An Azobenzene-Bridged Nonporous Adaptive Framework Enables Photo-Regulated Desorption of Iodine

Adsorption is one of the most convenient and efficient techniques for capturing and enriching various molecules. However, current strategies for the absorbent regeneration still face the challenges of labor-intensive and/or environmentally unfriendly procedures. In this study, a novel nonporous adaptive framework (NAF) was constructed through rigid π-stacked azobenzene (Azo) bridges and flexible non-stacked amino joints. The precisely tuned flexibility of this framework enables adaptive and accessible pores, and sensitively photo-responsive behavior. The results demonstrate that Azo-NAF exhibits a remarkable iodine adsorption capacity up to 5.8 g/g. Notably, the adsorbed iodine molecules can be readily released by ultraviolet (UV) irradiation, allowing for facile regeneration and reuse of Azo-NAF. Mechanistic studies reveal that iodine molecules interact more strongly with cis-Azo-NAF than trans-Azo-NAF. Thus, accompanying the UV-induced transition from cis- to trans-configuration of Azo units, the trapped iodine molecules are released from the framework. Moreover, this unique feature of Azo-NAF enables remote regulation of iodine-catalyzed organic reactions. Our finding thus provides a new design strategy for dynamic frameworks and establish how their switchable configurations can be harnessed for a tunable adsorption and desorption performance.