Study On The Construction And Properties Of Co-assembly Based On Porous Organic Cages

As a kind of discrete porous organic molecules,porous organic cages have good solubility in most organic solvent.After the removal of the solvent,porous organic cages accumulate to form porous crystal through non-covalent bond interaction.Therefore,porous organic cages have become a new kind of building blocks in chemical self-assembly.The study of the co-assembly behavior of porous organic cages with other building blocks is of great significance to prepare functional derivatives of porous organic cages and to broaden the application of porous organic cages.CC3 is a kind of porous organic cages prepared by imine condensation reaction.CC3 is synthesized and named by Professor A.I.Cooper at University of Liverpool.CC is abbreviation for covalent cage,and 3 is the serial number.Each CC3 molecule contains a cavity of 0.72 nm in diameter and four windows of 0.58 nm in width.In this dissertation,CC3 was selected as the main building blocks for the assembly studies.A series of co-assemblies based on porous organic cages were prepared by co-assembly of CC3 with surfactants or inorganic nanoparticles through the emulsion confined assembly strategy.The application of those functional co-assemblies in the fields of adsorption,catalysis and surface-enhanced Raman scattering were studied.The main research contents and conclusions are as follows:(1)Study on the interaction between porous organic cages and alkyl chain:Molecular dynamics simulation was used to show that there is "high energy water" in CC3 cavity,that is,CC3 can interact with hydrophobic alkyl chain through hydrophobic effect driven by enthalpy.Then the interaction energy between a CC3 molecule and a hydrophobic alkyl chain was calculated by density functional theory.Since CC3 is insoluble in water,it is impossible to determine the interactions between aliphatic chains and CC3 through conventional techniques,such as nuclear magnetic resonance or isothermal titration calorimetry.Alternatively,the adhesion force between AFM tip functionalized with aliphatic chains and porous organic cages crystal was measured under water,and their strong interactions demonstrated that the hydrophobic interactions present between CC3 and alkyl chains.(2)Study on construction and formation mechanism of hierarchically porous organic cages:Due to the interaction between CC3 and hydrophobic alkyl chain,CC3 assembly with mesoporous characteristics was prepared by co-assembly of CC3 and ionic surfactant dodecyltrimethylammonium bromide(DTAB)by emulsion confined method.Due to containing both micropore and mesopore,the CC3 and surfactant co-assembly was denoted as MesoCC3.In order to demonstrate the universality of CC3 and surfactant co-assembly forming MesoCC3,a series of ionic surfactants with different counter ions,different hydrophobic chain lengths and different number of hydrophobic chains were used to co-assemble with CC3.Control experiment was designed by changing the type of porous organic cages and the type of surfactant,which revealed that CC3-alkyl chain complex spontaneous aggregation in the oil phase to form reverse micelles and break the van der Waals accumulation of CC3 molecules leading to the formation of mesopores.(3)Study on the adsorption properties of hierarchically porous organic cages:MesoCC3 has similar properties with the polar ends of ionic surfactants due to the polar ends of ionic surfactants exposed in the mesopores of MesoCC3.The surface electrical properties of MesoCC3 prepared by co-assembly of CC3 with pH-responsive surfactants could switch between positive and negative as the pH changes.Based on this fact,the electrostatic gated MesoCC3 was used for selective controlled release of small charged molecules such as dyes and drugs.MesoCC3 prepared by co-assembling of CC3 and surfactant containing sulfhydryl groups could adsorb heavy metal ions in water.(4)Construction and catalytic performance study of enzyme-hierarchically porous organic cages hybrid materials:Since the size of MesoCC3 mesopore is similar to the size of Cytochrome c,biological enzyme-hierarchically porous organic cages hybrid materials(Cyt c@MesoCC3)were prepared by electrostatic interaction between Cyt c and MesoCC3.Zeta potential measurement demonstrated that the surface charge of MesoCC3 prepared by amphiphilic surfactants was too weak to destroy the protein configuration of Cyt c.Enzyme kinetics tests showed that the micropore of Cyt c@MesoCC3 could enrich hydrogen peroxide.It was proved that the mesopore could promote the substrate mass transfer by changing the number of mesopore in the Cyt c@MesoCC3.The catalytic activity of Cyt c@MesoCC3 is nearly five times that of free Cyt c because of the synergy between micropore and mesopore.(5)Study on the fabrication and properties of porous organic cages-nanoparticle superlattice:Superlattice heterostructures were prepared by co-assembling of inorganic nanoparticles coating alkyl chain with porous organic cages.The epitaxial growth mode of nanoparticles on porous organic cages crystal was regulated by changing the shape of the nanoparticles,nanoparticles surface of alkyl chain length,the size of the nanoparticles and the type of porous organic cages.Superlattice heterostructures with core-shell structure or heterodimer structure were prepared.By calculating the interaction energy between nanoparticle-nanoparticle and nanoparticle-porous organic cages substrate,the reasons for the influence of the above factors on the epitaxial growth of nanoparticles were clarified.The surface-enhanced Raman properties of CC3/Au assembly were investigated.