Microscopic Mechanism of Chiral Induction in a Metal-Organic Framework.

The recently reported process of chiral induction in a metal-organic framework (MOF) by nonchiral guest adsorption, demonstrated on the prototypical MOF-5, may revolutionize the production of MOFs for enantioselective separation and catalysis. Herein, we describe an investigation employing multiscale molecular simulation to discover the microscopic mechanism of chiral induction and investigate the stability of the resulting framework. Our results explain how the molecular size and chemical nature of N-methyl-2-pyrrolidone (NMP) give rise to the chiral transformation in MOF-5, whereas it cannot occur for other guest molecules, such as N,N-dimethylformamide (DMF). Moreover, we show that the guest-free CMOF-5 structure is energetically unstable, with either the achiral conventional structure or a closed pore structure preferred, demonstrating that chirality will not be retained upon activation of CMOF-5. While this limits the usability of chiral induction in MOFs, our study opens new avenues for the use of other guest molecules and provides microscopic insight into this unexpected outcome of guest-framework interactions in a soft porous crystal.