Construction Of Water-Stable And Emissive Rare Earth Metal-Organic Frameworks For The Detection Of Small Molecules/Ions

The human body is rich in a large number of ions and small molecules.These substances play important roles in human life activities,and their high or low content is closely related to a variety of diseases.For example,dopamine(DA)is an important neurotransmitter in the mammalian central nervous system and is related to mental activities such as learning and memory.DA can be used as a biomarker for some diseases,such as Parkinson's disease,schizophrenia,etc.Iron ion(Fe3+)and ascorbic acid(AA)are two important substances in the human body.Nevertheless,the abnormal expression of Fe3+ and AA is associated with some serious systemic diseases.In addition,the coexistence of Fe3+ and AA causes a redox reaction to generate free radicals,which can induce platelet activation leading to cardiovascular disease.Furthermore,phosphate(PO43-)plays an important role in the signal transduction,energy storage,and gene construction.But when the concentration of PO43-is higher than the normal concentration,it will cause hyperphosphatemia.On the other hand,aluminum ions(Al3+)is harmful to the human body,and the precipitation of AIPO4 formed from Al3+ and PO43-will cause hypophosphatemia.Therefore,it is particularly important to devise a method that can easily and efficiently detect such small molecules or ions.In this thesis,three water-stable and emissive metal-organic frameworks(MOFs)(?)sfully constructed from the reaction of quaternized carboxylic acid with lanthanide ion and applied to the detection of dopamine,as well as the successive detection of Fe3+ and AA,and PO43-and Al3+ pairs.The results are summarized below.In the first part,three water-stable and emissive MOFs{[Ln(Cmdcp)(H20)3]2(NO3)2·5H2O}n(Ln = Tb(1),Eu(2),Sm(3),H3CmdcpBr =N-carboxymethyl-(3,5-dicarboxyl)pyridinium bromide)were successfully constructed by the reaction of quaternized carboxylic acid with lanthanide ion(Tb3+,Eu3+,Sm3+).Among them,MOF 1(16.7%/750 ?s)shows higher lifetime or quantum yield than MOFs 2(14.9%/303 ?s)and 3(2.8%/178?s).Thus,MOF 1 was chosen for the detection of DA,Fe3+ and AA,and PO43-and Al3+.With the aromatic rings in the three-dimensional(3D)structure with extended surface exposure,MOF 1 was successfully used for the detection of DA with a detection limit of 0.41 ?M.Under the basic condition,DA was self-polymerized into pDA which was adsorbed on the surface of MOF 1,resulting in fluorescence quenching.The detection mechanism was due to the overlap between the absorption of pDA and the excitation and emission spectra of MOF 1.In the third part,with the dissociative NO3-in the pore of MOF 1,it was successfully used for selectively and reversibly detecting Fe3+ and AA,yielding detection limits as 4.0 ?M and 5.9 ?M with detection time as 1 min and 2 min,and surpass several reported MOFs.The mechanism study from both experimental and DFT calculations suggested that MOF 1 detects Fe3+ and AA by a competitive energy absorption(for Fe3+)and a redox process(for AA)without the destruction of the MOF scaffold.In the fourth part,with the dissociative NO3-in the pore of MOF 1,and with Tb3v coordinated by water molecules,MOF 1 was successfully used for selectively and reversibly detecting PO43-and Al3+,yielding detection limits of 1.2 ?M and 7.3 uM with detection time of 2 min and 1 min,and surpass several reported MOFs.The mechanism study suggested that MOF 1 detects P043-and Al3+ by ion exchange and weak coordination interaction(for PO43-),and a chemical association(for Al3+)without the destruction of the MOF scaffold.