Designed Construction of One‐Dimensional Positional‐Isomeric Chiral Covalent Organic Frameworks for Asymmetric Aldol Catalysis

ABSTRACT

Chiral covalent organic frameworks (COFs) represent a versatile platform for heterogeneous asymmetric catalysis. However, constructing positional‐isomeric chiral COFs by regulating the position of chiral moieties to enhance their asymmetric catalytic performance remains a significant challenge. In this study, two V‐shaped positional‐isomeric chiral monomers, namely 4‐ L ‐DTP‐Boc and 5‐ L ‐DTP‐Boc, were designed and synthesized using naturally occurring L ‐proline as the chiral source. Subsequent condensation with 4,4′,4′′,4′′′‐(pyrene‐1,3,6,8‐tetrayl)tetraaniline (BFPPQ) and Boc deprotection afforded two one‐dimensional (1D) positional‐isomeric chiral COFs (4‐ L ‐DTP‐BFPPQ and 5‐ L ‐DTP‐BFPPQ). The resulting chiral COFs were evaluated as heterogeneous catalysts for asymmetric aldol reactions. Remarkably, 4‐ L ‐DTP‐BFPPQ COF exhibited superior catalytic performance, particularly in terms of enantioselectivity (87%–92%), significantly outperforming 5‐ L ‐DTP‐BFPPQ COF (62%–78%). The distinct catalytic behaviors of two chiral COFs could be attributed to the synergistic effects of chiral‐unit positioning on packing behavior and local chiral microenvironment. These findings establish a correlation between regioisomerism in 1D chiral COFs and their asymmetric catalytic performance, providing a blueprint for the rational design of heterogeneous chiral COF catalysts.