Organic solids composed by weak van der Waals forces are attracting considerable attention owing to their potential applications in gas storage, separation and sensor applications(1). Herein we report a gas-induced transformation that remarkably converts the high-density guest-free form of a well-known organic host (p-tert-butylcalix[4] arene) to a low-density form and vice versa(1), a process that would be expected to involve surmounting a considerable energy barrier(2). This transformation occurs despite the fact that the high-density form is devoid of channels or pores(3). Gas molecules seem to diffuse through the non-porous solid into small lattice voids, and initiate the transition to the low-density kinetic form with similar to 10% expansion of the crystalline organic lattice, which corresponds to absorption of CO2 and N2O (refs 4,5). This suggests the possibility of a more general phenomenon that can be exploited to find more porous materials from non-porous organic and metal-organic frameworks that possess void space large enough to accommodate the gas molecules(6-13).