized as follows:Synthesis,Structures and Luminescence Properties of two PF-encapsulated Zinc(Ⅱ)MOFs based on 1,3,5-benzenetricarboxvlate and 1,2,4,5-enzenetetracarboxylate ligands.(1)In this context,two kinds of dye-encapsulated based MOFs formulated as[Zn(BTC)(HPF)(H2O)](1)and[Zn(H2BTEC)0.5(BTEC)0.5(HPF)(H2O)2](2)have been synthesized under one-pot hydrothermal process treating Zn(II)ions with 1,3,5-benzene tricarboxylic acid(H3BTC)and 1,2,4,5-benzene tetracarboxylic acid(H4BTEC)ligands with proflavin(PF)respectively.Meanwhile,a supramolecular self-aggregation of PF with solvent molecule[PF(H2SO4)(DMF)(EtOH)](PFa)was also determined for the first time.Furthermore,another two Zn-MOFs formulated[Zn3(BTC)2(H2O)8](H2O)4 and[Zn2(BTEC)(H2O)6]-2H2O were also obtained without PF molecules during experiments.The structures of these compounds were characterized by PXRD,elemental analysis,TGA and single-crystal X-ray diffraction.Photophysical properties of 1 and 2 shows that the emission of both compounds is mainly attributed to the electron transition of PF molecules.The luminescence behavior of dye in confined space is associated with the changes in the molecular packing modes.In contrast,to take benefits from the intrinsic properties of PF,the sensing ability of 1 and 2 towards different anions and nitro-aromatics was explored.The strong emission of 1 could be quenched significantly by Cr2O72-ion in aqueous media even in the presence of other competing interference analytes.Furthermore,2 exhibits highly selective and sensitive detection of Cr2O72-and TNP in aqueous media having quenching efficiency are 80%and 79%respectively.Whereas,other anions and nitro-aromatics compounds do not cause emission quenching.The fluorescence quenching mechanism was also discussed.Synthesis,Structures and Luminescence Properties of PF-encapsulated Zinc(Ⅱ)MOFs based on 5-nitroisophthalate ligand.(2)Compound[Zn(NIPH)2(HPF)2](3)has been synthesized under the same conditions by using 5-nitroisophthalic acid(5-H2NIPH)as a bridging ligand.Compound 3 possesses Diamond dia topology with Zn(II)as center and NIPH can act as a 2-connected bridging ligand.Protonated PF situates in the channels of 3 as a guest molecule for charge balancing,space-filling,and structure-directing.The fluorescent properties of the compound in solid-state maximum at 596 nm is mainly attributed to the PF dye.This compound shows red fluorescence in crystal and green emission in solution.The intense green emission of 3 in solution is used to explore the sensing properties towards different anions and metal ions.Therefore,it can detect sensitively and selectively Cr2O72-and Fe3+ions.The possible detection mechanisms have been analyzed by UV-vis absorption spectra,powder X-ray diffraction(PXRD),and emission lifetime decay measurements.Synthesis,Structures and Luminescence Properties of two PF-encapsulated Cd(Ⅱ)MOFs based on 1,3,5-benzenetricarboxylate and 1,2,4,5-benzenetetracarboxylate ligands(3)Two dye-encapsulated Cd(II)based MOFs formulated as[Cd(BTC)(HPF)(H2O)](4)and[Cd(H2BTEC)0.5(BTEC)0.5(HPF)(H2O)2](5)have been synthesized by using 1,3,5-benzenetricarboxylic acid(H3BTC)and 1,2,4,5-benzenetetracarboxylate(H4BTEC)as co-ligands under hydrothermal condition,respectively.Crystal structure of compounds 4 and 5 were investigated and it was found that there are novel hydrogen bonding pattern in 4 and 5 with protonated PF function as donors are found between the layers and forming a three-dimensional network.In the meantime,a supramolecular[(HPF)(H2BTEC)(BTEC)(H2O)2]PF-BTEC has been synthesized by the self-aggregation process with proflavin(PF)dye and H4BTEC ligand.These above-mentioned results are indicating that this method could be used to obtain new fluorescent dye-encapsulated MOFs with different metal ions.This work is providing significant outcomes that,the one-pot process is a stable method for the dye@MOFs system.Thus,these findings may expand the application area in the field of MOF.