Preparation And Functionalization Of Large-sized SiO₂ Macroporous Materials

We found a new method for the preparation and functionalization of macroporous materials in this paper. A large sized macroporous three-dimensional (3D) SiO₂ material has been prepared by using a 3D skeletal polymer as template through surface replica technique. We have solved low cost preparation problems of the large sized macroporous materials and used the SiO₂ as the platform for functional studies. Due to the effects of structure-direction and strong capillarity from the porous silica template, functional Nanomaterials could be in situ synthesized and shaped as a 3D continuous film covering the silica layer. Using SiO₂ as a support, we have prepared TiO₂/SiO₂ catalyst with a better activity for photo-degradation and a novel C/SiO₂ composite with a better electrical conductivity. Details of the research as follows:By adopting a new method which was based on a two-step phase separation to synthesize 3D skeletal polymers materials with different pore sizes and through the control of the reaction induced phase separation and ion induced phase separation, we can adjust the pore sizes in a range of 1-2μm. By changing the refractive index of solid materials through the introduction of ZnSO4 and CdSO4 in polymer matrix, we have established a qualitative relationship between the wavelength range of transmitting light and the pore size with its distribution in a 3D skeleton and presented a fundamental explanation of the new optical phenomenon.A large sized macroporous SiO₂ support was obtained by using a 3D skeletal polymer as template through an in situ sol-gel process of ethyl silicate and a subsequent calcination at a high temperature. This silica materials show typical 3D ultrathin structure and its thickness of silica layer was 20-30 nm, these pore network formed a special microenvironment with two virtues of microgravity and dustless space. After studying the relationship between polymers and SiO₂, We have optimized surface replica technique and reached the batch prodution of SiO₂.Photocatalysis composite were prepared by using the large sized macroporous SiO₂ as support. By immersing the support in a solution of tetrabutyl titanate in cyclohexane followed by in situ hydrolysis in air and a final calcination, TiO₂ was loaded on the surface of the support to provide TiO₂/SiO₂ complexes and the TiO₂ formed 3D continuous thin films sandwiching the central silica thin layer. The TiO₂/SiO₂ catalyst exhibited a better activity for photo-degradation of methyl orange and the highest rate constant of 1.78 h-1 was obtained from the catalyst containing 54.5 wt% of TiO₂ calcined at 600℃. New carbon materials were prepared by using the large sized macroporous SiO₂ as support. A series of large sized and macroporous C/SiO₂ 3D composites could be obtained, by immersing the support in the Acrylonitrile solution undergo a sequent polymerization and a final calcination. The carbon in the composites was shaped as a 3D continuous film covering the silica layer. The thickness of the carbon film was related to the conductivity. When the concentration of acrylonitrile was 33 wt% and Coating twice, the novel C/SiO₂ composite exhibited a better electrical conductivity, which has an volume resistance of 16 ??cm, an average thickness of 16 nm of the carbon films and the BET surface area of 93 m2·g-1.