Carbide-derived-carbons with hierarchical porosity from a preceramic polymer

Synthesis of carbon by extraction of metals from carbides has been successfully used to produce a variety of micro-porous carbide-derived carbons (CDCs) with narrow pore size distributions and tunable sorption properties. This approach is of limited use when larger mesopores are targeted, however, because the relevant synthesis conditions yield broad pore size distributions. Here we demonstrate the porosity control in the 3-10 nm range by employing preceramic polymer-derived silicon carbonitride (SiCN) precursors. Polymer pyrolysis in the temperature range 600-1400 °C prior to chlorine etching yields disordered or graphitic CDC materials with surface area in the range 800-2400 m² g⁻¹. In the hierarchical pore structure formed by etching SiCN ceramics, the mesopores originate from etching silicon nitride (Si₃N₄) nano-sized crystals or amorphous Si-N domains, while the micropores come from SiC domains. The etching of polymer-derived ceramics allows synthesis of porous materials with a very high specific surface area and a large volume of mesopores with well controlled size, which are suitable for applications as sorbents for proteins or large drug molecules, and supports for metal catalyst nanoparticles.