Enantioselective Separation Using Chiral Mesoporous Spherical Silica Prepared by Templating of Chiral Block Copolymers

Abstract

In this work, we synthesized chiral mesoporous silica (CMS) spheres, which can be used as a potential candidate for chiral separation. The CMS spheres with controllable pore sizes (of 2-3 nm) and high surface areas of ca. 614 m(2) g(-1) were synthesized by chiral templating with chiral block copolymers based on poly(ethylene oxide) and dl-glutamic acid [PEO(113)-b-(GluA)(10)]. The ordered structure of the chiral mesopores was characterized by high-resolution transmission electron microscopy, and the average pore diameters of chiral mesopores were estimated from the nitrogen adsorption-desorption measurements. The enantioselectivity properties and chiral resolution kinetics of the mesopores of silica spheres, after extraction of chiral polymers of PEO(113)-b-(l/d-GluA)(10), were scrutinized using a racemic solution of valine and measuring the circular dichroism and optical polarimetery. A chiral selectivity factor of 5.22 was found with a specific enantiomer of valine adsorbed preferably. These results raise the new possibilities of CMS spheres for enantiomeric separation and other enantioselective applications.