(49d) Molecular Modeling of Small Chiral Molecules in a Homochiral Metal-Organic Framework

Homochiral metal-organic frameworks (HMOF) are a new class of microporous, crystalline materials synthesized by a building block approach. HMOFs may be used as chiral stationary phases for preparative enantioselective separations. The high porosity and extremely high surface areas of HMOFs may lead to better production rates compared to conventional non-porous chiral stationary phases. Also, the regular structure of HMOFs makes the detailed interrogation of chiral separation mechanisms possible. In addition, the vast variety of structures and compositions available to MOFs may lead to structures tailored to special separation requirements.

It is difficult to separate small chiral molecules that do not have a marked difference in the stereogenic center. In this study, molecular simulation was employed to predict the enantioselective adsorption of over 20 small chiral molecules in a homochiral MOF with a well-defined, open cavity of a size comparable to the small chiral molecules. High enantioselectivities were observed for almost all of the small chiral molecules that are able to enter the cavity. Factors affecting the enantioselectivity and the separation mechanism are discussed in detail.