Effects Of Guest Molecules On Structure And Properties Of Some MOFs

As a new generation of potential materials,metal-organic frameworks（MOFs）have been greatly developed and applied in the practical fields of optoelectronic devices,industrial catalysis,separation and purification,etc.In particular,guest molecules in MOFs play an important role in the crystal structure and properties of MOFs.Appropriate host-guest effects can regulate the structure and properties of MOFs,making MOFs more designative.Therefore,MOFs can be endowed new characteristics using the host-guest interaction.In this thesis,three kinds of MOFs were synthesized,and the influence of guest molecules on their structures and properties was studied.Main content is as follows:（1）An anionic MOF[C₈H₂Mn O₅·C₄N₂]_n（Mn-MOF-3）with perfect 1D channel structure was synthesized.The guest molecules of Mn-MOF-3 were successfully exchanged with cationic dyes to produce four new crystals.Based on the crystallographic structural analysis,the exchange of guests can affect the crystal space group without the change of crystal skeleton.The optical determination showed that Mn-MOF-3 emitted strong fluorescence by exchanging guest molecules and its emission peaks were redshifted with the increasing concentration of cationic dye.（2）A porous Cu-MOF[C₁₀H₄Cu₂O₉（H₂O）₄]_n（HNNU-2）with guest water molecules was synthesized.HNNU-2 has highly water and acid-base stability.Variable-temperature single crystal XRD analysis showed that the water molecules in the channel of crystal HNNU-2 are arranged differently at different temperatures.At low temperature,water molecules are arranged in s type,while at high temperature,they are in a linear band.At different temperatures,the proton conductivities of HNNU-2 are diverse,and it can reach 1.2×10^-3 S cm^-1 at 95℃ under 98%RH.Based on the analysis of crystal structures and proton conductivity,water molecules are the transfer medium and their arrangement can change the transmission speed of protons,thus result in difference in the conductivity.（3）Two 1D compounds 1-αand 1-βwere synthesized by the coordination of Zn（II）ions and the organic ligand with AIE.After removal of the guest water molecules of the central symmetric 1-α,1-αtransformed into the non-central symmetric 1-β.Thermal stability analysis showed that 1-βcan maintain stability within 455℃ and its stability is better than 1-α.In addition,1-βinherits and improves the fluorescent property of the ligand,and produces better phase matching SHG than 1-α.