Seemingly non-porous organic solids have the ability for guest transport and have also been shown to absorb gases, including hydrogen, methane and acetylene, to varied extents. These materials also show potential for gas separation technology, display remarkable water transport through hydrophobic crystals, and clearly show that molecules within crystals are capable of cooperating with guests as they move through non-porous environments. This work is presented within a broader topic which also encompasses crystal engineering and (microporous) metal-organic frameworks (MOF's).
Dalgarno, S. J., Thallapally, P. K., Barbour, L. J., & Atwood, J. L. (2007). Engineering void space in organic van der Waals crystals: calixarenes lead the way. Chemical Society Reviews, 36(2), 236-245. https://doi.org/10.1039/b606047c