Template-free synthesis of hierarchically porous SiBCN monolith from organic gel precursors

Abstract

A novel template-free method to synthesize hierarchically porous SiBCN monolith from a tailor-made organic gel precursor is proposed. The process includes four steps: the condensation reaction of tris[dichloromethylsilylethyl]borane and bis(trimethylsilyl)carbodiimide, the replacement of byproduct trimethylchlorosilane by styrene solution, the polymerization of styrene and the pyrolysis at 1000°C. The structures and thermal properties of organic gel precursors and SiBCN monolith, as well as the high temperature properties of SiBCN monolith were studied. This work demonstrates that the introduction of polystyrene is the key to obtain stable three-dimensional porous SiBCN network. The obtained SiBCN monolith displays a hierarchically porous structure with an average pore size of 1.95nm, a pore volume of 0.335cm3g−1 and a specific surface area of 31.78m2g−1. It is also observed that such hierarchically porous structure could be maintained after annealing at 1500°C. A pore size homogenization process is proposed to clarify the changes of porous architectures during the high temperature annealing.