Synthesis Of Mesoporous Silica With Controlled Morphology And The Regulation Of Nanochannel Direction Of Mesopores

Ordered mesoporous materials have been studied extensively in the fields of adsorption, separation, catalysis and so on, since the discovery of M41s by Mobil in 1992. Methods to tune the morphology, pore and particle size of the mesoporous materials, as well as control the direction of the nanochannels of mesopores have become a hot issue for the purpose of practical applications. Current work mainly focused on the synthesis of mesoporous materials with particular morphology at the interface of oil-liquid and solid-liquid, especially on the direction control of the nanochannels of mesopores. The details are as follows:Hollow silica spheres with a mesoporous shell perforated by hexagonally-arrayed cylindrical nanochannels have been synthesized by sol-gel method with TEOS as silica source, P123 as template agent, and benzene microemulsion droplets as a core template for hollow sphere. The initial orientation of P123 micelles determined by the role of benzene decides the direction of the nanochannels of mesopores which perforate the shell along radial direction. The nanochannels are inter-connected. Hollow carbon spheres with a mesoporous shell are synthesized via nano-casting method using mesoporous hollow silica spheres as hard templates, furfuryl alcohol as carbon precursor, and oxalic acid as polymerization catalyst.Silica nanotubes with a mesoporous wall are synthesized in the channel of Anodic alumina oxide membrane (AAO) by sol-gel method using TEOS as silica source and P123 solution as template agent which are added to the channels one after another. The morphology of the silica nanotube depends on the pore structure of AAO. The thickness of the gel formed via the hydolysis of TEOS and acid solution of P123 on the channel surface of AAO determines the direction of the nanochannels of mesopores in the silica nonotube wall. When the thickness of the gel is less than two repeat distances of mesopores, the nanochannels of the mesopores perforate the silica nanotube wall vertically; when the thickness of the gel is thicker than two repeat distances of mesopores, the nanochannels of the mesopores surround the nanotube axis or parallel to the axis. And the thickness of the nanotube wall is about 15 and 40-60 nm respectively. The size of the hexagonally-arrayed mesopores in the silica nanotube wall is about 10 nm. Adding benzene to TEOS can expand the diameter of mesopores to 15 nm, and the arrangement of the mesopores is less ordered. SiO2-AAO composite membrane with perpendicular nanochannels of mesopores can be synthesized with precursor solution of SBA-15 formed via pre-hydrolysis of TEOS in the acid solution of P1 23. After the dissolution of Anodic alumina oxide membrane by hydrochloric acid, silica nanorods with nanochannels of mesopores parallel to the long axis are obtained.Silica nanotubes with mesopores perforating the wall vertically are also synthesized on the channel surface of polycarbonate membranes. The diameter of the silica nanotube is determined by the diameter of the pores of polycarbonate membranes, which is about 200, 100,50 nm respectively. Due to the curvature impact of the silica nanotube, the order degree of the mesopores in the wall reduces with the decreasing of the nanotube diameter, namely, hexagonally-arrayed mesopores trend to arrange irregularly.