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Aqueous asymmetric catalysis using chiral covalent organic frameworks (COFs) represents a significant advancement but remains to be explored. Herein, we present the first example of aqueous asymmetric catalysis catalyzed by a primary amine-tagged chiral D -ADP-TAPB COF. The D -ADP-TAPB COF was synthesized by the postsynthetic deprotection of D -ADP-TAPB-Boc bearing a protective tert-butoxycarbonyl (Boc) group, which was constructed by a Schiff-base reaction between an alanine-derived chiral building block ( D -ADP-Boc) and 1,3,5-tris(4-aminophenyl)benzene (TAPB). The crystalline D -ADP-TAPB COF exhibits a uniform, spherical morphology with abundant, well-distributed chiral primary amines, rendering it highly active in the asymmetric aldol reaction between cyclohexanone and 4-nitrobenzaldehyde. Notably, this reaction is conducted entirely in water, achieving impressive yields and enantiomeric excess (ee) values of up to 90 and 85%, respectively. To the best of our knowledge, D -ADP-TAPB COF represents the first chiral COF catalyst with high reactivity and enantioselectivity for an asymmetric aldol reaction solely in water, eliminating the need for conventional organic solvents. Moreover, a plausible mechanism for D -ADP-TAPB COF-mediated aqueous asymmetric aldol reactions is elucidated. This work not only expands the toolbox for designing rare primary amine-functionalized chiral COFs for asymmetric catalysis but also opens exciting avenues for developing green and water-based enantioselective catalysis.
Li et al. (Thu,) studied this question.