Mesoporous boron nitride and boron-nitride-carbon materials from mesoporous silica templates

Abstract

We report the synthesis of mesoporous boron nitride materials (boron nitride and a boron-nitride-carbon), via a nitridation/chemical vapour deposition (CVD) route, using mesoporous pure silica SBA-15 or Fe-SBA-15 as hard template, with BH₃·NH₃, ammonia and acetonitrile as boron, nitrogen and carbon sources respectively. Fe-SBA-15 is obtained by impregnation of Fe(NO₃)₃·9H₂O in SBA-15. The boron precursor, BH₃·NH₃, is converted into boron nitride within the pores of SBA-15 during nitridation with ammonia at 1150 °C. The boron-nitride-carbon material is obtained by first incorporating carbon (viaCVD at 900 °C using acetonitrile as a carbon source) into the SBA-15/BH₃·NH₃ composite, followed by nitridation at 1150 °C. The obtained boron nitride materials are porous with relatively high surface areas of 204–380 m² g^–1 and pore volumes in the range 0.46–0.89 cm³ g^–1. The boron nitride materials exhibit considerable levels of graphitisation despite the low synthesis temperatures. The use of Fe-SBA-15 as template results in better graphitised boron nitride compared to pure silica SBA-15. The boron-nitride-carbon material exhibits the best graphitisation, and higher surface area and pore volume compared to boron nitride samples. The successful utilization of mesoporous silica, rather than carbon, as a hard template is attractive as it reduces the number of steps in the preparation of the mesoporous boron nitride materials