Direct Synthesis of Periodic Mesoporous SilicoBoron CarboNitride Frameworks via the Nanocasting from Ordered Mesoporous Silica with Boron-Modified Polycarbosilazane

Periodic mesoporous SilicoBoron CarboNitride (Si3.0B1.0C3.9N1.8) frameworks with p6mm hexagonal symmetry are prepared by a direct nanocasting process of ordered mesoporous silica. After a double infiltration/thermal cross-linking cycle with a boron-modified polycarbosilazane (BmPS) of the type [B(C2H4SiCH3NH)3]n (C2H4=CHCH3, CH2CH2), the derived BmPS confined in the porous structure of the periodic mesoporous silica template is subjected to a thermal process up to 1000 degrees C under N2 to be converted into the Si/B/C/N phase. A short chemical etching with dilute HF eliminates the silica template, which results in the formation of an open, continuous and highly ordered 2D hexagonal Si3.0B1.0C3.9N1.8 framework as demonstrated by EDX, LA-XRD, and HRTEM analyses. The highly ordered mesoporous Si3.0B1.0C3.9N1.8 ceramic displays a specific surface area of 337m2g1, a high pore volume (0.55cm3g1) and a narrow pore-size distribution centered on 4.6nm by N2 sorption with an amorphous network remaining stable during continuous heat-treatment to 1400 degrees C in a nitrogen atmosphere.