Synthesis of Chiral Covalent Organic Frameworks via Asymmetric Organocatalysis for Heterogeneous Asymmetric Catalysis

A general and efficient organocatalytic asymmetric polymerization approach for the synthesis of chiral covalent organic frameworks (CCOFs) has been developed. With a chiral 2-methylpyrrolidine catalyst, a series of tris(N-salicylideneamine)-derived β-ketoenamine-CCOFs are directly constructed from prochiral aldehyde- and primary amine-monomers. The adopted aminocatalytic asymmetric Schiff-base condensation herein is performed under ambient conditions with clear green synthetic advantages over the conventional acid-catalysed solvothermal methods. The obtained β-ketoenamine-CCOFs can be further metalated by a solid-state coordination approach, and the resulting CuII @CCOFs can highly promote an asymmetric A3 -coupling reaction. Specifically, a CuII @CCOF@chitosan aerogel was fabricated as a highly efficient fixed-bed model reactor for scaled-up catalysis. The concept of aminocatalytic asymmetric polymerization might open a new way for constructing the CCOFs via asymmetric organocatalysis.