A Macro-mesoporous Chiral Covalent Organic Framework for Enhanced Asymmetric Catalysis in Water

Introducing macropores within chiral covalent organic frameworks (COFs) offers a potent solution to the low-efficiency mass transport common in micro- and mesoporous chiral COFs. Nevertheless, this attempt remains untapped to date. Here, we report the first hierarchically macro-mesoporous chiral COF, termed macro-L-DTPC-TP, using a template-assisted approach. Through this strategy, a β-ketoenamine-linked chiral COF bearing pyrrolidine moieties was assembled around monodisperse polystyrene (PS) nanospheres (∼200 nm), during which in situ deprotection of the tert-butoxycarbonyl (Boc) group occurred. Subsequent removal of the PS template produced macro-L-DTPC-TP COF with high crystallinity, macro-mesoporous structure, and inherent chiral pyrrolidine sites. The introduction of interconnected meso- and macropores significantly improved the catalytic efficiency of COF in the aqueous asymmetric aldol reaction. Compared to the pristine mesoporous L-DTPC-TP COF (51% yield), macro-L-DTPC-TP COF exhibited a remarkably high yield of 98%, underscoring the pivotal role of macropores in enhancing mass transport and substrate accessibility. This work presents the first example of a hierarchically macro-mesoporous chiral COF and establishes macropore incorporation as an effective strategy to overcome diffusion limitations and advance the performance of COF-based asymmetric catalysis.