Preparation, Characterization And Properties Of Metal Complexes Functionalized Layered Double Hydroxides

Layered double hydroxides (LDH), also known as hydrotalcite-like compounds, are a group of anionic clays. LDH consist of positively charged metal hydroxides sheets based on the brucite structure with intercalated anions and water molecules. Calcination of LDH procduces mixed oxide phase (LDO) and the LDO can be transformed into the original layered structure with Br(?)nsted base sites between the new layers by exposure to water. The metal complexes are excellent homogeneous catalysts which can effectively catalyze many kinds of reactions under mild conditions. Functionalization of LDO with metal complex, and then reconstruction of it by exposure to water can prepare a novel multifunctional catalyst which simultaneously holds Bronsted base sites and metal complex active species. Delamination of LDH into their unilamellar form can create a new type of nanosheet with two dimensional anisotropy and positive charge. Immobilization of metal complexes on LDH nanosheet can not only increase the loading amount of metal complexes, but also prevent the nanosheets from reconstructing to their original LDH structure and increase the surface areas of the prepared hydrid materials. In this thesis, two different strategies were employed to prepare metal complex functionalized LDH hybrid materials, and the prepared hybrid materials were characterized by different physicochemical technologies.Ⅰ. Preparation, characterization and catalytic performances of CuSaldien functionalized LDH hybrid materialsThe carbonate intercalated LDH with different Mg/Al molar ratio was prepared by coprecipitation and the influences of calcination temperature on the structure of the formed LDO were investigated. Saldien (N, N’-bis-(salicylidene)diethylenetriamine) functionalized silane (Saldien-CPTS) was prepared by reaction of Saldien and 3-choloropropyltriethoxysilane (CPTS). CuSaldien-CPTS-LDO was prepared by grafting Saldien-CPTS on LDO and then coordinating with Cu ions. CuSaldien-CPTS-LDH simultaneously holding Bronsted base sites and metal complex was prepared by rehydration of CuSaldien-CPTS-LDO. The results of XRD, FTIR, SEM and UV-vis confirmed successful grafting CuSaldien on LDO and coordinating to Cu ions, and CuSaldien-CPTS-LDO can be reconstructed to layered structure by rehydration. The catalytic performances of the prepared CuSaldien-CPTS-LDO were investigated in phenol hydroxylation with H2O as solvent. CuSaldien-CPTS-LDO exhibited higher catalytic activity and selectivity to catechol and hydroquinone than CuSaldien-CPTS-SBA-15 prepared by the similar grafting method. The unique catalytic performance of CuSaldien-CPTS- LDO in phenol hydroxylation with H2O2 is due to the synergistic effects between the CuSaldien and the Br(?)nsted base sites formed in the reaction system.Ⅱ. Synthesis and characterization of metal complex functionalized LDH nanosheetsFirst, the glycine intercalated LDH with high crystallinity was synthetized (the product denoted as LDH-gly) by coprecipitation, then the delamination performance of LDH-gly in different solvents and the stability of the formed LDH nanosheets were investigated, at last CuSaldien functionalized LDH nanosheets (CuSaldien-LDH-bc) were prepared by grafting CuSaldien-CPTS on delaminated LDH. The measurement results of XRD, AFM, tyndall effect, FTIR, UV-vis and NMR showed that LDH-gly materials can rapidly delaminated into nanosheets, which is stable to long-term stroage in formamide, then, CuSaldien-CPTS can be effectively grafted on the formed LDH nanosheets.