Photoinduced Electron-Transfer (PIET) Strategy for Selective Adsorption of CO2 over C2 H2 in a MOF.

Similarities in sizes, shapes, and physical properties between carbon dioxide (CO2 ) and acetylene (C2 H2 ) make it a great challenge to separate the major impurity CO2 from products in C2 H2 production. The use of porous materials is an appealing path to replace current very costly and energy-consuming technologies, such as solvent extraction and cryogenic distillation; however, high CO2 /C2 H2 uptake ratio with minor adsorption of C2 H2 at standard pressure was only unexpectedly observed in scarce examples in recent years although the related research started early at 1950s, and general design strategies to realize this aim are still absent. This work has successfully developed an efficient PIET strategy and obtained the second highest CO2 /C2 H2 adsorption ratio for porous materials in a proof-of-concept MOF with a photochromism-active bipyridinium zwitterion. An unprecedented photocontrollable gate effect, owing to change of interannular dihedral after photoinduced generation of radical species, was also observed for the first time. These findings will inspire design and synthesis of porous materials for high efficient gas adsorption and separation.