Pre-Crosslinked Network-Mediated Dual Exchange Enables Boosting Chiroptical Activity and Decoupled Two-Level...

The construction of crystalline covalent organic frameworks (COFs) with strong and tunable chiroptical responses remains challenging due to rapid crystallization that limits effective chirality induction. Here, we report a pre-crosslinked network-mediated dual-exchange strategy that enables both amplified chiroptical activity and decoupled multilevel chirality in β-ketoenamine-linked COFs. In this approach, monomers are first immobilized within a pre-crosslinked amorphous imine network, which kinetically regulates subsequent framework formation. The crystallization proceeds through a dual-exchange process involving concurrent amine and aldehyde exchange, thereby retarding reaction kinetics and prolonging the chirality induction window. As a result, the obtained COFs exhibit pronounced propeller-like conformational chirality with dissymmetry factors (|g_abs|) up to 0.071, representing an order-of-magnitude enhancement over conventional systems. Furthermore, by integrating supramolecular transcription, mesoscopic helicity and molecular chirality are decoupled and independently incorporated within a single framework. Their cooperative or antagonistic interplay leads to enhanced or attenuated chiroptical responses. This work provides a general strategy for boosting chiroptical activity and programming multilevel chirality in crystalline frameworks.