Syntheses,Structures And Properties Of Metal–Organic Frameworks Based On Dipyridylthazolo [5,4-d] Thazole

As a kind of distinctive ordered porous materials,metal–organic frameworks?MOFs?,have been imparted various potential applications owing to their intriguing structures and the interesting properties.In order to be applied well,tuning the size or shape of channnel and chemical properties,by changing inorganic SBUs consciously and selecting organic ligands rationally,has been one of the research hotspots.2,5-Bis?4-pyridyl?thiazolo[5,4-d]thiazole?Py₂TTz?has good luminescence property.Meanwhile,it integrates the features of both thiazolo[5,4-d]thiazole and pyridine,possessing multiple coordination sites.If Py₂TTz liand is introduced into the structure of MOFs,it will be very interesting to modulate their structure and fluorescence.However,study on MOFs based on Py₂TTz has been reported rarely.In this thesis,through dual-ligand strategy,Py₂TTz liand has been introduced into the structures of MOFs successfully,and moreover,the performance of their fluorescence,gas adsorption,heterogeneous catalysis,etc,have been investigated systematically.This paper includes four parts as follows:1.Through dual-ligand strategy,three mixed ligands MOFs?1–3?have been synthesized under solvothermal conditions successfully.The three compounds possess similar two-fold interpenetrated 3D framework structures.Additionally,compounds 1 and 2 display good fluorescent properties and aqueous water stability,which endow them potential aqueous sensors.The results show that compounds 1 and2 can serve as good fluorescent sensors for nitroaromatics 2,4,6-trinitrophenol?TNP?and antibiotics nitrofurazone?NZF?detection in aqueous system.Furthermore,luminescence quenching mechanism has been investigated systematically.Density functional theory calculations,coupled with spectral overlap experiments,indicate that the luminescence quenching mechanism is dominated by the photo-induced electron transfer?PET?process and the F?rster resonance energy transfer?FRET?process simultaneously.Moreover,luminescence decay experiments implies that the luminescence quenching mechanism involves dynamic and static quenching mechanism simultaneously.2.Two amino functionalized Zn/Cd-Metal-Organic Frameworks?4 and 5?have been successfully synthesized by assembling Py₂TTz,2-NH₂-H₂BDC and according metal salts under solvothermal conditions.They possess similar 2-fold interpenetrated three-dimensional bipillared-layer framework structures composed of the typical binuclear metal nodes,2-NH₂-BDC²⁺two-dimensional layers and Py₂TTz bipillars.The two MOFs possess good chemical and thermal stability,their channels are decorated with the numerous thiazole nitrogens and pendant-NH₂ groups,which impart them good performance of gas adsorption and catalysis.The results demonstrate that MOF 4 can selectively adsorb gas carbon dioxide,and moreover,MOFs 4 can 5 can be employed as efficient heterogeneous catalyst for Knoevenagel condensation reaction under solvent-free conditions.3.Nine novel Zn/Cd-MOFs based on Py₂TTz ligand?6-14?,through introducing various rigid aromatic dicarboxylic acids as auxiliary ligands,have been synthesized under solvothermal conditions successfully.The nature of metal ions,as well as the shape and size of auxiliary dicarboxylate ligands play critical role for their final structures.Even slight variations from various substituent groups have resulted in diverse architectures,which change from monomeric SBU to dimeric SBU,from2D layered structure to 3D interpenetrated structure.Linear dicarboxylate ligands(2-CH₃-BDC²⁺,2,5-di-CH₃-BDC²⁺,1,4-NDC²⁺,2,6-NDC²⁺)generate 3D multi-fold interpenetrated structures,while V-shaped dicarboxylate ligand(5-CH₃-BDC²⁺)affords 2D layer structure.However,linear 2,5-di-OH-BDC results in a 2D layer structure owing to the influence of hydroxyl group.The diverse structures have caused their structure-dependent emissions ranging from blue to blue-white and blue-green,accompanying the change of luminescent intensity.This indicates that the structures of MOFs may be modulated by rational choice of rigid auxiliary dicarboxylate ligands,and furthermore their luminescent properties also may be changed.4.The C₃ symmetric rigid tricarboxylic acids H₃BTC and H₃BTB as auxiliary ligands are introduced into the reaction system of Py₂TTz and corresponding metal salts,and as a results,six new Zn/Cd-MOFs?15-20?have been obtained successfully under solvothermal condition.The difference of solvents have resulted in the diverse coordination modes of ligands.The diversity of coordination modes,coupled with the difference of the size of auxiliary rigid tricarboxylate ligands,have resulted in diverse architectures,which change from monomeric SBU to dimeric SBU,to trimeric SBU,to pentameric SBU,from 2D layered structure to 3D porous structure,to 3D interpenetrated structure.Meanwhile,the diverse structures of MOFs 15-20 have further caused changes of luminescent emission position and intensity.This indicates that the structures of MOFs may be modulated by rational choice of rigid auxiliary tricarboxylate ligands and reaction solvents,and furthermore their luminescent properties also may be changed.In summary,a series of metal organic frameworks based Py₂TTz ligand have been designed and synthesized successfully,and moreover,their structural diversities,fluorescence changes,fluorescence sensing,gas adsorption and heterogeneous catalysis properties have been investigated systematically,which may provide the reference for the study of multi-functional MOFs.