Solvent‐Directed in Situ Stacking Modulation of 2D Covalent Organic Frameworks for Selective Separation of Xylene Isomers

The precise regularity of stacking modes in two-dimensional covalent organic frameworks (2D COFs) remains insufficiently understood, and achieving precise control during synthesis is highly challenging. Here, we show that the interlayer stacking arrangement can be in situ modulated simply by varying the reaction solvent, allowing the selective formation of either eclipsed (AA) or staggered (AB) stacking. This direct solvent-driven regulation, achieved without post-synthetic modification, underscores the dynamic nature of COF assembly. Notably, the AA-stacked COF exhibits promising separation performance for xylene isomers compared to its AB-stacked counterpart.