Design,Synthesis,and Property Study Of Metal-Organic Frameworks Built Of Multi-Nuclear-Clusters

Metal-organic frameworks(MOFs),a class of crystalline material,consist of metal-nodes and organic ligands which connect each other by coordination bonds.Due to their high surface area and porosity,MOFs have been intensely investigated in different applications including gas adsorption and separation,heterogeneous catalysis,water capture,detection,energy transformation,and biology.MOFs with different structures can be rationally designed and synthesized by judicious choices of various metal and organic ligands.The research of MOFs is particularly important in both fundamental science and practical applications.Among many MOFs materials,MOFs with multi-nuclear metal-cluster secondary building units(SBUs)have received extensive attention,which showed great stability and structural diversity since the stability and regular spatial configuration of multi-nuclear metal-clusters.By using specific metal and highly functionalized organic ligands,these MOFs showed potential applications in a variety of areas.Besides,the most effective way to construct multi-nuclear metal-cluster-based MOFs is the molecular building blocks(MBBs)strategy.By using predesigned inorganic and organic SBUs with different connectivities and shapes,MOFs with anticipated or novel topology can be easily designed and synthesized.In the thesis,based on MBB strategy,we designed and synthesized seven MOFs by the combinations of a triangular and a linear ligand with In³⁺,Fe³⁺,Eu³⁺,and Zr⁴⁺.The properties of these MOFs in dye adsorption,photocatalysis,and luminescent detection have been studied.Besides,we explored the water-phase synthesis of Zr-MOFs for water adsorption and catalytic hydrolysis.The results are presented in three sections as followed:(1)Trinuclear metal-clusters-based MOFs with nitrogen-rich ligand for dyes adsorption.In this section,the highly effective and rapid removal of anionic carcinogenic organic dye molecules was achieved through the use of a novel cationic MOF.In the modern chemical industry,organic dyes have been widely used.The over-discharge of toxic and carcinogenic dyes could be an extreme threat to the ecosystem.Therefore,the development of highly efficient adsorbents for the removal of toxic dyes is urgent and necessary.We used a nitrogen-rich triangular organic ligand(4,4',4''-s-triazine-1,3,5-triyltri-p-aminobenzoate,H3TATAB)and In³⁺or Fe³⁺to construct two MOFs materials(In-TATAB and Fe-TATAB)with a novel(3,6)-c topology.In-TATAB is inherently cationic due to the[In3(?3-O)(COO^-)6]⁺units,which thus favors interaction with anionic guests.Several organic dye molecules of varying charge and size,such as acid chrome blue K,acid red 26,congo red,direct black 38,and orange II,were used to test the sequestration potential of the MOF material.The results showed that In-TATAB performed great selective adsorption of anionic dyes,and the electrostatic attraction dominated the adsorption processes.In addition to electrostatic attraction,it is shown that hydrogen-bonding originating from the highly functional bridging ligand and terminal H2O ligands enhances the interactions between the framework and guest dye molecules.(2)Anthracene-based MOFs for Photodegradation and Luminescent Detection.In this section,we designed and synthesized two MOFs materials for photodegradation and luminescent detection.With the rapid evolution of modern science and technologies,the abuse of antibiotics,discharge of dyes,and the use of nitroaromatic explosives have threatened the water system.Therefore,developing highly efficient methods for the removal and detection of the contaminant in wastewater such as photodegradation and optical sensing is urgent and necessary.Guided by the MBB approach,an anthracene-based linear organic ligand 4,4'-(9,10-anthracenediyl)dibenzoic acid(H₂ADBA)was selected to synthesize two MOFs(Eu-ADBA and In-ADBA)by solvothermal reaction using a modulator method.Eu-ADBA consists of 12-connected Eu6-cluster and exhibits fcu topology.In-ADBA consists of a 6-connected In3-cluster and exhibits a 3-folded acs topology.Both MOFs showed high thermostability and water stability.Eu-ADBA performed broadly visible light absorption and highly photocatalytic degradation of tetracycline,rhodamine B,and methylene blue in water.In-ADBA exhibited excellent fluorescence detections of antibiotics(nitrofurazone and nitrofurantoin)and nitroaromatics(2,4,6-trinitrophenol,2,4-dinitrophenol,and 4-nitrophenol)in water.(3)Zr-MOFs with different functional groups for gas adsorption.In this section,we designed and synthesized three iso-structural Zr-MOFs with different functional groups.One of the most important applications of MOFs is the gas adsorption-related one,which can reflect the advantages of high porosity and tunable pores of MOFs.To investigate the relationship between organic ligands and gas adsorption properties,the best strategy is to use iso-structural MOFs with different organic ligands.To this end,we designed and synthesized three organic ligands with the same shape and length but different functional groups,2',5'-dimethyl-[1,1':4'1''-terphenyl]-4,4''dicarboxylic acid(H2TPDC),4,4'-(9,10-naphthalenediyl)bis-benzoic acid(H2NDBA),and H2ADBA.Then,we used these ligands to build three iso-structural MOFs,Ui O-68-DM,Ui O-68-N,and Ui O-68-A,which exhibited the same structure as Ui O-68.Due to the different functional groups,these MOFs showed different porosity and surface area.They also performed different adsorptive properties towards various gases.We also investigated the property-structure relationship based on gas adsorption results.(4)Water-phase synthesis of zirconium-based MOFs for water adsorption and catalysis.In this section,we developed a water-phase synthesis of zirconium-based MOFs.Among many MOFs,zirconium-based MOFs(Zr-MOFs)have demonstrated the potential to address challenges in a variety of practical applications due to their excellent chemical and thermal stabilities.However,Zr-MOFs are typically synthesized using flammable and toxic organic solvents.An effective green,scalable route to obtain high-quality Zr-MOFs has yet to be developed as these procedures typically yield Zr-MOFs with relatively lower crystallinities and porosities than those obtained via the former route.Herein,we report the aqueous synthesis of MOF-808,a versatile Zr-MOF,that yields products with high crystallinities and porosities that are comparable to those of solvothermally synthesized MOF-808.We demonstrated that modifying the carboxylic acid-based modulator used in this hydrothermal procedure enabled the straightforward tuning of the pore environment in MOF-808.This approach can be leveraged to tune both the water adsorption properties of MOF-808 and the solid-state catalytic performance of MOF-808 towards the hydrolysis of a nerve agent simulant.