Photocontrolled Reversible Guest Uptake, Storage, and Release by Azobenzene-Modified Microporous Multilayer Films of Pillar[5]arenes.

Using the pillar-shaped architecture of pillar[5]arenes, we constructed microporous multilayer films with azobenzene groups on the top surface by layer-by-layer assembly of cationic and anionic pillar[5]arenes. Guest uptake, storage, and release by the microporous films were regulated through photoreversible isomerization of azobenzene groups attached to the pore outlets. Azobenzene was regarded as a "molecular valve" to control guest access: the trans form of the azobenzene acted as an open valve, allowing guest-free access from/to the micropores. Conversely, the cis form of the azobenzene behaved as a closed valve, completely blocking guest access from/to the micropores. Photoresponsive reversible uptake, storage, and release of guest molecules were demonstrated through photoisomerization of the azobenzene valves by irradiation with ultraviolet and visible light.