Fluorinated Azobenzenes in UiO‐66: Unveiling Unprecedented Photoswitching Stability and Efficiency in Azobenzene‐Based Switch@MOF Systems

Abstract

Understanding the interactions between hosts and guests in two‐component systems remains a formidable challenge due to the diverse array of adjusting factors at play. Particularly intriguing within the realm of two‐component systems are those incorporating a photoswitchable molecule within a porous metal‐organic framework (MOF) host. In such configurations, the non‐covalently attached guest molecule undergoes distinct physicochemical changes influenced by factors like guest structure, guest density, and the shape of the MOF pores. In this study, fluorinated azobenzenes (Fx‐AZB) were introduced into the rigid UiO‐66 host, and the resulting optical properties were examined with a focus on the degree of fluorination. The photoisomers of all examined compounds exhibited remarkable stability under repetitive light exposure, showing no signs of fatigue. Moreover, both photoisomers remained stable at room temperature, defying the typical T‐type photochromism associated with azobenzenes. Most notably, all fluorinated azobenzene derivatives displayed nearly complete photoswitching upon exposure to visible light within the UiO‐66 MOF host. This positions these composite materials as leaders in the realm of azobenzene‐based switch@MOF systems.