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.