Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation.

The nano-composites FeO@SiO@(-OSi[(CH)NH])P([double bond, length as m-dash]O)(NH-(+)CH(CH)(CH)) (FeO@SiO@PTA(+)) and FeO@SiO@(-OSi[(CH)NH])P([double bond, length as m-dash]O)(NH-(-)CH(CH)(CH)) (FeO@SiO@PTA(-)) were prepared and used for the chiral separation of five racemic mixtures (PTA = phosphoric triamide). The separation results show chiral recognition ability of these materials with respect to racemates belonging to different families of compounds (amine, acid, and amino-acid), which show their feasibility to be potential adsorbents in chiral separation. The nano-composites were characterized by FTIR, TEM, SEM, EDX, XRD, and VSM. The VSM curves of nano-composites indicate their superparamagnetic property, which is stable after their use in the separation process. FeO, FeO@SiO, FeO@SiO@PTA(+) and FeO@SiO@PTA(-) are regularly spherical with uniform shape and the average sizes of 17-20, 18-23, 36-47 and 43-52 nm, respectively.