Synthesis And Characterizations Of Porous Liquid Based On Coordination Ionic Liquid And Nanoscale Metal-Organic Frameworks

Metal-Organic Framework(MOF)is a type of porous crystalline material with high surface area.Conventional MOF materials are generally in the form of polycrystalline solid powders or large single crystals,which do not have fluidity.The lack of fluidity limits their application as delivery medium for gas and small molecule transportation,energy conduction,and material exchange.In this thesis,based on nano-sized MOF particles,a surface modification method based on coordination interactions is proposed to synthesize porous liquid.A type of bulky ionic liquid with coordination sites for both cations and anions(C ooridnation Ionic Liquid,COIL)is designed and synthesized.The coordination interactions between the unsaturated coordination sites on the surface of MOF nanoparticles(NPs)and the COIL ligands significantly enhance the solvation effect and improve the dispersion degree and colloidal stability of the MOF NPs in the ionic liquid.The synthesized COIL ligand also has a large size and cannot enter the pores in the MOF structure due to steric hindrance.Therefore,the synthesized MOF fluid,termed as MOFluid,posseses both the porosity of the MOF material and the mobility of the ionic liquid.In addition,the MOFluid also has a high degree of tunability in chemical composition.It can b e precisely tuned from the aspects of MOF structure,porosity,metal nodes,size,and loading ratio to prepare porous liquid material with controllable properties,laying the foundating as a medium for the application of small molecule transportation,energy conduction,etc.(1)Based on the basic principles of crystal growth,we control the growth process of MOF NPs by tuning the concentrations of modulator.In this thesis,MOF structures such as Ui O-66,Ui O-67,PBA,ZIF-8,MIL-101,and HKUST-1 are selected as model structures.By tuning the synthetic conditions of MOF nanocrystals such as modulator concentration,reaction time,reactant concentration,etc.,we successfully obtained a series of MOF NPs of different sizes.We then carried out a series of characterizations on the synthesized MOF NPs.For example,we used scanning electron microscope(SEM),dynamic light scattering(DLS)and other technologies to characterize the morphology and size of the MOF NPs.We used X-ray diffraction(XRD)to characterize their crystal structures.The synthesized MOF NPs were used to prepare porous MOFluids with tunalbe porosities and mechanical properties.(2)Design and synthesis of COIL.In order to synthesize porous MOFluids with high porosity,good fluidity,and high colloidal stability,the ionic liquid needs to meet the following requirements:(1)The molecular size of the ionic liquid should be large enough so that it cannot enter the MOF pores,researving the porosity;(2)Ionic liquid itself should have good fluidity;(3)Ionic liquid molecules should have strong interactions with MOF NPs,thereby improving colloidal stability.Having considered the above requirements,we designed and synthesized an ionic liquid(COIL)containing multiple coordination sites and having bulky size larger than the pores of most MOF structures.The COIL was used as the surface capping ligand and dispersion medium for MOF NPs.By using characterization methods such as electrospray ionization mass spectrometry(ESI-MS),proton nuclear magnetic resonance(~1H NMR),and Fourier transform infrared spectroscopy(FT-IR),the structure of the COIL was fully characterized.The synthesized coordination ionic liquid was used for the subsequent synthesis of MOFluid.(3)Preparation of porous liquid based on COIL and Ui O-66 NPs.We chose Ui O-66 as the model structure to synthesize the porous Ui O-66 MOFluid through the interaction of the coordination unsaturated zirconium cluster exposed on the surface of MOF NPs and the coordination moietie on COIL molecules.The physical and chemical properties of Ui O-66 MOFluid were then systematically characterized.We used FT-IR,X-ray photoelectron spectroscopy(XPS),SEM,transmission electron microscope(TEM),XRD,thermogravimetric analysis(TGA),etc.to characterize the surface coordination bond,morphology,crystal structure,and MOF loading percentage of the prepared porous Ui O-66 MOFluid.In addition,by testing the room temperature and high-pressure methane adsorption and Sudan II dye molecule adsorption properties,we proved that the porous Ui O-66 MOFluid maintained most porosity of the original Ui O-66 material.We also used the peristaltic pump to demonstrate the fluidity of the synthesized Ui O-66 MOFluid.We further used the rheometer to systematically study the effects of the mass loading and particle size of Ui O-66 on the rheological properties of the prepared Ui O-66 MOFluid.(4)Use the COIL approach to prepare different types of MOFluids.In order to demonstrate the versatility of the COIL approach to prepare porous MOFluid,we applied this approach to six different MOFs to synthesize six different corresponding MOFluids(Ui O-66,Ui O-67,MIL-101,HKUST-1,PBA,and ZIF-8).We performed molecular dynamics(MD)simulations on these six MOFluids.The simulation results showed that the COIL molecules cannot enter the pores of any MOFs,further indicating that the prepared MOFluids retained the porosity of the initial MOF NPs.By comparing the colloidal stability of the MOFluid synthesized by the COIL approach with the MOFluid obtained by the physical mixing method previously reported,we found that the COIL-MOFluid showed significantly improved colloidal stability,showing COIL can stabilize larger sized MOF particles.To sum up,by combining the fluidity of the ionic liquid with the porosity of the MOF material using surface coordination chemistry,we synthesized a series porous MOFluids with enhanced stability,high porosity,and good adjustability.The porous MOFluids synthesized in this thesis have sound adsorption properties and high mobility,which can be forseed to serve as a new class of carrier flow medium for potential applications in circulation systems or transportation systems in the near future.