Porous Liquids Responsive to Light.

Porous liquid is a unique liquid medium that combines cavity of porous solid with the fluidity of liquid, and this special characteristic makes it potential in various applications. Here we report the type II photoresponsive porous ionic liquid (PPIL) by dissolving photoresponsive metal-organic polyhedron (PMOP, constructed from dicopper and azobenzene-containing carboxylate) in polyethylene-glycol-functionalized bulky ionic liquid (IL). Owing to favorable ion interactions, bulky IL molecules encircle outside PMOP, and the inter cavities are maintained. The azobenzene moieties can be isomerized freely in the obtained PPILs to expose and shelter active sites upon visible and UV light irradiations. Hence, the adsorption capacity of PPILs is controllable by light irradiation, and the change in CO2 uptake is up to 30% than neat IL with negligible change. This study may inspire the development of new adsorption process regulated by light instead of pressure and temperature swing adsorption.