Boosting Enantioselectivity of Chiral Organocatalysts with Ultrathin 2D Metal–Organic Framework Nanosheets

The development of methodologies for inducing and tailoring enantioselectivities of catalysts is an important issue in asymmetric catalysis. In this work, we demonstrate for the first time that chiral molecular catalysts can be boosted from completely non-selective to highly enantioselective when installed in nanostructured metal-organic frameworks (MOFs). Exfoliation of layered crystals is one of the most direct synthetic routes to unltrathin nanosheets, but its use in MOFs is limited by the availability of layered MOFs. We illustrate that layered MOFs can be designed using ligand-capped metal clusters and angular organic linkers. This leads to the synthesis of two 3D layered porous MOFs from Zn4-p-tert-butylsulfonyl calix[4]arene and chiral angular 1,1’-binaphthol/-biphenol dicarboxylic acids, which can be ultrasonic exfoliated into one- and two-layer nanosheets. The obtained MOF materials are efficient catalysts for asymmetric cascade condensation and cyclization of 2-aminobenzamide and aldehydes to pr...