Selective Adsorption of o ‐Xylene From all C8 Aromatics via Secondary Connectivity Manipulation in B←N Frameworks

ABSTRACT

Separating o ‐xylene from all C8 aromatic isomers ( m ‐xylene, p ‐xylene, and ethylbenzene) is critical for industry but remains a formidable challenge due to their quite similar physicochemical properties. While metal‐free frameworks offer an ideal solution via selective adsorption, their development lags behind metal‐based systems. For instance, due to the limited connection modes and lack of suitable linkers, B←N frameworks (BNFs) struggle to handle complex separations. To address this limitation, we report a programmed assembly strategy by rationally integrating secondary connectivity into bridging linkers. Implementing this strategy yielded stable BNFs, BN‐DPTA1 and BN‐DPTA2 , featuring tunable and confined cavities. BN‐DPTA1 exhibits specific abstraction of toluene, while BN‐DPTA2 selectively adsorbs o ‐xylene from benzene derivatives. Notably, BN‐DPTA2 represents the first metal‐free framework to achieve highly selective adsorption of o ‐xylene over all C8 aromatic isomers. The multiple non‐covalent interactions between the BNF cavities and guest molecules facilitate tight encapsulation, enabling the effective removal of toluene and o ‐xylene from the atmosphere (97.4% and 96.0% removal efficiency at 50 ppm, respectively). The dynamic, reversible adsorption/desorption behavior of BNFs allows for single‐step purification of toluene and o ‐xylene via solid‐phase extraction columns, achieving purities exceeding 99.9%.