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Molecular modeling of enantioselective adsorption in homochiral metal-organic frameworks

Posted on:2011-10-09Degree:Ph.DType:Thesis
University:Northwestern UniversityCandidate:Bao, XiaoyingFull Text:PDF
GTID:2441390002466327Subject:Engineering
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Enantioselective separation is of key importance to the pharmaceutical industry. Homochiral metal-organic frameworks (HMOFs) are organic-inorganic hybrid microporous materials that can be used for enantioselective separation. One of the most prominent advantages of using HMOFs for enantioselective separation is their high capacity. Also, the pore sizes of HMOFs can be finely tailored, which makes them good candidates for chiral separations through inclusion complexation.In this thesis research, molecular simulations were carried out and revealed a number of interesting phenomena related to enantioselective adsorption in HMOFs. It was found that while some of the adsorption sites in a pore may favor the adsorption of one enantiomer, other adsorption sites may favor the adsorption of the other enantiomer. The collective effects of multiple chiral linkers on enantioselective separation were also investigated. Even if one chiral selector has very low enantioselectivity to the guest enantiomers, several of them packed in an HMOF can act synergistically to enhance enantioselective separation. Furthermore, the effect of pore smoothness on the consistency of enantioselectivity was assessed for a homologous series of structurally related chiral compounds in HMOFs. For example, a zinc saccharate-based HMOF with smoother pores is selective exclusively for the R-enantiomers of chiral alkan-2-ols, while an indium thiophene-2,5-dicarboxylic acid-based HMOF with rougher pores shows inconsistent enantioselectivities for the enantiomers of chiral alkan-2-ols.The three-point model was used to understand the enantioselectivities of homologous chiral compounds when they are interacting with a common chiral selector. The three-point model explains how the enantioselectivities of homologous chiral compounds may go down, go up, remain the same or even change preference if one of the four substituents at the chiral center is perturbed.Lastly, molecular modeling techniques were used to screen a number of HMOFs for their enantioselective separation capabilities. It was found that HMOFs with pore sizes matching those of the guest chiral molecules are excellent candidates for separating small chiral molecules, which are traditionally difficult to separate due to their simple structures.
Keywords/Search Tags:Chiral, Enantioselective, Adsorption, Hmofs, HMOF, Molecular
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