Synthesis Of Mesoporous Aluminosilicates Materials,Biomimetic Application Of Mesostructure And Functionalization Of Nanocavity Investigation

In 1992, the Mobil Scientists reported the synthesis of a new family of inorganic/organic hybrid materials by the use of self-assembled surfactant molecular aggregates as the structure-directing agents. After removing the organic species, mesoporous aluminosilicates M41S were obtained with uniform pore size and high surface areas. For the past ten years, such materials have attracted considerable attention in the areas such as separation of large molecular, biosensors, catalysis, adsorption, microelectronics, optics, and fabrication of novel nano-objects because of their uniform and adjustable pore properties (pore sizes and pore structures), rich surface functional groups, and designable morphologies (film, fiber, sphere, etc.). However, the application of mesoporous materials was limited due to: 1 difficulty in controlled preparation of mesoporous materials (especial non-silica mesoporous materials), the detail formation of the mesostruture is not very clear, and short of proper in-situ characterization tools for the mechanism of the mesoporous materials; 2 can not achieve function direct synthesis of mesoporous materials; 3 properties of mesoporous materials such as hydrothermal stability and acidity etc. are expect to be improved; 4 new application fields are urgent needed to be explored; 5 more convenient and time-saving as well as low-cost synthesis methods are also obligatory. The current contribution concerning on the following topics: 1 preparation of mesoporous aluminosilicates in strong acidic media, in-situ NMR technique are used to investigate the conversion of inorganic species during the formation of mesostructure; 2 biomimetic preparation of MnO2 nanostructure using mesostructured silica (SBA-15 and SBA-16) with different morphologies; 3 modify the mesoporous silica SBA-15 tunnels and surface using molecular engineering method. Mesoporous aluminosilicates (MAS-X1-7) with different mesophase are prepared by using Pluronic P123, F127, Brij 56, 76, and Triton X100 as structure-directing agents (SDA) and high aluminum content zeolite such as FAU-X, LTA, and SOD etc. as silica source in a strong acidic media. Both the mesophase and cell parameter of the MAS-X1 and MAS-X3 are the same, but the pore size of MAS-X3 is 6 nm while the pore size of MAS-X1 is 8.5 nm. And the wall thickness of MAS-X3 (6 nm) is much thicker than that of MAS-X1 (3.5 nm). The Si/Al ratio of MAS-X1 is 16, and that of MAS-X3 is lower than 8. High ordered cubic Im3m mesoporous aluminosilicates MAS-X2 and MAS-X4 are prepared using F127 or F108 as SDA. Low ordered MAS-X5-7 are also prepared using Brij 56, 76 and Triton X100 as SDA. The salt NaCl, which is introduced by dissolving the zeolite FAU-X, can dramatic enhance the self-assembly ability of organic species, thus high ordered mesoporous aluminosilicates (MAS-X1, MAS-X2 and MAS-X4) are resulted. The dynamics radius of P123 micell decreased due to the salt effect, led to formation p6mm mesoporous aluminosilicates MAS-X1 and MAS-X3 with different wall-thickness. Mesoporous aluminosilicates MAS-Y, MAS-Y1, and MAS-TY with different acidity are prepared using zeolite FAU-Y structure directing agent (performed zeolite seeds) as precursor in a strong acidic media. The formation procedure is characterized by in-situ 27 Al NMR and 29 Si NMR techniques. The formation of the inorganic framework is due to the condensation of the silica species,accompanied by loss of the aluminum species form the inorganic framework. Zeolite primary and secondary structured units decomposed in acidic media, and re-assembled each other. So, any operation that can avoid the decomposition of the zeolite primary and secondary structured units will lead more zeolite units in the inorganic wall of mesoporous aluminosilicates. As the properties of the mesoporous solid such as acidity are directly relative to the composition of the wall of the mesoporous materials, MAS-Y synthesized by adjusting pH value slowly can preserve more zeolite units in the wall so the acidity of MAS-Y are higher than that of MAS-Y1 and MAS-TY. Mesostructured silica templated by block copolymer such as P123 or F127 possess periodical array of inorganic-organic structure with organic chain penetrated into inorganic wall. Mesoporous tunnels and micropore are leave after removal of organic template. When mesostructured silica SBA-15 or SBA-16 with different morphology is impregnated in high oxidated solution of acidic potassium permanganate, the organic template can be oxidated to small molecule, such as formaldehyde, glycoldehyde, formalacid, and acetic acid etc.. These small molecules released from the mesopore and micropore of mesoporous silica, then react with potassium permanganate, MnO2 nanostructures with different morphology are then formed on the surface of the mesoporous solid. Such a procedure is terribly similar to the biomimetic progress, which characterized by the nucleation and growth of inorganic mineral are controlled by organic species secreted by organism. Disordered nanostructured MnO2 composed of 1-D nanorods with diameter 20 ~ 50 nm, length several handed nm are grew on the surface of the wheat like SBA-15; when rod like SBA-15 with mesopore parallel to long-axel of the rod is used as template, the growth direction of MnO2 nanorods are nearly upright to the mesoporous silica rod; flower like MnO2 nanostructure are formed on the surface of single crystalline like mesoporous silica SBA-16; crew like MnO2 nanostructure composed of nanowire with diameter about 20 nm are formed on the surface of monolith of SBA-15 under...