A Cavity-Tailored Metal-Organic Cage Entraps Gases Selectively in Solution and the Amorphous Solid State.

Here we report the subcomponent self-assembly of a truxene-faced Zn4L4 tetrahedron, which is capable of binding the smallest hydrocarbons in solution under ambient conditions. By deliberately incorporating inward-facing ethyl groups on the truxene faces, the resulting partially-filled cage cavity was tailored to encapsulate methane, ethane, and ethene via van der Waals interactions at atmospheric pressure in acetonitrile, and also in the amorphous solid state. Interestingly, gas capture followed a contrasting selectivity in solution and the amorphous solid state, in which an order of methane > ethane > ethene was observed for the former. The selective binding may prove useful in designing new processes for the purification of methane and ethane as feedstocks for chemical synthesis.