Clathrates are guest/host framework compounds composed of polyhedral cages, yet despite their prevalence among tetrahedral network formers, clathrates with a carbon host lattice remain unrealized synthetic targets. Here, we report a type-I carbon-based framework—a ubiquitous clathrate structure type found throughout compounds containing tetrahedral building blocks. Following a boron-stabilization scheme based on first-principles predictions in the Ca–B–C system at high pressure, type-I Ca ₈ B _x C _{46− x} ( x ≈ 9) was synthesized in the archetypal Pm 3 ¯ n lattice with stability derived from substitutionally disordered boron atoms on hexagonal ring framework positions. The synthesized clathrate, which is recoverable to ambient conditions, expands topological network similarity across tetrahedral systems and opens possibilities for a broad family of diamond-like, carbon-based compounds with tunable properties based on the wide potential for guest/host-atom substitutions and framework versatility.

Controlled partial decomposition of 2-selenonicotinic acid in the presence of Co²⁺ or Ni²⁺ resulted in the in situ formation of an unusual MOF based on triselenane ligands (RSeSeSeR) coordinated to M²⁺ centers as NSeN-pincers.