Metal-Organic Gels Induced By Fe³⁺:Self-assembly And Applications

Gel is a kind of solid-like soft materials, which is constructed by 3-D networks. Supramolecular gels (also called as low molecular mass gel, LMMG) are referred as three-dimensional network structures consisting of rod-like, belt-like or fiber-like aggregates, resulting from the self-assembly of small gelators in organic solvents through various non-covalent interactions, including van der Waals force, hydrogen bonding, electrostatic interaction, hydro/solvo-phobicity,π-π stacking, coordination, and host-guest interaction.Metal-organic gels (MOGs) are series of supramolecular organic gels induced by metal ions, which exhibit many unique properties, such as high conductivity, strong magnetism and photo response, and have potential applications in catalysis, gas adsorption, chemical sensor, medicine chemistry, and so on.In this dissertation, two organic polybasic acids are used as gelator, and prepared metal-organic gels by the introduction of Fe(NO3)3. The main driving force is proved to be coordination, and their applications in arsenic adsorption, nano-material preparation and photocatalytic degradation of dye are investigated.Chapter I is a brief introduction of the supramolecular chemistry, gels and metal-organic gels. The emphasis of this chapter is the research progress of gels and metal-organic gels, including the driving force and the application of MOGs.In Chapter II, MOGs were prepared by NDC and Fe3+ in ethanol. The main driving force of the MOG formation was considered to be the metal coordination interactions. The microstructures of the MOGs were 3D networks of nanosheets. Dynamic rheological studies proved that the mechanical strength of the MOGs increased with the Fe3+ concentration. The obtained xerogels exhibit highly efficient adsorption capacity for the adsorption of arsenate from water. The adsorption capacity can reach to be 144 mg·g-1, which is dramatically higher than those of the reported various adsorbents. The kinetics studies confirmed that the adsorption data well fit the pseudo-first-order model. The thermodynamic analysis confirmed that the adsorption is spontaneous and the adsorption isotherms can be well described by the Langmuir isotherm model, suggesting the monolayer adsorption of arsenate on uniform surface. Our results demonstrate the MOGs for the highly efficient removal of arsenic from water, which should open the way for the exploration of the metal-organic gels in the environmental protection.In Chapter III, MOGs were prepared by Fumaric Acid and Fe3+ in ethanol. The main driving force of the MOG formation was also considered to be the metal coordination interactions. The microstructures of the MOGs were 3D networks of nanosheets. Dynamic rheological studies proved that the mechanical strength of the MOGs increased with the FA and Fe3+ concentration. The FA-Fe MOG was used to prepare α-Fe2O3 nanoparticles, and the MOGs and the as-prepared α-Fe2O3 nanoparticles were used to remove As(V) from water. The adsorption capacity of MOG was calculated to be 168 mg·g-1, which is dramatically higher than α-Fe2O3 nanoparticles. To explore the reason why there is a big difference between the two adsorbents, we measured the specific surface-area and Zeta potential of the two aadsorbents. It turned out that MOG had bigger specific surface-area and more positively charged than α-Fe2O3 nanoparticles. That resulted in the higher As(V) removal efficiency of MOG.