Construction And Application Of Lanthanide Organic Polyhedron@Mesoporous Silica Composite Materials

With the development of supramolecular chemistry,self-assembly of discrete metal-organic structures has become one of the attractive research projects in materials science and supramolecular chemistry.Based on the research foundation of coordination-directed self-assembly and the inspiration that functional supramolecular metal complex materials can be used as a good platform in chemistry,materials,energy,pharmacy,biology and other disciplines,the aim of this thesis is to solve the problems like the week stability of current multi-core lanthanide organic polyhedra and agglomeration.In this dissertation,considering the high efficiency of coordination bond guided self-assembly behavior and the spatial limitation effect of mesoporous materials,we embedded lanthanide organic polyhedra（LOPs）into the mesoporous silica matrix（MSNs）and successfully constructed the LOPs@MSNs composite materials.In addition,the optical and catalytic properties of composite materials were explored and studied.The specific researches include the following parts:Firstly,the research progress of coordination-directed self-assembly and multifunctional lanthanide complexes were briefly introduced,and the construction of functional complex composite materials and their important practical applications were expounded.Then,at the end of this chapter,the significance and design ideas of the issues are proposed.Secondly,based on pyridine-2,6-bi-tetrazole as the ligand H₄L,Eu₈L₁₂@MSNs luminescent complex composite materials were constructed for tumor cell imaging through the strategy of"ship-in-a-bottle".Due to the protective effect of confined space,the competitive coordination of Eu₈L₁₂ complexes by solvent molecules and oxyanions is inhibited,and the nonradiative decay is reduced.As a result,the luminescence quantum yield of Eu₈L₁₂ complexes in aqueous solution is significantly improved from 5.50%to44.04%,and its stability in PBS buffer solution and acidic solution has also been greatly improved.Further biological experiments showed that the composite material showed good tumor cell imaging ability,and the composite material was superior to Eu₈L₁₂ alone in terms of both imaging performance and the dosage of the complex.In particular,Eu₈L₁₂@MSNs-biotin with biotin surface modification showed excellent fluorescence imaging performance and targeting property,even if the dosage is further reduced to 0.2μM（the amount of complex contained）,tumor cell imaging can still be performed well.Thirdly,we also selected pyridine-2,6-bi-tetrazole as the coordination units to construct the Gd₈L₁₂@MSNs composite material through a"ship-in-a-bottle"strategy and applied it to the degradation of organic dyes.The Gd₈L₁₂@MSNs composite materials exhibit semiconducting characteristic,enabling electron-hole separation and producing stable photocurrent under light.Further photocatalytic experiments show that the composite material can be used as a photocatalyst to catalyze the degradation of common organic dyes such as Methyl Orange（MO）,Neutral Red（NR）,Methylene Blue（MB）,Rhodamine B（RhB）.The control experiments show that the Gd₈L₁₂ complex is crucial in the catalytic process.The enrichment of the compound increases the local concentration of the catalyst,which can improve the dye degradation rate,and the catalytic rate for MO is 3.4 times that of the Gd₈L₁₂ complex.Studies on the catalytic mechanism show that·OH radical,·O₂^-radical and h⁺are the active species in the process of dye degradation.This dissertation provides a new idea for the construction of water-dispersed and water-stabilized lanthanide organic polyhedra materials,broadens the application of lanthanide organic polyhedra,and also provides a new class of supramolecular nanomaterials for early diagnosis of tumors and degradation of organic pollutants.