Flexible Hydrogen‐Bonded Organic Framework with Anthracene Core for Recognition of Benzene Over Cyclohexane

Abstract

Abstract Flexibility is considered one of the most critical features of framework materials, playing a vital role in applications such as adsorption and separation. Hydrogen‐bonded organic frameworks (HOFs) exhibit unique flexibility derived from their weak, reversible hydrogen‐bonding interactions; however, realizing controlled and functional flexible behavior in HOFs remains a synthetic challenge. Herein, we report a flexible hydrogen‐bonded organic framework, HOF‐FJU‐119 , constructed from an anthracene‐core, that exhibits multimode guest‐responsive behavior. Upon activation, HOF‐FJU‐119a undergoes distinct gate‐opening transformations in response to CO 2 at 196 K and benzene vapor at room temperature. Single‐crystal X‐ray diffraction (SCXRD) and vapor adsorption isotherms reveal the emergence of new adsorption sites in the benzene‐loaded phase, driven by strong interactions and the flexibility of C≡N⋯H─C hydrogen bonds, enabling selective benzene/cyclohexane separation. Notably, the adsorption of benzene induces a visible color change in fluorescence emission and a red shift of approximately 60 nm. Structural and density functional theory (DFT) analyses confirm increased molecular planarity, extended conjugation, and a narrowed bandgap. This work demonstrates a rare integration of selective adsorption, molecular recognition, and signal transduction within a single crystalline framework, offering a versatile platform for the development of intelligent porous materials with real‐time visual tracking capabilities.