Guest escape and uptake in nonporous crystals of a gold(I) macrocycle.

The nonporous gold(I) diphosphine complex [Au(2)(cis-dppe)(2)](NO(3))(2) [1, cis-dppe = cis-1,2-bis(diphenylphosphino)ethylene] is robust enough to trap guests, but at the same time, it is flexible enough to allow guest release without destruction of its crystal lattice. This nonporous gold(I) compound 1 is also efficient at capturing and releasing carbon dioxide in a controlled manner.