Carbon-boron clathrates as a new class of sp ³ -bonded framework materials

Abstract

Carbon-based frameworks composed of sp³ bonding represent a class of extremely lightweight strong materials, but only diamond and a handful of other compounds exist despite numerous predictions. Thus, there remains a large gap between the number of plausible structures predicted and those synthesized. We used a chemical design principle based on boron substitution to predict and synthesize a three-dimensional carbon-boron framework in a host/guest clathrate structure. The clathrate, with composition 2Sr@B₆C₆, exhibits the cubic bipartite sodalite structure (type VII clathrate) composed of sp³-bonded truncated octahedral C₁₂B₁₂ host cages that trap Sr²⁺ guest cations. The clathrate not only maintains the robust nature of diamond-like sp³ bonding but also offers potential for a broad range of compounds with tunable properties through substitution of guest atoms within the cages.